6.5 CM to .260 AI question

[omega1]

Hello. I am hoping with the wealth of knowledge on this site someone already has the answer to my question. My plan is to take a Ruger American 6.5 CM and have the chamber recut to .260 Ackley Improved. If I'm thinking correctly since the barrel on the Ruger is attached and headspaced with a barrel nut this should be a relatively easy job for a good gunsmith. I know some people will ask "why?" but much of the pleasure I get from this hobby is experimenting with the possibilities.
Thanks for any help.

 

[codyadams]

So what is your question exactly?

If it is will it work, then yep, it will, and it will be pretty easy as well. I really like my .260 AI as well. 140 class bullets well over 3000 fps, and also I only trimmed my lapua brass once in 12 fireings.

 

[omega1]

Thanks for the reply. I guess I should have been clearer on my question. I was wondering if a .260 AI reamer would totally clean up a 6.5 CM chamber? Since you don't have to deal with a shoulder on the Ruger American barrel I was hoping it would be a simple job. I am familiar with the. 260 AI as I've owned one for several years and love it. It's just that it weighs about 13-14 lbs and not practical as a hunting rifle.

 

[Edd]

...........I was wondering if a .260 AI reamer would totally clean up a 6.5 CM chamber? .......

It depends on the exact specs of the reamer. Unless you have a custom reamer made, there is a better than average chance a 260AI reamer will not clean up a Creedmoor chamber.

 

[omega1]

My idea is to use a .260 ackley improved reamer and was thinking since a Ruger American headspaces in the same manner as a Savage (with a barrel nut) that I could actually run the reamer in just a hair further past the existing chamber shoulder and still have no issue setting the proper headspace. Am I correct in this assumption?

 

[Edd]

My idea is to use a .260 ackley improved reamer and was thinking since a Ruger American headspaces in the same manner as a Savage (with a barrel nut) that I could actually run the reamer in just a hair further past the existing chamber shoulder and still have no issue setting the proper headspace. Am I correct in this assumption?

Yes, you can ream it with a 260AI reamer and set the headspace without issue.

 

[omega1]

Thanks for the confirmation. Made sense to me but I wanted some feedback before I commit to this project

 

[98dyna]

The early Ruger American 6.5(retail) and .260(dealer samples) rifles, some had a deep throat/magazine problem. The throat was to deep and the magazine was short (a gunsmith on YouTube has a video on the reamer spec problem). To fit the magazine with an 140 ELD-X I had .190 bullet jump, wouldn't group. Use a 140 Interloc(big ogive difference) and we're talking 3 shot .400 groups. Research this and make sure you get the correct chamber.

 

[omega1]

Thanks for the information i had not heard that. I'm going to use the Ruger American model that takes the AICS spec magazine. Hopefully I can avoid some potential problems this way.

 

[MNbogboy]

Having rechambered several 6.5/257 Bob AIs from 260s I know dimensionally yours will clean up because you will be totally going past the original CM shoulder and the Ackley shoulder is larger diameter. I have also gone the other way and chambered the CM in 260s but setback is required. No problem with "nutted" barrels.
The biggest hurdle depending on the original barrel condition and shot count may be firecracking & "hard spots" that the reamer won't like.
My .02
Edit: upon further research it appears the Ackley does not have larger shoulder diameter and will not clean up creedmoor without some barrel setback.

 

[omega1]

Perfect! Thanks MNbogboy. That was exactly the information I was hoping to hear.

 

[osok-1k]

I would go with the 260AI as well, especially since you already have what you need for that cartridge. I just picked up a very nice Pierce/Obermeyer/Jewel/ custom Fclass stocked complete rifle in 6.5x55AI. I'm going to sell my 6.5 Creedmoor (pictured) as soon as I take some good photos I'll post it in classified with a full description.

 

[Edd]

Having rechambered several 6.5/257 Bob AIs from 260s I know dimensionally yours will clean up because you will be totally going past the original CM shoulder and the Ackley shoulder is larger diameter. I have also gone the other way and chambered the CM in 260s but setback is required. No problem with "nutted" barrels.
The biggest hurdle depending on the original barrel condition and shot count may be firecracking & "hard spots" that the reamer won't like.
My .02

Do you have a reamer print, that you can post or link to, of a 260AI that has a larger diameter shoulder than a Creedmoor?

 

[MNbogboy]

Do you have a reamer print, that you can post or link to, of a 260AI that has a larger diameter shoulder than a Creedmoor?

Sorry Edd I don't have that print but after study of some published prints it is clear that the creedmoor chamber may not clean up without setback.
Sorry to the OP for misinformation. Creedmoor reamer print shows .4630 to .4634 at shoulder with taper at only about .007 per inch. The 100 thou deeper won't make up the difference of the A.I. at .4600 to .4604.
Good catch Edd...better now than his smith catching it or worse yet stuck case after first shot.
If anyone wants I can do the math for the amount of setback but my guess would be a min of 1/2 inch.