AR-10 build

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  • lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Finally, finally got around to assembling my AR-10 today. Had the parts sitting in a bin for probably a year+ now. Aero M5 upper and lower. Aimsports 13.5" handguard. Classic Firearms (pray for me) .308 18" fluted HBAR. Brownell's BCG. Just total mixer of other parts.

    Turns out I never got a stock for it, so I've got my OD green spray painted M4 carbine stock from my first AR-15 build on there. No muzzle device. Spare cant scope mount. Cheap no-name gas block.

    Spent the last couple of days (anticipating yesterday building it today and realizing a couple things I was "missing". So I ordered an MFT minimalist stock and a BRT 7.62 linear comp to dress it up.

    Today I ordered a 10 round SR-25 PMAG. I found out that the Hexmags I have do NOT fit an M5 lower. Not with all of the prayer and persuasion I could bring to bear. (short of trying a mallet, which I wasn't about to do). I've got some 20 rounder PMAGs that fit just fine I got out of state a couple of years ago. I've heard rumblings Hexmag has changed designs on their SR-25 mags, but not sure if mine are old or new design. Annoying, but at least I'd only sunk money on 3 of them at an out of state gun show.

    I also ordered an MFT grip. I have an MOE on there now and its fine, but I am going FDE on this rifle, I figured if I am in for a penny, might as well be in for a pound and I figure the FDE will match the stock (or it had BETTER since they are both MFT).

    The thing is pretty darned rear balanced with that long heavy receiver. So I figure the lighter stock should help that.

    No idea if it'll work, but I found an aluminum barrel nut that LOOKS like it might work with my Aimsports handguard. The handguard itself is pretty nice and certainly light, but that barrel nut is almost 5 ounces all on its own! Its a JL Billet 308 aluminum barrel nut. Design is different, but I measured the OD of the Aimsports barrel nut and its the same to within about .005" (should fit over this nut fine). A question of where the grove is located in the nut for the handguard screw. I am pretty sure I can make this work. If not I am out less than $30 in trying to shed about 2.5oz of weight.

    Next up is an Aero Precision FDE 1" scope mount. Cause its like 3oz lighter than the generic one I've got on there now.

    Lastly, a 2A armament Ti gas block.

    All told, I think I am looking at around 6-7oz of weight shaved off, even figuring in the muzzle device.

    Which is good, because this thing is a pig! 9lbs 5.5oz with scope (no sling or swivels yet. Using a black M1 Carbine sling and a simple stud. Total weight should be about 3.5oz based on prior experience with other ARs).

    So I am hoping with sling, muzzle device and all this on there I can get the weight down to barely over 9lbs. I've got a lighter scope also than the 4-12x40 Bushnell Engage and I might swap also (Weaver 9-12x40, which weighs about 15oz, vs the Engage at 20oz. Save the engage for a precision build, not a hunting build). So I might be able to get this under 9lbs.

    I hope. Its looking nice. A BEAR to cock the thing. AR-10s take a lot more force than an AR-15 to yank the charging handle!

    Plans to get it to the range this Friday to try it out. Obviously I won't have the final parts in hand by then, but it should be in fully working order now.

    PS it does make me appreciate my 18" 6.5 Grendel build which tips the scales at almost exactly 8lbs, with scope and sling. I suspect I won't mind the extra ~1lb or so when it comes to recoil though. Does make me wonder if it would be worth going to an adjustable gas block and a lightweight BCG and tune it from there. Seems like a lot of effort to probably reduce reliability.

    Range report to follow. Pictures too. Both "now" and "after" once the build is done.
     

    woodline

    Ultimate Member
    MDS Supporter
    Jan 8, 2017
    1,947
    Good luck on the build! My first (and only) large frame AR build was a 16” .308 suppressed pencil barrel that had enough separate issues to require Clandestine’s time and effort to get it running reliably. Hopefully you have none of the troubles I did, and it works great for you.

