It should work with the DD lite rail (im pretty sure its listed on their site as working with the lite rail).  Its bigger than the DD MK18 rail im trying to put it under.  And its barely fitting under the DD MK18.

And no reason why it wouldnt work with the 6.5 Grendel.

I thought I read the entire thread but maybe I missed something.  I tried asking this question to AA via their contact form but instead of receiving any type of answer, I was subscribed to their newsletter....gee, thanks.

For those of us with existing AA piston systems, is the XLP gas block backwards compatible?  If so, can we purchase just the gas block and integrate it into the existing system or is there more to it than that and is the stand-alone gas block even available for purchase?  

Please advise, thank you.

I believe they said the rod was and you could just replace the gas block, but the XLP gas block is not a pull through system like the standard blocks so to clean the piston rod you have to remove the block. The selector on the block is part of the block itself. Make sense? So yes the XLP block is compatible with existing kits it's just not a pass through block like the others.

Thanks for the response Seawolf504.  I appreciate the info.

Don't suppose you know where I need to go to purchase just the gas block?  I can't find that part on the AA website.  It sure would be nice if someone from AA would create a new post or add to the existing OP clear-cut information regarding backward compatibility with existing systems and a link to where users can purchase the new XLP gas block.

I wanted to post an update with my issues with my XLP kit.

I contacted Cody_AA at adams arms.  We bounced emails back and forth for a week.  He ended up sending me out a new 5 position gas block to replace my first run 6 position gas block, and a new piston since I did a little sanding on mine to attempt to make it fit better (which wasnt the problem).  He went above and beyond getting the parts out to me.  He sent them out that day and I had them 2 days later.  I didnt pay a dime.  He just wanted to see me getting my kit up and running.

The new 5 position gas block fit much better under the Daniel defense rail.  And when I fired the gun, it wasnt getting bumped down the the next lower setting due to recoil.  And before I reassembled the rail this time, I put a flat on the spring bushing with a dremel.

I got the gun all put together and took it out to test fire it.  Its running perfect now!!!  Before it was only ejecting the shells but not picking up a new round.  I had to cycle it by hand to get a new round.  The gun and piston kit was working perfect with the rail off.  But as soon as I put the Daniel Defense rail back on it turned it into a single shot.

I think the old gas block was putting the front of the kit in a bind and I think the bushing was also putting the piston in a MAJOR bind when I tightened down the rail when it was reassembled.

Again, I want to thank Cody_AA at adams arms for all his help.  I wouldnt have got it running without him.

Is the Carrier Melonited?

Thanks for the info.  Is the block alone enough to work with the carbine length piston kit or do we also need to purchase a new rod?

Any chance we could get photos of the kit with the updated 5 block and a Daniel defense rail? I have an RISii 12'' and would like to know if this kit would work or not.

I will post some later on this week.  I am changing out the caliber to 5.45x39.  The barrel wont be in until Wednesday.  I will post pics when I get it all put back together.

Any plans on a clamp version?

Also, since we are finding out of all the rails it doesn't work under, what rails will work besides a Samson?

I wanted to add my experience to this discussion.

I was a big fan of AA Piston Systems, especially when the XLP came out, because I thought "Hey, finally a Gas Piston System which will fit under my favorite Troy TRX Alpha handguard!"

Well, that's what I thought and believed too, because Adams Arms told us so. Now I am quite p***ed off by Adams Arms, who praised their system as "fitting under almost every handguard".

Now I can say, that there is one manufacturerer less, whos handguards could be compatible with the XLP System: Troy.

Troy Alpha, Bravo and Delta handguards won't be compatible with the XLP, because in order to install them, you have to pull them over the barrel until you reach the barrel nut. Then you need to twist it clockwise on the 1 o'clock position and push it onto the standard barrel nut, then twist is back.

With the XLP already installed THIS WILL NOT WORK, because the XLP Gas Block and the piston rod do not allow this twist. The only alternative is, to install the handguard first, then the XLP Gas Block and piston rod. But if you want to use a handguard, which reaches too far over the gas block, you will have a problem by bringing the gas block in line with the hole in the upper reciever, so the piston rod can move freely. Just because your ability to manipulate on the gas block is gone, the handguard is in your way.

One additional word about "fitts under almost any handguard". This COULD work, IF Adams Arms had thought about the fact, that the minority of all handguard manufacturers utilizes the standard barrel nut for their handguards. Only Troy and Samson offer these handguards and as you see, only Samson is left over, if you are not a lucky one with a Troy TRX Extreme handguard (which will work like all Samsons do).

Therefore my recommendation to Adams Arms: your system COULD work with more handguards, if you offer different piston rod lengths to the customer, depending on what handguards are used. This is no big deal! Just test your system with different handguards and the only working step you need to take during the production of the piston rods is, to lathe down the spring holder on the piston rod, until it works with e.g. Geissele barrel nuts, Midwest barrel nuts, a.s.o. It is just about the position of the spring holder on the piston rod. Very easy!

