AR308 Short Barrel, Long Gas? Discussion/Build

[A.James]

On 3/22/2020 at 9:32 PM, 98Z5V said:

This is correct.  If it's really AR-10, it's the Armalite pattern.  If it's stated as DPMS or LR-308, it's DPMS-based in design.  That's why we call everything a .308AR.  That covers them all.

The most common pattern out there for building your own rifles from parts is definitely the DPMS pattern.  There are just more companies that went that route. 

Gas tubes, length, proper gas port position - is a giant clusterfuck in the Big-AR industry.  It either uses AR15 gas tubes, or Armalite AR-10 gas tubes (EDIT - Wilson Combat is doing some of their own gas port positions on their own excellent barrels, and special-length gas tubes that they make in-house).  Thank barrel sellers for that one, with funky gas port positioning.  You really need the barrel in your hands to see what you've got - and an appropriate AR15 gas tube.  If it's too short, you wait, and buy the Armalite AR-10 gas tube to solve the problem.

Thank you so much for setting me straight! I must have read and wrote AR10 too many times, leading to my confusion. Hopefully I haven't confused anyone else in this thread, but assuming  they read the responses, we should all be able to "clean up" the way we speak about the .308AR platform, being more specific with our verbiage in regard to Armalite vs. DPMS/SR-25 patterns. In all this research I'm jonesing to build my second AR as an Armalite pattern, and compare the differences... For now DPMS is gonna give me quite a few more options, and perhaps problems which I'll have to debug - and thus learn from. When I order my barrel I'll be sure to measure it to ensure I grab the proper gas tube. I'll probably buy parts one at a time and make sure everything fits properly before adding the next piece of the puzzle. Slow and steady, I'll learn and grow in my understanding of the dreaded .308AR lack-of MilSpec. Thank you again for the assist, you're helping more people than just myself by setting this straight, preventing the spread of misinformation/incorrect nomenclature from my future posts. I agree it sucks when everybody has problems and heads here just to be told they bought incompatible parts... I'm hoping I plan and research enough to avoid this conundrum in my first build. 

-Side note: I love how you speak about Wilson Combat in this post vs. others I've found. Different levels of "BBQ priming?" Tehee....

On 3/22/2020 at 9:34 PM, 98Z5V said:

Hit this thread  - there's a ton of info in here, with numbers, details, explanations, etc.

 

It's so ironic you tagged this thread here... This was the first thread I read that made me think... DAM. I don't even know WTF is going on here... That thread is what made me open this [slightly] more specific can o' worms. In replying to one of your last posts in this thread, before the last two you made, I was laying in bed thinking, "I hope I can dig up that thread again - the one with all the pics of the gas tube in the upper and how it should align. Maybe @98Z5V will have some insight/agreements with what I read there..." 

Lo and behold! You were "that guy." Small world. After realizing that you are the one whose posts pushed me into this theoretical exploration, I have even more respect and reverence for the words you've shared with me in this thread. Thank you again for your experience and expertise. I also appreciate how black and white you are considering all this manufacturer-inter-compatibility (or lack thereof), especially with barrels. Definitely gave me the heads up on what to watch out for, you've already helped me to play defense on myself and these "marketing dimensions," if you will. I feel I won't get blindsided, 'cuz I'm definitely putting all the time I need into doing my homework.

Again, thank you and @survivalshop, as well as all the others who put in some serious time and energy in that thread, as well as in the one linked therein.

Again, thank you all so much for your dedication to this community. 🙏

 

Edited March 24, 2020 by A.James

[A.James]

So on that note, I'm going to table the gas port distance / gas tube length discussion. I've been schooled by some of the best here, and I've been pouring over barrel schematics to reference the claims brought up here. Absolutely not will rifle length fit on a 14.5" - not even DPMS pattern. But I'm starting to think that a 15" barrel with a <1" gas block length and typical .7" muzzle thread length MIGHT be able to fit a rifle gas system. (Maybe Armalite gas would still be too long, perhaps DPMS would just barely squeeze in there.)

