11.5" SBRs

[Son of Dorn]

So I'm wondering:

Let's say you have a choice between a direct impingement and a piston AR. For ease of argument, let's say the choices are an HK416/MR556 and a Daniel Defense DDM4V7S.

Both SBRs are identical in configuration, except for the gas system: 11.5" barrels with A2 flash hiders; rail-mounted BUIS; Eotech holo sight, magnifier, and AN/PEQ-15; same model foregrip, pistol grip, and stock; same model suppressor. From a distance they'd be all but indistinguishable from each other.

Is the HK's piston (or any piston AR) really worth it in the end? Does it have any particular advantage over the DI rifle, or are the differences negligible? "Less gunk going back into the chamber and better reliability with a suppressor fitted" is usually how I've seen the debate end in favor of a piston, but is it really justified?

 

[MCHOG]

I feel like the ability to interchange parts gives the direct impingement an edge.

 

[Son of Dorn]

I feel like the ability to interchange parts gives the direct impingement an edge.

Relatively easy replacement of the BCG and gas tube, for example?

 

[Hollywood 6mm]

Agreed on DI for the same reason MCHOG gave. An adjustable gas block really negates most of the advantages of a piston system IMO, and using high quality parts ensures reliability, especially with a can.

 

[kl3309]

And since you're talking about suppressor use, a piston gun may be louder since it's venting to atmosphere under the handguard (port pop).
(If you really want to go down a rabbit hole, there's also carrier tilt and piston-induced barrel deflection to argue about.)

 

[MCHOG]

Relatively easy replacement of the BCG and gas tube, for example?

Correct. I'd add also that the piston system will be a little heavier.

 

[Son of Dorn]

Agreed on DI for the same reason MCHOG gave. An adjustable gas block really negates most of the advantages of a piston system IMO, and using high quality parts ensures reliability, especially with a can.

The difficulty there would be finding an adjustable gas block that mated well with the rail (either the DD MK18 RIS II or the DDM4 Rail 9.0, if not one slightly longer). By default DD rifles have a low-profile gas block and usually feature rails that extend over it, so if I wanted to just buy an off-the-shelf DD SBR and swap the gas block, I might have some trouble and need to swap the rail too.

And yes, @MCHOG , I did consider the marginal weight increase, plus having extra moving parts would have some effect too, yes?

 

[Hollywood 6mm]

The difficulty there would be finding an adjustable gas block that mated well with the rail (either the DD MK18 RIS II or the DDM4 Rail 9.0, if not one slightly longer). By default DD rifles have a low-profile gas block and usually feature rails that extend over it, so if I wanted to just buy an off-the-shelf DD SBR and swap the gas block, I might have some trouble and need to swap the rail too.

And yes, @MCHOG , I did consider the marginal weight increase, plus having extra moving parts would have some effect too, yes?

Adjustable gas blocks that fit under a DD Mk18 rail are easy. I'm running an Ergo under mine (Currently with a SOLGW 10.5" barrel after my LMT 10.5" barrel started to die), but a Seekins adjustable (not the lever style one) or most similar blocks should fit just fine. With the Ergo block, I can reach the side screw through one of the cooling holes in the RIS II handguard and the front screw from the end of the handguard with a long allen key.

 

[Son of Dorn]

Adjustable gas blocks that fit under a DD Mk18 rail are easy. I'm running an Ergo under mine (Currently with a SOLGW 10.5" barrel after my LMT 10.5" barrel started to die), but a Seekins adjustable (not the lever style one) or most similar blocks should fit just fine. With the Ergo block, I can reach the side screw through one of the cooling holes in the RIS II handguard and the front screw from the end of the handguard with a long allen key.

Ah cool then. Would be nice to have an FAL-style block, though, with numbered settings to switch between. Would make things easier IMO. There's a gas block by ODIN Works that uses a ball detent system to "click" the settings in place without risk of over-turning the allen key; it seems to be well-received, but isn't quite as helpful with remembering what to set it on as a FAL's system. But I suppose you'd only need to remember how many clicks to change it between suppressed and unsuppressed, no?

There's also one by Seekins with a nifty lever for simple adjustment settings but lever =/= low profile.