All is not lost with the Troy Alpha rail! The rail has to be installed first, then the Piston System.

Using the basic  Alpha rail, not the VTAC, I am able to access 2 of the 3 set screws after the alpha rail is installed, these are the closest to the receiver.

I would opt for the Alpha rail rather than the VTAC (even though VTAC looks cooler) because the open sections at the 6 o clock position extends further than the VTAC.

I have a mid length 16" barrel and got the 11" rail. This way, i can fully access the adjustment.

If you want the same. get 2" extra rail over the length of your gas port hole.

9" rail for Carbine
11" rail for Mid length
14" for Rifle length






I am contemplating drilling a small hole in the rail for the 3rd set screw or just running 2 screws.

If anyone wants to know if their block lines up with the holes if their alpha rail, PM me and I will send you the dimensions of where the screws land.

Also, Adams Arms, if you're reading this, please make a heavy barrel 16.5" rifle length barrel!

I may just run 2 set screws in case I want to sell the rail later. besides, my barrel is dimpled. One screw will be in the dimple, one will not. Both are closes to the gas port hole.

@AZ Mike:  Can you post a pick of your build when you are done and your thoughts on function?  I'm running an ASA side charger / Phase V setup and looking to re-build to an 11.5 barrel and the XLP kit for suppressed use.  Lastly, any idea how much weight the XLP piston system adds to the rifle?

I tried my XLP system at the range with the Troy 11" alpha rail today.

I was able to get bolt lock back on the half position with casings ejecting at the 2-3 o clock position using Steel Cased Monarch .223 55gn ammo. this was with a 16" middy and a .223 AAC 51T Brake

It was a bit more recoil than my previous DI SPR build with the DI block adjusted and with an AAC .308 51T brake. But that was expected, as more mass is coming back with the piston build.

By the way, anyone know the weight of the Gas Block? I forgot to weight it before putting it on..

I built my 6.5 with it and only shot it few times but it worked great for me.

@ joshv06:

Your way might have worked, but it sounds like too much tinkering for my taste. Especially when it comes to aligning gas block and rod with the hole in the upper.

Also on my rifle I had to punch the gas block on the barrel with a dinging hammer, because the tolerances at the gas port area of my barrel where so thight, that it was nearly impossible to mount the gas block without some kind of force.

But meanwhile I have thought about a solution for those people, who want to use a non-standard barrel nut handguard with this system:

You need to check the total length of the barrel nut on your non-standard barrel nut handguard. Then you need to check, whether there is enough space on the non-standard barrel nut to support the aluminium cup, in which the recoil spring of the gas rod is placed. If this is not the case, then a solution could look like making an additional support for this cup by cutting a 2mm thick piece of steel to the interior shape of the handguard, then drilling two holes, one .750 for the barrel and one small for the gas rod. Then the gas rod has to be lathe faced to the length of the standard barrel nut PLUS the additional lentgh of the non-standard nut PLUS the 2mm steel base plate.

I think this is a project I will make a start on, since I have a spare AA gas rod ans since this is the only part which has to be manipulated. I will give you feedback, once I am done.

Yes, I was lucky enough to have my barrel already pre-dimpled from the factory. So all I had to do was screw the screw in the the dimple with red loctite and that was it.

If there was no dimple, I would use the inside of the Troy rail to Eyeball it and align the gas block while it was bottomed out on the should of the barrel.

Hello,

For those who are interested in using the XLP with handguards, that utilize a non-standard barrel nut, I have an idea for you:

http://www.directupload.net/file/d/3654/36nkbxy3_jpg.htm

This is what I would call a "piston rod guiding piece", in this case for a barrel with 21.5cm outer diameter (I have an Oberland Arms OA-15, which has metric dimensions) and fitted to be used with Geissele handguards. The idea behind this is, that if you intend to use a handguard with a non-standard barrel nut, you pull this piece over the barrel and fix it with the screw seen below on the picture.

Of course it will be necessary to lathe face the piston rod, so that the spring on the rod is in the exact same position and compression as if you use it on a mil-spec barrel nut. Also you need to restore the exact profile, where the spring sits on the rod, but that's all very easy to make.

But how do you know how much you have to lathe face on the piston rod?

A mil-spec barrel nut has an OAL of 0.850 in.

