BigNate Posted July 29, 2021 Report Share Posted July 29, 2021 In digging through Raley's tech corner I stumbled on a document titled: TECH NOTE 61 ERRATA SHEET FOR AR-10(T) ULTRA MAGNUM 110404 REV 1.pdf in his Tech Notes #5 thread. Has anyone actually shot one of these? What about "buildable" AR-10s in other faster / flatter cartridges? I've been doing some homework on the platform and have been looking into a variety of cartridge options for things that are faster and flatter than the 7.62X51 - so this really caught my eye and the idea of an AR-10 in .300 SAUM gives me (in the words of James May) "the fizz." I had been looking at whether it might be feasible to build a new platform AR-10 in 6.5 PRC but COAL for match bullets looks to be much too long (2.950). So - mostly a pipe dream - but hey - a fella can dream. Quote Link to comment Share on other sites More sharing options...
Sisco Posted July 29, 2021 Report Share Posted July 29, 2021 A James May fan? You have to talk with ARTrooper, He wants to build a short action AR magnum. I think they did have an AR10 in 260 Remington for a short time that The Army Marksmanship Unit worked on with them for Camp Perry rifle matches. I contacted Armalite about it but they never got back to me. I thought about doing a rebarrel of an AR10 with a 260 barrel but got turned off by the price of a AR10 compatible 260 Remington barrel. Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted July 30, 2021 Report Share Posted July 30, 2021 @98Z5V has a 260 Remington. Quote Link to comment Share on other sites More sharing options...
Sisco Posted July 30, 2021 Report Share Posted July 30, 2021 45 minutes ago, Armed Eye Doc said: @98Z5V has a 260 Remington. So does Trooper and Unforgiven, but they are DPMS pattern, not Armalite. Quote Link to comment Share on other sites More sharing options...
BigNate Posted July 30, 2021 Author Report Share Posted July 30, 2021 Thanks gents…. If / when I do this I’ll probably do this as a new build. I picked up a bare Aero M5 lower that I plan to do something with one of these days. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted July 30, 2021 Report Share Posted July 30, 2021 You have a few options for a "better cartridge than .308 Win", if flatter shooting over long range is the goal. I will say - and you'll shoot it someday - my .308 Win-shooting Mk11 build is a bad bastard, running those Hornady 178 ELD-X projectiles. That thing delivers the mail!... I have a .260 Rem build that blows that Mk11 away, though - the thing is just a laser. Other options are 6.5 Creedmoor, 7mm-08, .243 Win. Those are all know, proven performers that out-pace the .308 Win cartridge. Furthest I've had the .260 out to is 1200 yards. I have a .243 Win bolt gun, but that's kinda cheating, with a 26" heavy barrel. Then you look at that list of cartridges - they all started from Wildcats, that someone came up with, that they made work from a .308 Win parent case - well, except for that weirdo fucker the 6.5 Creedmoor. That didn't come from a .308 Win case. They all, though, beat out most .308 Win loads at distance, when you're playing the long distance game. For other weird AR calibers, I've got a .338 Federal, and that thing HITS some steel! I have a .358 Winchester that I haven't fully finished up yet, but it's 90% right now. The GUN is done. I need to build ammo to shoot through it. It's gonna be a THUMPER. Not a long-distance gun (neither of those two are), but they'll deliver some foot/pounds of energy onto what they hit. Quote Link to comment Share on other sites More sharing options...
ARTrooper Posted July 30, 2021 Report Share Posted July 30, 2021 https://www.kakindustry.com/lr-308-parts/magnum/kak-300-wsm-complete-19in-magnum-upper-w-m-lok Kak makes BCGs and uppers, and other parts just for the Winchester Short Magnum calibers. Sadly they only offer the .300 wsm complete upper. the difference is kinda like running a 6.5 grendel in an AR15; need a difference size bolt because of the wider case diameter, and they added another extractor to help with reliability. I am not sure if this is necessary, but the added bolt face area is. also, just like with the grendel, the wider case body to these Short Magnums create feeding issues in magazines. I have seen review of bulging in mags with to much loaded in. Best results seem to come from lancer mags, aluminum mags, or 10 round mags. And it took me a while to figure this out, but from what I can tell, KAK’s upper has a larger cut ejection port for ejecting the larger size cases. At first I was worried about getting these Winchester short magnums to fit in standard 308ar mags, so I played around at several of my local gun stores and have been able to get several 270 wsm and 300 wsm factory loads to fit in the mags. sadly 300 wsm is over $4.00 a round right now, 270 wsm is over $2.50 a round, and 7mm wsm is over $2.00 a round. oh and barrels seem to be impossible to find so would have to more than likely go custom. I plan on doing a 270 wsm hopefully within the next year or two because I like how flat it shoots and it has lower recoil than the other short magnums. Plus 270 wsm has grown in popularity around me for taking deer and pre Covid was getting more common in the stores. And 270 bullets are are one of the more common ones thanks to the decades of popularity of the 270 Winchester. My whole point of wanting one is for big game at those 300+ yard shots. Which in my area isn’t that uncommon. Flatter shooting and more energy in target creates a more humane kill. If I was just shooting steel out to 1000 yards, I would just use my 260 Remington. Quote Link to comment Share on other sites More sharing options...
