SO! I have an adams arms evo that I have been wanting to swap out the hand guards for awhile now and frankly, it has turned into a pain in the ass. I've done a ton of research and will be compiling the information into this thread in the coming weeks as to hopefully make this an easier issue for those wanting to swap out guards on their piston systems.

***I did not take the images provided

I am going to start with the two short stroke systems I know the most about, the Adams Arms kits and the Superlative kits. To fully understand how to fit the guards to these systems you must first understand how the systems support the drive rod

The adams arms uses a bushing that is placed against the barrel nut to help hold the drive rod in place. See picture



The trick with them regardless of which block you use (micro, xlp, etc) is that it needs to be installed on a system with a barrel nut that has the same dimensions as a standard barrel nut. There are a couple exceptions that will touch later that designed barrel nuts that have cuts that when timed correctly will allow for clearance of the barrel nut. As a rule of thumb though, if it is a standard barrel nut, the adams arms will fit.

Their website lists quite a few that fit that they know of, and a few that need slight modification to fit.

Per the website:

clearance requirements

The Free Floating or Drop In rails available on our website
Star-C (carbine only)
Samson Star-C- EX-P (carbine only)
Samson Star-M (mid only)
Samson Star-M- EX-P (mid only)
Samson Star-R (rifle only)
Samson Star-4 (pistol only)
Samson Star-4-DI (pistol only)
Samson Star-4-EX (pistol only)
Samson Star-DI (pistol only)
Samson Evolution Series 4 EX (pistol only)
Samson Evolution Series 7 (carbine only)
Samson Evolution Series 7 EX (carbine only)
Samson Evolution Series 9 (mid only)
Samson Evolution Series 9 EX (mid only)
Samson Evolution Series 12.37 (rifle only)
Daniel Defense Standard Length Omega Rails
Daniel Defense Standard Length Lite Rails
Daniel Defense Standard Length Omega X Rails
Daniel Defense 9.5 FSP Lite
Daniel Defense 12.5 FSPM Lite
Daniel Defense EZ Car 7.0
Ergo Grip AR Z Float
Ergo Grip AR Z Rail
Midwest Industries Gas Piston Two Piece Free Float Forearm
Arms #50 Bi-Level S.I.R. System
Magpul MOE handguards (most recent version cut to accept gas pistons)
Troy Industries Drop In Carbine (Mid length and Rifle length require removal of handguard tension screw and arm)
Troy Industries TRX Battlerail Extreme 9" and 7.2"
PRI Gen III Delta Carbon Fiber Forearm
Newtown Firearms Modular Free Floating Carbine Rail
The modified M4 style handguards provided with our standard system
Odin Works KMod Forend (XLP/Micro - slight modification to barrel nut)
Odin Works Sport Forend (XLP/Micro - slight modification to barrel nut)
Yankee Hill SLR (XLP/Micro)
Troy Industries VTAC Alpha Rail (XLP/Micro)
Troy Industries Alpha rail (XLP/Micro-slight modification to rail to allow access to set screws, and special installation instructions.)
Midwest industries SS/SSK/SSM. (XLP/Micro-barrel nut modification)
Diamondhead VRS-T (XLP/Micro-barrel nut modification)
Brothers & Arms USA 3RGS M-Lok Hand Guard (XLP/Micro - request piston barrel nut from B&A)
Brothers & Arms USA 3RGS Keymod Hand Guard (XLP/Micro - request piston barrel nut from B&A)
X-Products Viper Free Float Rail System (XLP/Micro)
Black Dawn Free-Float Handguards (XLP/Micro - contact on top of block, may require some slight modification)

The Superlative system is different. The bushing is optional and is installed directly into the receiver. The entire system is open and does away with the standard barrel nut dilemma



the .750 dimensions per the website with the clamp on (I list this because it is the largest, if this one fits then so will the other ones)


as long as the handguards clear then theoretically the system should fit.

Bravo Co KMR and MCMR-this rail is popular and while it is tight, should fit all systems.



