Lets talk 10.5" AR recoil system

[SJan]

Here is my setup, I just assembled it 2 days ago.

Precision Point receivers
Johnny's secret BCG. (It appears to be quality in every way, just dont know who made it. The bolt is marked MPI, full auto carrier, extractor has o-ring, gas key is tight and properly staked)
Rainer match barrel
BCM gas block, properly aligned with gas port
Midwest rail
Spikes T2 buffer

The buffer tube and spring are from Joe Bob outfitters. It was a package that included the end plate, nut, and a standard buffer. The tube is "mil-spec" but actually measures 1.130-1.132 along its length (should be 1.148) I noticed this and measured it when my stock fit was loose, even with the friction lock engaged, it has slop. While shooting my whiskers caught between the stock and tube... This makes me doubt the quality of the spring as well. Before firing I went ahead and ordered a name brand buffer tube and spring.

I test fired today. I used some of the following ammo:
Federal XM855
Federal XM193
American Eagle 223
these all functioned 100% all fed, fired, ejected, and locked back on empty mag.

I also fired some:
PMC 223
Aguila 223

These had some issues. Sometimes would not lock back on empty mag. Sometimes would not feed next round at all, bolt would close on empty chamber. Sometimes would partially feed next round but not even clear the feed lips.

It was obvious the weaker 223 did not fully cycle this gun, or created an under-gassed situation. I was stupid in not bringing another rifle with me today so I could not try a different bolt. All my other rifles use the same T2 buffer without problem, with all ammo.

The only other buffer I have is the questionable quality standard carbine buffer from the Joe Bob kit, and a Palmetto Armory standard carbine buffer. I had neither with me today.

In my research, 10.5" ARs can be finicky. Buffer weight recommendations often are followed with "YMMV" or "Depending on ammo used"

Should I be satisfied with running fine on quality 5.56 or hotter 223 ammo? Maybe... But I like to know my stuff runs on any ammo.

Next time out I will have a proper buffer tube, spring, and a lighter buffer to try.

Those of you with an AR SBR, what recoil system combination do you run? How does it run on various ammo?

Here is a photo of rifle, because its sexy

 

[ColdDayInHell]

Nice SBR. 10.5" would be my shortest AR that I'd want. 11.5" being more preferable.

IIRC there are a few members with 10.5" and that have tested buffers out.

 

[Another_David]

I don't have a 10" AR but fwiw, a 10" AR will not recoil with as much power because you don't have as much barrel in front of the gas block to create the back pressure you would have with a longer barrel.

it might just improve with break in, e.g. do nothing! I don't suppose you greased the recoil spring because if you did I would clean the grease off and it'll probably run fine. some say grease (and provide a little tube of grease), others say grease then remove later, but you certainly don't want any more than a tiny bit of grease in your buffer tube.

or try a lighter buffer

or you could trim the recoil spring. I like this option the LEAST and normally wouldn't even suggest messing with the spring but if you have an extra spring that sounds like you'll never use anyway, then it might be worth experimenting with.

also you can check the gas tube to bolt carrier alignment: take the top off, remove the bolt from the carrier, put the carrier back in the upper without the bolt and slide it back and forth. doesn't it float over the tube or does it get hung up? It might click a little but shouldnt give too much resistance. you can just bend the gas tube accordingly to make it fit right. there's also always the chance the barrel nut is pressing against the tube, which is no good.

good looking gun though!

 

[SJan]

thanks for the suggestions

I don't have a 10" AR but fwiw, a 10" AR will not recoil with as much power because you don't have as much barrel in front of the gas block to create the back pressure you would have with a longer barrel.

I am aware of this

it might just improve with break in, e.g. do nothing! I don't suppose you greased the recoil spring because if you did I would clean the grease off and it'll probably run fine. some say grease (and provide a little tube of grease), others say grease then remove later, but you certainly don't want any more than a tiny bit of grease in your buffer tube.

I did not grease the spring, upon assembly I did a lightly oiled rag wipe of the spring

or try a lighter buffer

I plan on it

or you could trim the recoil spring. I like this option the LEAST and normally wouldn't even suggest messing with the spring but if you have an extra spring, then it might be worth experimenting with.

I wouldn't consider cutting the spring. Like I said, I don't trust the quality of the spring I currently have. Maybe thats the only problem. I have a trusted name brand spring on the way.

also you can check the gas tube to bolt carrier alignment: take the top off, remove the bolt from the carrier, put the carrier back in the upper without the bolt and slide it back and forth. doesn't it float over the tube or does it get hung up? It might click a little but shouldnt give too much resistance. you can just bend the gas tube accordingly to make it fit right. there's also always the chance the barrel nut is pressing against the tube, which is no good.

This was checked when assembled

good looking gun though!

thanks!