 

[Hollywood 6mm]

Ah cool then. Would be nice to have an FAL-style block, though, with numbered settings to switch between. Would make things easier IMO. There's a gas block by ODIN Works that uses a ball detent system to "click" the settings in place without risk of over-turning the allen key; it seems to be well-received, but isn't quite as helpful with remembering what to set it on as a FAL's system. But I suppose you'd only need to remember how many clicks to change it between suppressed and unsuppressed, no?

There's also one by Seekins with a nifty lever for simple adjustment settings but lever =/= low profile.

I run my SBR suppressed full time, so having a "quick adjust" or switch-style GB was pretty meaningless to me. I have seen people make cutouts in handguards for those switch-style GBs to allow them to work under the rail, however.

 

[Shooter McGavin]

For adj gas blocks take a look at Superlative Arms

https://suparms.com/collections/adjustable-gas-blocks-direct-impingement

 

[Son of Dorn]

I run my SBR suppressed full time, so having a "quick adjust" or switch-style GB was pretty meaningless to me. I have seen people make cutouts in handguards for those switch-style GBs to allow them to work under the rail, however.

If you can help me find any photos of cutouts like that, I'd appreciate them. The Odin GB needs an allen key tucked down the front of the rail to change the settings. Not as convenient on the fly but doesn't require any changes to the rail.

Now, you say you have yours suppressed all the time. If I had mine set for suppressed use, then just took the suppressor off and didn't change the gas setting, would I run into issues using it unsuppressed and need to change the gas setting ASAP or would it keep going fine, broadly speaking?

 

[Hollywood 6mm]

If you can help me find any photos of cutouts like that, I'd appreciate them. The Odin GB needs an allen key tucked down the front of the rail to change the settings. Not as convenient on the fly but doesn't require any changes to the rail.

Now, you say you have yours suppressed all the time. If I had mine set for suppressed use, then just took the suppressor off and didn't change the gas setting, would I run into issues using it unsuppressed and need to change the gas setting ASAP or would it keep going fine, broadly speaking?

Mine will not run unsuppressed because I have the gas block set up to run properly with the can. I can set it up to be over-gassed to an extent with the can and then it'll run unsuppressed, too.

Googling "Mk18 gas block rail cutout" got me this thread on M4C as the first link. There's photos of using a Noveske Switchblock with a Mk18 rail using a cutout on the top of the rail.

 

[MCHOG]

Depending on a lot of factors (your suppressor, your buffer spring, your buffer, weight of your BCG, etc.) there might be some overlap between proper function with and without the supressor. You're probably just going to have to test it out and fiddle with it. If you find that sweet spot, you're probably stuck with that particular projectile and charge weight. If it works suppressed, I'd put money on it short stroking unsuppressed.

 

[Son of Dorn]

Mine will not run unsuppressed because I have the gas block set up to run properly with the can. I can set it up to be over-gassed to an extent with the can and then it'll run unsuppressed, too.

Googling "Mk18 gas block rail cutout" got me this thread on M4C as the first link. There's photos of using a Noveske Switchblock with a Mk18 rail using a cutout on the top of the rail.

Sweet that's exactly what I wanted to see. Thank you!

Also that Noveske block isn't too far off from what I was thinking of earlier. Geez, my google skills just aren't doing today. Must be Monday.

 

[Son of Dorn]

Depending on a lot of factors (your suppressor, your buffer spring, your buffer, weight of your BCG, etc.) there might be some overlap between proper function with and without the supressor. You're probably just going to have to test it out and fiddle with it. If you find that sweet spot, you're probably stuck with that particular projectile and charge weight. If it works suppressed, I'd put money on it short stroking unsuppressed.

Which is why the adjustable gas block helps, right? Setting X for unsuppressed, setting Y for suppressed, and a little bit of leeway for both before the issues really start to happen?

 

[mavrick10_2000]

I run Superlative or SLR Adj Gas Blocks on most of my AR's and have for several years with Zero issues. All are run suppressed.

 

[Jigstick]

Here’s a BCM KMR handguard machined out to clear a Noveske Switchblock

 

[lash]

I’m using the Superlative Arms low profile block and it works fine under the tight Seekins rail. It comes with an extra long Allen key for adjustment if yours ends up really far under the forearm, which I doubt would happen with an 11.5” barrel.

