AR SBR and Suppressed issues

[HRnightmare]

I have a 10.5" RRA SBR. I shoot steel and brass through it and have no issues with a std buffer, unsuppressed. Suppressed it shoots steel cased fine but brass does not load the next round.

I convert to a H2 buffer. Today I shot it...It shoots brass and steel just fine supressed, but unsupressed it did NOT like the brass.

The rounds failed to eject before the next round chambered. I got an empty shell lodged nearly EVERY fire.

What do I need to do to shoot both steel and brass reliably unsupressed and supressed?


Thanks.

 

[WestKentucky]

Open up gas key just a touch if it's adjustable. Otherwise go back to your standard buffer.

 

[Elkins45]

That's backward of what I would have expected. Normally the suppressed rounds cycle harder because the suppressor increases gas blowback by retarding the gas exit from the muzzle.

Maybe a lighter spring?

 

[HRnightmare]

That's backward of what I would have expected. Normally the suppressed rounds cycle harder because the suppressor increases gas blowback by retarding the gas exit from the muzzle.

That is exactly what I thought.

I beleive the cheap steel Russian ammo is lower powered.

Brass did not cycle when I had a std buffer suppressed but ran fine UNsuppressed. Now with an H2 the problem has reversed.

I will probably upgrade the extractor just in case but I know that is not the issue. It seems the round was being loaded into battery before the fired casing had time to eject...OR the fired casing did not have enough pressure to be ejected, causing it to connect with the round being loaded.

I'll call Yankee Hill, RRA and anyone else I can think to bug about this to try and get an answer.

 

[Sam1911]

The actual load will be important, but the case material is pretty irrelevant.

Is one of these loads .223 instead of 5.56? Most (good) 5.56 is loaded to higher pressure, and that's what AR-15s are designed to operate with. Most of them will work well with average .223 rounds as well but shorty guns are less forgiving.

 

[HRnightmare]

Just got off the phone with Yankee Hill. They did not have an answer to the problem as I had hoped. He initially said the problem might be that the lacquer coating was gunking up the gun and causing the shells to get stuck, but that really doesn't make sense because Steel was cycling just fine and brass was cycling fine with the suppressor.

It really makes no sense.
Steel unsupressed = least amount of pressure
Steel suppressed = a lil more pressure
Brass unsupressed = more pressure than steel.
Brass suppressed + A LOT of pressure

If the issue was with steel not cycling I would chalk it up to not enough pressure to eject and cycle the round.

If brass supressed was the issue I would say too much pressure.

Maybe a different buffer spring? But would I need to go lighter or heavier?

 

[HRnightmare]

Is one of these loads .223 instead of 5.56? Most (good) 5.56 is loaded to higher pressure, and that's what AR-15s are designed to operate with. Most of them will work well with average .223 rounds as well but shorty guns are less forgiving.

I'll check the steel when I get home. I know the brass was .223 for sure because it was the ammo I had left over from a course we took so I know exactly when and were I bought it. To be exact it is Federal American Eagle .223 55GR FMJ. I texted a buddy who shot with me and he says the steel casing Tula and Wolf is .223, also 55GR and FMJ.


So with this said, what do you think is the solution? Because again, the brass which is typically higher pressure than steel was the problem, not the steel cased.

 

[HRnightmare]

Open up gas key just a touch if it's adjustable. Otherwise go back to your standard buffer.

It is not adjustable and the std buffer did not cycle brass ammo when it was suppressed. So going back to the std buffer wouldn't do me any good.

 

[LocoGringo]

As an idea, what MAY be happening is that the brass ammo is cycling TOO fast for the BCG to catch the next round as presented by the magazine. I can think of a couple possibilities to try to fix this. First, how used are the magazines...fairly new or have they been used quite a bit? If the mags are fairly used, try a new mag spring or a new mag. The new spring might be able to keep up with the speed of the cycling BCG.

I have a 11.5" barreled 5.56 NATO chambered SBR and when I use a suppressor (6.8 SPC, 6 inches), I have to use an adjustable gas block to turn the gas down with the suppressor. It requires a bit of tuning.

I agree with the idea it's not necessarily the material used for the case so much as the loading of the round. I won't shoot an AR with a suppressor without an adjustable gas block. I just don't want to beat my rifle to death with the added gas pressure from a suppressor.

 

[Bartholomew Roberts]

I'd venture to guess the problem with the standard buffer is you are overgassed. A 10.5" has a very, very narrow window where it works. Usually, they open up the port in order to compensate for the very short dwell time. When you add the suppressor, you are increasing the dwell time (more gas through big port).

The steel case runs because it is less elastic than brass and doesn't flare out as much due to pressure. The brass is more elastic, so it flares out more. However, you are still getting a lot of gas through the gas port, even though it is taking the pressure in the barrel longer to drop due to the suppressor - so your bolt is trying to unlock before the brass has shrunk back from the chamber wall. By the time the brass shrinks, the bolt has used up/vented most of its gas and it short strokes.

