AR 308 action calibers - why many times more is less and less ends up being more

[1stmarine]

I am not sure why people are trying to make the AR10 to shoot magnums and other high maintenance rounds.
This is to discuss what is available, what is not being used and why many of the current options end up being more than anyone would need for any reasonable purpose.

This is a quick list of the 308 and its offspring and other amazing rounds that work with this action. Please send anything you have tested and why is useful for you (purpose) even if
it is in bolt action but would fit the portfolio.

22-250
300 savage (parent of the 308 Winchester)
308 winchester (parent)
243 winchester
260 remington
6.5mm-308 *30
7mm-308 *30
7mm.08
338 federal
358 winchester

Same Bolt face
6mmBR (BR king)
6.5mm BR
6.5creedmore
6.5x47 lapua
7mm BR
30BR

etc..

Here is something "constructive" for someone with a nice AR10 type of action...
Left 6x47 lapua . Right 308winchester necked to 6.5mm with a 30 degree shoulder.
Both they are very good hunting as well as tactical rounds.

[BFL]

Don't forget the 22-250!

[LocoGringo]

Please educate me...why do you have an *30 next to 6.5mm-308 and 7mm-308? I thought the 7mm-08 was the .308 necked down to the 7mm and the same with the .260/6.5mm-308. Not trying to sidetrack the thread...just wanting more info.

[OdDuMet]

I got the bug to build something more powerful than my .556 & 6.8 ... just because ... if you know what I mean. I looked at all sort of wildcats & uncommon calibers that could be shoved into an AR-15 platform. At the end of the day, none of them were impressive enough ballistically to get me excited beyond my 6.8's ... or they had other serious issues like brass and/or component shortage or quality of specialized component concerns (.30 RAR & .300OSSM come to mind). My main application is deer and pigs, mostly pigs. If I had a light enough gun that would blow pigs in half like a gopher, that would be perfect to me, but....

After going round and round, I ended up building a .308. I did a lot of load & weight research. For me a 16" barrel is max, and I will prob end up with an SBR in the 13" range eventually with this gun since a supressor turns a 16" gun into a 23" gun. A magnum caliber with such a short barrel, even 16", didnt seem to make sense.

With a Ti can and a D-730 NV scope, I can make up the weight diff., possibly even lighter, than my 6.8 rig that I am perfectly happy with.

Looks like 3000 FPS from a 16" with a 125gr nosler Ballistic tip is very doable. A nice boost of 500 FPS over my 6.8 with a 16". I'll probably end up using 150's, but the 3000fps is a nice fun number.

I am still interested in some of the 6mm and .25cal options in the AR-15 platform though like the 6mm WOA (6.8 SPC to 6mm) or a .25 or .243 WSSM for a flat shooting varmint/coyote smacker. Those seem pretty viable from a technical standpoint, and get the benefit of the smaller platform.

[OdDuMet]

Don't forget the 22-250!

Speaking of this.... I read last night that Olympic has some sort of modified lower and mag that allows loading out to 2.4" in an AR-15 platform for a .22-250 gun they sell. Anyone know anything about this? I hear too many bad stories about Olympic to get real excited about it, but it sounds interesting no doubt.

[1stmarine]

Please educate me...why do you have an *30 next to 6.5mm-308 and 7mm-308? I thought the 7mm-08 was the .308 necked down to the 7mm and the same with the .260/6.5mm-308. Not trying to sidetrack the thread...just wanting more info.

Good question those are chambers that are very similar but the shoulder is 30 degrees. You also have 40 degrees and AI versions. I just picked those ones because they are easy to form (no fireforming neeed) and give the best performance.

[1stmarine]

Speaking of this.... I read last night that Olympic has some sort of modified lower and mag that allows loading out to 2.4" in an AR-15 platform for a .22-250 gun they sell. Anyone know anything about this? I hear too many bad stories about Olympic to get real excited about it, but it sounds interesting no doubt.

Yes they do. They also shoot a .30 caliber OSSM out of their WSSM receivers. I am currently working in a 300 savage to be shot from a AR15 reciever but unlike oly arms instead of radically change the reciever I radically change the feeding device (magazine) and the AR15 receiver remains standard.

[1stmarine]

I got the bug to build something more powerful than my .556 & 6.8 ... just because ... if you know what I mean. I looked at all sort of wildcats & uncommon calibers that could be shoved into an AR-15 platform. At the end of the day, none of them were impressive enough ballistically to get me excited beyond my 6.8's ... or they had other serious issues like brass and/or component shortage or quality of specialized component concerns (.30 RAR & .300OSSM come to mind). My main application is deer and pigs, mostly pigs. If I had a light enough gun that would blow pigs in half like a gopher, that would be perfect to me, but....

After going round and round, I ended up building a .308. I did a lot of load & weight research. For me a 16" barrel is max, and I will prob end up with an SBR in the 13" range eventually with this gun since a supressor turns a 16" gun into a 23" gun. A magnum caliber with such a short barrel, even 16", didnt seem to make sense.

With a Ti can and a D-730 NV scope, I can make up the weight diff., possibly even lighter, than my 6.8 rig that I am perfectly happy with.

Looks like 3000 FPS from a 16" with a 125gr nosler Ballistic tip is very doable. A nice boost of 500 FPS over my 6.8 with a 16". I'll probably end up using 150's, but the 3000fps is a nice fun number.

I am still interested in some of the 6mm and .25cal options in the AR-15 platform though like the 6mm WOA (6.8 SPC to 6mm) or a .25 or .243 WSSM for a flat shooting varmint/coyote smacker. Those seem pretty viable from a technical standpoint, and get the benefit of the smaller platform.

Nothing wrong with that approach. Also keep in mind that 16, 18 is not a huge difference. A 18" pipe with a short efficient brake is about the same as a 16" with some of those fancy brakes they sell today.
I am working with the 20" and 18" 6.8 ARP barrels and with the 120gr and 130gr loads power factor is brutal w/o getting into the red. So I cannot find many things the 6.8 cannot do in the real world.
But I get your point the 308w is the 308 so no worries there. Another development you might consider interesting is the 6.5BR. I had the LBC for a while but could not reproduce one single claim from AA on performance so I looked into another options. I even though about necking down the 30 RAR, that by itself is a pretty mighty little round but the complexities compounded along with new reamers, dies, etc... So I looked at the BR case and I was presently surprised to find out that AR15performance not only had some great bolts but they already had barrels reamed for the 6.5. The result (no surprise) is amazing. With 32 grains of powder I am putting a 6.5mm 120gr nosler BT out to 2807fps out of a 20" krieger 5R barrel . A little hot but not into the red. That to me is as good as it gets efficiency wise. If you look at the 6BR, 6.5x47, 30BR same thing. 101% efficiency is the name of the game. The consistency and strength of lapua with work champion barrels out of work champion cases, what else one could ask for from the little AR that could.

[1stmarine]

Don't forget the 22-250!

Thanks. Added! I am sure I am missing many others. I hope is not you in the picture cause I am having some palpitations.

[FLS]

Anything other than a 308, seems like a problem in need of a solution. It was designed to operate in a gas gun, so its optimum powders and projectiles work well. Is accurate, with affordable, easy to locate brass and bullets. It does everything pretty well. Plus its a hellva lot of fun at a match to get in a group of 5.56 shooters and start smackin steel. There is no doubt whose shooting major when you touch a compensated 308 off.