So my amended plan is as follows:

I'm gonna grab a 16" rifle gas barrel - probably try X-Caliber, heard some good things about the quality and like the customization/price ratio. This is my first build, not trying to grab the best barrel money can buy, but I'm interested in SOME level of quality. I'll report back on my experience with the brand. This opens me up to a ready-to-build (without SBR stamp or pin/weld brake) barrel length that I can use while I save $$$ for my suppressor/QD brake. Then I can chop to whatever length will fit will my gas block and muzzle device (I'm thinking 15" would be cherry), pin and weld at that time. This lets me play with my new toy and test other parameters before adding another grand to the overall price tag. Baby steps.

So its time to look at bolts/carriers, as well as buffer mass and spring. @98Z5V you had mentioned in one of the two threads pinned before that you had your sight jump off target. After increasing buffer weight AND adding mass to the BCG itself, your rifle stayed flatter... Can you give me a bit of info on BOLT mass vs. BUFFER mass?

In my objectives #4 (low mass); and #5 (soft shooting recoil impulse), I understand there will be compromises between the two factors. Please elaborate to your hearts content on your take of where in the firing system the mass can/should be added. I'm intrigued by your fix on the rifle you mention in that thread, heavier bolt carrier. I've also heard a tighter spring with a lighter buffer could also be "soft." REMEMBER: I WILL BE USING AN ADJUSTABLE GAS BLOCK, and thus foresee a general tune-ability to most combinations. I've looked into HeavyBuffers and I'm liking what I'm reading, as well as other users' experiences with this high-er mass buffers and respective spring combos. I understand more mass moves away from objective #4, but closer to objective #5... I think personally on this build I'd rather lean toward #5. Not opposed to [up to 10 oz] rifle buffer/tube, but if I can achieve 99% of the result with a [5.4 oz. +] carbine buffer/M4 tube with a collapsible carbine stock, then objective #2 takes the cake. Let's talk bolt carrier mass, followed by buffer mass. Started with the barrel, let's move back from there. To get a guarantee of MOA on any X-Caliber barrel, has to be factory headspaced with a JP bolt (among other brands - but I'm liking what I read about the JP High Pressure deal). Not opposed to grabbing that bolt, but the full BCG from Aero is cheaper than the JP bolt alone. I've read that bolt does well in DPMS branded carriers, I think Fulton Armory is rebranded DPMS. Correction?

Could grab:

-Aero BCG for around $200 (no "stripped" option, comes with bolt)

-JP bolt and Fulton carrier for around $325 (stripped carrier around $100, JP bolt around $225)

-JP bolt and JP full mass carrier for around $450

Currently looking at the midrange option, sell me on the JP/JP? I'll be fine with JP/Fulton? Go cheap with the Aero? Please advise.

Then we can choose the buffer length/mass/spring to play nicely with the BCG ass'y I decide on.

Thanka ya's in advance!

Edited March 24, 2020 by A.James

[jtallen83]

2 hours ago, A.James said:

probably try X-Caliber,

I bought a 16 inch rifle gas barrel from them when they first started doing them for large frame AR's, 

Interesting thread with their comments and customer service,they pop in on the third page;

 

[A.James]

1 hour ago, jtallen83 said:

I bought a 16 inch rifle gas barrel from them when they first started doing them for large frame AR's, 

Interesting thread with their comments and customer service,they pop in on the third page;

 

Thanks for dropping by and welcome! Thank you for the links, as well! I’ve got more reading to do! I’ll probably add another post after I dive into those threads, to ask questions if there are any holes in my understanding. 

By all means, feel free to send links on the bolt/carrier front as well! I do my best to search before posting, but forum searches aren’t my strong suit. I can handle a web search, but for some reason in my past I have searched what I would consider exhaust-ably numerous terms before posting, only to have the first reply to my new thread be the link to a page that never came up in my searching. I’m forever sorry to any forum that had “yet another” post that has been beaten to death 100x before... 🤦‍♂️

[98Z5V]

6 hours ago, A.James said:

So its time to look at bolts/carriers, as well as buffer mass and spring. @98Z5V you had mentioned in one of the two threads pinned before that you had your sight jump off target. After increasing buffer weight AND adding mass to the BCG itself, your rifle stayed flatter... Can you give me a bit of info on BOLT mass vs. BUFFER mass?

