6.5 CM differences

[HavasuMike]

I finished my first 308ar recently and I'm quite happy with it.  It took my quite a while to build.since I'm a novice and had to do a lot of reading.  It was a struggle but thanks to you guys and some other blogs,  i got through it.  Now I would like to build a 6.5 CM upper.  What parts are different from the 308?  What parts are the same?  My 308 is a DPMS style and I am assuming that an upper will go right on the 308 lower.

[EngrBob]

1 hour ago, HavasuMike said:

I finished my first 308ar recently and I'm quite happy with it.  It took my quite a while to build.since I'm a novice and had to do a lot of reading.  It was a struggle but thanks to you guys and some other blogs,  i got through it.  Now I would like to build a 6.5 CM upper.  What parts are different from the 308?  What parts are the same?  My 308 is a DPMS style and I am assuming that an upper will go right on the 308 lower.

The barrel is different.  Everything else is the same.

[Robocop1051]

There are a few specific 6.5 muzzle devices, but they're all generally threaded 5/8x24, so you can still use a .308 size if you'd like. 

The 6.5 Creedmoor and the .308 are only about .001 off in measurements. The BCG's are interchangeable. 

This goes for .260 Remington too

[D.R.D.]

The folks over at Proof Research and JP seem to feel that it's best to use a "high pressure" bolt with the 6.5CM.  Proof, has also come out with an extended length gas system barrel which included the gas tube to accommodate the pressures for the 6.5

[D.R.D.]

This is my 6.5 upper plan.  So far, I've got the receiver.

6.5 Creedmoor AR Upper

• SI-Defense Billet .308 Upper Receiver                                                               
• Falkor upper parts (port cover, spring, forward assist)                                        
• Odin Works 15.5” M-Lok DPMS High (.210) Handguard                                        
• 24” Proof Research Extended-Length 416 SS 4-groove .875 with gas tube          
• Falkor High Pressure BCG                                                                                
• Mega Arms Slide Lock Charging Handle                                                                 
• PRI (.875) Adj. Lo-pro Gas Block                                                                 
• Nathan Wright’s 3-port Beast Brake (.875)       

 

Edited May 26, 2017 by D.R.D.

[HavasuMike]

Thanks for the info.  It will be valuable.  Are the magazines the same?

[D.R.D.]

Yes,  As long as the OAL of the round fits and chambers, a 7.62 PMAG or the like will work for 6.5CM.

[HotRod308]

 just removed a 6.5 CM barrel, 24 inches made by DPMS - 8.5 twist. Probably has some 2,000 -2500 rounds through it, 50$ and it's yours. If your interested in it.

[HavasuMike]

Thanks for the offer, but not quite ready to get started yet.  Is the 8.5 twist the most common twist rate?

[D.R.D.]

1:8

[HavasuMike]

Can you use the same buffer and spring?

[D.R.D.]

Yup.  Just want to be sure you've got an adjustable gas block to tweak as needed.

[Big Ironfoot]

I am also building a 6.5 upper, trying to choose a adjustable gas block now. I have the Ballistic Advantage 22" barrel. Need a .936 block. Any suggestions, as I have never used one before. 

[jtallen83]

SLR, I have had good luck with them.

http://slrrifleworks.com/index.php?route=product/category&path=57_103_168_105

[Matt.Cross]

I 2nd SLR, they are great gas blocks.

[Big Ironfoot]

Well learned a lesson today. Don't assume anything when ordering parts in AR308 format. I purchased a DPMS a couple months ago, the rifle was purchased from a friend who had only had it a few months, and he purchased new. So I assumed it was a Gen 2. WRONG

So the upper I bought won't fit. Big decision to make, send back and start over with finding Gen 1 upper in 6.5 or build a lower!!!!

Ordered Aero Precision stripped lower to match my upper. Ordered A2 buffer tube, David Tubb buffer Spring, and buffer for rifle length gas system, Magpul PRS stock. Standard lower kit, and Magpul MOE grip.

Should be here by the end of the week. Am so excited about this build. I just hope I get it right this time.

[392heminut]

Keep everything and build more rifles!

[Big Ironfoot]

Thanks to all, I have ordered the SENTRY 9 SET SCREW ADJUSTABLE GAS BLOCK. I am so anticipating the completion of this build