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View Full Version : Quad rail fitting on gas vs piston?


NorCalAthlete
05-26-2011, 1:43 PM
If I have a set of quad rails from a gas upper, will they fit on a piston upper or is there a difference in clearances? School me on dimensions and whatnot here....

Droppin Deuces
05-26-2011, 1:48 PM
There is no standard for gas pistons yet, so some may fight while others will not. Better to tell us what piston system you have and go from there.

Most piston companies will have a list of what brand/model of rail will fit over their systems.

NorCalAthlete
05-26-2011, 2:42 PM
Don't have any piston system yet, just an extra set of quad rails...thinking about building another AR and don't know if the rails will work or not.

Droppin Deuces
05-26-2011, 2:50 PM
Don't have any piston system yet, just an extra set of quad rails...thinking about building another AR and don't know if the rails will work or not.

I guess all you can really do is look at different manufacturers sites and see if the rail you have will fit over their system. I don't know if I would build an entire rifle around the spare rail I have in my parts drawer, though.

NorCalAthlete
05-26-2011, 2:53 PM
Hahahaha nah me neither, but I have a few more parts than just rails. I just need a stripped lower, upper w/ barrel + gas system/bolt carrier. So maybe 50% of the rifle. I have a buttstock, buffer tube, spring, buffer, trigger, mag release/bullet button thingy, rails, flip up sights, pins, pistol grip, and rails. Missing is the barrel, gas system, bolt carrier group, barrel nut, upper+lower receiver.

MrPlink
05-26-2011, 5:06 PM
So you are only missing the important/expensive parts?
Build away! :D

NorCalAthlete
05-26-2011, 6:35 PM
Hehehe. Well, here's the lower/upper combo I'm looking at for it...

Lower:
AXTS ambidextrous AX556
https://www.axtsweapons.com/products/AX556
or the POF
http://www.pof-usa.com/lower/lowerreceiver.htm

Both seem pretty much identical other than looks and minor price differences.

As for an upper....I really like this one:
http://www.americanspiritarms.com/products/ASA_AR_15_M4_Side_Charger_Upper_Receiver_with_Modi fied_Carrier-38-12.html

That particular one includes the bolt carrier...but I don't know if it includes the firing pin and everything else within the carrier (though I would assume so...). Which just leaves a barrel, barrel nut, and gas system. Anyone other than Adams Arms make a drop in piston system for Frankenbuilds?

rattlesnake_nm
05-26-2011, 6:47 PM
Midwest industries will work with most gas pistons.

emy
05-26-2011, 6:56 PM
As long as the rail you have in your parts bin has a channel cut out on the 12 o'clock position for the rod to fit, your GTG like rattlesnake said some MI has the cut out and will work with a piston kit.

rareair
05-26-2011, 9:05 PM
Midwest industries will work with most gas pistons.

No they won't. I purchased a MI-T7 hand guard, it came no where to fitting my STAG/CMMG piston system. Ended up having to buy a Daniel Defense Omega hand guard before it was all said & done.

OP- Which hand guard do you have?

goodlookin1
05-26-2011, 9:42 PM
If youre looking for a piston that will fit most rails, it will probably be the Osprey. Heard good things about it, but havent used it. Apparently, you use your existing gas block and the piston is low profile.

I have an Adams Arms with a rail that is made specifically to fit over top the AA gas block (Profile pic).

You need to get the dimensions of the piston kit and the clearance on the rail before moving forward.

Don29palms
05-27-2011, 6:25 AM
If youre looking for a piston that will fit most rails, it will probably be the Osprey. Heard good things about it, but havent used it. Apparently, you use your existing gas block and the piston is low profile.

I have an Adams Arms with a rail that is made specifically to fit over top the AA gas block (Profile pic).

You need to get the dimensions of the piston kit and the clearance on the rail before moving forward.

According to Osprey you need a 2" diameter hand guard to work.
To the op it would be easier to say what handguard you have. My GPU is using an Adams Arms kit and a Samaon Evolution handguard. Works and fits perfect without modification.

rareair
05-27-2011, 5:05 PM
Just got back from the range. I had installed a Spikes Tactical/Adams Arms' piston kit onto one of my ARs. Have to do some minor clearancing on the Knights Armament hand guard, but got everything to work in harmony.

When I compared the CMMG piston system on my Stag against the Spikes Tactical/Adams Arms, the Adams Arms version is very low profile & will probably fit most hand guards.

NorCalAthlete
05-27-2011, 10:56 PM
I have the Knight's Armament quad rail, carbine length. I think if I were to take that little metal heat shield thingy out of the top half of the rail that'd give me enough clearance yeah?

rareair
05-28-2011, 2:50 PM
I have the Knight's Armament quad rail, carbine length. I think if I were to take that little metal heat shield thingy out of the top half of the rail that'd give me enough clearance yeah?

Hmmmm...The heat shield on my KAC R.A.S is located on the bottom half of the guard. Being so, I left the heat shield in place. I did have to remove the (2) clamps that are on the top half, and did some minor filing to open up the front edge of the guard. This allowed the piston to travel rearwards. And with the end cap on, you can't see the modification

NorCalAthlete
05-28-2011, 3:43 PM
Hmmmm...The heat shield on my KAC R.A.S is located on the bottom half of the guard. Being so, I left the heat shield in place. I did have to remove the (2) clamps that are on the top half, and did some minor filing to open up the front edge of the guard. This allowed the piston to travel rearwards. And with the end cap on, you can't see the modification

Pics of the modification? And the top half didn't have a metal heat shield I forgot.

rareair
05-28-2011, 4:41 PM
Pics of the modification? And the top half didn't have a metal heat shield I forgot.

Give me a few hours. I'll post pics later tonight or tomorrow

rareair
05-28-2011, 5:37 PM
I did have to remove the (2) clamps that are on the top half, and did some minor filing to open up the front edge of the guard. This allowed the piston to travel rearwards. And with the end cap on, you can't see the modification
Pics of the modification?

Ok, had nothing better to do except help a fellow CalGuner out ;) Here's a few pics of the modification I had to do to fit the Adams Arms'/Stag piston conversion.
KAC R.A.C hand guard-
http://i151.photobucket.com/albums/s146/RareAirResto/Armory/DSC_2168Large.jpg

Opened up to allow piston rod to travel through
http://i151.photobucket.com/albums/s146/RareAirResto/Armory/DSC_2169Large.jpg

Everything buttoned up, looks factory to me :D
http://i151.photobucket.com/albums/s146/RareAirResto/Armory/DSC_2171Large.jpg

rattlesnake_nm
05-28-2011, 7:03 PM
No they won't. I purchased a MI-T7 hand guard, it came no where to fitting my STAG/CMMG piston system. Ended up having to buy a Daniel Defense Omega hand guard before it was all said & done.

OP- Which hand guard do you have?


Sorry guess I should have said decent gas pistons lol. :43: