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RFI - AR-10, 16+" bbl, <8 lbs

DJL2

Retired Sapper
Full Member
Minuteman
Oct 16, 2013
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OCONUS / on the move
I was wondering what it would take to put together a jack-of-all trades gas gun (likely running a 6 CM or 6.5 CM) and I quickly surmised the biggest hurdle would be weight. Getting a bolt gun with 24" barrel that weighs less than 8lbs (and 10lbs all in) - easy-peasy. An AR-10? Not so much. Even AR-15s are hefty in comparison to a good bolt gun. At this point, I'm starting to wonder if it's even possible to put something together with enough barrel girth to enjoy at the range and still make weight.

Thoughts?
 
2A Xanthos with Proof barrel feels like a rimfire.

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2A-XRC20SC15CAM-2-3.jpg
 


the 18" 6.5 Creed is 8.6lb

16" 308 is 8.3lb

its a little bit overweight but when you say general purpose i think of a gun that needs to be nails tough because its going to be getting banged around in the field or as one of your defensive rifles and the DD is as light as you can get without going into the exotic stuff which i would avoid for a gun with a "job"
 
You can do a light rifle, but there are tradeoffs. I would not even attempt with an AR10. @LRRPF52 suggests what I do - stick to an AR15 and do the 6.5G or 6ARC. You can easily build a 10lb all-in AR15 that'll shoot out to 1000yds consistently well. If you want to get down to 6-8lbs, there's many more tradeoffs involved. Going with a bolt gun will get you there with less tradeoffs, but also lacking semi-auto and the modularity. I find an AR15 + one of those two calibers to be about the perfect balance. If I were primarily hunting the largest of the CXP2+ game, with range use secondarily, I'd probably err to the 6.5G. If primarily shooting at the range and hunting deer and pigs or smaller, then the 6ARC. Either will do both relatively well, so there isn't really a bad choice. I'm partial to the 6ARC since I spend more time at the range than out hunting, but I love the Grendel too.

@LRRPF52 do you mind laying out that build? I'm curious about your barrel profile. My 10.5" 6ARC is 6lbs 10oz, and 18" 6ARC is 7lbs 9.6oz without optic, but the barrel profile holds up to long strings of fire. Here's the 10.5" and the 18", at 1lb 6.7oz and 2lb 4.9oz respectively (including the notoriously heavy Keymo brakes). Most of the ultra-light AR15 builds I see are pencil profiles. 0.750" gas block journal for reference.

IMG_2823 (1).jpeg
 
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Agreed. Lightweight ar10s are not pleasent to shoot and effect fundementals moreso than a bolt gun.

If you are just plinking the 6.5g is hard to beat..cheap, plentifull, cheap to reload, can get a larue uu kit for $900 and its a good 1000yard gun for banging steel about as cheap as can be done.

The place where proof barrels make sense on the ar10 is being able to run a longer barrel without it becoming a boat anchor.
 
Well, sadly...I just turned a Ducati 899 Panigale into the funds that will get my wife something nice and finance this project (well, whatever my next project it...). I guess it's time to look on the bright side and embrace the fact that shooting is an all together safer and more useful skill set. I bet I can buy something nice, put something together and have enough left over to visit Frank and the gang at a class, time permitting.

ETA, because I missed some of the replies:
- I actually sold a 6.5G to someone here on the forum. Pretty excited to never go back, still not sure what to do with the ammo.
- 6mm ARC seems cool...except what I actually want is a 6mm CM. I'd just as soon get a Valk...

Seriously, though, I'm already invested in the "why wasn't I smart enough to just stick with .223/5.56?" AR game with a 6.8 SPC because that's what my Dad shoots (which is my fault as well, gave him a kit back when...and now he owns several and has worn out at least one barrel at ~25k rounds...no, that's not a typo...)

It looks like I'll just keep giving the old -10 a miss...like a SPC on maintenance Monday. Hard to see a reason to spend custom bolt gun money on trying to make this work. I've got a T3x project rifle that could use a stock upgrade, a nice bow that could use a new case, etc.
 
