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Trouble with .308 not cycling properly


Adamc55

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6 hours ago, Adamc55 said:

Just got back from the range. Gun ran great with the enlarged gas port and orange spring. A small adjustment on the gas block was all that was needed. Gun seems to like 168 grain, might try some heavier stuff eventually. I need to start reloading...

Pretty damn good news, man - well done.  What did you end up taking the gas port to, in size?  This is something we need to add to the gas port thread here.  :thumbup:

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59 minutes ago, 98Z5V said:

Pretty damn good news, man - well done.  What did you end up taking the gas port to, in size?  This is something we need to add to the gas port thread here.  :thumbup:

 

27 minutes ago, Albroswift said:

.0995, wasn't it?

That's what I'm trying to confirm. 18" rifle-gas Faxon heavy match barrel, fluted.

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39 minutes ago, Adamc55 said:

.0995" gas port

Rifle length gas system on 18" faxon barrel

Armalite gas tube

Sprinco orange spring

5.4oz 2.5" buffer

7" buffer tube

Seekins lopro adjustable gas block

Was it this exact barrel?  Faxon has 3  different 18" rifle-gas barrels...

https://faxonfirearms.com/match-series-18-heavy-fluted-308-win-5r-416r-nitride-nickel-teflon-extension/

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I'm asking for a reason, @Adamc55, and it's not against you, man, not in the least.

I'm asking because of all the people that "know everything about .308ARs" and all the comments on what you should and shouldn't do to get your gun running. I'm asking based on all the amount of HUGE BULLSHIIT there is out there on other boards, and about the bullshiit on 3.8oz buffers, etc - that will never work, without compromising your whole recoil and gas systems, both, in whole.  I'm asking, just because I ask questions of people, on their setup, and I provide direct information that will get their gun running right.   I then get questioned on the very info that I provided...  I'm no rocket scientist, but I'm no Afghani in a cave smashing an AK together from sheet-steel and a rock, either.  I've been dealing with these platforms for 3 decades +.  Solely, these platforms, ARs only. 

I'm no "gunsmith," but I've been dealing with them long enough, and professionally enough for 20+ years, to know what is right, what is wrong, what works, and what doesn't work - to be able to tell when your gun isn't running right, and why. 

To those that doubt what I say, I only say...

 

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On 9/28/2019 at 10:45 AM, Adamc55 said:

Just got back from the range. Gun ran great with the enlarged gas port and orange spring. A small adjustment on the gas block was all that was needed. Gun seems to like 168 grain, might try some heavier stuff eventually. I need to start reloading...

Now the gun is running better, try some 155 gr ,165 gr and 175gr projectiles. The 168gr Bthp are a sweetspot weight projectiles for our gun . Also 180gr ammo may not feed well in every chamber, try a box before you buy a lot of it.

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On 9/29/2019 at 5:35 AM, Adamc55 said:

Yes it is that exact barrel. Also running a Fortis r.e.d. brake, not sure if that makes a difference in the gas system

You mind if I put your barrel details in the "gas port thread" ?...

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@Adamc55, I'm just glad your gun is running like it should.  I have to ask, though - is your gun running as it should, based on information I've stated?  Did you get your gun running, on information I gave you?  Was your dwell time what I stated it would be?  I gave a ballpark figure on it, but after I looked at it close, I think I nailed the dwell time.  Gas port size?  I think I projected 0.090"~0.095" for your barrel gas port diameter, and it was pretty close to that.  When you told me you were running adjustable gas, I think I said "just drill it to 0.100" and run your adjustable gas block.  You did that, pretty damn close, at 0.0995" drill bit. 

You're running a 5.3oz buffer, 7" internal depth receiver extension, and a Sprinco Orange spring - which is NOT for "severely overgassed .308ARs" - it just the normal spring from Sprinco for .308ARs running 7.000" internal depth carbine extensions (AR15 parts) on a .308AR, with a 2.500" buffer, of the proper weight (which is near, or on, 5.4oz, in a .308AR). 

I'm just happy your gun is running - but if you have feedback, I'd greatly appreciate it. If I ever told you something wrong - I'd greatly appreciate that, too, right here, openly. :thumbup:

Edited by 98Z5V
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10 hours ago, 98Z5V said:

You mind if I put your barrel details in the "gas port thread" ?...

