358 win in ar-10 idea am I on the correct path...

[CATTLEMAN]

I've been pondering a 358 win chambered AR-10 and would like a sanity check on the plan...

I want a ar-10 version of a 300blk ar-15 in that I can load it with PB cast boolits below 1600 fps and cheaply
(both ammo cost and the time savings of tumble lube and no gas checks) shoot. My only application for the rifle would be plinking / practice / recreation out to 200 yds.

I would need a pointy boolit some thing like a 360365 to make it feed easily. Any ideas for another design that would feed well?

I would want to shoot it at lower velocity and have it cycle. Using a subsonic 300blk ar as a guide. My current thought is that a faster twist barrel probably 1 in 10 due to the heavy boolit and low velocity with a short gas system probably carbine length and a barrel length of 18 to 20 inches. Am I on the correct path with this?

Am I overlooking anything or heading the wrong direction?

I would appreciate constructive feedback on the idea, before I start spending on this project.

[runfiverun]

you need gas volume to make an ar rifle work.
gas volume and low velocity aren't exactly compatible companions.
save yourself abut 1,000 bucks and work with a 308 bolt gun.

[C. Latch]

That's not a project I'd want to undertake. I might consider a .375 Reaper AR15, at most.

[dragon813gt]

You have the same idea I had. I'm waiting it out for more standardization in AR10s before I move forward. Gas volume will need to be tuned along w/ the buffer so I will let others be the guinea pigs

[bhn22]

Nobody seems to agree what the AR10 should be, so I wouldn't count much on things getting any more standardized. About half the AR10 type makes would have to go out of business first. The barrels on AR15s and AR10s are getting to be a pain now. S&W & Ruger seem to use proprietary barrel designs now in both receiver sizes. Look at some of the pics, the front sight mounting pins are on the top on some of them.

[garym1a2]

I would pick 308 ar10 instead. Lots more bullet choices, no need to make special brass. I have a 300 blackout, which does well with cast bullets in the 1700fps range and lower, but I rather have a lower twist rate to enable better velocity so range would be better.

[popper]

458 SOCOM or 300BO (does what you spec'd), maybe 7.62x40WT ( more powder space). AR10 is ~ 4# heavier.

[osteodoc08]

The 300 BLK will do what you want and if recreation out to 200 yards, I couldn't imagine anything better than the 300 BLK. It's pretty much standardize and getting ammo and supplies is cheap. You can also get a companion bolt fun gun in 300 BLK as well.

[CATTLEMAN]

I appreciate the input

I already have and love a 300blk in an ar-15 and have a bolt gun to shoot CBs so I agree with those comments. I have a lot of experience with tuning ar gas systems and loading to optimize gas volume for cycling at lower velocities so that is not a concern for me. It appears that the AR-10 style rifles are primarily grouped in the armalite pattern and the dpms pattern. I will pick one and stay with it so the standardization issue is not a concern for me. Looking at the ratio of case size between a 358 win and a 300 blk when loaded with mid 200 grain CBs it is obvious to me that the 358 is going to make a lot more gas even without optimization.

I want an AR-10 type rifle that is very very CB friendly.

I really want feedback on the chambering, boolit design, twist rate, barrel length and any issues I might have missed.

[Smoke4320]

Actually I don't think it will be as big an issues as most think .. Should feed easily out of a 308 Mag .. Adjustable gas block would be a great help in tuning
There are 338 AR , 300 mag AR's so a 358 is certainly doable
My 458 Socom AR is very cast friendly as well It shoots 300 to 500 grn bullets Very Well

[popper]

DPMS pattern is becoming the standard, small pins, AR15 fire control, etc. I have a 24" barrel I won't take into the field due to weight. Twist will depend on the length of boolit and fps. 140-150K RPM appears to work best, and what you can find available.
Light boolits will go 2200, heavies 2000. 308W is in the same range up to 200gr. boolits. My 308 feeds FP fine, the extra 0.5" may give you fits with normal feed ramps, like the BO - the hole is smaller.

[Blammer]

I would get the same twist that a 358 win uses.
You should be able to use a few different choices of projectiles, a pointy one like the 358365 is not going to be a MUST. RCBS 35 200 comes to mind as a good one.

Adjustable gas block would be a must in my book.

[AK4570]

I just can't think of a single thing to dislike about an AR10 in the lovely .358... The only downside I can think of is weight... I thought I had seen where someone (DPMS?) was building one in 338 Federal. Could be an off-the-shelf-option...

[beltfed]

FWIW, at one time, the Springfield Armory offered a 358 Win chambered M1A
Wanted one later, but that chambering was discontinued.
So I have to be happy with my 358W bolt gun- 250 gr PPed 358318 at 2350 out of 24" barrel.
Kills deer real well, and little bloodshot meat.
beltfed/arnie

[bhn22]

JD Jones also designed a full line of Whisper cartridges for the 308 platform too. There are some really interesting designs out there.

[Pilgrim]

I am damn near ignorant when it comes to the ar rifles. That being said, I am studying up on available AR-10's but have only found DPMS offering the 24" barrel. Everybody else seems to be stuck at 16" and a few seem to offer 1 version with a 20" barrel. I wish I understood why the short barrels. I don't think we are going house to house hunting the liberals yet, so why the fixation on short tubes is beyond me. I guess I'm just weird as muzzle blast from a 16" tube would be too painful for me. I'd be happy with a 22" or 24" barrel, but am amazed that all of the rifles with tubes over 16" seem to be 10# to 11#+ in weight! Why can't they produce a barrel with a lighter contour? I like lighter rifles but had my BLR rebarreled with a medium contour 22" barrel. Is it heavier than the 18.5" skinny barrel Browning put on it? Hell yes. But it also holds offhand much better. Muzzle blast is significantly reduced and recoil is also reduced. I ain't no kid so packing more weight is a big deal to me, but the trade-offs to get the longer - heavier barrel far outweigh the negatives. Anyway...I heard/read about a fellow up in Alaska with an AR-10 in .358. He loves it. Based on the .308 case, I'd guess a .358 is probably just a different barrel, but where we'd find one is not obvious to me as of yet. FWIW....Pilgrim

[popper]

A lot of reports show the 16 is as accurate as the 24 but the 24 will give higher fps. Pencil barrels are OK but? 338 is 308 brass, 358 isn't. 338 whisper (?) 2700 fps is quiet?) is 444 brass.

[bhn22]

338 Whisper should be 7BR cases. 338 Whisper #2 should be on 221 cases.

http://sskindustries.com/cartridges/

[MarkP]

I did see an AR-10 in 338 Federal at a LGS.

[dkf]

You can get an AR-10 barrel in .358win. http://ar10barrels.com/calibers.shtml Drill the gas port out in small increments until you get reliable cycling with lower power loads you want to shoot.