LWRCI REPR MKII Elite 6.5-CM Suppressor Issues ...

[rustyinbend]

Long story short ... I'm really struggling with finding a gas-adjustment and buffer combination that allows me to shoot my 6.5 REPR suppressed, without hurling cases out in front of the firing line and blowing out primers. First tried adjusting the gas down to the lowest non-zero setting ... didn't help. Then I tried heavier and heavier buffers and currently have the JP Silent Capture Spring (Heavy Version) for AR-10 ... which is about the heaviest damn buffer assembly on the planet.

Currently with the gas set to "1" on my REPR, and with the JP-SC AR-10 Heavy Spring, I'm barely getting ejection at about 2:00-to-3:00 o'clock, and still blowing primers on ammo that works just fine in my other two 6.5-CM bolt rifles (both factory and handloads).

What am I doing wrong? Am I doomed to "not" be able to suppress this rifle? Any suggestions I haven't thought of? I shoot everything suppressed, and if I can't figure this out, I'll probably sell it ... cuz I'm tired of picking spent primers out of the action.

Anybody out there shoot their 6.5-CM REPR suppressed, and if so ... how the heck did you do that?

 

[psmith23]

If you're blowing primers it sounds like the loads are too hot or there might be a headspace issue. If you can turn the gas completely off I'd start there and see what the load look like. Also verify headspace with a fresh Vs fired case. With a can you are adding a bunch of dwell time past the gas port and really ramping up the pressure. What are your load details? Rifle gas I'm assuming and barrel length?

 

[hlee]

Which suppressor?

The issue you are experiencing is not due to gas flowing through the gas system and actuating the bolt. The pierced primers are likely from back pressure caused by the can- which flows back through the barrel. A lower back pressure can is your solution...

 

[rustyinbend]

If you're blowing primers it sounds like the loads are too hot or there might be a headspace issue. If you can turn the gas completely off I'd start there and see what the load look like. Also verify headspace with a fresh Vs fired case. With a can you are adding a bunch of dwell time past the gas port and really ramping up the pressure. What are your load details? Rifle gas I'm assuming and barrel length?

Answers (and Thanks! for the help) ...

1. Gas completely off ... reacts as you'd expect. Bolt doesn't move. That said ... I haven't looked at the rounds, or tried several in a row with gas off to see if I blow any primers. That's a great idea and I'll try that next range trip. Note: On factory ammo, I blow a primer "once in a while". With handloads, I blow a primer about 25% of the time.
   
   
2. Verify head-space with a fired round ... what do you mean here? What should I do with that fired case? Based on this question, I dropped a fired case into the chamber and released the bolt. It chambered correctly, but removing it (as you'd expect) took a lot of rearward pressure on the charging handle, but it ejected correctly. Does this tell me anything?
   
   
3. Here's the part that's really confusing me ... when comparing fresh to fired with a comparator, the fired brass is actually "shorter" than the fresh brass by 2-to-3 thousands. That's just weird ... the fired brass is supposed to be "longer". Based on this, I'm going to try a few things ... (a) try "new" brass that's never been fired, (b) recalculate my head-space with my OAL tool and see if I got it wrong the first time, and (c) based on what I find in (b) I'm going to meticulously build a few rounds that are "guaranteed perfect" to fit in this rifle.
   
   NOTE: I can totally see how screwing up the shoulder bump and presenting a "too long" case against an AR-10 with a heavy spring-fed BCG release ... could jam a case into the chamber and blow a primer on cycling. Is this a valid assumption? Is this my problem? (Epiphany in progress.)
   
   
4. Load details ...
   1. Hornady 1x brass
   2. StaBall 43.2gr
   3. Hornady 147gr ELDM
   4. Mandrel .2625
   5. Seat .550 (mag limited)
   6. CCI #200 Large Rifle Primers
5. Piston LWRCI rifle length gas system on a 22-in Proof Research carbon fiber barrel

I think my problem is that I've screwed up the headspace, and my "too long cases" are getting "jammed home" by my heavy spring buffer, compressing the case and shoving the primer rearward when the action cycles. If this is what's happening, it's (a) an easy problem to fix, and (b) a stupid mistake to make.