 

[Jigstick]

Seekins makes a nice 10.5in complete upper with their new quick throw adjustable gas block. I used it on my newest build. It’s very slick the handguard is machined out on the sides to give you access to the throw lever the top of the rail is continuous to allow mounting of MAWL, PEQ, DBAL, etc

 

[Son of Dorn]

View attachment 7346574
Here’s a BCM KMR handguard machined out to clear a Noveske Switchblock

Oh now that I like. Is that a Magpul ASAP end plate?

 

[Jigstick]

Yeah

 

[Son of Dorn]

Yeah

How do you like it? My only AR has an old pre-A1 fixed stock on it, so no end plate, but I always seem to come back to the ASAP when I look at doing a newer style build.

 

[MCHOG]

Which is why the adjustable gas block helps, right? Setting X for unsuppressed, setting Y for suppressed, and a little bit of leeway for both before the issues really start to happen?

Exactly

 

[Jigstick]

I like it. Depends on what I’m doing. I prefer 2 point slings when I’m shooting on the move a lot.

 

[Son of Dorn]

Seekins makes a nice 10.5in complete upper with their new quick throw adjustable gas block. I used it on my newest build. It’s very slick the handguard is machined out on the sides to give you access to the throw lever the top of the rail is continuous to allow mounting of MAWL, PEQ, DBAL, etcView attachment 7346575View attachment 7346577

Can you get a better closeup of the cutout, please? The Seekins 10.5" doesn't seem to exist on their website anymore, and I wanted to go with a 11.5" anyway, but I'd love to get a better look at it, and at the other cutout rail you shared, for some ideas.

 

[Jigstick]

Yeah Seekins doesn’t list their 10.5 CQ PDW upper on their website. But I called them and placed an order for one. They do have a SKU number for it. I’ll snap a pic of my upper when I get home

 

[bfoosh006]

FWIW , I just got a few of the Aero Precision Adjustable gas blocks ( exactly the same profile as their low profile gas block ).... at $65 per, for a click adjustable Block.

With a carbon cutter integral to the adjustment screw.... ( I think, I can't seem to find that GIF anymore )

 

[Son of Dorn]

FWIW , I just got a few of the Aero Precision Adjustable gas blocks ( exactly the same profile as their low profile gas block ).... at $65 per, for a click adjustable Block.

With a carbon cutter integral to the adjustment screw.... ( I think, I can't seem to find that GIF anymore )

I hadn't looked closely at the Aero, but then I also wasn't considering an adjustable gas block in the original question. Seems to be a lot like the Odin Works one but with fewer settings, which might be an advantage since potentially fewer clicks to worry about changing the settings.

 

[bfoosh006]

15 clicks available on the Aero... and the Aero is more svelte then the Odin with its driver side bulge.

I have high hopes for the Aero one, I usually buy SLR's... so "If" the Aero can do the same thing for less money... well, you know how that works.. Mo' Money for ammo !

 

[Asiparks]

I have a DDM4v7 pistol and it runs superbly with or without the can. Changed the charging handle for a PRi tactical ambi and added silicone sealant to the gap around it= no gas in the face. I'd run the rifle first and see if need the adjustable block.

I have a couple of piston ARs too, LWRCi and POF. I like them fine, but there's no difference big enough in everyday shooting to blow my skirt up...

 

[Son of Dorn]

Thanks for your replies, y'all. This wasn't intended to be a "help me build" thread but I appreciate the advice and suggestions and now I have some ideas for when I get around to doing an SBR myself.

Seems like so far DI wins out, but I'd still welcome any arguments for the piston being better, of course. To further the question:

Would you still pick your DI SBR if it went full-auto (or burst if that's your thing) and you had your choice of it or a piston SBR in a general-and-CQB combat situation? Or would you reconsider a piston for the job? See, I figure there must be some kind of advantage to the piston (outside of "it doesn't shit where it eats") or else the HK416 and SIG MCX wouldn't be steadily gaining traction in the military world. Ditto with a 7.62 rifle, since the HK417 is set to replace the DI M110 and has already been adopted by other nations. But if it's just a matter of "Nah, they could put adjustable gas blocks on the M4s and it'd be all good."...?

 

[oldfatguy]

(If you really want to go down a rabbit hole, there's also carrier tilt and piston-induced barrel deflection to argue about.)
[/QUOTE]

PWS long stroke piston takes care of carrier tilt.

