So here is my Defender 10 with the Armalite 15" KeyMod rail and UBR. Function has been 100% so far over about 70 rounds of PMC 147gr FMJ. Both the IMI 20 round mags and the PMAG LR 25 round mags work great, hold the bolt back after the last round, and drop free full or empty. I’m using a standard AR15 carbine spring and a heavybuffers.com AR10 heavy buffer with the UBR.
I also used a little jig I got from Rainier Arms a while back to dimple the barrel for the set-screw type low-profile gas block. I tried to use one of the clamp-on gas blocks I have laying around but none would adequately clear the inside of the handguard.
Primary optic is a TA11D with .308 horseshoe reticle; I believe this config with the FDE anodizing and SDO-type lens caps was exclusive to RSR. Secondary is an offset Aimpoint Micro H-1.
Weight is 9lb 13oz 10.5lbs (reweighed just to make sure; turns out my memory sucks) with no mag inserted. IMHO that’s not half bad.
Nice rig, caporider!
I have a vaguely similarly setup Armalite AR-10A that I bought last year. It came with plastic handguards and a railed gas block, which I swapped to a MI 15" Keymod Rail and a low-pro gas block (soon to be swapped out for a Syrac adjustable).
If I had known Armalite was going to start offering factory guns with decent freefloat Keymod, I would have saved myself the trouble and just waited, but I got it on a nice discount.
I picked up a spare bolt, just in case (you never know). The rifle has eaten 147 through 180 grain, although I only have about 150 rounds through it. Accuracy has been good enough that I probably can’t outshoot the gun. It’s a 16" chrome-lined, lightweight barrel, so I don;t think anyone is expecting world records in that regard.
It’d be wise to check and see if the short LR-308 carbine pattern buffer body is longer than your AR-15 carbine spring when fully compressed. I’m betting it isn’t.
Is the principal concern here that the buffer ought to be contacting the rear of the receiver extension when the spring is fully compressed? I know heavybuffers.com sells a specific spring for using an AR10 heavy buffer with an AR15 receiver extension…
Good point.
I am unfamiliar with the UBR and if it uses a different buffer tube than the stock (pardon the confusing pun - as in from the factory) Armalite AR-10.
The Armalite AR-10 uses a carbine buffer tube that is longer than the AR-15 carbine buffer tube, and also longer than DPMS LR-308 pattern carbine buffer tubes.
As for buffers, the AR-10 comes with the H3 buffer (at least mine did). As such, if you are going with a heavybuffers.com buffer, you will need to use on of the various AR-15 (and NOT the CAR-10) buffers. He makes them in several different weights, but you will need the AR-15 ones.
I’m sure Clint can explain it better than I can.
Yep, I’m using one of the buffers Clint designed to allow an AR15-sized receiver extension (like the one that ships with the UBR) to be used on an AR10. The buffer is very short but heavy. I have years of experience with Clint’s buffers, but I had not heard the concern about the spring before.
Yes, you want the buffer to bottom out in the extension, not the spring. That’ll reduce the lifespan of the spring and if your tolerances were tighter could prevent the BCG from getting it’s full length of travel (short stroke). The cut-down Armalite EA1095 spring that HeavyBuffers sells will also work.
The UBR extension has the same internal depth as an AR-15 carbine length extension.
I am curious, what, if any effects/changes would this have the force of the spring on the BCG in the operating cycle (bolt closure through full retraction and back)?
Thanks. Did not know that. I really like this stock, and am mulling adding it to my AR-10A to balance it rearwards a bit (the UBR is stout).
Let us know if you do this and how it turns out. I may follow your lead.
Here is a shot of the DEF10 with an IMI FDE 20rd mag.
The IMI mags are very nice and the followers ride smoothly in the bodies. Spring tension seems just right. I can load a full 20 rounds and seat the mag with the bolt closed. The windows are not “calibrated” like the ones on the Magpul LR25s, so not quite as useful but I guess they’re good to see if there are SOME rounds remaining.
