Certified noob in need of some help here!

[merrymarksman]

So, as you can tell I just recently signed up here. I'm from Germany, and after I got my hands on the H&K MR308 while in the army decided to buy a Remington R25 GII soon as i heard of it. I wanted a .308 in a slim and lightweight package since said H&K was far too bulky and heavy for hunting, what is the main purpose of my rifle (also it was way too expensive).

Anyway, I bought the gun in 2016, got a suppressor in 2017 and therefor had to make the first upgrades, muzzle threading and an adjustable gas block. But ever since the gas block was changed I had to turn the "gas screw" pretty much all the way down when running the rifle suppressed and about 1 turn further out when unsuppressed. That wasn't actually a problem, it ran reliably with all sorts of ammo once i figured out the right setting. 

Trouble started when I decided that I wanted a collapsible stock, bought a mil-spec AR-15 7" FAB-Defense Reciever Extension and a Kyntec .308 Shorty Buffer (https://www.kyntec.com/product/rb5004-kynshot-marksman-recoil-buffer-.308-shorty-collapsible-stock-2.5-inches-6/) as well as a Heavy Buffer Carbine .308 spring (http://heavybuffers.com/springs.html).

I really thought i had perfected my setup, but when I took the rifle to the range for the first rounds after these upgrades weird stuff started happening: First off, it absolutely demolished the brass, leaving deep marks of the double ejectors and blowing out 8 primers of about 40 rounds. I also had to turn the gas screw even further in to reach 3-o'clock ejection, somewhere between a 1/4 to a 3/8 turn from complete lockdown/single fire.

After reading a bunch of threads on gas system and recoil system topics I realized that my rifle is most likely under-recoiled or over-gassed respectively. I'm pretty clueless on how to solve this in the most efficient way and I don't have an experienced gunsmith with deep knowledge on the AR10 platform on hand so I'm turning to you guys for advice. 

Now, I know this issue has been adressed a hundred times on here, I just can't figure out what's the proper solution in my case. So I'm hoping someone will have the patience to break it down for me again 🤔

Would a CAR-10, or maybe a CAR-10 XH, be able to solve this problem or do you think the issue might be the gas block (i.e. poor fitting of the gas block on the gas port by the gunsmith?) ?

Or would you simply say I'm running a setup that's doomed to fail and that I should put the factory recoil system back on the rifle and be done with it?

 

I'd be really grateful for any input!

Edited February 12, 2020 by merrymarksman

[Armed Eye Doc]

How much does your buffer weigh?  I would be willing to bet that it is too light.  As you suggested, a heavier buffer would likely help your situation.  You need to rebalance your gas and recoil systems.  

[jtallen83]

3 hours ago, merrymarksman said:

Kyntec .308 Shorty Buffer

You won't find many that have a positive opinion on those hydraulic buffers here.

Blown primers doesn't immediately make me think of a gas or buffer system issue, I would be checking the headspace and trying some different ammo.

[shooterrex]

Your rifle worked fine till you changed the stock and recoil set up. Underrecoiled is my best guess. Buffer needs to be in the 5oz range. Armalite sells the whole kit. Buffer,tube, and spring for $65.00.

[98Z5V]

5 hours ago, merrymarksman said:

 

Anyway, I bought the gun in 2016, got a suppressor in 2017 and therefor had to make the first upgrades, muzzle threading and an adjustable gas block. But ever since the gas block was changed I had to turn the "gas screw" pretty much all the way down when running the rifle suppressed and about 1 turn further out when unsuppressed. That wasn't actually a problem, it ran reliably with all sorts of ammo once i figured out the right setting. 

Trouble started when I decided that I wanted a collapsible stock, bought a mil-spec AR-15 7" FAB-Defense Reciever Extension and a Kyntec .308 Shorty Buffer (https://www.kyntec.com/product/rb5004-kynshot-marksman-recoil-buffer-.308-shorty-collapsible-stock-2.5-inches-6/) as well as a Heavy Buffer Carbine .308 spring (http://heavybuffers.com/springs.html).