Thoughts ???

BTW ... here's the velocity table from the range trip yesterday (Avg 2662 - SD 8.8 - ES 29) ... which is also weird since irrespective of the ejection issues and blown primers ... the results are actually quite good.

 

[rustyinbend]

Which suppressor?

The issue you are experiencing is not due to gas flowing through the gas system and actuating the bolt. The pierced primers are likely from back pressure caused by the can- which flows back through the barrel. A lower back pressure can is your solution...

SilencerCo Chimera-300 ... although I'm struggling with your advice, since this can works great on two other 6.5-CM rifles, and two 300-WM rifles. See the other response of mine ... I think we've zero'd in on a headspace/shoulder-bump "mistake".

 

[psmith23]

Lot to digest there but a general rule of thumb is to bump the shoulder .003 for semi use from a fired case. Depending on the throat you should also know you bullet jump as well to make sure you aren't jamming the bullets into the rifling. Check those things and report back. An easy check for jamming is to load up a dummy round and black Sharpie the bullet then drop and press into the chamber. It should fall out if you turn the rifle upside down and you can check for rifling marks in the bullet.
I'm not up to date on staball but a quick search shows similar results to h4350 so 43.2 grains with a 147 (heavy for caliber bullet) loaded to mag length sounds like a decent high pressure bolt gun load that's probably not the best for a gasser. A can just makes it worse.
Regardless of what you find out on headspace a lighter load with a 120-130 grain bullet will be much happier with the gun.

 

[psmith23]

Also you can use a HP bolt as well which is available that helps with primer piercing. For clarification are you piercing primers or simply blowing them out of the case?

 

[rustyinbend]

Also you can use a HP bolt as well which is available that helps with primer piercing. For clarification are you piercing primers or simply blowing them out of the case?

Just blowing them out of the case.

 

[rustyinbend]

Lot to digest there but a general rule of thumb is to bump the shoulder .003 for semi use from a fired case. Depending on the throat you should also know you bullet jump as well to make sure you aren't jamming the bullets into the rifling. Check those things and report back. An easy check for jamming is to load up a dummy round and black Sharpie the bullet then drop and press into the chamber. It should fall out if you turn the rifle upside down and you can check for rifling marks in the bullet.
I'm not up to date on staball but a quick search shows similar results to h4350 so 43.2 grains with a 147 (heavy for caliber bullet) loaded to mag length sounds like a decent high pressure bolt gun load that's probably not the best for a gasser. A can just makes it worse.
Regardless of what you find out on headspace a lighter load with a 120-130 grain bullet will be much happier with the gun.

Got it ... working on all that now. I'll also retool to 140gr bullets (lightest I have), and a lighter load.

 

[rustyinbend]

So today, I built three 6-shot groups of cartridges ... all with a down-sized charge weight (42.5gr) and all with Berger 140 LRHT projectiles, and all confirmed to have shoulders "at least" .003 shorter than yesterday's fired brass.

Group #1 ... Virgin (never fired) Peterson Brass, neck-mandrel only
Group #2 ... Newly sized 1x fired Hornady brass
Group #3 ... Cases sorted from previously 1x fired and sized ready-to-load Hornady brass that measured the proper shoulder bump (many did not)

Looking through and measuring previously "Ready to Load" cases has convinced me that I SUCKED at shoulder-bumping for this rifle. Maybe I just thought since it's a gas-gun, it wouldn't matter ... but I don't actually remember thinking that. The crazy part is that I did all the measurements on the other calibers I handload (300-WM, 300-PRC, 338-LM) ... and they all measure with proper shoulder bumps from fired brass.

Anyway ... headed to the range on Thursday to see if I still blow primers and have gas problems (the gun that is ...) or not.

 

[Maelstrom]

I am wondering if the chamber was cut to tight. I had to send back 2 LWRCI AR-15 rifles. One was a M6 the other was an SPR bought about 6 years apart. Both had the chamber cut to tight and would blow primers occasionally. After contacting LWRCI I sent both back and they replaced the barrel on the M6 and recut the chamber on the SPR.