OFG

 

[Son of Dorn]

PWS long stroke piston takes care of carrier tilt.

OFG

From some stuff I was looking at last night, seems carrier tilt isn't as much of a problem now that manufacturers have found ways to mitigate it, no?

 

[AMGtuned]

Agreed on DI for the same reason MCHOG gave. An adjustable gas block really negates most of the advantages of a piston system IMO, and using high quality parts ensures reliability, especially with a can.

And since you're talking about suppressor use, a piston gun may be louder since it's venting to atmosphere under the handguard (port pop).
(If you really want to go down a rabbit hole, there's also carrier tilt and piston-induced barrel deflection to argue about.)

This is, and has been the answer. We're all owners and users. We know how to service and use these systems. When you take inexperience out, DI wins in my book.

Unless you swim with your rifle a lot

 

[Son of Dorn]

Unless you swim with your rifle a lot

Condom over the muzzle; if there's water in the barrel, slightly retract BCG with the muzzle pointed down and don't forget to reseat it.

Or that's what I've always read.

 

[Jigstick]

Here’s the Seekins quick throw adjustable gas block on their new 10.5in upper. I believe it has 40 detents in total to get it tuned. All the way right is suppressed. All the way left is unsuppressed. But you have 10-12 detents in between. So you can add / subtract gas precisely as needed.

 

[Jigstick]

Do get back on topic. I’ve shot all my DI rifles suppressed and unsuppressed. I use Young chrome plated BCGsc. They do get dirty even with adjustable blocks. I’ve never had a reliability issue with them. However I can tell you that the BCG on my buddys LMT piston rifle is way more clean than mine after hundreds of rounds. Is a piston upper worth the money? To me it isn’t.

 

[MPDS13]

I recently got into the piston game with a PWS MK111. I am very happy with it and it shoots well. I would agree completely with some of the previous statements especially the one above. The bolt and carrier are noticeably cleaner after hundreds of rounds. But its still dirty and gassy and slightly heavier in the front. I like the piston system, but I am not sure if it is that much better than a DI even if it is shot suppressed always.

 

[Buzzbait]

I own both types of systems and while each has its own merits, it comes down to personal choice. I hate cleaning guns, therefore, the piston design is my choice. Both will get dirty when suppressed, however, the piston design will always run longer simply because it's not cooking off the lube in the receiver/BCG.

 

[RC556]

View attachment 7346574
Here’s a BCM KMR handguard machined out to clear a Noveske Switchblock

Wow that is clean. Congrats

 

[accurate_okie]

I have two piston setups, PWS mk111 7.62x39 and a Superlative Arms piston kit on a 5.56, both about 11.5" or so. The PWS did not run at all out of the box but is fixed now. The Superlative Arms has never had a hiccup. Both are more enjoyable suppressed as compared to any of my DI guns, adjustable gas block or not, simply because of the gas and debris not being blown in your face. I honestly can't hear the gas coming from the gas block so it must be lower than the supersonic crack of the bullet. Weight isn't an issue for me since the SBR is heavy anyway and then I screw on Specwar 7.62, so I'm already hanging a cinder block of a silencer off the end of it.

I would personally recomend the piston for anything with a silencer.

 

[Son of Dorn]

I have two piston setups, PWS mk111 7.62x39 and a Superlative Arms piston kit on a 5.56, both about 11.5" or so. The PWS did not run at all out of the box but is fixed now. The Superlative Arms has never had a hiccup. Both are more enjoyable suppressed as compared to any of my DI guns, adjustable gas block or not, simply because of the gas and debris not being blown in your face. I honestly can't hear the gas coming from the gas block so it must be lower than the supersonic crack of the bullet. Weight isn't an issue for me since the SBR is heavy anyway and then I screw on Specwar 7.62, so I'm already hanging a cinder block of a silencer off the end of it.

I would personally recomend the piston for anything with a silencer.

There are ways to mitigate the gas/debris, are there not? And is it really that bad in the first place?

Also, follow up for all: The Noveske switchblock only has three settings (suppressed, unsuppressed, and 0) while the Seekins has a lot. I like the Noveske for its simplicity, switching between the two easily, but I have a concern that it wouldn't perform as well as a gas block that can be adjusted with more precision. Thoughts?