As to the H2 buffer unsuppressed, that is an odd one. Whose ammo are you using?

You might try splitting the difference and going with an H buffer.

 

[jmorris]

Are your brass rounds reloads?

 

[HRnightmare]

First, how used are the magazines...fairly new or have they been used quite a bit? If the mags are fairly used, try a new mag spring or a new mag

Initially I was using a box of used USGI's I bought recently. They cycled brass fine in my friends 16" and steel fine in my SBR. So I assume they were good. I went through about 4 of them with no changes in the brass not feeding. Then I went to a nearly brand new PMAG which did not solve it as well.

My mags are usually well cleaned and lubed because of the amount of gunk that gets in them when shooting SBR's and suppressed.

 

[HRnightmare]

As to the H2 buffer unsuppressed, that is an odd one. Whose ammo are you using?

Brass = Federal American Eagle 55gr .223
Steel = Tulammo and Wolf 55gr 223

You might try splitting the difference and going with an H buffer.

Pardon my ignorance but that is just a "standard"" weight buffer correct?

I started with that and it would not cycle brass suppressed with a std weight.


Are your brass rounds reloads? no, Federal American Eagle 55gr .223

 

[Bartholomew Roberts]

Pardon my ignorance but that is just a "standard"" weight buffer correct?

No. The standard weight buffer has no marking on the face. The H buffer is slightly heavier (in between standard and H2) and marked "H" on the face - although it does come standard on some ARs like the Colt 6920.

It is really puzzling that it would run steel and not brass unsuppressed with the H2 though. It almost sounds like your ejector might be bound up with tiny brass shavings, which wouldn't be unusual to get with a 10.5" and suppressor (the brass extrudes into the ejector pin hole a little and gets 'bit' off). But it appears to be ejecting steel cases OK.

While Federal usually makes good ammo, they put out bad stuff as well on occasion. I might give a different brass 5.56 ammo a try first.

 

[HRnightmare]

It almost sounds like your ejector might be bound up with tiny brass shavings, which wouldn't be unusual to get with a 10.5" and suppressor (the brass extrudes into the ejector pin hole a little and gets 'bit' off). But it appears to be ejecting steel cases OK.

I figured the extractor upgrade kits were like $4 so I went ahead and put the o ring on and a new spring. I hope it is as easy as, the brass expands unlike the steel and it couldn't fling the brass as easily.

While Federal usually makes good ammo, they put out bad stuff as well on occasion. I might give a different brass 5.56 ammo a try first.

My intention next time is to try 2 or 3 types of 5.56 and maybe more types of .223. If those work I will go back to Federal 223 and try my luck.

 

[Bartholomew Roberts]

The extractor upgrades won't hurt but what you are describing sounds like an ejector issue (the little spring loaded pin in the face of the bolt that kicks the brass loose after the extractor pulls it out of the chamber). It is a pain in the ass to clean (easy to disassemble but a little more challenging to reassemble - keep an empty case handy for that - and maybe a plastic bag to catch flying springs) but probably worth looking at in this case.

The .223 vs 5.56 is a good idea. That is also what is weird though, if it was overgassing, the suppressor should make it worse. My first thought was that the buffer was too heavy but you are saying the steel cased .223 runs just fine unsuppressed.

 

[HRnightmare]

The ejector and extractor springs in the bolt are nearly new. I think I have only about 1K rds through it. It is a Nickel Boron Coated BCG also.

I replaced the extractor spring and added the O-ring. I will replace the ejector spring as well just to make sure I know its a good one and brand new. I read the ejector spring is the same as the safety detent. Which I am glad to hear because I have plenty of those on hand.

 

[Bartholomew Roberts]

You probably don't need to replace the ejector spring; but if the rifle has been trying to extract early due to dwell time issues, one thing that frequently happens is the pressure pushes the brass into the ejector pin hole and when the ejector ejects, tiny little shavings of brass get nipped off that can bind up the spring eventually. You may just want to take the spring out, shake out the ejector pin hole and look for little brass shavings. A new spring is likely not necessary but I usually replace the spring anyway because they are cheap and I hate messing with the ejector.

 

[HRnightmare]

So I fired 3 rds of brass, the same Federal 223 American Eagle that I originally had issues with. Fired them fairly rapidly and no issues and the 4th rd chambered fine.

I then fired 2 or 3 rds with no issue and then the next chambered fine.

I am beginning to believe the theory that the brass was getting stuck because the barrel and chamber was gummed up with the lacquer and the whole steel cases don't expand like brass does....

That or the ejector O ring was the trick. In a few days I will go and fire alot of rds to see if it functions. IF it does I will then blow through a couple hundred steel and switch back to brass to try and replicate the issue to confirm the problem.