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Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

slm9s

Sergeant
Full Member
Minuteman
Aug 18, 2008
780
72
WA
Looking to buy a high-end semiauto for "precision plinking" out to mainly 600, occasionally to 1000. Thinking of the GAP-10 but haven't decided completely. Would like input on what others have chosen theirs to be chambered in. 308 would have the most available ammo, but I reload anyway so it doesn't matter. 308 would have the easiest time being resold, though hopefully I'll enjoy shooting this rifle and own it for a long time. From my limited understanding the 260 has better ballistics and a little less recoil. And the 6.5 Creedmore has similar ballistics but longer bullets can be used. Can others chime in? Can owners of the gap-10 chime in as well as owners of other platforms? I know this has been discussed before, but the gap-10 hasn't been out long so I'm wondering what recent purchasers decided and how it turned out.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

If you reload, .260 if you want to use Lapua brass, Creedmore if you don't care about brass. If you don't reload, .308. The 6.5's win past 800yds, but you could get there with a .308 as well.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USACS</div><div class="ubbcode-body">I would say .308. Go with something that is more common. If you don't reload, or you reload and you happen to not have any rounds on-hand and want to go shooting, sourcing .308 ammo is the easiest. I've found .308 ammo at gas stations. </div></div>

My thoughts exactly. The .308 round will do anything I want or need it to do inside a thousand yards and the availability of ammo makes it a very attractive round, whether reloading or not.

Yes, I know there are many who have pushed it beyond 1000yds that but realistically, there will never come a time when I will need to make a 1000yd shot whether it be for hunting, competition, or the fabled 'SHTF' scenario.

With such a variety of different bullet weights, the .308 is good for hunting anything you'll find short of the African safari.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FCS</div><div class="ubbcode-body">6 Creedmoor</div></div> Exactly what I'm thinking of running for my next build. I've been at a toss-up between it and .260, but I believe the 6CM will be it. Barrel getting ordered next month.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GAP10</div><div class="ubbcode-body">I like the .308 but take a look at this GAP-10 thread.

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2814921&page=1</div></div>

I saw that, but first wouldn't the barrel life be pretty short with the 6cm? And second, I just feel that a 6mm isn't that much bigger than the 5.56. I'd rather go at least 6.5mm if I'm stepping up to an AR10 size rifle. I know that it doesn't make much logical sense, it is just what I want.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The Punisher</div><div class="ubbcode-body">My vote is for the 260 Rem, I have a dpms and with140 smk its a sweet shooter!</div></div>

One of the "advantages" of the 6.5CM is the ability to load the longer bullets and still feed from the mag. Is it actually a problem with the 260? Having to seat the heavy bullets deep into the case? Or is this just theoretical and doesn't show up in the real world?
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KillShot</div><div class="ubbcode-body">

My thoughts exactly. The .308 round will do anything I want or need it to do inside a thousand yards and the availability of ammo makes it a very attractive round, whether reloading or not.
</div></div>

I won't use this for hunting, plenty of rifles for that. This will be for shooting small groups and steel at 200 (my local range) to hopefully 1000.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

Since you reload ammo cost is pretty moot, so I think it depends on barrel length. The .308 is more efficient out of a shorter barrel than either of the .264's (.308 is hardly efficient though). If you want a barrel less than 20" you should go .308, if not you should go with one of the .264's. Any of them will get you to a thousand---the .264's will do it more reliably, especially in the wind.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

I reload the GAP 10 in 308 with 155 scenars. It is pretty accurate out to 1000 yds. I plan to purchase another upper in the much heralded 6 CM one day
I wished I would have got the rifle initially chambered in 260 rem. The 308 has it's inherent drawbacks if you shoot long range.
 
Re: Which cartridge in semi-auto 308 vs 260 vs 6.5CM?

I have all three. All are DPMS.

I would have to agree that if you do not reload you should go with the 308. 260 ammo is just too damn expensive and can be hard to find. 6.5 CM ammo is pretty reasonably priced but you have to buy a bunch of it when it is available because it is frequently out of stock.

If you do reload (or plan to), I would recommend the 6.5 CM. At mag length, the 260 doesn't get you any more velocity than the CM does. Additionally, I and several others have experienced port pressure problems with the 260. I had to put an adjustable gas block on mine to get it under control.