 

[Another_David]

- - - Updated - - -

thanks for the suggestions
I am aware of thisI did not grease the spring, upon assembly I did a lightly oiled rag wipe of the springI plan on it I wouldn't consider cutting the spring. Like I said, I don't trust the quality of the spring I currently have. Maybe thats the only problem. I have a trusted name brand spring on the way. This was checked when assembled thanks!

ok. i thought that you had already got your new spring but since you haven't then, yeah, try the new spring first. and compare the two springs. as you probably know there are a gizillion makers of ar parts and one man's cut down spring is probably equal to another factory spring. yet, I agree, you shouldn't have to ever cut a spring--I just suggested it to try as a last resort since you have an extra.

just for kicks you can check the inside of the upper for scratches too. sometimes parts like the retaining pin can protrude just enough to drag

good luck and let us know where the brass flies! forward, to the side, behind you? my guess is it's flopping backwards--that's usually a sign of under gassed, but it's not all that reliable of a metric

 

[xtry51]

I'd go with a lighter buffer as a standard on a 10". It could break in, but you're still dealing with a lot lower dwell time.

 

[SIGPRO 226]

Looks great cant wait to get mine finished.

 

[exo]

Have you considered a muzzle device like the noveske kx3/5? It's supposed to help shorter barreled ARs run better, in addition to being a flash hider and directing the blast forwards.

 

[Mass-diver]

I have a 10.5 (DDMK18), preban lower. I have an H2 buffer, I have put about a case and 1/2 through it with no issues, but I only shoot 5.56 (m193), with a small ammount of expensive, heavy stuff.

If your rifle runs really well (as in 500+ Rounds with no issues), I wouldn't care if it didn't eat weak .223 loads. Just my 0.02 if course.

 

[lambchop]

I run a full auto BCG with a H3 buffer. The gas port is .078" in my SBR. Wolf gold is the cheapest ammo I have used and it ran flawlessly.

 

[SJan]

I run a full auto BCG with a H3 buffer. The gas port is .078" in my SBR. Wolf gold is the cheapest ammo I have used and it ran flawlessly.

I recently bought a case of wolf gold, but haven't shot any of it yet. I'll try it next time

 

[massBRS]

I have an 11.5 shooting 5.56. standard buffer. adams arms piston kit. It eats anything I feed it. waiting on a stamp for a 9.5 shooting 5.56, but that will have a pistol length gas system. Both with full auto BCGs.

 

[atilla]

i have an auto carrier with a standard buffer in my 10.5, i found the heavy buffer to be a bit much and put that over on my dissipator.

 

[SJan]

I hope mine is as simple as that. I might get to the range again this weekend

 

[SJan]

It ran 100% on standard carbine buffer

 

[atilla]

It ran 100% on standard carbine buffer

'merica. how many rounds fired? no other changes aside from that?

 

[SJan]

'merica. how many rounds fired? no other changes aside from that?

Only about 100 last time out, and 150 today
No other changes

 

[ScottS]

I have two 10.5" AR's that run like sewing machines.

Both have full-auto carriers pushing into H2 buffers. Both ran with standard buffers, but I wanted to cut down on the bashing a bit.

10.5" AR's are like a jar of win fell into a bucket of sex, then promptly spilled over into a vat of awesome.

 

[atilla]

Only about 100 last time out, and 150 today
No other changes

good. i'm glad it helped. enjoy your blaster.

 

[dcmdon]

It ran 100% on standard carbine buffer

I was about to tell you to do that.

The extra weight buffers are ideal for 16" carbine gas guns. The amount of bbl ahead of the gas port is ideal for a 14.5" military gun. The extra 1.5" of barrel means the pressure at the gas port stays around roughly 30% longer. This puts too much energy into the reciprocating parts. With the bolt moving too early and too quickly. This can cause everything from misfeeds to in extreme cases the rim being ripped off the case.

There are two ways to deal with this.

1) Decrease the energy that gets put into the system - adjustable gas block
2) Increase the reciprocating mass so that the bolt slows down. Still the same energy, but now its heavier and slower.

But you had the opposite problem. So the easiest thing is to decrease the reciprocating weight.

If the standard buffer didn't work, there would be a few other things you could to to try to fix. In decreasing order of preference.

1) go to a semi-auto (lighter) bolt carrier.
2) push the roll pin out of the forward end of the buffer and remove one of the buffer weights.
3) clip the spring

2 and 3 are unacceptable for a gun that might be depended on for "real" purposes.

In that case , after trying #1, the next step would be to check the gas port size.

Don

 

[Da_lucche]

H2 and FA BCG on my 10.3 DD MK18 barrel and it eats and locks back using everything from 77 Sierra to dirty tula.

PMC and Tula are notoriously under powered but DD MK18 barrels are notorious for being over gassed as well.

The only time I ever issues with the bolt not locking back was when I used my Tactical Link BAD lever.

10.5/10.3 aren't really finicky though, at least in my experience. One of the reasons CQB/MK18 Mods have been a mainstay in our military.

 

[dcmdon]

My 10.5" LMT was designed to run on 5.56. And it runs fine that way. On most .223, it doesn't cycle completely. I had a clipped spring I would use with Wolf.

I solved it by putting a silencer on it. ;-)

Don