 

Would a CAR-10, or maybe a CAR-10 XH, be able to solve this problem or do you think the issue might be the gas block (i.e. poor fitting of the gas block on the gas port by the gunsmith?) ?

Or would you simply say I'm running a setup that's doomed to fail and that I should put the factory recoil system back on the rifle and be done with it?

 

 

I'm taking two things away from what you posted. 

#1.  Once you figured out your gas block, your rifle ran, both suppressed and unsuppressed. Your gas system was working, and your gun ran.

#2.  You changed your recoil system, and not your gun is running poorly.

The issue is your recoil system.  That's the only thing you changed after you got the gas block dialed in - when it ran right.

You need a buffer that weighs the same as the one that you took out (the one that ran).  You need a recoil spring that's the same pressure as the one that you took out.  You'll need a spring that works (same pressure) for your carbine extension, as the rifle extension that you swapped out.

That's the issue you're having.  It's all recoil-system related, by your own accounting of what's going on.

[merrymarksman]

First off, thank you all for the immediate and precise answers! 98, jt, rex, Doc  👍 

As you said I'm pretty sure my buffer is nowhere near 5,4oz, could't find any specs on it though and haven't had the chance to weigh it

18 hours ago, jtallen83 said:

Blown primers doesn't immediately make me think of a gas or buffer system issue, I would be checking the headspace and trying some different ammo.

Headspace never seemed to be a problem, I had some ejector marks every now and then, but never flattened case heads, must be the ammo. Also my thinking was overly light buffer equals fast travelling BCG (especially since its a trimmed down DPMS 308 BCG) which might jam the cases in the chamber way too hard... Is that a thing or am I making stuff up?

I'm defenitely gonna follow your advice and get me a CAR buffer to go with the heavy buffer spring I got already, I'm leaning towards the XH since I'm running the suppressor more often than not.

16 hours ago, 98Z5V said:

It's all recoil-system related, by your own accounting of what's going on.

One thing that i forgot to mention that led me to believe it could be gas related is that the charging handle actually came loose and creeped towards my face after 2 or 3 shots, which is pretty annoying when you're dialed in and trying to print some tight groups. Any thoughts on that?

Also I'm planning on having the barrel cut down from 20" to 18" , that should decrease dwell time and overall pressure on the system, right? I'm just not sure whether that's gonna be a noticable difference.

 

Edited February 13, 2020 by merrymarksman

[jtallen83]

39 minutes ago, merrymarksman said:

I had some ejector marks every now and then, but never flattened case heads, must be the ammo. Also my thinking was overly light buffer equals fast travelling BCG (especially since its a trimmed down DPMS 308 BCG) which might jam the cases in the chamber way too hard... Is that a thing or am I making stuff up?

A light buffer would allow it to open early and cause more ejector swipe but not so much blown primers. With an adjustable gas block you should be able to slow that down, should . 

Can't say I ever heard of a "trimmed down" BCG, could you elaborate on that?

[merrymarksman]

17 minutes ago, jtallen83 said:

"trimmed down" BCG

What i meant was that the DPMS Gen II BCG is smaller and lighter than a LR308 BCG to fit these small frame 308 ARs, isn't it?

[98Z5V]

6 hours ago, merrymarksman said:

Also I'm planning on having the barrel cut down from 20" to 18" , that should decrease dwell time and overall pressure on the system, right? I'm just not sure whether that's gonna be a noticable difference.

That will indeed dut down on dwell time, and the amount of time that the gas port feeds pressure to the gas key on the BCG.  Correct.

You may need a "gas port adjustment" after having the barrel cut down.  Gas port diameter will probably have to go up in size, but not by very much, at all.  0.005" or less.