    Things to look out for: short throat, tight chamber, out of spec extractor, premature unlocking (even with an adjustable gas block), large gas port, and bcg overtravel. I believe I had all of those issues. On top of the work Clandestine did, I also took his advice and swapped out my .308 carbine buffer and spring with a tubbs .308 flatwire spring and 5.5oz buffer. I was definitely glad that I went with an adjustable gas block, because the thing would still be overgassed even with the work he did. Though some of his recent YouTube videos regarding issues with adjustable gas blocks has caused me to question how freely I have used them in my builds.

    Lessons learned: Clandestine has forgotten more than I will ever know about ARs, large frame ARs often require bigger britches than mine to build properly, and .308 ARs are awesome when they are (re)built by someone who knows what he is doing. That person is not me, but I’m glad to have this rifle as the end result.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Have done a few DPMS pattern AR10 builds now, the Aero M5E1 sets are about as builder friendly as it gets. Have only used BA and Faxon barrels though, both were in-spec, but my BA is right at the tight end of headspace. Barrels are everything, between the headspacing, gas port spacing and size, bore and extension specs etc, they really make or break a build, especially in AR10s. If you are looking to keep weight down, the barrel choice, more than anything is where weight can be saved, and it's where it makes the most difference in feel. You don't need to spend a fortune, but at least want something decent or you will be chasing problems. Even with a good barrel, you want to check headspacing, lug engagement, lap the upper and bed the extension to ensure an accurate and safe build. You will want an adjustable block, light mil-spec and Wolff ammo probably need as much gas as they can get, commercial and heavier 175gr ammo needs to be choked down, especially if you plan on suppressing it, 7.62/308 has a huge variety of powders/loads and in turn port pressures will vary quite a bit with ammo changes. For a stock, or more specifically for a buffer tube, go with an A5 and standard H2/H3 buffer instead of the shorty 2.5" "ar10" buffer/carbine tube, the A5 allows heavier buffers, and it runs noticeably smoother with fewer hiccups IMO, can use a standard carbine stock on A5 buffer tubes, of course use an appropriate ar10 spring.
     
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    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Thanks for the advice guys. Gauges are incoming, but likely will not be here in time. It appears to close properly on a dummy .308 I made up and will not close on the same one with electrical tape on the shoulder.

    Faxon is what I have my eye on if this barrel gives me issues. But I'd originally gotten the CF barrel with the intention of having the minimum necessary parts to make a build on the off chance stuff was suddenly hard to find a couple of years back.

    My problem with going with an even lighter barrel is this thing is already biased heavily rearward in weight. My 18" 6.5 build with a GWACs lower is (to me) perfectly balanced where a hand under the handguard just in front of the magazine balances almost perfectly. This one exhibits noticeably twist backwards with the same test. Lighter scope, rings and stock I think will help with that significantly (decided to get a Bushnell Engage 2-7x36. Its half a pound lighter and I generally don't need much magnification for actual hunting. Found one for a sweet deal and I really like my other Engage scopes. More a question of how well it does in really low light as I haven't put that to the test much. Probably going to spend some time playing with it off the rifle to see. If the cross hairs are too thing I might need something like a Vortex 2-7x32 or Nikon 2-7).

    I'll keep that in mind on the gas block. I can always use the 2A block on my Grendel build to shave another fraction of an ounce and get a AGB if I am having a lot of issues.

    For an A5 buffer tube, what spring do you use? .308 rifle with an H2/H3 buffer weight? I'll take a look.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Thanks for the advice guys. Gauges are incoming, but likely will not be here in time. It appears to close properly on a dummy .308 I made up and will not close on the same one with electrical tape on the shoulder.

    Faxon is what I have my eye on if this barrel gives me issues. But I'd originally gotten the CF barrel with the intention of having the minimum necessary parts to make a build on the off chance stuff was suddenly hard to find a couple of years back.

    My problem with going with an even lighter barrel is this thing is already biased heavily rearward in weight. My 18" 6.5 build with a GWACs lower is (to me) perfectly balanced where a hand under the handguard just in front of the magazine balances almost perfectly. This one exhibits noticeably twist backwards with the same test. Lighter scope, rings and stock I think will help with that significantly (decided to get a Bushnell Engage 2-7x36. Its half a pound lighter and I generally don't need much magnification for actual hunting. Found one for a sweet deal and I really like my other Engage scopes. More a question of how well it does in really low light as I haven't put that to the test much. Probably going to spend some time playing with it off the rifle to see. If the cross hairs are too thing I might need something like a Vortex 2-7x32 or Nikon 2-7).