Please do

8 hours ago, 98Z5V said:

@Adamc55, I'm just glad your gun is running like it should.  I have to ask, though - is your gun running as it should, based on information I've stated?  Did you get your gun running, on information I gave you?  Was your dwell time what I stated it would be?  I gave a ballpark figure on it, but after I looked at it close, I think I nailed the dwell time.  Gas port size?  I think I projected 0.090"~0.095" for your barrel gas port diameter, and it was pretty close to that.  When you told me you were running adjustable gas, I think I said "just drill it to 0.100" and run your adjustable gas block.  You did that, pretty damn close, at 0.0995" drill bit. 

You're running a 5.3oz buffer, 7" internal depth receiver extension, and a Sprinco Orange spring - which is NOT for "severely overgassed .308ARs" - it just the normal spring from Sprinco for .308ARs running 7.000" internal depth carbine extensions (AR15 parts) on a .308AR, with a 2.500" buffer, of the proper weight (which is near, or on, 5.4oz, in a .308AR). 

I'm just happy your gun is running - but if you have feedback, I'd greatly appreciate it. If I ever told you something wrong - I'd greatly appreciate that, too, right here, openly. :thumbup:

Gun works great with 168gr, I'll have to wait to try different loads and see how it does. Your advice did make a nicely working gun.

In Faxon and Wash's defense, faxons barrel specs were right in line with your numbers and the gun did operate after swapping the buffer spring to a lighter one. However I also didn't have a chance to test that set up with different loads. 

In the end I decided that your advice was good, as it gave me more room for overall adjustment without sacrificing a working set up, and I'm very happy with the outcome.

As a side note, to make the gun cycle with the orange spring, I did still have to open the gas block 1-2 full turns more than with the weaker spring. Even after drilling out the gas port.

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On 10/1/2019 at 7:17 AM, Adamc55 said:

 faxons barrel specs were right in line with your numbers

Those weren't "specs" at all - I had to come up with that gas port range, based on dwell time, pressure, and diameter at the gas block.  That's based on past experience figuring these things out.  If ended up being close to what I figured out, but needed a little more.

There's no "spec" on this stuff, man, not in the least.

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11 hours ago, 98Z5V said:

Those weren't "specs" at all - I had to come up with that gas port range, based on dwell time, pressure, and diameter at the gas block.  That's based on past experience figuring these things out.  If ended up being close to what I figured out, but needed a little more.

There's no "spec" on this stuff, man, not in the least.

I know your numbers weren't specs, but faxons were. At .093" gas port size and Dwell time of 4.875" those are their specs, since they make all the 18" match barrels to those numbers. I'm giving you a compliment, since your numbers that you calculated were right in line with the manufacturer. It must be my certain set up that necessitated a larger gas port to work with the orange sprinco spring. I am not discounting your input in the least, you helped me attain a well working rifle and I thank you for that. These numbers should be shared so that others may know what works and what doesn't. (It seems like a lot of people are using Aeros upper/lower combo and faxon 18" barrel)

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12 hours ago, Adamc55 said:

I know your numbers weren't specs, but faxons were.

My point is - they were guessing, too.  Because there is no spec on an 18" rifle gas barrel for a .308 Win.  Faxon guessed, and Faxon's smart people came up with 0.093", and it didn't work for you.  I gave a calculated range of 0.090"~0.095" as the best I could come up with, with the 0.875" gas block diameter.  Would it have worked at 0.095" instead of 0.093"?  Maybe not.  Would it have worked at 0.096"  Chances are better...  You get the point.  We can't call 0.0995" (that's a hair under 0.100", which is huge) a solid "spec" for this configuration because you have an adjustable gas block, and it's partially closed down to make your gun function for you.  Maybe 0.097" was the magic number?  We don't know. 

What we DO know is that if someone uses that same barrel, that you have, and they punch that thing to 0.0995" and run an adjustable gas block, they will for certain have a fully functional gun.  :thumbup:

We have it figured out for the 18" barrels with midlength gas - we've figured that out here.  This 18" rifle gas is all new - unless you take the proprietary info from Criterion, from Fulton Armory, on the Fulton Armory medium-weight 18.5" barrel with rifle gas, and run the numbers that Fulton Armory had Criterion make those barrels to - but those FA barrels were all 0.936" gas blocks.  If anything is a "spec" for the 18" rifle-gas, that one is it - even with 1/2" more barrel, and the larger diameter at the gas port. The gas port numbers would still be different, though, for dropping from a 0.936" gas port barrel diameter to the 0.875" gas port barrel diameter that you have...