[merrymarksman]

14 hours ago, 98Z5V said:

You may need a "gas port adjustment" after having the barrel cut down

I was hoping to be able to make up for the loss of pressure by opening the adjustable gas block. Do you think that that won't be enough? 

And I went ahead and ordered a CAR-10 5.5oz Carbine 2.5" Buffer along with a Radian DPMS 308 Ambi Charging handle. I'll let you know how the rifle runs as soon as I dropped those in 😁 (2-3 weeks delivery time though 😢😉) 

Thanks again for your advice! 

[98Z5V]

10 hours ago, merrymarksman said:

I was hoping to be able to make up for the loss of pressure by opening the adjustable gas block. Do you think that that won't be enough?

Thanks again for your advice! 

You can only open an adjustable gas block to wide-open, and it's gonna flow exactly what that gas port diameter lets it flow.  What an adjustable gas block does, is limit what the gas port diameter can do - an adjustable gas block can never allow more gas than the gas port diameter will flow...

You might need to drill the gas port diameter up - we won't know until you shoot it, or measure the gas port diameter that you have right now.  I can give you a pretty good idea of what you'll need to have.  You've never stated the barrel configuration - what's the barrel length, gas system, etc.  You need to know what your gas port diameter is.

[merrymarksman]

10 hours ago, 98Z5V said:

what's the barrel length, gas system, etc.  You need to know what your gas port diameter is.

It's a 20" barrel with rifle length gas system

Regarding the gas port size I found this chart in another thread:

DPMS LR-308 Style Rifle
18"	rifle	0.308		0.0960
18"	car	0.308		0.0635
16"	mid	0.308		0.078
16"	mid	0.308		0.081
16"	car	0.308		0.07
16"	car	0.308		0.073
16"	car	0.308		0.076
20"	rifle	0.308		0.0935
20"	rifle	0.308		0.096

 

So I'm assuming it's either 0.0935" or 0.096". That's on the wider end of rifle length gas ports, so I'm not exactly comfortable with the idea of drilling that out even further. 

From what I'm experiencing now, with the gun running with the gas block nearly fully closed in both suppressed and unsuppressed configuration I'd expect it to be still in the operational range with the barrel cut down and the gas block opened up a bit. 

[Armed Eye Doc]

The chart you referenced is the desired gas port diameter for best function.  Barrel manufacturers can and do drill whatever size gas port they want.  It is not standardized in the industry.

That is why he is asking what size your gas port is.  It may very well be the correct size but it is an unknown unless you measure it yourself.

[98Z5V]

10 hours ago, merrymarksman said:

It's a 20" barrel with rifle length gas system

Regarding the gas port size I found this chart in another thread:

DPMS LR-308 Style Rifle
18"	rifle	0.308		0.0960
18"	car	0.308		0.0635
16"	mid	0.308		0.078
16"	mid	0.308		0.081
16"	car	0.308		0.07
16"	car	0.308		0.073
16"	car	0.308		0.076
20"	rifle	0.308		0.0935
20"	rifle	0.308		0.096

 

So I'm assuming it's either 0.0935" or 0.096". That's on the wider end of rifle length gas ports, so I'm not exactly comfortable with the idea of drilling that out even further. 

From what I'm experiencing now, with the gun running with the gas block nearly fully closed in both suppressed and unsuppressed configuration I'd expect it to be still in the operational range with the barrel cut down and the gas block opened up a bit. 

That's cool.  We have that here.  But that's based on a 0.750 gas block diameter, too.  If you have a different gas block diameter, those numbers are close, but not what you need.

6 hours ago, Armed Eye Doc said:

The chart you referenced is the desired gas port diameter for best function.  Barrel manufacturers can and do drill whatever size gas port they want.  It is not standardized in the industry.

That is why he is asking what size your gas port is.  It may very well be the correct size but it is an unknown unless you measure it yourself.

Exactly.  What you have in that barrel is what matters. Gas port diameter, and gas block diameter. 