    I'll keep that in mind on the gas block. I can always use the 2A block on my Grendel build to shave another fraction of an ounce and get a AGB if I am having a lot of issues.

    For an A5 buffer tube, what spring do you use? .308 rifle with an H2/H3 buffer weight? I'll take a look.

    Balance is of course personal prefference, but the Long, heavy receiver places your hand out further than an AR15, and the rifle is heavier by design anyway. Cutting down barrel weight may place the balance point further rearward going by the placement on the handguard, but being the handguard of an AR15 starts at about the same length from your shoulder as the magwell in an AR10, it might "feel" better with a little more tail heavy balance. I also like a bit more secure stock/cheekweld being the weight of the rifle and recoil compared to an AR15. My first Aero M5 was a 46oz fluted 18" barrel and UBR2 stock adding up to 9.5# sans optics, balances at the outer front edge of the magwell, nice shooting from support, but wears you out shooting standing. The other was a 30oz 16" Faxon "big gunner" barrel and a lighter MOE SL stock at 8# sans optics, balances somewhere in the magwell. The lighter rifle is MUCH quicker handling, with less fatigue when standing, That 16oz lighter barrel DRAMATICALLY changes the feel. Next build, I'm probably going for sub 7#.

    A standard carbine buffer tube is about 7", and a carbine buffer is 3.25", ar10 bolts travel about .75" longer, so you either need a longer tube, or shorter buffer. The original Armailte solution was to use a 7.75" long tube and a standard H3 5.3oz buffer, it worked, the 3 tungsten weights add up to about the same mass as a 5.5oz rifle buffer. The DPMS solution, Aero included use a 2.5" 3.8oz buffer with a standard ar15 carbine tube, only enough room for 2 weights, although there are some tungsten and steel bodied buffers around that add up to the same 5.3oz as the longer 3 weight H3. IMO I like to use standard carbine buffers, and keep tungsten weights to make anything from 3-5.3oz depending on what the rifle needs, and more floating mass helps fight bolt bounce, and IMO feels better than heavier bodies with lighter weights. For a spring, Armalite AR10 carbine springs(13.5" OAL) are the "original", but there are a lot of others, the DPMS AR10 springs (for shorter tubes/buffers) are usually around 10". Most aftermarket springs run somewere between, but I have used DPMS springs with the longer AR/A5 tubes and they work just fine, shorter spring, but a higher rate. Most quality AR10 carbine springs will work, and measure between the 2.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Of course issues...

    First off, accuracy is awesome. About 2 minutes or under with the Aguilar M80 I tried. A little over a minute with 168gr Gold Dot. Ran a .52” and then a .26” 4 shot group (this was at 50) with PPU 168gr match. Not exactly the high rolling stuff. Wolf even managed about a 2.5” 20 shot group at 50, it being particularly careful (mostly it was within 1.5”.

    Anyway, I think it’s over gassed reading the other AR-10 issues thread. Stove pipes. Wolf was ejecting to about 1 o’clock though and I had 1 in 20 stove piping with it. I had 1 stove pipe out of 10 for Aguila M80, but I also had a Caldwell brass catcher on that caused a couple stove pipes on my AR-15 a couple minute earlier. So can’t be positive the Aguila stovepiped on it’s own.

    1 out of 7 with PPU. 1 in 3 with Gold Dot.

    I did not shoot a ton.

    Bolt is locking back every time. Other than the Wolf I was mostly shooting 3-4 rounds in the mag at a time.

    Ejection pattern for the brass stuff was around the 2:30-3. Wolf was 1 o’clock and only going maybe 3-4’ in front of me off the bench. The brass stuff I was catching with my open spotting scope case, but it didn’t seem to be getting thrown super hard, though it’s a padded case.

    None of the brass (other than the stove pipes and one case that got bent loading in to the chamber and getting pinched with a stove pipe) looked like it had issues. I’ll inspect it closer later, but I saw no extractor marks, or ejector marks or flattened primers. At least I don’t THINK there were extractor/ejector marks. Certainly no cracks or other deformities.