As a quick update, I’ve shot the following ammo through the rifle so far:
PMC 147gr FMJ .308Win: 100% function over 90 rounds, very nice ammo;
Hirtenberger 147gr 7.62NATO: 100% function over 20 rounds, great value for the price;
FN 144gr 7.62NATO, vintage 1981: 100% function over 5 rounds, have a bunch of this so good news;
DAG 150gr Bimetal 7.62NATO: consistent short stroking, no-go in this rifle, ammo most likely underpowered.
No real accuracy testing, but my various targets seem to indicate a 1-2MOA rifle depending on ammo. When I get a longer range session I’ll shoot some of my standard precision ammo, which is the Hornady 168gr Amax factory load.
I really like your setup.
Slim, (relatively) lightweight and compact .308 semi.
I also like your idea of getting the DEF10, then simply adding the handguard and a nicer stock and low pro gas block. Saves you some money over the Tactical 16".
Kudos. I might go this route. Thanks for the inspiration.
I have seen your rifle on TOS and like it a lot. That weight is not bad at all considering how much the TA11 by itself weighs.
I have pretty well made up my mind that I will be getting a DEF10 to fill my .308 battle rifle slot once I get my M&P 10 back and get it sold. It is between that and a SCAR 17. I like a lot about the SCAR, but not its lack of adaptability (particularly when it comes to handguards) and the thumb chopper charging handle. Plus I already have DPMS pattern mags. It helps that the DEF10 is about $1500 cheaper. I will probably go with a 12" MI-SS G2 handguard over a SLR low pro adjustable gas block for suppressed use with my pending Silencerco Omega, and the fixed stock setup I used to have on the M&P 10 with a Magpul MOE rifle stock. Should make a pretty slick little hearing safe hog gun, Run 'n Gun rig, and all around battle rifle. I used to not want to go as short as 16" on a .308 due to it being too loud for hunting without ear pro, but the Omega will cure all those concerns.
I thought about the DPMS GII AP4, but just heard too much negative feedback about reliability. Also after my M&P 10 experience, I am wary about getting a proprietary design that spare parts aren’t available for, and relying purely on one company’s CS for support. At least parts are available for AR-10s, and several other companies sell their parts and make aftermarket barrels and other accessories for them.
I forgot to ask about how you like the Armalite KeyMod handguard. They are pretty new, so I haven’t found any reviews out there.
I have a Midwest Industries KeyMod handuard on my AR-10A, and am looking at my handguard choices for my next AR-10A.
Have you been able to compare it in terms of thickness, sturdiness, weight, etc. to any other KeyMod/M-LOK options that are available for the AR-10 pattern?
I really like the Armalite KeyMod handguard. It is relatively light, high quality, and locks up using a well-designed mechanism.
I had an AR10A4C awhile back that I put an MI Gen 2 slick handguard on – you can compare it to my current DEF10 in the picture below. The new Armalite handguard feels quite thin in the hand and I have no problem doing a “half wrap” hold on the handguard using my support side hand with my thumb over the top of the rail and the meat of my palm pulling back against the VFG (not the Costa hold).
I just paid a deposit on my 2nd Armalite AR-10A. I wasn’t really planning on getting one, but a local deal came up, and it was half off retail, so I had no choice in the matter.
It’s the very basic configuration, railed gas block, plastic handguards, etc.
I am planning on adding the following:
Armalite KeyMod handguard
BCM Gunfighter Grip
Either a Magpul PSR, UBR or STR, not decided yet.
and lastly
a beefier barrel, 16" length. My 1st AR-10A has the skinny profile barrel, and it works OK, but this one will be geared more towards the “precision” end of the spectrum. I am now searching for a barrel to fit the Armalite pattern. All I am seeing is Rainier and Noveske.
The Noveske is VERY beefy, quite pricey, but I’m not sure if I can get an adjustable gas block on there, as it comes drilled for the pinned gas block it comes with.
The Rainier, is a but less beefy, but beefy enough, costs WAY less, and would work with an SLR adjustable gas block.