That was this gun right here that it went into - Tubb Carrier Weight System - this is it's thread here, but not where I talked about it, and why adding it back into this gun - I'll try to find that comment...

 

[98Z5V]

7 hours ago, A.James said:

So its time to look at bolts/carriers, as well as buffer mass and spring. @98Z5V you had mentioned in one of the two threads pinned before that you had your sight jump off target. After increasing buffer weight AND adding mass to the BCG itself, your rifle stayed flatter... Can you give me a bit of info on BOLT mass vs. BUFFER mass?

Damn, that was Placeholder 6 in the "Gas tubes, barrel gas ports, and buffer weight" thread.  It was pretty well explained in that post. 

With the buffer and BCG moving through the recoil cycle together, it's not gonna matter which one you add weight to.  It really won't.  The reciprocating weights inside the buffer body are there to counter "bolt-bounce", but other than that - if your scope is jumping off target, add more weight to the recoil system. Calm that gun down.  Excessive recoil is why the scope is jumping off-target. Whether you add it to the buffer or the BCG doesn't matter - HOWEVER...  The Tubb CWS is discontinued.  You can't get that anymore, it's gone from the market.

(Hint,.. @Matt.Cross...)

For me, already running a 5.4oz .308AR rifle buffer, AND having a Tubb CWS on hand - the easiest thing for me to do was put that CWS into this gun, right into the back of the BCG, and test it.  Whammo - another 1/4lb in reciprocating mass.  Solved the issue I was having, too.  So, with no way to get a CWS now, what can you do IF you have this issue?  Buy a 10oz buffer from Slash.  Hit up HeavyBuffers.com, and buy this 10oz gem right here:

http://heavybuffers.com/ar10rifle.html

[98Z5V]

11 hours ago, A.James said:

I've been schooled by some of the best here, and I've been pouring over barrel schematics to reference the claims brought up here.

You can look at schematics all you want, reference claims brought up here all you want.  We've already done it, and most of that was by challenging ourselves to do it - "YOU THINK THIS WILL WORK?@!"     "No WAY IN HELL, but since you thought about it, then just TRY IT!!!"  And we did, years ago.

From what you don't know, that's really how this place works.  Someone posts up something that sounds un-possible. It's either proven, or debunked.  You have no idea about how much money has been wasted - or proven - right here, between us all.  Trying different things, or drilling out barrels.

If we tell you something, and we're solid and serious about what we're telling you - then you need to know right now that you're wasting your time "pouring over barrel schematics to reference the claims brought up here..."  You can research, whatever it is that you want to research, all you want.  You can "reference any claims" that you want. Come back here with the information that our "claims" might be off - that helps ALL OF US.  But you better bring some pretty solid proof on that shiit, because we have alot of experience on this platform.  You better be "shadow of a doubt" on all of it.  With facts.  Facts that you can prove.

We don't get paid, based on how you respond - nor do we care.  You can say anything you want - doesn't bother us.  Don't care.  What really bothers us is when people doubt the information presented, talk shiit, but can't refute the information presented.  That's not you, right now...  but that's the big one.  If you have other information that strikes anything stated, DOWN - then post it up and make all of us smarter.  If you don't have that information...  then...  was the original information wrong?... 

[98Z5V]

11 hours ago, A.James said:

 I've been schooled by some of the best here, and I've been pouring over barrel schematics to reference the claims FACTS brought up here.

FIxed that for ya. 

If any of those facts are wrong - just simply prove them wrong, with data and other supporting facts.  We're good with it. 

Edited March 25, 2020 by 98Z5V

[A.James]

9 hours ago, 98Z5V said:

You can look at schematics all you want, reference claims brought up here all you want.  We've already done it, and most of that was by challenging ourselves to do it - "YOU THINK THIS WILL WORK?@!"     "No WAY IN HELL, but since you thought about it, then just TRY IT!!!"  And we did, years ago.

From what you don't know, that's really how this place works.  Someone posts up something that sounds un-possible. It's either proven, or debunked.  You have no idea about how much money has been wasted - or proven - right here, between us all.  Trying different things, or drilling out barrels.