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You can do a light rifle, but there are tradeoffs. I would not even attempt with an AR10. @LRRPF52 suggests what I do - stick to an AR15 and do the 6.5G or 6ARC. You can easily build a 10lb all-in AR15 that'll shoot out to 1000yds consistently well. If you want to get down to 6-8lbs, there's many more tradeoffs involved. Going with a bolt gun will get you there with less tradeoffs, but also lacking semi-auto and the modularity. I find an AR15 + one of those two calibers to be about the perfect balance. If I were primarily hunting the largest of the CXP2+ game, with range use secondarily, I'd probably err to the 6.5G. If primarily shooting at the range and hunting deer and pigs or smaller, then the 6ARC. Either will do both relatively well, so there isn't really a bad choice. I'm partial to the 6ARC since I spend more time at the range than out hunting, but I love the Grendel too.

@LRRPF52 do you mind laying out that build? I'm curious about your barrel profile. My 10.5" 6ARC is 6lbs 10oz, and 18" 6ARC is 7lbs 9.6oz without optic, but the barrel profile holds up to long strings of fire. Here's the 10.5" and the 18", at 1lb 6.7oz and 2lb 4.9oz respectively (including the notoriously heavy Keymo brakes). Most of the ultra-light AR15 builds I see are pencil profiles. 0.750" gas block journal for reference.

View attachment 7499026
My Lilja 17.6” build uses one of the Wasp profile barrels, with it being .650” under the handguard, steps up with normal shoulder, down to .750”, then .740” to the muzzle. Very light.

I used an Aero M4 upper without forward assist, standard carrier weight (currently has a Bootleg adjustable gas carrier in it), Midwest Industries lightweight handguard, BCM Gunfighter CH, carbine RET, SPR grip.

I was shooting it the other day, 2 days back-to-back. Even in Grendel with a lightweight gun, you know you’re not shooting .223 Rem.

.308 or 6.5CM in a lightweight gasser is going to be a handful, will break position significantly with each shot even in real solid position with support. You’re going to come off the target in the sight picture and feel quite a bit of muzzle blast and reciprocating mass moving the gun around.

With 120gr 6.5CM, it will be more pleasant, but do you want to set it up around that? Most factory loads are in the 140-147gr range, and pressure-up the gas system with pretty significant port pressure.

In .260 Rem, things start to get kinda out of hand for me when I’ve tried to get the performance I should be able to get from a .260 Rem/140gr, so I have to dial them down. It’s why I like 130gr so much more in the large frame gasser in 6.5-08 class. I’ve bent at least 3 firing pin retaining pins with my .260 Rem, and pierced primers that flowed around the firing pin into little rings. Didn’t even know it until I broke it down. That could have gone really bad.
 
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Well, sadly...I just turned a Ducati 899 Panigale into the funds that will get my wife something nice and finance this project (well, whatever my next project it...). I guess it's time to look on the bright side and embrace the fact that shooting is an all together safer and more useful skill set. I bet I can buy something nice, put something together and have enough left over to visit Frank and the gang at a class, time permitting.

ETA, because I missed some of the replies:
- I actually sold a 6.5G to someone here on the forum. Pretty excited to never go back, still not sure what to do with the ammo.
- 6mm ARC seems cool...except what I actually want is a 6mm CM. I'd just as soon get a Valk...

Seriously, though, I'm already invested in the "why wasn't I smart enough to just stick with .223/5.56?" AR game with a 6.8 SPC because that's what my Dad shoots (which is my fault as well, gave him a kit back when...and now he owns several and has worn out at least one barrel at ~25k rounds...no, that's not a typo...)

It looks like I'll just keep giving the old -10 a miss...like a SPC on maintenance Monday. Hard to see a reason to spend custom bolt gun money on trying to make this work. I've got a T3x project rifle that could use a stock upgrade, a nice bow that could use a new case, etc.

Glad to hear you'll be living a good bit longer with how people drive on the roads nowadays!

Wow, sounds like you had quite the experience with 6.5G. Curious what happened there. 6mm ARC vs. .224V, if you think that's even a discussion, good luck in life! On the 6mm CM - enjoy your 1000-1500 round barrel life. If you're going short-action sized full power cartridges, at least gain something tangible from it without throwing away barrel life by being significantly overbore. Just because all the PRS guys are running it right now doesn't make it smart. If you want a 20+lb rifle to play that game with, it's a decent option, but there's better. From your original post, I assumed you wanted something different.