OP, it's not hard toremoved that gas block and check the journal size and port diameter.  Once you know that, you can then compare it to available information.  Or, the journal size is different - and I can help with that, and what you'd need to have for a port diameter.

[merrymarksman]

Oh alright, I thought there were some kind of manufacturer-standards which they would stick to 🤔  well anyway I'm going to wait with anything gas system related till after the barrel's been cut down and then see what the gun does with the gas block fully opened and the 5.5oz buffer in there.

I actually measured the gas block diameter before ordering the adjustable one, it's 0.75", cause I wouldn't want to buy parts that won't fit my rifle 😜 (don't know why I didn't stick to that, considering the kyntec buffer 😅😅)

Anyway I'm pretty excited about that next step, I'm expecting the whole setup to become even more compact and maneuverable than it is already. Pretty mindblowing to have the whole capacity of a .308 in a package that looks more and more like a AR15 MSR/DMR or something. And it reliably produces sub-MOA groups, with decent (factory) ammo even half MOA all day long. I'm in love with this thing! 😄 Also I ordered some stuff that's more on the handling related side, Radian Charging handle and Ambi short throw safety as well as a Magpul Ambi bolt Release, just for the hell of it.

I'm starting to run out of ideas on what else might need some tweaking 😆 Input is kindly appreciated 😏

[merrymarksman]

Sooo, my rifle finally found its way back to me 😊 thought I'd give you guys a quick update: barrel's been cut to 18" and threaded again. For testing I ran some 30 rounds of the ammo that gave me the issues with blown out primers and whatnot. Same as before, every third primer blown, cases pretty scratched and beat up, so my take is these are just poorly manufactured with tolerances way bigger than the chamber of the gun allows. Not going to use this ammo again. But then I grabbed some Magtech FMJ 150gr, Federal Trophy Copper 150gr and 165gr, Federal Gold Match 168gr, Barnes TTSX 130gr, 150gr, 168gr... All these cartridges worked without any of the problems mentioned above! With the rifle suppressed and the Heavy Buffer CAR-10 that is. My gas port setting had to be changed of course, now it's perfect when the screw is at a quarter turn for supressed and about 1.25 turns when running a muzzle brake. 

The rifle runs like a charm now, once I had the gas block dialed in no issues whatsoever the first 150 rounds i put through that thing, switched through all the ammo types I mentioned like a maniac, not caring for groups only testing the gas system. I actually loaded a mix of 130gr, 150s and 168s in one magazine in no particular order to see if there would be any FTEs or FTCs with the gas block setting I dialed in on, but nothing. Smooth sailing, no matter what I fed the rifle 😄 I'm really glad that turned out so well!

Also it's looking like a beast now, the seamless transition from handguard to supressor really adds to the look and the balance of the gun as well. 

[98Z5V]

Job well done, man - very well done.  

[shooterrex]

That is a good looking rifle. Glad you got it running right.

[Sharpshooter]

Sweet!

[392heminut]

Damn nice rifle! It's great when you get them running good, then you just pull the trigger and have fun!

[unforgiven]

Outstanding job brother and rifle looks good to.

[jtallen83]

Nice! Gotta love it when they run all comers for ammo. 

[merrymarksman]

On 5/6/2020 at 2:49 PM, 392heminut said:

Damn nice rifle! It's great when you get them running good, then you just pull the trigger and have fun!

Thanks guys, appreciate your support! 

Best thing is, it doesn't only run smooth as hell, it also holds really nice groups. 

That's 5 shots magtech 150grs FMJ @100m, and then zeroing my red dot @50m with 2 shots between clicks 🤗

[merrymarksman]

The flyer was totally my fault btw 😅

[DNP]

1 hour ago, merrymarksman said:

The flyer was totally my fault btw 😅

Oh come on now...no sun in the eyes, a gust of wind maybe?  I’ve heard those can be quite the problem indoors.