If we tell you something, and we're solid and serious about what we're telling you - then you need to know right now that you're wasting your time "pouring over barrel schematics to reference the claims brought up here..."  You can research, whatever it is that you want to research, all you want.  You can "reference any claims" that you want. Come back here with the information that our "claims" might be off - that helps ALL OF US.  But you better bring some pretty solid proof on that shiit, because we have alot of experience on this platform.  You better be "shadow of a doubt" on all of it.  With facts.  Facts that you can prove.

We don't get paid, based on how you respond - nor do we care.  You can say anything you want - doesn't bother us.  Don't care.  What really bothers us is when people doubt the information presented, talk shiit, but can't refute the information presented.  That's not you, right now...  but that's the big one.  If you have other information that strikes anything stated, DOWN - then post it up and make all of us smarter.  If you don't have that information...  then...  was the original information wrong?... 

I didn’t mean to sound like I didn't believe you, I echoed your statement. I was pouring over the schematics to try to figure out what the minimum barrel length could be on the RLGS, I wasn’t trying to disprove any info provided because I recognize the caliber of people I’m dealing with here. I’m the new kid in class. I’m learning new things. But I always read ahead, and ask questions for retention and understanding. 
 

14.5” ain’t long enough, that’s a FACT. Never doubted ya. Like you said, until I have the barrel in my hands I won’t know for sure, I’m just speculating that 15” could be long enough. Maybe 15.1” - maybe 15.2” - maybe 15.3” etc., depending on how my barrel is drilled. And once again, we won’t know what’s possible with any given barrel until it’s in hand - because different manufacturers are doing different things with their .308AR barrels...

9 hours ago, 98Z5V said:

FIxed that for ya. 

If any of those facts are wrong - just simply prove them wrong, with data and other supporting facts.  We're good with it. 

Haha no worries, brother. My apologies if I seemed like a brat. Once again, based on everything I’ve read in your posts in this thread and in others, you’re very good at providing data to back up your facts. I’ve really begun to rely on your knowledge because it’s some of the only stuff out there that I trust. There is a lot of internet mumbo jumbo out there (claims), but the way you present your experience and back it up makes it super easy to swallow (facts). 

Didn’t mean to downplay the merit of your contribution by using the word “claims” - you’re legit. I’m very thankful for what you share!

[A.James]

14 hours ago, 98Z5V said:

That was this gun right here that it went into - Tubb Carrier Weight System - this is it's thread here, but not where I talked about it, and why adding it back into this gun - I'll try to find that comment...

 

Damn. Those are a couple of cute little fur balls. 

Now, what was I reading about...?

...?

...Oh that’s right! 98’s Mk11 Mod 0!

[A.James]

15 hours ago, 98Z5V said:

Damn, that was Placeholder 6 in the "Gas tubes, barrel gas ports, and buffer weight" thread.  It was pretty well explained in that post. 

With the buffer and BCG moving through the recoil cycle together, it's not gonna matter which one you add weight to.  It really won't.  The reciprocating weights inside the buffer body are there to counter "bolt-bounce", but other than that - if your scope is jumping off target, add more weight to the recoil system. Calm that gun down.  Excessive recoil is why the scope is jumping off-target. Whether you add it to the buffer or the BCG doesn't matter - HOWEVER...  The Tubb CWS is discontinued.  You can't get that anymore, it's gone from the market.

(Hint,.. @Matt.Cross...)

For me, already running a 5.4oz .308AR rifle buffer, AND having a Tubb CWS on hand - the easiest thing for me to do was put that CWS into this gun, right into the back of the BCG, and test it.  Whammo - another 1/4lb in reciprocating mass.  Solved the issue I was having, too.  So, with no way to get a CWS now, what can you do IF you have this issue?  Buy a 10oz buffer from Slash.  Hit up HeavyBuffers.com, and buy this 10oz gem right here:

http://heavybuffers.com/ar10rifle.html

Thanks! Just went back to read that one again. You already corrected me, using the standard buffer weight, adding mass ONLY to the BCG. I hear you loud and clear, mass could be in either position because it’s all working together. 

This “if I have that issue” is what I’m trying to avoid. Based on what I’m reading from you, other posters, and at HeavyBuffers, it seems more mass in the buffer/carrier will equate to softer recoil impulse - just plain physics, right? Is there a point of diminishing returns? 