In my example, I want to use the XLP with a Geissele handguard. The Geissele barrel nut has an OAL of 2.25 in. and an outer dia. of 1.35 in. On my piston rod guiding piece, I decided to make the surface, on which the spring and spring cup will rest, 4mm thick. Therefore the calculation for knowing, how much you have to lathe down the piston rod, looks as follows:

OAL length of custom barrel nut MINUS OAL length of mil-spec barrel nut PLUS 4mm = length you have to relocate the spring holding profile on the piston rod (measured in shooting direction).

in case your handguard has a custom barrel nut, which is shorter than the mil-spec, you probably will get a negative result. There are two options: if you have a pistol, carbine or mid lentgh system, you can buy an AA rifle piston rod and lathe face it OR, if you have an AR in rifle length, you will need to adjust the dimensions of the piston rod guiding piece.

All in all: my solution is a totally custom made. I designed this for my own rifle and its special dimensions without any regard to the fact, that other rifles can have other dimensions (barrel dia., etc.).

But it is just an idea how a technical gifted AR user can compensate the deficite in Adams Arms design, which is, that the XLP in its original form only works with handguards utilizing the mil-spec barrel nut.

Pics?  I have a geissele rail and am very curious about what you just said.  I am not as technically and mechanically sufficient as you clearly are, but I would like to see the finished product.

I have no pics, since I did not give it into production yet. But I will post the plans and pics, as soon as I can say, that it truely works.

If you don't have the technical skill, it does'nt matter. With my plans you could go to a machine manufacturer, who has the machines necessary for this job.

This is what I am going to do, since I don't have CNC machines myself.

Also the part will need a coating. Depending on the material, either Melonite (if I choose steel) or hardcoating (if I choose aluminium). I don't know yet, but I will give you feedback, once I have it.

OK, now it's definite: Geissele and XLP are not compatible, the height of the XLP gas block is still to much to fit under the Geissele. Too bad.

I have an Adams Arms piston kit mounted on this rifle. I had to cut a rectangular opening in the rail just over the gas block and this is with the original large block the new small one might have fit.

http://i146.photobucket.com/albums/r245/908ssp/machinework/_1012508_zps1fd1c00f.jpg

Has anyone been able to get a midwest rail to work? I fear the worst as the MI rails are very narrow.

Bwahahaha!

I have 3 MI rails......... To AA, does cutting the spring alter performance or reliability? Also, It would be nice if AA made modified bushings that fit major rail systems. It would be cheap, and the market penetration possibilities are huge.   I work in semiconductor manufacturing as an engineer, and this was huge for us. Also, any 4th of july sales??

I wouldn't cut the spring down.

Why do you want to cut the spring down?  And what is wrong with the bushing?

Another thing that pisses me off is the original 6 position gas block has smaller dimensions than the newer 5 position gas block.  


I ordered my first kit the week it came out.  I got a 6 position gas block.  It fit under my Daniel defenses MK18 rail.  2 weeks later I got another  for my 16" mid length.  I received a 5 position that time, and it wouldn't fit under my 12" Daniel defense lite rail on my mid length. I tried it on my MK18 and it wouldn't fit under it either.  I had to buy a new troy two piece free float to make it work on my mid length.

People at Adams arms need to stick to the same dimensions when releasing products.  I shouldn't have to buy a new rail because the kit I bought 2 weeks ago fit and the one I got this week didn't.  Total BS!  AA should be ashamed!

To walker77, in the post above, MI suggest cutting the spring instead of altering the barrel nut. The only thing holding many buyers back from buying the xlp kit is the fact that the bushing does not many rails without modification.

I had to grind a big flat on my bushing for my MK18 to make it work.  It was putting the piston in a bind.  It wasnt a big deal to grind a flat on the bushing.

AA, would you be willing to swap out the new XLP for an unused LP?  I got the LP thinking it was an actual low profile block....but it didn't work so I never used it.  I also have an unused railed version.  I'll give you back both of them for the XLP.   Deal?

I will probably try to grind the bushing first as it can be replaced. I don't like the idea of altering my barrel nut. What kind of grinder/jig did you use Walker77? Thanks

Dremel and put the bushing in a vice.  What rail do you have?

I have to ask, why the very high Height Over Bore?

I have the Midwest Industries SSK keymod rail. I just got the piston kit in today. Ill mock it up and take pics this weekend.

How did you get the barrel nut to work?

How did you get around the huge barrel nut on the Seekins rail?

Could we put ( if not done already) together a list of FF rails that will work with your piston's

Looking at this
YHM SLR-Quad Series Forearm





Please let me know what options I have

It looks like the Fortis REV rails might fit over the XLP block.  They also use the standard barrel nut.  Anybody with one of these that can chime in?

http://www.rainierarms.com/img/shop/product/10546b2ebf435d789315dc5771568c7f.jpg

yes. these work....at least they fit over the block. I haven't test fired it yet

the rev will work

Do the Troy Alpha rails work with the XLP piston? I have a piston sitting out at my ranch waiting to be put on with my Alpha rail, but I am wondering if I am going to be disappointed later tomorrow?

Any luck getting this combo to work?

Funny how Adams Arms has abandon their own thread.