6.5 saum ar build....how?

[toddcdozer]

Looking at 2 options to build a 6.5 saum ar10.
I will use it for deer hunting out to 1k. My edge is just too heavy and I would like a semi for what I plan to do.
Option 1. Buy a 300 saum used from armalite dpms etc and change barrel.
option 2. Buy a new 260 and ream to 6.5 saum.
With option 1 I just need a barrel correct?
Option 2 I will need a mag and bolt only? With an adj gas block?
What is the best way to proceed? I fear the stock saums as most seem to be less accurate than what I need. I would like to acheive .5 MOA m/l at 100 and deer accuracy to 1k.
Also would it be best to buy a lower and then any ar10 upper and switch parts that way.? The 6.5 is the only ar10 combo I feel is a realistic 1k deer gun. And since I am userd to shooting a 300 tommy and 338 edge and 338 chey its hard for me to settle for a 300 saum or 7mm due to coal concerns in the mag + I like the 140 for multiple shots as I will have 40+ tags for dmap.
Thanks for the help Im just a long term bolt guy so I neeed the help.

 

[FCS]

Re: 6.5 saum ar build....how?

After doing a short mag AR, wouldn't do it again.
Mags are hard to find. Might be able to find the followers and make some 4 rd mags for the SAUM from 5 rd 308 mags.

Have to run a really long gas system if you don't want to nuke brass. Too much gas volume.

You don't get bolt gun performance, have to tone it down quite a bit.

6.5 Creedmoor is about ideal.
7-08 would be solid choice.

YMMV

 

[blksno]

Re: 6.5 saum ar build....how?

I asked a lot of the same questions you have here about a year ago.
My suggestion would be to buy used, and re-barrel. I know of one place that still will do a build, but they are spendy, and I know of another that has a 7mm WSM that is being released in the next couple weeks. They could potentially do one for you as well.

15 months ago, I was looking to build a 7mm SAUM and after a LONG search, decided it would be easier to just buy a used upper and re-barrel because finding a complete bolt is not easy.
I found a well priced Armalite 300SAUM and got a PRI adjustable gas block (I shoot suppressed).
The mag issue is non-existent with the Armalite, because their Gen II mags feed SAUM perfectly fine. Also, the factory barrel from Armalite was a 24" stainless with a 1:10 twist. Not something that you'd get from DPMS.
I DID find a place that had a bolt on hand, but trying to find an extractor was another issue. Neither Armalite, nor DPMS had one, nor did they have any info on where to get one.
Some research found a few gunsmiths willing to modify a .308 extractor but I wasn't yet sold.

I decided to test the 300 first, and I'm glad I did. Sub 1/2 at 100 with 3 different bullets as well as a few different charges. A VERY accurate factory rifle and so, I decided to just keep it as a 300 for now.

You're right about the 7mm being a mag length concern, but it's bullet specific. 7mm 180s at mag length will be tough, but a LOT of others will work just fine. With the 300, I have found the 185, 190 and 210 Berger VLD's loaded to mag length in an Armalite mag are excellent.
The 6.5 is going to be a lot more rough on your barrel, but you will have less issue with mag lengths.

After doing my load develpment at 100 and sending 2 shots to get a MV, I sent the next three to 1105 yds using Shooter, to verify.

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[PowerstrokeOBX]

Re: 6.5 saum ar build....how?

I just found a 300 SAUM here on the hide going to try and get GAP to rebarrel it to 6.5 SAUM.

McCourt what cartridge did you do? I'm guessing you didn't run an adjustable block?

 

[rideHPD]

I just found a 300 SAUM here on the hide going to try and get GAP to rebarrel it to 6.5 SAUM.

McCourt what cartridge did you do? I'm guessing you didn't run an adjustable block?

Let's pump some life back into this now that the 6.5 SAUM 4S is really catching on. Powerstroke, did you ever get GAP interested in this, or are there any plans for 6.5 SAUM GAP-10s?

 

[PowerstrokeOBX]

Let's pump some life back into this now that the 6.5 SAUM 4S is really catching on. Powerstroke, did you ever get GAP interested in this, or are there any plans for 6.5 SAUM GAP-10s?

I started tinkering with it and gave up and sold it. I had to scrounge to find a couple followers to fit in 308 mags. Followers only seemed to work in 5 rd metal mags. You could only fit 3-4 rds in the magazine. I really wanted to make a 10+ magazine out of a pmag but it didn't work. Someone with more know how could probably make it work. I'd also end up spending 2000-3000 on the gun and it may work beautiful or could have been a waste of money. Not a fun gamble. Also I'd hate to know the gun would probably eat up 3$ pieces of brass till it would run right.

For what I wanted to do the 6 Creedmoor worked very well .570ish BC at 3050. Yes a .570 BC at 3250 would work better but not worth the has at this time.

 

[PowerstrokeOBX]

6.5 saum ar build....how?

Oops

 

[rideHPD]

Gotcha PS, that brass really is pricey. Hopefully GAP will get it going down the road and set it up for a GAP-10. Would make a damn impressive package in a gas gun.

 

[PowerstrokeOBX]

6.5 saum ar build....how?

Yes it would. I'd be interested if they could get more than 7 rds in a mag.

 

[FCS]

6.5 SAUM in a gas gun is going to be nothing but a PITA.
300 and 7 SAUM / WSM in my experience you are already way overbore and port pressure/gas volume are working against you. 6.5 SAUM with even slower burn rate powders is going to be even worse. 2.800" OAL isn't helping either.

I've been wrong before and probably be wrong again but I'd be surprised if GAP ever plans to do GAP-10 in 6.5 SAUM.

I did a 300 WSM w/rebated rim. Does it work, yes. Was it a PITA? Yes, more so then I expected it to be. Would I ever do another SAUM/WSM on AR platform? Maybe but probably not. If I do, will be SAUM based as it is better fit then the WSM but I'd keep it 30 cal or bigger so I could run faster burn rate powders to keep port pressure and gas volume to a more reasonable level.

YMMV