25 CM AR10?

[ARlife4me]

Mine started as an Armalite 300 SAUM. Fed and functioned great, shot it out to a mile with 190 VLDs. (killed my antelope in 2012 at 931 yds) Sat on my shelf for a LONG time before i decided to rebarrel. Since i already had the Mag bolt head, it made sense to do a another one. I always wanted to do a 7 SAUM, but the bullets I want to use just aren't ideal in a 2.8 mag, so when the 6.5 PRC came up...it seemed like the obvious answer.

300 UltraSASS

2.800 is way to short for every short mag for sure, unless you're using the bottom 3 weights per caliber (mostly flat base). having both the 6.5prc and 7saum and true kac mags you could get out to 2.880" (with larue 2.865" is what i get). pmag m118's get just over 2.830 w/o mods. i based my 6.5 off the pmag and limited bullet weight to 135's (and lapua 144fmj's work great at that length). i sent my 3 dummy rounds that were 144fmj's @ 2.830" and throated +.100" for other possible projectiles. only shot 7 rounds of factory norma 143 golden target's that were factory oal'd @ 2.860". for the 7saum 168's are about the best for that length and maybe some 175's? 180 and up are seating deep.

1 good suggestion would be use an a5 buffer system (large frame rifle spring with ar15 adjustable carbine buffer). this way you have a wide range of buffering weight to adjust for against your loads. flatwire works just fine also. i know this combo works

 

[blksno]

2.800 is way to short for every short mag for sure, unless you're using the bottom 3 weights per caliber (mostly flat base). having both the 6.5prc and 7saum and true kac mags you could get out to 2.880" (with larue 2.865" is what i get). pmag m118's get just over 2.830 w/o mods. i based my 6.5 off the pmag and limited bullet weight to 135's (and lapua 144fmj's work great at that length). i sent my 3 dummy rounds that were 144fmj's @ 2.830" and throated +.100" for other possible projectiles. only shot 7 rounds of factory norma 143 golden target's that were factory oal'd @ 2.860". for the 7saum 168's are about the best for that length and maybe some 175's? 180 and up are seating deep.

1 good suggestion would be use an a5 buffer system (large frame rifle spring with ar15 adjustable carbine buffer). this way you have a wide range of buffering weight to adjust for against your loads. flatwire works just fine also. i know this combo works

I have both mine set up with A5 systems in a Magpul UBR stock...the 6.5 PRC has 3 tungsten, an orange Sprinco spring, a +2 gas tube, and the gas turned down to cycle smooth.
The 6.5 Creed has all the same but has 2 tungsten and 1 steel (IIRC) I should check.
I did notice, the 6.5 Creed cycles flawless, but the Armalite upper doesn't eject very well on slow mo. The brass deflector is almost like it's to big and doesn't let the case eject fully.
I'll have to see if I can put it on IG or something and upload the slow mo video clip

 

[ARlife4me]

I have both mine set up with A5 systems in a Magpul UBR stock...the 6.5 PRC has 3 tungsten, an orange Sprinco spring, a +2 gas tube, and the gas turned down to cycle smooth.
The 6.5 Creed has all the same but has 2 tungsten and 1 steel (IIRC) I should check.
I did notice, the 6.5 Creed cycles flawless, but the Armalite upper doesn't eject very well on slow mo. The brass deflector is almost like it's to big and doesn't let the case eject fully.
I'll have to see if I can put it on IG or something and upload the slow mo video clip

so, in the 300saum what buffer are you using to have 3 weights? never mind, i guess you have the a5 buffer. what does the 1 with the 3 tungstens weigh? i'm hoping to get buffer weight down to 4.5-5.5ozs. with it (my 6.5) ejecting at the 1-2 o'clock makes others think it's overgassed. it would be if the brass wasn't ejecting so close to me (within 3'). i have a 357sig that would do the same thing, cause the brake i had on was for a pcc. the weight of it delayed the ejection so much it ejected brass at my feet. removed the brake and it started ejecting them in the next county.

my goal on every ar is to have the lowest recoiling mass as possible. but even with the 9.5oz buffer with an 18oz bcg, the recoil is almost nil. recoil is delayed so much is why, but still doesn't function like i want it to.

 

[blksno]

6.5 PRC
7.65 oz

Don't know whT the 300 SAUM was. It was a 12" gas system, a standard AR10 Rifle buffer with a Tubb flat wire spring.

 

[blksno]

6.5 Creed is 5.85oz

 

[lyle2231]

Has anyone here built 1? I am contemplating what to build with an AR10 lower. I am a quarter bore fan, so a 25CM seems like an interesting option.

Do you like your build, are there better options?

My other thought for the build is 180* the other direction and to build a 12" 308 pistol!

I had a 6mm X 22-250 Armalite built years ago. Enjoyed shooting with it.
Good luck with your project!

 

[blksno]

Home build Matrix Aerospace Corp 6.5 Creed on top (pre cerakote) when it's "finished" it's gonna have OD green furnature and an M81 pattern

Armalite 6.5 PRC on bottom (pre cerakote)
When it's all t7ned, it's gonna be more of a desert tan flavor.

 

[ARlife4me]

Home build Matrix Aerospace Corp 6.5 Creed on top (pre cerakote) when it's "finished" it's gonna have OD green furnature and an M81 pattern

Armalite 6.5 PRC on bottom (pre cerakote)
When it's all t7ned, it's gonna be more of a desert tan flavor.
View attachment 630458

I have a few of their receiver sets, but the barrel nut threads are dpms instead of Armalite. So I have armalite cut receivers with dpms parts and gas system