Still TRYING to keep OAL down, I see a few options with the AR15 carbine vs. AR10 carbine vs. AR rifle buffer tubes and stocks:

7” AR15 Carbine tube with 6.5oz buffer allows shortest collapsible carbine stocks, improved recoil over standard 5.4oz buffer. Objectives #2 and #4 are upheld, #5 could still see improvement.

7 5/8” AR10 carbine tube with 8.5oz buffer allows more reciprocating mass with a slight addition to overall length - unless there is some collapsible/lightweight stock out there for this length receiver extension that I have yet to stumble upon. Objectives #2,4,5 are balanced here.

9 5/8” (I’ve also read 9 11/16”) AR rifle tube with 10oz buffer provides softest recoil at the cost of running a longer (and heavier) stock. Objective #2 goes right out the window, #4 is compromised, #5 is GOLD. To reiterate, I prefer to chase objective #5 at the cost of #4, but we’re losing a lot of clearance in order to make this gun shoot smoother.

Again, does it need to be any smoother? Diminishing returns? I assume it will come down to shooters preference if/when to surpass a buffer weight that keeps the crosshairs on target. But I do feel like there is a minimum mass to aim for in order to balance the entire system. Anything beyond that is [mostly] comfort?

Edited March 25, 2020 by A.James

[A.James]

@jtallen83, I looked over those threads and read them from where you linked until the end. 

Had a GOOD laugh at the X-Caliber rep and all the flame he caught after his post. LOL!!!

The threads there were pretty old, can you update me on how things worked out in the end? Have you heard of others running into similar problems with these barrels? I've read some bad reviews but also read a lot of good ones. Any comment on QC in recent years from X-Caliber?

Thanks for sharing your experience!

[jtallen83]

26 minutes ago, A.James said:

how things worked out in the end?

It didn't turn out to be anything special, not bad accuracy but nothing to brag about. Fit and finish is nice, cleans up easy due to the mirror finish on the bore. I have a BA match barrel that easily outshoots it for the same or maybe less money depending on sales.

[jtallen83]

1 hour ago, A.James said:

Is there a point of diminishing returns? 

The more mass the more the barrel wants to dip when the bolt slams home, you would have to shoot a lot in rifles set up with opposite weights to even notice though.

[Matt.Cross]

32 minutes ago, jtallen83 said:

The more mass the more the barrel wants to dip when the bolt slams home, you would have to shoot a lot in rifles set up with opposite weights to even notice though.

This is a great point, probably especially noticable in unsupported firing positions. I would think supported firing would mitigate this almost if not completely.

[jtallen83]

12 minutes ago, Matt.Cross said:

I would think supported firing would mitigate this almost if not completely.

I have done some side by side off bags with my low mass AR15 and a pretty standard carbine with H2 buffer, I noticed more movement through the scope on the standard carbine but you would have to be a real fast shot to get the advantage the low mass gives you. For me the most telling difference is the round count, from wife to grandkids they always pick that low mass rifle for the range so it gets near three times the rounds fired than the other AR-15's, it's been very reliable beyond one incident with the nib flaking and causing the ejector to stick, still feel better about using the standard carbine with the H2 buffer as a personal defense weapon.

[98Z5V]

7 hours ago, A.James said:

This “if I have that issue” is what I’m trying to avoid. Based on what I’m reading from you, other posters, and at HeavyBuffers, it seems more mass in the buffer/carrier will equate to softer recoil impulse - just plain physics, right? Is there a point of diminishing returns?

Are you talking about going straight to a 10oz buffer, right away?  "Dimishing returns" in that regard?  One big one would be -the gun doesn't function, because the gas system isn't up to par.  That's one fast way to find out, though.  You'll know before the first mag is gone. 

[A.James]

11 hours ago, 98Z5V said:

Are you talking about going straight to a 10oz buffer, right away?

Hypothetically, yes. I’d hope I can find a solution in a carbine extension for a collapsible stock. I’m not sure 10oz would be necessary or even appropriate for my goals, so I guess that’s what I’m looking for advice on. The marketed applications on HeavyBuffers recommend more mass for suppressed weapons - from what I understand, to compensate for increased pressure that the suppressor might contribute to. Balancing the entire system.