Re: your seriously/why wasn't I smart enough comment, ok, but 6.8SPC was never a great choice. 6.5G and 6ARC have some pretty serious advantages depending on what you want to do, if you want to stick to a small frame AR (and you generally do, if shooting an AR).

That's probably a good question to ask - what is this rifle actually for? Perhaps then we can help more, but your last line makes it sound like you've already made up your mind. Good luck!
 
OP: "I was wondering what it would take to put together a jack-of-all trades gas gun.."

For me, that ended up being 6.5 Grendel in a lightweight package. Pick a barrel length between 12-18” and drive on.

Truck gun...
Hunting....
Distance...
CQM/HD....

.223 doesn’t really cut the mustard for distance. I’m used to spotting Mk.262, 69gr, and 75gr a lot in my courses on steel out to 600yds. If there is no wind, it’s easy to hear and register impacts. Once above 5mph wind, the sound seems to carry away and visual impacts are difficult to register anyway. Depending on State, you may or may not be legal for hunting medium game. It’s great for HD/CQM.

Grendel does all of these nicely. Recoil at close range increases your shot-to-shot pattern in rapid strings, but all are still within A zone or less. Blows through barriers even with basic cup and core bullets, fragments cinder blocks into pieces like an AK, has twice the supersonic reach of the AK, better stab factor than .308 especially where most 12 twist .308s start to fall apart at 800yds, indistinguishable terminal effects on animals between it and .308 Win. There isn’t much doubt when you impact steel out to at least 600yds. Depending on wind and target size, it becomes harder as you get farther out, just like with 6mm.

 
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I built 2 AR-10s in .308 that were exactly 8 lbs. Full Aero Precision set with the 15" S-One handguard. Faxon 18" heavy fluted barrels and MFT lightweight stock. The barrel and stock were key to keeping it light and they shoot just fine if the gas is dialed in.
 
@ormandj , I appreciate the kind wishes, but alas success in life has long since passed me by. That wish for luck is a few years over due ;-). You're not kidding about how people drive...and the generally poor state of the roads, for that matter. Hard to ride a bike like that how it's meant to be ridden anywhere but a track. Trundling along in traffic does (did, I guess) nothing for me as a rider. On the bright side, it did help me stay in proper mounted movement trim, head on a swivel, knowing that death could come in a moment from any direction. It definitely made me a better driver.

The whole family of "not a 5.56" AR cartridges are all nice for their niches. I just don't find the performance compelling, as I used to. There was a time where I was super excited about everything from the .257x45 to the .50 Beowulf. Having toyed with a few has moderated that. None of them do anything my plain Jane 5.56x45 doesn't well enough (for me) to justify the extra expense - that was the genesis of my joke. It's never just the rifle/upper. It's the ammo, the mags, the dies, the powders, the brass, etc. It's an inventory management challenge that might hold more appeal if I earn my way to more free time.

As for the 6.5G, whatever enthusiasm I had for the 6.5G was soured pretty thoroughly by my experience with the rifle I chose (poorly) to shoot it. The amount of effort I went through to try to get it to simply shoot as well as M855/SS109 spec ball was part of it. The rifle components being out of spec and the customer service I received is the other part. That's chronicled elsewhere on this sight - suffice to say, there's one company from whom I no longer buy anything. If I had a true need for more than .223, but not quite short action, my 6.8 SPC can provide that. That's a family thing, not a "it makes sense" thing.

That's what got me thinking about something on the -10 - an unambiguous upgrade in terms of performance. Of course, I realized that my 6.8 SPC with a 16" tube already weighs as much (more?) than my M70 w/ 24" barrel. It seems like there are a few options that address that gripe. Honestly, if some of the factory options were offered in a caliber other than .308 Win they might even be compelling. Though ubiquitous, it's never a caliber I've had any love for personally. I suppose that ultimately I'm just asking too much from the AR design and all the bulk/weight that goes with it. You're right in that I don't want a 20 lb gaming rig.

