I'm still confused on the M4 feedramp thing when directly related to 6.8.  (I've read Bigbore's excellent thread for the 5.56, so I'm good there)

I have read on this board from some people who SUGGEST the 6.8 SPC may have feed/reliability issues unless M4 ramps are used, but never a definitive word from anyone that I consider to be knowledgeable on the subject.

SO, I'd love to hear from someone with experience (like Zak) on this one...  I've got the $$$, and I'm so ready to buy a barrel and bolt, but here's the problem.

I'm trying hard to decide between the brand new GTS recon in 6.8, waiting for CMMG to have a medium contoured 6.8, or having Randall make me an 18" barrel.  All of them (except I'm not sure about Randalls, but I have e-mailed him) DO have M4 ramps.

The RRA upper I have doesn't have M4 cuts.  

I'd hate to sell my upper at a loss just to purchase one with cuts if I don't absolutely need to, and I'm not dremmelling my upper.

My options:

Sell my upper and buy another CMT from GTS.
Wait for a barrel without M4 cuts (IF the 6.8 can work reliably without them)

I have a CMMG 14.5" mid with M4 ramp installed on a CMT upper with M4 cuts, so I guess I COULD swap that barrel over to the RRA barrel and then use the CMT for the 6.8.  I just really like having the right parts for the job.  M4 ramps in a non-M4 upper (to me) seems mismatched, but I guess if it didn't cause me problems...  

Input MOST appreciated.  Thanks

Sell the upper, get a new one from Denny and start with virgin parts. This is 6.8....$30 will buy you like 40 rounds...... Or save the upper for a retro build. Then you'll spend more money but won't feel hard done.

$30 bucks is less than 1 mag.

Simon

OK, here is where I am coming from with my answer.  First of all none of my rifles see any use other than punching paper so SHTF scenarios are out of the question.
When I had CMMG do my pistol upper build it arrived with Dremmelled M4 feed ramps.  Thousands of rounds later it shows no wear on the ramps what so ever and I could not be happier.
Then I did a 6.8 build on DPMS parts.
The round feeding from the left side of the magzine would hit below the feed ramp if the cartridge was all the forward in the mag and it would hang up, which was about 50% of the time.
So I Dremmelled in some feed ramps like the pistol has.  Worked much better but once in a while, again from the left side only, a round would hang up jamming into the upper right below the feed ramp.  Then it hit me, why take the feed ramp to the bullet when a little work on the PRI mag lips with smooth jawed duck-bill pliars would take the bullet to the feed ramp?  I bent the left side feed lip up some which raised the bullet's nose and presto, no more jamming.
Problem solved once and for all.
(see, I was too quick to think it was the DPMS barrel and upper that was the problem and not possibly the 3 PRI mags I have)
Do I wish I had thought of altering the mag lips before I Dremelled the feed ramps in?  Sort of.
Am I the least bit concerned about it?  No.
Do I care if the exposed aluminum of the upper ever scratches up? Not in the least so long as it feeds and it feeds as smooth as a puppy's nose now.

Thanks for the replies...

Makes sense big-bore, thanks for the tip.

Simon - It isn't about "the money" exactly, it's the principal.  I don't want to spend money I don't need to spend just because of the "latest thing".  If it's neccessary, then I'll do it.

Also, for some reason, the CMT upper I just got fits SO tight on my RRA lower I had push very hard to get them together.  Then I had to prop the magwell over my knee and push REALLY hard to get them apart again.  I was actually concerned that I was going to break the stock.

The RRA upper fits like a glove on the RRA lower, and I'd hate to give that up if I didn't absolutely have to.