11 hours ago, 98Z5V said:

One big one would be -the gun doesn't function, because the gas system isn't up to par.

More mass needs more gas? The hypothetical shortfall of “too much buffer mass” being a gas port diameter that’s too small, right? (Including wide open on an adjustable gas block?) Conversely, more gas needs more mass? “Over-gassed” meaning buffer mass is too low...? Trying to test my understanding of the balance required.

 I’m beginning to foresee some of the issues I’ll probably run into in my first build, and it seems a lot of solutions have already been shared in the attached posts in this thread. The fix to having too much mass for the system would be to drill a larger diameter of the gas port? 

Sounds like lower total mass of the recoil system will jump up more vs. higher mass might dip down... This is more what I’m looking to address when I said diminishing returns. Then I could drill the gas port wide enough for proper cycling/function, and finally dial it into the zone with the adjustable gas block. 

The overall question is, “assuming I match my buffer mass to gas port diameter/entire gas system for the balance required for proper operation, what level of total mass will keep me the flattest?”

[Matt.Cross]

1 hour ago, A.James said:

Hypothetically, yes. I’d hope I can find a solution in a carbine extension for a collapsible stock. I’m not sure 10oz would be necessary or even appropriate for my goals, so I guess that’s what I’m looking for advice on. The marketed applications on HeavyBuffers recommend more mass for suppressed weapons - from what I understand, to compensate for increased pressure that the suppressor might contribute to. Balancing the entire system.

More mass needs more gas? The hypothetical shortfall of “too much buffer mass” being a gas port diameter that’s too small, right? (Including wide open on an adjustable gas block?) Conversely, more gas needs more mass? “Over-gassed” meaning buffer mass is too low...? Trying to test my understanding of the balance required.

 I’m beginning to foresee some of the issues I’ll probably run into in my first build, and it seems a lot of solutions have already been shared in the attached posts in this thread. The fix to having too much mass for the system would be to drill a larger diameter of the gas port? 

Sounds like lower total mass of the recoil system will jump up more vs. higher mass might dip down... This is more what I’m looking to address when I said diminishing returns. Then I could drill the gas port wide enough for proper cycling/function, and finally dial it into the zone with the adjustable gas block. 

The overall question is, “assuming I match my buffer mass to gas port diameter/entire gas system for the balance required for proper operation, what level of total mass will keep me the flattest?”

Suppressor weight and overall suppressor effectiveness will also factor into the equation. A very effective suppressor will capture enough gas to drastically reduce muzzle rise, but also sends more gas to the receiver area. A heavier suppressor will not only reduce muzzle rise, but also tame the effect of the extra gas to the recoil system.

[A.James]

8 hours ago, Matt.Cross said:

Suppressor weight and overall suppressor effectiveness will also factor into the equation. A very effective suppressor will capture enough gas to drastically reduce muzzle rise, but also sends more gas to the receiver area.

Precisely what I was thinking. Looking at TBAC Ultra 7, the greater mass on the muzzle end has more inertia which would “fight” muzzle rise, the can captures some gas before bullet leaves barrel, lessening gas system pressure over time, but extending dwell time (perhaps marginally) compared to a bare muzzle... If I recall my homework correctly, the Ultra 7 is [anecdotally] pretty forgiving in the sense of back pressure to the receiver area relative to other suppressors I’ve looked into, which may require a lesser mass than [for discussions sake] HeavyBuffers’ maximum recommendations (up to 10 oz. rifle buffer) for suppressed use - especially if their evaluation of “suppressed use” involved testing of suppressors including those that have been reported to add significant back pressure to the receiver area. I’m still HOPING for a carbine length extension (either AR15 7” or AR10 7 5/8”) for a shorter collapsible stock length, but I feel if @98Z5V had issue WITHOUT suppressor on AR10 length rifle extension and rifle gas, 16” barrel length - pushing him toward 9.5~ish oz. of buffer + added [BCG] reciprocating mass total, I *MIGHT* need a similar amount of mass to sling those heavier projectiles with perhaps lighter powder loads, to stay on target, especially when suppressed.

