I'm having trouble finding any information on a .300BLK 10"ish barrel with a Carbine length Piston gas system. I figure this is mostly because .300BLK doesn't have the pressure to operate in that fashion. But I'm still curious if I can run that system, yes, I'm going to use subsonic and yes, I'm going to get a suppressor. I have found pistol length piston gas system, but I just don't like the fact that I need to lessen the weight on the BCG and what not. I'm rather new to the gun building scene, so any information would help. Thank you in advance.
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.300BLK Piston Operated Rifle Build
- Thread starter Yonder
- Start date
I have this long-stroke piston Primary Weapons System (PWS) Mk109 9.75" , NP3 bolt carrier system, with other modifications and a variety of optics.
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Correct, with subs you may have trouble getting a carbine length gas system to run.
You lost me with that last sentence, what do you mean exactly?
I found some Piston Gas Systems, that are pistol length, but to get those systems to work you have to make the Bolt Carrier Group weigh less, so it can cycle, or so I hear. But I'm trying to make a freak, an HK416 clone that fires .300BLK, but to have the clone well be a clone, I'm going for a carbine length gas system to make it look like an HK416.
So, it's a 9.75" barrel with a carbine length gas system, or a pistol length gas system? Sorry I'm just having a hard time following.
EDIT
I'm also looking to use short stroke if possible.
I do not think you can avoid a low mass bcg in the set up you want unless you go with an adjustible gas piston (think POF dictator)
So it can HELP to have a lightweight BCG but isn't necessary on a pistol-length gas system. POF makes a very nice piston gun, the P415, and they have a full weight BCG. You're able to buy just the complete upper and I highly recommend their piston systems. Very robust gun. I have the 5.56 12.5" SBR version and it's built like a tank.
Link to just the POF upper, no affiliation: https://www.cflgunandtactical.com/pof-usa-gen4-P415-edge-upper-receiver-10-5-300BLK-p/01515.htm
I would have gone this route myself but wanted a buffer-less system and ended up with the Sig LT. I have a home-built 8" 300 blackout but it's DI, not piston, and I use an RCA titanium lightweight BCG in it with the Unrivaled competition dead blow buffer. Very lightweight so it's quite fun to shoot.
Not sure what length gas system the Sig LT is but it's longer than pistol for sure. You're able to buy the complete upper on those as well and they'll work with a mil-spec lower, just need the Sig adapter. Be warned though, the barrel is a 1:5 twist which can get dicey with supersonic bonded bullets. I only run monolithic bullets in mine.
Link to just the POF upper, no affiliation: https://www.cflgunandtactical.com/pof-usa-gen4-P415-edge-upper-receiver-10-5-300BLK-p/01515.htm
I would have gone this route myself but wanted a buffer-less system and ended up with the Sig LT. I have a home-built 8" 300 blackout but it's DI, not piston, and I use an RCA titanium lightweight BCG in it with the Unrivaled competition dead blow buffer. Very lightweight so it's quite fun to shoot.
Not sure what length gas system the Sig LT is but it's longer than pistol for sure. You're able to buy the complete upper on those as well and they'll work with a mil-spec lower, just need the Sig adapter. Be warned though, the barrel is a 1:5 twist which can get dicey with supersonic bonded bullets. I only run monolithic bullets in mine.
Keep in mind, you cannot swap barrels on a POF by yourself. Has to be sent back to POF. They use a proprietary extension
My advice to you regarding your plan for a carbine length piston on such a short barrel is that unless you are willing to do significant re-engineering or use a proprietary upper that has already been proven to run with this system, just use a pistol gas system and install a fake 416 piston gas block. It sounds like what you really want is an upper that looks like a 416.
That's only true for the Revolution and the Rogue which are .308 gas guns that are the size of a 5.56 and use a proprietary extension. I don't think that's true on the P415 or any of their small frame DI 5.56 guns.
I have this upper and like it. Most of its use has been with subs and a SF SPS300 on--I think--the "light normal" gas setting. Its definitely heavier (beefier?) than the Noveske 10.5 DI I have, but thats more data point than outright bad.
Things I've noticed with the POF is the handguard shape feels good in hand, the gas adjustment cutout location potentially messes with end-of-gun accessory mounting, and the top rail is taller than normal so, for example, an XPS Eotech mounts more like an EXPS.