392heminut Posted July 30, 2021 Report Share Posted July 30, 2021 9 hours ago, ARTrooper said: https://www.kakindustry.com/lr-308-parts/magnum/kak-300-wsm-complete-19in-magnum-upper-w-m-lok they added another extractor to help with reliability. How does that work? Are you sure you didn't mean two EJECTORS? Quote Link to comment Share on other sites More sharing options...
ARTrooper Posted July 31, 2021 Report Share Posted July 31, 2021 4 hours ago, 392heminut said: How does that work? Are you sure you didn't mean two EJECTORS? Yes you are correct, my mistake. Quote Link to comment Share on other sites More sharing options...
BigNate Posted August 2, 2021 Author Report Share Posted August 2, 2021 On 7/29/2021 at 8:52 PM, 98Z5V said: You have a few options for a "better cartridge than .308 Win", if flatter shooting over long range is the goal. I will say - and you'll shoot it someday - my .308 Win-shooting Mk11 build is a bad bastard, running those Hornady 178 ELD-X projectiles. That thing delivers the mail!... I have a .260 Rem build that blows that Mk11 away, though - the thing is just a laser. Other options are 6.5 Creedmoor, 7mm-08, .243 Win. Those are all know, proven performers that out-pace the .308 Win cartridge. Furthest I've had the .260 out to is 1200 yards. I have a .243 Win bolt gun, but that's kinda cheating, with a 26" heavy barrel. Then you look at that list of cartridges - they all started from Wildcats, that someone came up with, that they made work from a .308 Win parent case - well, except for that weirdo fucker the 6.5 Creedmoor. That didn't come from a .308 Win case. They all, though, beat out most .308 Win loads at distance, when you're playing the long distance game. For other weird AR calibers, I've got a .338 Federal, and that thing HITS some steel! I have a .358 Winchester that I haven't fully finished up yet, but it's 90% right now. The GUN is done. I need to build ammo to shoot through it. It's gonna be a THUMPER. Not a long-distance gun (neither of those two are), but they'll deliver some foot/pounds of energy onto what they hit. Thanks 98Z - Interesting set of options. As I'm chewing on this I'm pretty convinced that I want to go with a round that does not dramatically lower round count per magazine. It seems odd to see .243 there - just because my only experience with that cartridge is a single-shot breech-break youth gun that I bought for my kids. Funny how you get a stereotype in your head around a cartridge from something like that. I found this article: https://www.accurateshooter.com/cartridge-guides/243win/ that includes a pretty glowing review of the cartridge (for bolt gun precision shooting). I guess I should give it a look as well. Quote Link to comment Share on other sites More sharing options...
BigNate Posted August 2, 2021 Author Report Share Posted August 2, 2021 On 7/30/2021 at 6:35 AM, ARTrooper said: My whole point of wanting one is for big game at those 300+ yard shots. Which in my area isn’t that uncommon. Flatter shooting and more energy in target creates a more humane kill. If I was just shooting steel out to 1000 yards, I would just use my 260 Remington. I think I'm coming to the same sort of conclusion... I doubt I'd ever hunt anything with an AR-10 platform gun. Not that you can't - just that IMHO the strengths of that platform lie elsewhere. OK - well - I guess if I were to move to TX and get into hog hunting I could see a build for that purpose - but today I don't live in TX, and I'm not hunting anything here where a semi-auto rifle would be the right tool. So - as a paper / steel gun - I'm coming to the conclusion that the juice (fastest / flattest available cartridge) in the WSM / SAUM / etc. space probably ain't worth the squeeze (reduced magazine capacity, cartridge cost, etc.). Thanks again for the good info. The fat cases and reduced capacity are taking the WSM stuff out of consideration. For game at longer range the simple old bolt .300 WM is the ticket for me. Quote Link to comment Share on other sites More sharing options...
ARTrooper Posted August 2, 2021 Report Share Posted August 2, 2021 8 minutes ago, BigNate said: I think I'm coming to the same sort of conclusion... I doubt I'd ever hunt anything with an AR-10 platform gun. Not that you can't - just that IMHO the strengths of that platform lie elsewhere. OK - well - I guess if I were to move to TX and get into hog hunting I could see a build for that purpose - but today I don't live in TX, and I'm not hunting anything here where a semi-auto rifle would be the right tool. So - as a paper / steel gun - I'm coming to the conclusion that the juice (fastest / flattest available cartridge) in the WSM / SAUM / etc. space probably ain't worth the squeeze (reduced magazine capacity, cartridge cost, etc.). Thanks again for the good info. The fat cases and reduced capacity are taking the WSM stuff out of consideration. For game at longer range the simple old bolt .300 WM is the ticket for me. Sounds like you can’t go wrong than with 6.5 creedmoor or .260 Remington. as for me, I tell everyone that questions me about hunting with a 308ar, “1 bullet is for the deer, the other 24 are for the crazies out there on two legs.” After all, Wisconsin did have a several hunters murdered over a trespassing incident years ago and when I was a kid we had permission to pull a deer out through some private property at noon and when we did we ended up in a stand off with other hunters that were given permission to hunt there. Cops were called and things were worked out, but still it was a stressful 10 min or so. But I have never had to shoot a deer with my .260 or .300 blk with more than one round from a large magazine. Quote Link to comment Share on other sites More sharing options...