Which would mean my ideal stock and buffer system might be “not enough,” proving to require rifle buffer and stock. I’m trying to dial in the theory as close as possible before purchasing. Buy once.

8 hours ago, Matt.Cross said:

A heavier suppressor will not only reduce muzzle rise, but also tame the effect of the extra gas to the recoil system.

If it “tames” gas to recoil, then that would imply I need less total mass than 98 did based on his findings. The suppressor being added (as far as muzzle rise, inertia, physics; are concerned) kind of seems counter intuitive to the general “marketed” recommendation of additional buffer mass for suppressed use. I’m looking to find the best balance possible before adjusting the gas block. The adj. gas still reads [to me] as being the last step. Am I wrong here? Please correct any theory that is out of line. I feel like I’m being tutored for a test, and when I put my parts list together here (hopefully by page 3 😂) it will be my final exam as far as “should it work!?!” goes...

I feel like we are getting into “set” gas block territory, and the adjustable gas block kind of greys-out some of this black and white. I think I’m really getting the hang of this .308AR theory, PLEASE correct me if I’m wrong. The more I understand about the scientific/physics variables to this overall equation, the more success I’ll have when I fire that first 20rd mag.

For the record, the more time goes on in this thread, I’m beginning to feel like going for cheapest components at first may be my best bet. Gaining experience building/troubleshooting, as well as experience shooting and familiarizing myself with feel seems like the biggest win from my first 308 build. From there I could potentially increase buffer mass, improve parts one at a time until I have a bombproof weapons system. Then all those replaced parts (now spare parts) could be the foundation of my next experimental build. I’m not trying to skip steps, just trying to take as much time researching step 1 so I don’t shoot myself in the foot, METAPHORICALLY SPEAKING. 

Edited March 27, 2020 by A.James

[Matt.Cross]

18 minutes ago, A.James said:

Precisely what I was thinking. Looking at TBAC Ultra 7, the greater mass on the muzzle end has more inertia which would “fight” muzzle rise, the can captures some gas before bullet leaves barrel, lessening gas system pressure over time, but extending dwell time (perhaps marginally) compared to a bare muzzle... If I recall my homework correctly, the Ultra 7 is [anecdotally] pretty forgiving in the sense of back pressure to the receiver area relative to other suppressors I’ve looked into, which may require a lesser mass than [for discussions sake] HeavyBuffers’ maximum recommendations (up to 10 oz. rifle buffer) for suppressed use - especially if their evaluation of “suppressed use” involved testing of suppressors including those that have been reported to add significant back pressure to the receiver area. I’m still HOPING for a carbine length extension (either AR15 7” or AR10 7 5/8”) for a shorter collapsible stock length, but I feel if @98Z5V had issue WITHOUT suppressor on AR10 length rifle extension and rifle gas, 16” barrel length - pushing him toward 9.5~ish oz. of buffer + added [BCG] reciprocating mass total, I *MIGHT* need a similar amount of mass to sling those heavier projectiles with perhaps lighter powder loads, to stay on target, especially when suppressed.

Which would mean my ideal stock and buffer system might be “not enough,” proving to require rifle buffer and stock. I’m trying to dial in the theory as close as possible before purchasing. Buy once.

If it “tames” gas to recoil, then that would imply I need less total mass than 98 did based on his findings. The suppressor being added (as far as muzzle rise, inertia, physics; are concerned) kind of seems counter intuitive to the general “marketed” recommendation of additional buffer mass for suppressed use. I’m looking to find the best balance possible before adjusting the gas block. The adj. gas still reads [to me] as being the last step. Am I wrong here? Please correct any theory that is out of line. I feel like I’m being tutored for a test, and when I put my parts list together here (hopefully by page 3 😂) it will be my final exam as far as “should it work!?!” goes...

I feel like we are getting into “set” gas block territory, and the adjustable gas block kind of greys-out some of this black and white. I think I’m really getting the hang of this .308AR theory, PLEASE correct me if I’m wrong. The more I understand about the scientific/physics variables to this overall equation, the more success I’ll have when I fire that first 20rd mag.