The SLR Helix and Ion lines should fit, however from my understanding is the barrel nut needs to be modified slightly. This doesn't make sense to me as the Superlative Arms op rod is listed as the same dimensions as a gas tube. If a gas tube fits then this should fit however Per the member who has it on here they needed to Dremel out the barrel nut slightly so i'm not going to argue. The solo has the opposite issue. The rail does not fit, but the barrel nut does.




more to get updated later

Hey, brother. The ERGO Z-float rails will be discontinued when stock runs out. Regular z-rail for carbine length will stay.
All ERGO superlite and ultralite free float rails should work with the Superlative arms system.

thank you. I'll get those up next

next update plans:
M.I. barrel nut diagram
URGO
d.d.
UTG
seekins

edit*** oh and geissele

also, feel free to post pics of your system with the rail. If you do please list who makes the system, what configuration it is in (IE .750 or .625, etc) barrel length, handguard and length and if there was anything special you needed to do in order for it to fit. Thank you.

Finished my Adams arms to superlative tonight to fit an mcmr-it’s tight but has 360 clearance.

One thing to note-the Adams arms uppers have a gas tube hole specifically cut for their op rod. It happens to fit superlatives op rod perfectly with the exception that the bushing will not fit.

My pics













More updates inbound this weekend hopefully

Can you run that in a .300 Blackout and tell me how it goes? I have a pistol lower and the BCM 12.5 Upper in .300 Blackout and was thinking of doing it to mine! I know a little off topic but you would be doing me a favor?! Please? I heard its a no no to do that but not sure, would rather someone with some more funds try it out first that can afford to break their shit, because I can't.

Superlative piston systems are not 300blk compatible. I’ve heard through the grapevine that a piston system is in the works

Adams Arms has a 300 Blackout kit that will work on subs and supers, https://www.adamsarms.net/300blk-piston-kit-p-series-adjustable-micro-block.

I was actually just stopping by to post that. Thanks phil

Thanks, much appreciation for it, and it would definitely work with the BCM MCMR 10 Inch Rail?

And hoody2shoez thanks for the information as well, really appreciate you doing the pictures please share more! I built my own version of the SR-16 11.5 (5.56) Inch Upper, sort of, but I do have the URX 3.1 Rail on it and Looking through at both uppers it seems that there is more clearance with the URX 3.1 but it's also not a .300 Blackout barrel, would you know if SA Piston Kit would be compatible the URX 3.1, or even be able to try it if you own one and post pics?

The Adams arms kit IS NOT compatible with the bcm kmr-a or mcmr.

I believe the superlative arms does fit under the urx 3.1. I will double check the dimensions and get back to you.

***EDIT TO THE BOLD***

The Adams arms micro/xlp WILL fit under an mcmr. The barrel nut is going to b the limiting factor. See phil’s comment a few posts down. You will need to cut out a notch on the mcmr barrel nut to match the dimensions for a mil spec barr k nut. The length needs to be .85”

So my .300 Blackout with the Adams Arms kit and the MCMR is not compatible, damn, so hopefully SA will get something out for the .300 BLK at some point.

We have had customers use both the BCM KMR and the MCMR, however you will have to notch the barrel nut, so it is .85" in length.

-Phil-

Edited my post above for correctness

The Midwest Industries Gen 3 freefloat handguard is not a direct fit with the AA P-series piston conversion kit.  However...

The AA piston kit presumes the use of the toothed USGI barrel nut and uses the teeth at the front of the barrel nut to support the op rod spring cup.  The USGI barrel nut is .850" tall.  The MI G3 barrel nut is about 1.165" tall and compresses the op rod spring too much and limits op rod travel, and doesn't have teeth at the .850" dimension.  cutting a notch in the MI barrel nut would be required at this end to provide the correct dimensional environment for the AA op rod, in addition to some means to provide support for the op rod spring cup, I guess, would be recommended.  Otherwise the spring cup might be slightly cock-eyed on the op rod and cause binding?  just my thoughts.  maybe if you put the flat part of the spring at the bottom, you could get away with no vertical support, unless the spring rotates in operation.

The AA P-series gas block will not fit inside the MI Gen 3 without some judicious metal contour reprofiling of the GB.  could be done with a Dremel.



fine print: if you do try this, be sure to leave the required free-play in the op rod (business card thickness) in the setup.

The Superlative Arms solid-block, .625" gas journal, mid-length system is compatible with the Leapers/UTG Pro handguards. MTU019SS (15" version) fits great on a 16" barrel.

Here is a image provided to me by AA on the barrel nut modification and some instructions. I am in the same boat as others but worse by the fact that I need a handgaurd for a 7.5" barrel. There is little to nothing out there with a GI barrel nut in lengths shorter than 7". In any case hope this image and information helps. In for answers and to contribute.