They're definitely beefy. I looked hard at my 12.5", in terms of possibly trying to loose some weight but it's just so well engineered I left it alone. I know there's one meltdown video on YouTube where they went 2,000+ rounds with really crappy ammo, without a stoppage. Once it cooled down, it continued to function like normal. In comparison, the Sig LT went 1,000 rounds and they had barrel droop so it became non-functional and had to be sent back to Sig.
The P415 is a very solid gun that doesn't get enough credit and is likely as close to an HK416 as we can get, even better in some ways I suspect. I own both the Sig and POF so no skin in the game.
The 300 blackout upper should also be longer than pistol-length just like the Sig so should have a longer dwell time than pistol-length DI systems. I believe POF uses hammer forged chrome lined barrels too. There's lots of videos out of Ukraine of soldiers using the P415 (or P416 really since full auto). If they ever did an AR18-style buffer-less system, I'd be all over it.
One thing I haven't really checked vs. a pistol-length DI setup is bullet velocity and powder burn (muzzle flash) with supers and subs. I'll need to do that next time I hit the range. Barrels are within an inch of one and other so not apples to apples. I will say the Sig has a LOT more felt recoil than my DI setup with lightweight BCG. Not sure how the POF is but I'm guessing it's BCG is a bit lighter than the Sig's setup. I'll weigh both and report back.
The P415 is a very solid gun that doesn't get enough credit and is likely as close to an HK416 as we can get, even better in some ways I suspect. I own both the Sig and POF so no skin in the game.
The 300 blackout upper should also be longer than pistol-length just like the Sig so should have a longer dwell time than pistol-length DI systems. I believe POF uses hammer forged chrome lined barrels too. There's lots of videos out of Ukraine of soldiers using the P415 (or P416 really since full auto). If they ever did an AR18-style buffer-less system, I'd be all over it.
One thing I haven't really checked vs. a pistol-length DI setup is bullet velocity and powder burn (muzzle flash) with supers and subs. I'll need to do that next time I hit the range. Barrels are within an inch of one and other so not apples to apples. I will say the Sig has a LOT more felt recoil than my DI setup with lightweight BCG. Not sure how the POF is but I'm guessing it's BCG is a bit lighter than the Sig's setup. I'll weigh both and report back.
Take these as relative weights to one and other. It's a low budget, cheap scale that I think is about .3oz off (high).
First POF BCG. This is the same one that comes in the 300 Blk. upper. Take into account the actuation rod is not included in the weight of the reciprocating mass and on this one I'm using a JP silent capture SBR/Suppressed buffer setup. Add .5oz for carbon. I kid. Going to guess, with the operating rod, the entire system weighs about 20oz. for the 12.5" barrel. It'll weigh slightly less with the 10.5" barrel. The 12.5" is verified carbine length gas.
Here's the Sig, which like the POF, is NOT a pistol-length gas system so longer dwell time than pistol-length. This includes the actuation rod which is affixed to the BCG. Surprisingly, it's lighter. I've always felt mine was over gassed so likely why the recoil impulse/felt recoil is more severe by a good bit than my DI 300 blackout or any of my 5.56 rifles. I believe the military gets a titanium version of the BCG to save more weight. Would love to get my hands on one of those!
Lastly, the RCA titanium BCG in my 300 DI with the Unrivaled dead blow competition buffer. I've never had any issue with the piston guns cycling various ammo and the same can be said with the DI setup except for some factory ammo, particularly the Hornady 208 grain A-Max. I've tried a handful of different powders using this setup as well and it's not that finicky although I'd say Lil'Gun is the worst of what I've tried in terms of consistency. I do use an adjustable gas block (Riflespeed).
First POF BCG. This is the same one that comes in the 300 Blk. upper. Take into account the actuation rod is not included in the weight of the reciprocating mass and on this one I'm using a JP silent capture SBR/Suppressed buffer setup. Add .5oz for carbon. I kid. Going to guess, with the operating rod, the entire system weighs about 20oz. for the 12.5" barrel. It'll weigh slightly less with the 10.5" barrel. The 12.5" is verified carbine length gas.