 

[accurate_okie]

There are ways to mitigate the gas/debris, are there not? And is it really that bad in the first place?

Also, follow up for all: The Noveske switchblock only has three settings (suppressed, unsuppressed, and 0) while the Seekins has a lot. I like the Noveske for its simplicity, switching between the two easily, but I have a concern that it wouldn't perform as well as a gas block that can be adjusted with more precision. Thoughts?

The Radian charging handle designed for silenced rifles and works pretty good on my 308 with a SLR gas block but not as well as my pistons.

PWS uses 3 settings but thats a little bit of an apple orange comparison.

 

[jasonfaz]

 

[jasonfaz]

 

[CrabsandFootball]

Civilians don't need a 416.

Are you doing OTB insertions? Are you shooting lots of full power full auto suppressed?

Even then the 416 with its German vundersteel bolt still shears lugs under hard use.

There was a very specific mission profile where the 416 made sense, and that was with CAG/DEVGRU who shoot more in a month than most people will in a lifetime.

Today, those guns are getting phased out anyway. The only people you will see with them in JSOC are support folks looking cool.

Piston ARs are a solution looking for a problem, with the exception of the 416.

I'm sure people will come in chiming how great their pws or lwrc or whatever shitty gun they overpaid is. I don't care. They are wrong.

 

[Forgetful Coyote]

Civilians don't need a 416.

Are you doing OTB insertions? Are you shooting lots of full power full auto suppressed?

Even then the 416 with its German vundersteel bolt still shears lugs under hard use.

There was a very specific mission profile where the 416 made sense, and that was with CAG/DEVGRU who shoot more in a month than most people will in a lifetime.

Today, those guns are getting phased out anyway. The only people you will see with them in JSOC are support folks looking cool.

Piston ARs are a solution looking for a problem, with the exception of the 416.

I'm sure people will come in chiming how great their pws or lwrc or whatever shitty gun they overpaid is. I don't care. They are wrong.

What are they getting phased out for/whats replacing them?

 

[Son of Dorn]

What are they getting phased out for/whats replacing them?

I'd like to know, also. Seems odd since last I checked, the Marines were working on switching their M16s and M4s to M27 IARs, and the Army's changing their M110s for HK417-based M110A1s. Maybe he mixed up the HK416 and the SCAR-16? 'Cause the SCAR-16 definitely went somewhat out of favor with DEVGRU and them after a while and they cancelled orders for more in favor of SCAR-17 conversion kits or using alternatives. But I could be wrong, maybe the HK really is going out of style with the US. How 'bout all them other folks around the world who use them?

(Also the "civilians don't need" line holds no water with me. By that reckoning, civilians don't need an AR-15 because we're not fighting in the jungles of the Indochinese peninsula and don't need a weapon specifically geared toward weight-reduction in miserable tropical conditions, or 30-round magazines because we're not going out on LRRPs into absolutely-not-Cambodia-we-swear. Doesn't someone on here (Sirhr maybe?) have a cannon or some other extra-fun piece of artillery? Yeah I'm sure nobody needs one of those since rank-and-file Napoleonic infantry are a thing of the past.)

 

[CrabsandFootball]

The marines are going down a path they will regret trying to replace their m4 with a more accurate rifle at the expense of heavier weight, cost and lack of sustained firepower. (Using the replacement of the m249 as the work around)The I27 is a solution looking for a problem and alot of marines will die on the battlfield as a result. A 12 man squad will not have the internal base of fire to gain fire superiority. This is a mentality of target shooting that has plauged the corps for over 50 years and how we end up with shitty rifles like the m16a2.

The 417 is another solution looking for a problem. A very expensive solution.

416s in JSOC are getting worn out and the contract is ended. Its possible they will make some more small purchaeses but what i have read from people i trust, they are moving on. Lots of new weapon procurements going on. Rumor is they are most likely going with the SR16 , or atleast ome element is.

Again you fail to grasp the reason why civilians dont NEED a 416. Need has nothing to do with want. Are you doing diving your gun? Are you shooting a metric shitload of suppressed full auto, full power loads in a very short amount of time. Otherwise a DI is a better tool and is a lot cheaper. The OP asked what should he buy and there is zero reason to buy the 416 unless looking cool is more important than performance.