Attached File


"You will see that some of the rails say that there is a modification needed to the barrel nut in order for them to fit correctly. This is done by cutting a “channel” or “seat” into the barrel nut itself, you would want to install it and time the barrel nut first. Then measure from the receiver towards the muzzle .85 inches. and make your mark on the barrel nut. This way the Drive rod bushing can sit properly and allow the approximately ½ inch of travel needed for the drive rod. the diagram attached shows an example of this mod."

Bump to keep this out of archives

Bought a .750 SA piston kit for my 16" build (lo pro). The dimples are drilled in the barrel so it's ready to go but but holy fuck, I had no idea it would be this hard to find a FF tube to fit. I had a STNGR VYPER rail that's amazing quality and design but of course it doesn't fit soooooo I need recommendation of an M-Lok tube that looks as close to the Vyper and of course, and close to them in price. I definitely want one that uses a barrel nut that is similar to Stngr's ( I do not want one that uses a nut that requires lining up holes). So far, none of the ones mentioned in this thread meet my requirements.

When I called SA they did not have a good answer or an approved list of compatible handguards, they were correct though that the handguard mfgs do a terrible job of showing all dimensions where the actual piston gas block goes.

What part doesn’t fit? Do you have pictures for reference? You could always use a BCM MCMR. Mine fits with a clamp on.

The dimensions are relatively similar as listed for the vypr-please post some pics

The width of the gas block lobe is too wide to fit in the opening under the rail, heigth wise it's fine, the gas block is .425 wide (remeasured) and the opening in the FF tube is .400 (close but no cigar). I specifically chose the non-clamp on to make sure it would fit.  I dont like the appearence of the BCM units, no pics.

That sucks man. I’ll see if I can find something close to it that you may like. I’ll post some new ones in here to add to the thread if that’s all right with you.

I just remeasured and updated my post.

I see your update. The new Adams arms rails would work and look fairly similar. I’m checking out the vltor freedom right now, a few seekins offerings, and the fortis switch. I’ll keep posting as I find more. If one suggestion catch’s your eye let me know.

Also—-Samson sxs series

Sxs

***EDIT***

CMT UHPR HRX fits

Appreciate the assist, I'll look at them to see if they'll fit the bill.

Yes sir! Keep us posted

Both the Samson and Fortis don't have a full length rail so they're out even if they fit, the Vltor is the leading contender except they're only showing Key Mod not the M-Lok I want.

Just looked at the Adams Arms rail and it looks like it fits the bill for what I need though it's almost twice what I paid for the Stngr for the necessary .025" more clearance for the gas block😡.

The cmt is going to be up there in price too. I’ll try to post up a few more that I can find

Also, check out SA Facebook and Instagram. You can see what others built with. It may be able to help narrow a few things down

Wish DD still made the Omega piston.

Good idea.

I recently finished a build using a Superlative Arms Piston kit with Strike Industries Strike Rail.  The Superlative Arms Piston kit includes the bolt carrier.

The Superlative Arms piston kit and the Strike Industries Strike Rail are a perfect match. The rail is held on by one allen head bolt, easy on, easy off for cleaning. The Piston gas block fits in the rail without modifications. The piston fits the barrel nut gaps like they were made by the same guy. First few shots were a little over gassed. Followed the Superlative Arms directions and got it dialed in perfectly in about 10 rounds. Huge difference with the Piston set at the sweet spot. The Piston kit is either restricted or bleed off. Check out the Superlative Arms website for more information. Strike Industries website says the Strike Rail is "Not compatible with most gas piston systems". FYI works with the SA piston kit. After building 9 DI AR's it was time to try a piston. If you're looking to build something a little different or want to change an existing DI to a piston, this combination fits like a glove and works great..

www.suparms.com/collections/retrofit-piston-kits/products/copy-of-750-adjustable-piston-system-pistol-length-solid-melonited-low-pro-ar15

www.strikeindustries.com/shop/products/ar/handguard/strike-rail.html

Why did they have to design the barrel nut that way, its just as bad as having to line up an original barrel nut.

Smooth would have been nice, but they needed a way for a wrench to grab it.   It doesn't have the tight gap tolerances of a delta ring.   The nut wasn't difficult to time.

OK

I'm running the AA Micro (non-adjustable) system on a 12" SBR.  I originally had the Ergo Grip Z Float Rail System (Spectre), which fit nicely, and is specified in the AA FAQ as a compatible rail.