    The setup is an Aero M5 upper and lower. Classic Firearms .308 fluted HBAR SS barrel with a mid length gas (will mic the port soon). Off brand gas block. Not adjustable. Carbine buffet tube. Aero 308 carbine buffer spring and weight. Brownell’s BCG.

    I’ve got a 2A Ti has block on the way I wanted to slap on for lighter weight. Yes, I know an adjustable GB would be the best option. Especially if it’s over gassed. And yes I don’t have an issue getting one if that’s the advice that it is over gassed. If my absolute best option is an adjustable gas block, what (hopefully vaguely priced option) should I go with?

    Would an A5 buffer tube and standard length H2 or H3 buffer weight help? Or would it just reduce the recoil violence.

    Thanks!
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Oh, and what she looks like today (different scope, different scope mount, stock and muzzle device are en route. Should have all the goodies in the next few days).

    Oh last thing if it helps, I was running a 20 round PMAG. I have some 5 and 10 round steel Mossberg MVP mags and a 10 round PMAG on the way. But no other mag options right now.
     

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    calicojack

    American Sporting Rifle
    MDS Supporter
    May 29, 2018
    5,348
    Cuba on the Chesapeake
    Every time I look at building an AR 10 platform rifle, I see all of the horror stories (including from a coworker) and decide against it. I MIGHT one day buy a complete rifle but probably will not build one. If you like the challenge and it makes you happy, then go for it. It's not for me.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Okay. I got it rebuilt. 9lbs 2.7oz with sling on there. It was 9lbs 7.6oz without sling, but the muzzle devices on. So even adding on a sling stud, swivel and sling (granted, it’s a light sling) and I still managed to get the weight about 5oz lighter.

    I was not able to use the barrel nut. It’s going to have to be machined to be used. The notches are not in the correct locations for the hand guard bolts. Figured it was worth a try. That steel barrel nut is 4.4oz. The aluminum one is 1.3oz...

    For shits I might try machining it to accept the hand guard figuring I am more likely to mess it up than get it correct. More likely to just get a new hand guard eventually. I like the look, but it’s not the lightest and getting a real lightweight handguard at around 12” rather than this one at 13.5” would likely go a long way towards dropping weight. Not much I can do out back other than a reduced mass BCG, which seems like not a great idea even with the adjustable gas block on there. Though dunno, maybe I‘ll play with that at some point. I guess I can try to find a Ti mag catch and take down/zoo to pins to trim half an ounce or an ounce (at a not insignificant cost).

    Maybe KE Arms will make an all polymer lower like they are about to release for AR-15s (I love my GAWCS lowers and combined they are like 3oz lighter than a typical AR-15 lower build with a lightweight stock. I’d imagine with the much larger receiver of an AR-10 you’d probably be talking 5-6oz lighter).

    Might get this to the range later this week to get the gas block dialed in.

    Here is the finished AR-10 along with its little brothers.

    Left to right my 16” .223 wylde HBAR. My 18” 6.5 Grendel and my 18” .308.
     

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    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Oh, as it turns out those hex mags do fit. Just too awkward to insert them in to a nearly bare lower. Works assembled, but extremely tight. Will not drop free and a tiny bit tricky to insert. PMAGs work a lot better (easier to insert and they do drop free).
     

    LongRanger300

    Banned
    BANNED!!!
    Jul 14, 2020
    74
    Oh, as it turns out those hex mags do fit. Just too awkward to insert them in to a nearly bare lower. Works assembled, but extremely tight. Will not drop free and a tiny bit tricky to insert. PMAGs work a lot better (easier to insert and they do drop free).


    I’ve had the same problem with hexmags in an aero build. They will “wear in” after a while.


    Sent from my iPhone using Tapatalk
     

    Sirex

    Powered by natural gas
    Oct 30, 2010
    10,380
    Westminster, MD
    My Hexmags fit just fine in my S&W M&P10, but don't drop free. Not an issue for me, but I like the FDE 10rd Hexmags a lot.
     

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