Here's the Sig, which like the POF, is NOT a pistol-length gas system so longer dwell time than pistol-length. This includes the actuation rod which is affixed to the BCG. Surprisingly, it's lighter. I've always felt mine was over gassed so likely why the recoil impulse/felt recoil is more severe by a good bit than my DI 300 blackout or any of my 5.56 rifles. I believe the military gets a titanium version of the BCG to save more weight. Would love to get my hands on one of those!
Lastly, the RCA titanium BCG in my 300 DI with the Unrivaled dead blow competition buffer. I've never had any issue with the piston guns cycling various ammo and the same can be said with the DI setup except for some factory ammo, particularly the Hornady 208 grain A-Max. I've tried a handful of different powders using this setup as well and it's not that finicky although I'd say Lil'Gun is the worst of what I've tried in terms of consistency. I do use an adjustable gas block (Riflespeed).
Does anyone even know a of a .300BLK 10" ish barrel that has a carbine or mid length gas port??
I'm trying to make something unholy that even angles cower upon.
I'm trying to make something unholy that even angles cower upon.
Seriously doubt it, the gas system length for carbine is like 9.75" or so and mid length is about 11.5".
I recommend you spend some time reading up on how these things work. A mid gas 10" is pretty much dimensionally impossible, regardless of being functionally nonsensical. There's a reason you haven't seen any of this stuff in real life.
Veering off the OP...Take these as relative weights to one and other. It's a low budget, cheap scale that I think is about .3oz off (high).
First POF BCG. This is the same one that comes in the 300 Blk. upper. Take into account the actuation rod is not included in the weight of the reciprocating mass and on this one I'm using a JP silent capture SBR/Suppressed buffer setup. Add .5oz for carbon. I kid. Going to guess, with the operating rod, the entire system weighs about 20oz. for the 12.5" barrel. It'll weigh slightly less with the 10.5" barrel. The 12.5" is verified carbine length gas.
Here's the Sig, which like the POF, is NOT a pistol-length gas system so longer dwell time than pistol-length. This includes the actuation rod which is affixed to the BCG. Surprisingly, it's lighter. I've always felt mine was over gassed so likely why the recoil impulse/felt recoil is more severe by a good bit than my DI 300 blackout or any of my 5.56 rifles. I believe the military gets a titanium version of the BCG to save more weight. Would love to get my hands on one of those!
Lastly, the RCA titanium BCG in my 300 DI with the Unrivaled dead blow competition buffer. I've never had any issue with the piston guns cycling various ammo and the same can be said with the DI setup except for some factory ammo, particularly the Hornady 208 grain A-Max. I've tried a handful of different powders using this setup as well and it's not that finicky although I'd say Lil'Gun is the worst of what I've tried in terms of consistency. I do use an adjustable gas block (Riflespeed).
How does the FLOW 762 do with subsonic ammo?
Despite loving flow thru suppressors, Ive not used them on my 300blk
Now that I take a closer look, yeah kind of impossible, but most information on the internet doesn't relay that properly, so it was easy to get mixed up. I really have to be careful where I look these days. Gotta do better on my part.
Pretty well actually...I have the older version and the Flow is quieter. I'll be doing some back to back testing with the Flow and a very quiet standard baffle can (Diligent Defense). I've sort of tested them back to back before but I had to switch mounts in the field which is not a quick process. I now have a HUB mount on the DD and use a Huxwrx muzzle device so I can go back and forth in seconds. I can tell you this... the Flow is far, far better in terms of back pressure and gas to the face. Works really well on 300/308 supers, bolt gun and SBR 556 too.
Good to hear. I have... more than a few HUXWRX cans and *really* like them on my gas guns. Its only the 300blk (which mostly shoot subs) that have other cans (SF and DA)--mostly for [necessary?] backpressure as well as [real/ said on internet] sound performance.
I’m curious as to what buffer weight you are using? Just finishing up this build haven’t shot it yet. Fostech ultralight magnesium alloy upper and lower,VSeven hyperlite 9” handguard,JP scs buffer, faxon 10.5 match gunner, dead air keymo,SLR titanium adj block, and RCA titanium BGC and various titanium parts. I have different weights I can play with on the buffer just waiting on my OC polonium 30 that’s in jail. It’s my first suppressor so it will be a learning curve on the tuning. Currently setting up 4 more rifles to run it on.
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My Spear LT in 300 runs flawlessly with subs or supers, suppressed or unsuppressed.
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