That Fulton Armory barrel I described above is what I used on the first .308AR that I ever built, and I ran a rifle recoil system in it, with a 5.4oz buffer - zero issues from the gun, since day one, when I built it in 2010. 

I appreciate the compliment, I really do - I'm just trying to figure out guns for people, and make working systems that are smart - not "cobbled together parts, but you'd you stop when the gun runs, most of the time."  NOT a hit on you - but we see it here all the time, literally.  It needs to run all the time, on all the ammo, because we're not building race guns here, or gaming-guns-for-points.  

For the people that want the gaming gun, or the race gun, they can have that, easily - just spend the money on a complete JP rifle, give them your specs, and that thing will RUN exactly on your specs.  JP will do that, all day long.  Call them, tell them what you want, and hand over the money, and it will be on it's way.

Edited by 98Z5V
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6 hours ago, 98Z5V said:

 Because there is no spec on an 18" rifle gas barrel for a .308 Win. 

We have it figured out for the 18" barrels with midlength gas - we've figured that out here.  This 18" rifle gas is all new - 

I did not know that. This was my first attempt at delving into the large frame ar world.

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  • 2 weeks later...

Well, last range trip this gun ran flawlessly. Today was a different story. I had just finished a box of federal Berger 168 and that was running really good (has what seems like nickel coated cases) and started on a fresh box of Hornady match 168 with brass casing. Almost immediately ran into problems. The first round wouldn't fire, seemed like a light primer strike. What it ended up being is that the bolt wasn't going fully into battery. I fired about 3 rounds after getting it into battery. Loaded a new mag and chambered a round. 

Trigger pull no fire

I then attempted to pull the charging handle back and let it reseat it on the chambered round. Charging handle won't budge... The bolt was stuck somewhat into battery with a chambered live round. After trying multiple things to get the bolt back, including trying to knock the charging handle back with a small block of wood, I decided to instead tap it forward into full battery and just fire it. Fingers crossed it wouldn't explode in my face. It fired the round.

After that I didn't shoot anymore. I feel like something is up with the extractor. It's marring/burring brass like crazy, not so much on the harder cases of the federal. The gun also seems to be denting cases near the neck down. I somehow managed to get a mean scrape on the extractor (see silver in the pics) which may have been caused by try to force the bolt back. I know the gun needs a good cleaning but no reason that should have caused this.

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3 minutes ago, Adamc55 said:

Here's the extractor removed and uncleaned, should there be 2 o rings on the extractor spring?

You will see several varieties and combinations of O-rings, plugs, dual spring, and more I'm not thinking of. That dual ring sure looks like a firm set up. I'm a big fan of the Armalite extraction spring kit, it's pretty stout. My factory AR-10 didn't show signs of needing replaced till near 3,000 rounds. If you find an easy way to get the thing put together let me know, put three sets together myself with blood drawn each time............

https://www.armalite.com/product/10403030-ar10-extractor-spring-set/

1972308795_AR10extractorsproing.thumb.jpg.346dea95b90aa468d70fb9917ad29d3f.jpg

 

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6 minutes ago, jtallen83 said:

You will see several varieties and combinations of O-rings, plugs, dual spring, and more I'm not thinking of. That dual ring sure looks like a firm set up. I'm a big fan of the Armalite extraction spring kit, it's pretty stout. My factory AR-10 didn't show signs of needing replaced till near 3,000 rounds. If you find an easy way to get the thing put together let me know, put three sets together myself with blood drawn each time............

https://www.armalite.com/product/10403030-ar10-extractor-spring-set/

1972308795_AR10extractorsproing.thumb.jpg.346dea95b90aa468d70fb9917ad29d3f.jpg

 

It appears this one is a double spring double o ring set up. Seems really stiff

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So I smoothed up the damage and tried to ease a few of the sharper edges on the extractor and ejector. I then tried to polish those spots a little. I reinstalled everything with only 1 o-ring on the extractor spring. I sanded one of the spent brass casings until the imperfections were not visible then inserted it into the barrel. I had to drop the bolt from full lock to get it to seat all the way. I then ejected the casing. Here is the result-

 

Screenshot_20191014-130257_Snapchat-picsay.jpg

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