Re: .284 win ar-10
toddcdozer...don't listen to the naysayers selling you things like...
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Larger diameter body of the 284 is going to create issues. </div></div>Nonsense. The WSM and SAUM operate just fine and that's substantially larger than the 284. Armalite and DPMS discontinued them because of the market...not because of any issues with the weapon.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Not worth the hassle and you'll not exceed what a 260 or 7-08 does without special gyrations</div></div>Nonsense. A modified or custom built bolt is the only specialization that is NECESSARY and any of the WSM or SAUM's will smash the 260 or 7-08 to shit in ballistics.
You may CHOOSE to run an adjustable gas block and/or an improved buffer spring...but it's not necessary. I do because I shoot suppressed.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">You can not run the really large capacity flat shooting magnums out of it and even the fast 6mm and 6.5mm need a long barrel and moderately reloaded ammo.</div></div>Of course you can, and 24" is plenty long enough, but 26" isn't unheard of. The ONLY issues you'll have are running bullets larger than 210 for the 300 SAUM, bullets larger than 168 for the 7mmSAUM and MAYBE 140s in the 6.5. All else should operate just peachy.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Guys who are hunting over 900 yards are shooting the Allen Magnums from Bolt guns. </div></div>Nonsense. Took my pronghorn at 930 with my 300 SAUM AR10 and will be doing the same with my late season white tail tag any day now. 190 VLDs at 2915 carry PLENTY of energy to take game beyond 1000.
Accuracy Systems will build you just about anything you want, and to my knowledge, they are the only ones CURRENTLY producing rifles chambered in WSM or SAUM. (besides RND Manufacturing but those aren't AR platforms)
For DEER at the range your projecting...I would have them build you a 7mm SAUM chambered to run 168gr VLDs at mag length. You'll have NO problem pushing them at the speed needed to kill at 1200 yds and if you decide to run a 26" barrel, you'll be able to push it MUCH farther than that.
My Armalite 300 SAUM is an absolute HAMMER and I've taken it out to a mile on 13" steel. That's just about the distance it starts to go subsonic, so that's as far as I've pushed it...but with 190 VLDs at 2915 fps, 1500 yds is well inside it's killing radius.
The only reason no commercial entities want to carry the magnum calibers anymore is because the market is too small. The only reason smaller custom shops won't do it is cause I don't believe anyone makes a bolt anymore, so they would have to resort to modifying .308 bolts.
I believe Accuracy Systems still has a supply. Call and ask Carl what he can do for you. I know they don't have the 7mm SAUM listed on their site, but the last time I checked, it was because factory ammo was to scarce.
If you reload, he'll build you whatever you want.
Here's my factory barreled Armalite 300 SAUM and initial load development with 3 different bullets
I'll be building a couple more uppers as well, probably a 7mm SAUM as well as a 6.5 SAUM, since I already have a magnum bolt to swap between uppers.
Here's some load development targets at 500, 700 and 800 yds