 

[rustyinbend]

I am wondering if the chamber was cut to tight. I had to send back 2 LWRCI AR-15 rifles. One was a M6 the other was an SPR bought about 6 years apart. Both had the chamber cut to tight and would blow primers occasionally. After contacting LWRCI I sent both back and they replaced the barrel on the M6 and recut the chamber on the SPR.

That's a REALLY interesting thought. Over the weekend, I decided to reconfigure back to square-one and put back the stock buffer tube and spring, and I'm going to take it to the range on Tuesday and see if either suppressed or unsuppressed, factory or handload ... I can get it to stop blowing primers and eject in the right direction. If not, then I'll definitely call LWRCI and see what they have to say about this.

 

[cgbills]

I think those 147's are causing too high of pressure for a gas gun. Check out the Berger 130 Hybrid AR or Hornady 130 ELD-m

 

[rustyinbend]

43.2gr of StaBall with 147's is stout.

Just because you put an AR10 SCS in doesn't mean it's the heaviest. I added 2 more tungsten weights to my AR-10 SCS. Now it's the heaviest SCS. The buffer portion weighs 5.5oz. And that's still not the heaviest buffer you can buy.

Are your primer pockets loose or blown out? Certainly your once fired is ....

Went to the range yesterday with my REPR back to the stock buffer and spring, and with meticulously constructed cartridges. Everything fired correctly, I didn't blow any primers, and the velocity was in the 2600-ish range with 42.5gr of StaBall and Berger 140's. My only remaining issue is that shooting suppressed (which is how I roll), and with the gas setting on "1", I'm still ejecting out to about 2:00 o'clock out in front of the firing line.

Now that I have the code cracked on the right cartridge form-factor, I'm going to put the JP-SCS back in and see if (a) primer pockets start blowing again, or (b) the ejection pattern improves. BTW ... I too have the all three tungsten weights and the heaviest spring available. The buffer assembly weighs 7.8oz. Pretty sure that's the "peak" for buffer weight.

 

[rustyinbend]

It is for an SCS. I bought the standard weight and it came with one tungsten and had to add two more. Sounds like you're weighing the entire SCS assembly.

I'm shooting a 24" Proof suppressed with an SLR AGB and a Lantac heavy enhanced BCG. I'm 3 clicks off closed on the gas block. When I loaded 147's I was getting 2650. 42 something grains.

Maybe that proprietary system just doesn't have fine gas block adjustments. Is the BCG also proprietary?

Yes BCG is proprietary ... built for the REPR piston gas system. I'm hopeful that the ejection pattern will improve when I put the SCS back in, but at this point, nothing would surprise me.

One other thing I'm also considering is simply "not" handloading for this 6.5-CM AR-10 ... and using my reloading supplies for my other two bolt action 6.5-CM's (Tikka T3x TAC A1 and Barrett MRAD 6.5-CM barrel kit). From stocking up pre-pandemic, I have literally "thousands" of rounds of the Hornady 140gr American Gunner ammo that feeds and groups just fine into this rifle. I could shoot for about a decade in our local gas-gun monthly matches, and not use it up. Things to ponder ... maybe handloading for this REPR is more trouble than it's worth.

 

[rustyinbend]

Maybe that's the plan. Hearing this makes me happy about the route I went. Normally people talk about how impossible it is to build a functioning AR10. Mine took 6 rds to tune the AGB. I added an additional tungsten weight after completing load development and arriving at a full power load. That also allowed me to close the gas block one more click. I probably spent +$3K in parts but it was all Lego plug n' play.

This sort of reminds me of the AI vs custom action debate. Either way, let me know if you want to unload that Hornady brass

When I shot this LWRCI REPR "out of the box" ... it was wonderful, and almost "not fair" at our local gas-gun matches when shooting factory ammo and competing against everything else on the firing line. But that wasn't good enough, hence the tinkering. Two things have been kicking my ass of late ... (1) getting a proper ejection pattern when shooting suppressed, and (2) figuring out a handload config that doesn't blow primers. #2 is 'd off ... #1 is still a work in progress.

It's a $4,700 rifle ... maybe I should leave the damn thing alone ... and just "Shoot It and Clean It". LOL