But the rail is heavy, and I wanted something a little more "2019" than a quad-rail.  The AA FAQ lists "Midwest Industries Gas Piston Two Piece Free Float Forearm," but it's pretty model non-specific.  Some of the larger/taller MI models say "piston compatible."  I locked onto the MI-21M, which is listed as "AR-15/M4 Gen2 Free Float Handguard M-LOK(TM) Compatible Mid-length."  Unlike some of the other MI models, it does not say "Piston Compatible."  I have essentially the same rail in KeyMod on my .22LR SBR, and it's light (7 oz) and incredible slim.  Figured if it didn't fit, I'd have a spare rail for a future build.

It's a two piece rail that makes use of the USGI barrel nut.

Turn out, the fit is perfect.



120 rounds, 90 un-suppressed and 30 suppressed.  With the Armaspec H2 Stealth Recoil Spring, the brass drops with boring consistency in a nice neat pile at 3:30.



Add the Midwest Industries MI-21M to the list as working with the Micro Block.

Anybody know of anything other than the Lancer that will work on the Sig 516 Gen 2?  I need something for a 10 inch.

A heads up, the Troy SOCC battlerails may fit the Adams arms systems, as well as superlative systems. It uses a mil spec barrel nut as well.

The id is listed at around 1.58

I tested the SOCC rail on the floor at SHOT, it will work with Our micro gas blocks but will fit rather close to the sides of the gas block. It will also work with our standard railed gas block, as long as the rail is shorter than the gas length (7" for carbine, 9" for mid, & 12" for rifle"

-Phil-

Thanks Phil!

The site says that, but nothing's changed in what, 2 years?
I don't see why it couldn't be made to run if you give it enough gas.

I want to build a ~6" side charging bufferless upper, and if I could get a SA piston block to run, it would save me a lot of time on the mill/lathe...

Give it a go and let us know the results. That’s the point of this tread.

Anybody try the SA Adj. Piston System(https://suparms.com/collections/retrofit-piston-kits/products/750-adjustable-piston-system-pistol-length-solid-melonited-low-pro-ar15) with a DD RIS 2 handguard?

From looking at the measurements of the gas block and handguard, it should work, but I wanted to see if anybody had first hand experience. Thanks!

Chris

I think the only chance that would have of fitting would be with a barrel diameter of .625 with set screws. DD RIS II is a very slim quad rail. I have a .750 with the clamp on with a MCMR and it is TIGHT.

An MFR should work and the slim rail may work depending on barrel profile.

Do you have the piston system on hand? If it’s the clamp on then Another option would be to take the gas block to your LGS and slide it on a MK18 (over the muzzle device and all) to see if it fits. Pictures and follow up would be appreciated if you try any of this.

Thanks

Thank you for the response. I do not have the piston system on hand, but I do have the hand guard. I'll pull some measurements and possibly place an order for the piston kit, and if I'm able to get my hands on one I'll post pictures. In the mean time, I'll keep digging.

Chris

Just finished my latest build using a Superlative Arms piston kit.

I've always liked the UTG Pro Super Slim line of handguards, but they're not kidding on the "super slim" part.  But the SA kit slides right under.  The installation was easy, and took far less time than I anticipated.

Excuse the messy bench.





Took it out today, and it ran like a top.  4 turns open on the gas block and all the rounds were dropping in the same pile at 4:00.



Now I need to move it over to an FDE lower and finish up my all-FDE piston gun.

TL;DR The SA Piston Kit fits nicely under the UTG PRO Super Slim rail.

Thanks for the addition. Any chance we can get a picture looking down the handguard to see the clearance room of the gas block? Also what diameter was your gas block? Thanks!

Woof.  That's a hard picture to get with a shitty iPhone. I couldn't ge it to focus straight on, so it's a little off to the left (shooter's right) side.



I'm using a pencil barrel, with a .625 gas shoulder, so it's the .625 gas block.

Thanks for that update. My iPhone didn’t want to focus when I took pictures of the mcmr fit. Tight fit but it works!

So the question is, will the .750 gas block that most of us use fit?

It will be tight but I believe the set screw will fit. I am unsure of the clamp on. Looking at the specs I believe it would, but I am not 100% confident.

***EDIT*** after looking at the utg diagram and the bcm diagram I am about 90% sure it would fit.

That .625 looks damn tight, so I'm thinking it probably won't work. Still haven't enjoyed my setup since November because of this damn FF tube issue.