SCAR 17 low enough back pressure in subcaliber with can?

[ARKEMAXUS]

Bear with me here; So we all know a SCAR 17 is best run with a low back pressure (Surefire, OSS) can because of carrier speed issues destroying things in the SCAR....

I have no low-blowback suppressors, just what I would call bolt gun cans so......I happen to have a 6.5CM SCAR barrel and got to thinking; would shooting 6.5 through a 30 cal can lower the back pressure significantly enough as some of that pressure escapes out the end of the can upon firing since it's a smaller diameter round?

What do you think? Am I trying too hard or is that legit?

 

[Gasgun]

Since no one with real experience has responded, I will jump in with some speculative bullshit:

Without knowing exactly which can you have, I’m going to say that shooting 6.5 through a .30 can will not reduce the back pressure enough to make a difference.

 

[mewillis]

Just balance the system with the gas jets to find the perfect feel just like you would with any supressed weapon ie; tune for bolt hold open on empty. I don't remember what my final jets were as I sold them (2) off years ago but it can be tuned very nicely. My big problem with FN is they don't warranty your weapon if they think it's damaged by silencer use as they say it's not designed for it, despite the fact they put a gas adjustment lever on it. Even the civi manual says it's "adverse conditions" when the .mil manual says supressed/standard. FN customer service sucks, sold them both. YMMV

 

[ARKEMAXUS]

Thanks for the replies. Yes Gasgun, I'm guessing you're right. It was wishful thinking on my part.

Mewillis, agreed and yes, FN customer service does suck

 

[Clayman]

Bear with me here; So we all know a SCAR 17 is best run with a low back pressure (Surefire, OSS) can because of carrier speed issues destroying things in the SCAR....

I have no low-blowback suppressors, just what I would call bolt gun cans so......I happen to have a 6.5CM SCAR barrel and got to thinking; would shooting 6.5 through a 30 cal can lower the back pressure significantly enough as some of that pressure escapes out the end of the can upon firing since it's a smaller diameter round?

What do you think? Am I trying too hard or is that legit?

Overbore will absolutely reduce backpressure but likely not enough on very high backpressure silencers to even come remotely close to an OSS or low enough to reduce the chance of damage.

You can adjust gas jets or a scarburetor, this will help but it still won't delay bolt unlocking enough to use high back pressure cans without risking damage.

Jay of pewscience is doing a SCAR project. 13". He has adjusted jets and a scarburetor. Even tuned with other low backpressure cans (cgs Hyperion K & surefire RC2 762) it's still not operating like it does with an OSS. It seems to be a very gas sensitive host.

 

[the monk]

Answer to your question is no. There is not enough difference in bullet diameter. Its not like shooting a 556 through a 762 can and even then cans with lot of back pressure will still have back pressure.

I agree with everything @mewillis is saying. My scar 17 was fine with a high back pressure can after adjusting the jets. On a 17 in 762 I had no issue with jet size 1.35mm both suppressed and unsuppressed (https://www.parkermountainmachine.com/product/pmm-scar-1617-stainless-steel-gas-jets/). But I got rid of my scar for all the same reasons @mewillis mentioned. I was able to sell the used scar at the height of covid and get above retail. I really can't support a company that wont warranty their products. Your on your own is never ok but especially not for 3+k rifle. And even if you decide to go on your own, parts are impossible to get.

 

[GUNNER10]

Overbore will absolutely reduce backpressure but likely not enough to even come remotely close to an OSS or low enough to reduce the chance of damage.

You can adjust gas jets or a scarburetor, this will help but it still won't delay bolt unlocking enough to use high back pressure cans without risking damage.

Jay of pewscience is doing a SCAR project. 13". He has adjusted jets and a scarburetor. Even tuned with other low backpressure cans (cgs Hyperion K & surefire RC2 762) it's still not operating like it does with an OSS. It seems to be a very gas sensitive host.

Might be ok,

Sold my scar before i got a chance to run it with my sandman K

 

[Clayman]

Sandman K is very low backpressure. It would probably work fine with it. Sandman K is loud though lol.

 

[thehun]

6.5 will be more gassy than .308 will be out of a SCAR or any other semi auto...watch them primers on 6.5 SCARs too...those 6.5 SCARs pop them like popcorn...FN's 6.5 offering was and isn't really optimal...just saying...

As far as cans...go buy a MotoTech Eng SCARburator....

 

[GUNNER10]

Sandman K is very low backpressure. It would probably work fine with it. Sandman K is loud though lol.

I really like the Sandman K. It is loud, but honestly behind the gun, it sounds fine, and I really like the way most of my rifles run with it. Both low pressure and higher pressure cans have their place.

 

[thedude824]

The answer to your question is the Mototech 3 position selector. All of my cans are high back pressure. Ive got a factory 16" barrel and a factory 13" barrel with their respective gas port sizes. On the most restrictive settings both rifles are smooth as ban be with the high back pressure cans. I actually purchased 2 of them. One for each barrel.

 

[ARKEMAXUS]

All good info. thanks guys. I have looked into Mototech's offerings and read all the reviews I can find but wasn't quite convinced. Maybe his stuff is the way to go though, I'll reconsider.

 

[Pedro23]

Look into Pew Science for pressure deltas on each can he has reviewed. I use the scarburator 3 select with zero issues at 700 rounds so far.

 

[Mdrums]

I’m always concerned with my SCAR17 when I use my Sandman L on it. I‘m using 1.35 gas jet and no bolt or canted screws issues. I keep the factory stock too.

I haven’t shot it in a year and was thinking of selling it or just taking off the KGD rail and putting stock jets in it and stock brake and put in in the back of my safe.
I’ve been considering a bolt gun in 6.5 to use the Sandman L on.

 

[Pedro23]

Run your 17 hard. Or sell it. I bought the new Sig Sauer SLX762C-QD can. Low back pressure with high flow through. Sound reduction isn’t the number one quality for me. Flash and less gas in the face since Im a south paw. The can does enough sound wise like those before it but not the overall best.