BigNate Posted August 2, 2021 Author Report Share Posted August 2, 2021 Certainly not saying that you "can't" hunt with your AR-10. Just saying that I'm old, fat, out of shape, and the AR-10(T) with a 37 oz scope, bipod, and PRS buttstock on it probably weighs 18 lbs. I have enough trouble hauling my fat butt up the hill without carrying something that feels heavier than the M-60 that I lugged around in my youth. LOL. Now - I do agree with you that for protection from the 2 legged critters - things with many many rounds and lots of knock down are the happy spot... If I could take only one gun with me into the wilderness for defense and game gettin' - it would probably be my M1A. It's lighter than the heavy barrel AR-10(T), has enough umph to knock down the odd elk or "slow movin' elk (cattle... 😛 )around me, has enough range to let me stand off of things that might be looking for me, and over the years I've come to trust that it will go bang every time I pull the trigger (not that others won't - just that I know this one inside and out and it has earned my trust). 🙂 Quote Link to comment Share on other sites More sharing options...
Lonewolf McQuade Posted August 2, 2021 Report Share Posted August 2, 2021 4 minutes ago, BigNate said: Certainly not saying that you "can't" hunt with your AR-10. Just saying that I'm old, fat, out of shape, and the AR-10(T) with a 37 oz scope, bipod, and PRS buttstock on it probably weighs 18 lbs. I have enough trouble hauling my fat butt up the hill without carrying something that feels heavier than the M-60 that I lugged around in my youth. LOL You just need to weld a rotating turret on the front of a quad to mount the AR10 & you'll be good 👍 Quote Link to comment Share on other sites More sharing options...
ARTrooper Posted August 2, 2021 Report Share Posted August 2, 2021 2 hours ago, BigNate said: Certainly not saying that you "can't" hunt with your AR-10. Just saying that I'm old, fat, out of shape, and the AR-10(T) with a 37 oz scope, bipod, and PRS buttstock on it probably weighs 18 lbs. I have enough trouble hauling my fat butt up the hill without carrying something that feels heavier than the M-60 that I lugged around in my youth. LOL. I was a machine gunner a decade ago in Afghanistan, I know what you mean. But you should be able to build a long range 308ar at 12-14 pounds with scope. I went with a modified bull barrel on mine and that is the one thing I would change. I would go more for a gunner barrel. The rare few can even get down to 10 pounds. but the M1A is a great rifle, I would love to have one for the history of it. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted August 3, 2021 Report Share Posted August 3, 2021 @BigNate, you brought up something that reinforced the cartridges I listed... Reduced capacity in the magazine, compared to .308 Win capacity. If you build off a .308 Win parent case, the capacity stays exactly the same... It's the same case, just necked down... And that weirdo 6.5 creedmoor bastard is still 20 rounds in the 20-rd mag, too. .260 Rem is the TICKET, man. Those .264" projectiles are magic, but the real question is... is that something that you want to reload? Finding ammo is NOT really an option, because all the commercial offerings were for hunting, in a bolt gun. Reloading it is easy, if you're already reloading. After you size it down, you'll have to turn the neck diameter down, but I can tell you the exact tool that you'll need, and where to walk in and buy it locally. KM Precision neck turning tool from Bruno's. If you don't want to reload for it, then 6.5 Creedmoor is the obvious choice - TONS of good gas-gun ammo produced by manufacturers. Quote Link to comment Share on other sites More sharing options...
1Gun Posted September 24, 2021 Report Share Posted September 24, 2021 Just finished a build on an SR-25 in 300RSAUM and it weighs in at 12.2 pounds with everything on it. Running PSR stock, kak bcg, kak mag upper, 24" carbon fiber barrel semi bull 1:10, Vortex HSLR scope, 17.5" handguard, magpul Bipod, seeker precision gas block Quote Link to comment Share on other sites More sharing options...
BigNate Posted September 24, 2021 Author Report Share Posted September 24, 2021 19 hours ago, 1Gun said: Just finished a build on an SR-25 in 300RSAUM and it weighs in at 12.2 pounds with everything on it. Running PSR stock, kak bcg, kak mag upper, 24" carbon fiber barrel semi bull 1:10, Vortex HSLR scope, 17.5" handguard, magpul Bipod, seeker precision gas block Very cool! This post needs some video! 🙂 Quote Link to comment Share on other sites More sharing options...
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