I know it's popular in certain corners of the internet to talk about how practical our 18-24 lb rigs are for general purpose use...typically with some assertions that only weak, lesser creatures would have any problem carrying that weight however far it needs carried. I've done, I've got the t-shirt and I think it's stupid unappealing to do that to yourself on purpose. It's just not my cup of tea, but anyone that wants to is welcome to.

LRRP - I've read your stuff here and elsewhere. I always appreciate the time/effort you put into your posts, analysis, etc. Watching your (daughter?) run a 12" 6.5G on steel at range was pretty cool.
 
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If you already have a 6.8 SPC, do you reload for it by chance?

Shoot the Berger 130gr Classic Hunters with G1 BC at .497 (not the .277” 130 VLD at .452) and you’ll have your reach right there. That will do most of what a .308 Win. will do in terms of hit probability and supersonic reach. You’ll want at least a 1/10” twist. Berger’s calculator says that even at 2350fps, it is stable with a 1/10 twist.

846190.jpg


Load it in PRI mags for a longer COL and more propellant, and you will have really close trajectory to 175gr SMK .308 Win. from the same barrel length.

It’s expensive to shoot at 52 cents per tip, but there you go. You’ll never have steel case support, but it is what it is.

That or find a company that you have more trust in and do another Grendel.
 
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If you shoot that .277” 130gr Berger Classic Hunter at 2400fps, you’re still supersonic out to 900yds at sea level. I used G7 drag model for that.

That’s about as close as you can get to 6.5 Grendel with the 6.8 SPC, with that particular Berger bullet. SSA used to have a warm load for it that only fit in PRI mags and certain rifles. I think they said don’t shoot it in the Barrett 468, but it’s been years since they’ve been bought by Nosler.
 
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You know, I haven't been satisfied with SSA of late. I was happy to shoot some of the old/original stuff. Not the SSA stuff I've fired/chrono'd lately. Very clearly running well below spec for pressure based on ejection. Does seem to group well at 100 yds, though.

MSv3 from my last range range outing.
SSA115 BTHP2377 fps53.5 fps SD
PPU115 BTHP2409 fps12.0 fps SD
S&B110 FMJ2591 fps14.5 fps SD
Hornady110 BTHP2593 fps9.3 fps SD

I shot the S&B V-max loaded stuff as well and the Hornady 120 SST...not sure where that data disappeared to. I did/do use the SST on Hogs... a .400 G1 is very, uh, "modest" for anything that's not a .223 or 6.8 SPC load, but at ~50 yards that's less significant. I'm trying to work up some 110 grain range ammo for my Dad...figure if I can get something that runs around 2600 fps with AA2200 I will call it good.

My upper is a 1:11 SPC II IIRC...not quite enough for the Berger.
 
You know, I haven't been satisfied with SSA of late. I was happy to shoot some of the old/original stuff. Not the SSA stuff I've fired/chrono'd lately. Very clearly running well below spec for pressure based on ejection. Does seem to group well at 100 yds, though.

MSv3 from my last range range outing.
SSA115 BTHP2377 fps53.5 fps SD
PPU115 BTHP2409 fps12.0 fps SD
S&B110 FMJ2591 fps14.5 fps SD
Hornady110 BTHP2593 fps9.3 fps SD

I shot the S&B V-max loaded stuff as well and the Hornady 120 SST...not sure where that data disappeared to. I did/do use the SST on Hogs... a .400 G1 is very, uh, "modest" for anything that's not a .223 or 6.8 SPC load, but at ~50 yards that's less significant. I'm trying to work up some 110 grain range ammo for my Dad...figure if I can get something that runs around 2600 fps with AA2200 I will call it good.

My upper is a 1:11 SPC II IIRC...not quite enough for the Berger.
Is that from a 16” barrel?

Hornady really did a lot with powder formulation to get the best velocities they could get with that cartridge. Interesting that theirs is the fastest and tightest SD for you.
 
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I tried to be a POF early adopter back when...must be like 15 years ago now or some such. I was ready to kick in the 2k or whatever at the time...just appealed to me more than LWRC I suppose (back when that was Leitner Wise and not Land Warfare). After 9 months with nothing heard, I grabbed up my deposit (made with a LGS, Dick's Gun Room, good people), and moved on. Glad to see they're doing well and moving product. I think I saw Lowlight throw them in the "quality gas gun" pile, which is a good sign.