For the record, the more time goes on in this thread, I’m beginning to feel like going for cheapest components at first may be my best bet. Gaining experience building/troubleshooting, as well as experience shooting and familiarizing myself with feel seems like the biggest win from my first 308 build. From there I could potentially increase buffer mass, improve parts one at a time until I have a bombproof weapons system. Then all those replaced parts (now spare parts) could be the foundation of my next experimental build. I’m not trying to skip steps, just trying to take as much time researching step 1 so I don’t shoot myself in the foot, METAPHORICALLY SPEAKING. 

I shot suppressed and unsuppressed at long range for years with standard recoil system components, ie. what has already been recommended to you. You're overthinking this just a bit. The only change I've made with regards to that was an adjustable gas block to rebalance the gas forward/gas rearward ratio.

Do a standard Armalite buffer/tube/spring combo and be done with it until you have the experience needed to understand the nature of the modifications that will perfect it.

[A.James]

13 minutes ago, Matt.Cross said:

I shot suppressed and unsuppressed at long range for years with standard recoil system components, ie. what has already been recommended to you. You're overthinking this just a bit. The only change I've made with regards to that was an adjustable gas block to rebalance the gas forward/gas rearward ratio.

Do a standard Armalite buffer/tube/spring combo and be done with it until you have the experience needed to understand the nature of the modifications that will perfect it.

I think you are confirming my final sentiment from my previous post. My “cry once” will be worth the gains of experience and firsthand understanding. I appreciate your push in this direction, especially because it saves my wallet (until I get to the range for troubleshooting). I don’t think I’m over thinking it, but based on your comment here, I believe I may be thinking that the bandwidth of efficacy of these buffer changes is greater than it actually is. Perhaps I was thinking changing the buffer weight could have a 20x effect when in reality it could only be a 2x effect (just throwing out hypothetical/relative numbers). I’ve shot enough to know that comparable rifles shoot differently, maybe my strongest asset to gain would be range time and evaluation on a personal level. Then I could report back with my perceptions, refer to the ideas of the great minds here, and nail down some factual specs to go along with my [near future] experiences.

I get physics, and I know Mr. Stoner probably evaluated the ideas I’m bringing up here. But, he tested all his theories and solidified a working system through endless experimentation. I’m not trying to improve upon his parameters, just trying to sync the [never ending .308AR] modifications that we see today (including my goals on this build) with the proven specs he came up with - thanks DPMS! Lol...

Wasn’t he first concerned with overall gas pressure, which then led him to his design on barrel length vs. gas system length/diameter/flow vs. reciprocating mass?

[DNP]

Just a little longer and you’ll have all the lines full. 

[98Z5V]

2 hours ago, A.James said:

 maybe my strongest asset to gain would be range time and evaluation on a personal level.

You just nailed it,with that statement alone.

Don't over-think it.  Build with smart parts selection. Once you have a running gun - you look at what it's doing, what you want it to do, and figure out how to change it to meet what you want it to do. You NEED it to cycle, every single time, within what it was designed to do.  No matter what the ammo is...

[A.James]

13 minutes ago, 98Z5V said:

You just nailed it,with that statement alone.

Don't over-think it.  Build with smart parts selection. Once you have a running gun - you look at what it's doing, what you want it to do, and figure out how to change it to meet what you want it to do. You NEED it to cycle, every single time, within what it was designed to do.  No matter what the ammo is...

Thanks guys. I suppose I was trying to hit a homer on the first pitch... high hopes? Yeah I think so, but the higher we set our goals, the greater heights we can achieve. I’ll be paying a bit more in the long run probably, but those dollars will be well spent to acquire the experience to tune it myself, hopefully with the guidance of those willing to continue to lend a hand. I’ll put together a parts list tomorrow and post it here. If anything looks incompatible and you happen to notice, please let me know!

Thank you all again for the advice and schooling. So much. I have a bit more confidence moving forward at this point and I’m excited to get my hands dirty. I’ll update here as I grab stuff - might be kind of slow going from here on out, thanks for sticking around!

Knowing myself, I’m sure I’ll get onto some deeper topics as this thing starts to come together, but I’ll try to keep my future posts  on more an update basis rather than a request for full on lessons like I’ve been so blessed with. Thanks again everyone. I’m excited to talk more when I’ve got something to show from these great talks! 🙏