Rechamber 6.5 Creedmore to .260 AI

According to the chamber prints the 6.5 Creedmore is .4709" at the widest point on the case body. The .260 AI is .4714" at the widest point on the case body.

Question, is .005" enough material to keep a reamer centered when rechambering a mass production 6.5 barrel to a .260 AI?

Would setting it back a few threads increase the margin if the factory tolerances are too sloppy?

Would a long pilot shaft on the reamer help hold it?

Might as well do the .260AI. Go for more gain since you are thinking about it.

I have both 6.5 Creedmoor and 260 AI. Juice isn't worth the squeeze in my opinion.

A A Ron said:

According to the chamber prints the 6.5 Creedmore is .4709" at the widest point on the case body. The .260 AI is .4714" at the widest point on the case body.

Question, is .005" enough material to keep a reamer centered when rechambering a mass production 6.5 barrel to a .260 AI?

Would setting it back a few threads increase the margin if the factory tolerances are too sloppy?

Click to expand...

What do you hope to gain from your investment of time and money? I agree with @buckbrush

What pills are you throwing with the 6.5CM and how fast?

What do you want to throw and how fast?

It's actually more of an investment to go 6.5 Creedmore. I have hundreds of pieces of Remington and Lapua brass that feed my .260 and my .260 AI. I have dies for .260 AI.

I have nothing for Creedmore. I also have no desire to add another caliber to the stable.

Back to the point. Is .005" enough material to properly center the chamber reamer without slop or excessive runout?

I would make it a 6.5 Beanmore!

My 260AI significantly outperforms my buddy's CM, at least in terms of velocity. He runs 2780'ish in a 24" barrel and I run 2980'ish in a 24" barrel. He is using H4350/143ELDX and I'm running H4350/144 LRHT. If I use RL26, I widen the gap another 50+ fps.

I get noticeably less drop and drift at distance over him, both shooting out to 1500 yards.

A A Ron said:

It's actually more of an investment to go 6.5 Creedmore. I have hundreds of pieces of Remington and Lapua brass that feed my .260 and my .260 AI. I have dies for .260 AI.

I have nothing for Creedmore. I also have no desire to add another caliber to the stable.

Back to the point. Is .005" enough material to properly center the chamber reamer without slop or excessive runout?

Click to expand...

I doubt that it will work without setting the barrel back. You are comparing the body diameter at the base and that makes it appear to possibly be an acceptable change. BUT, the body diameter of the 260AI shoulder junction compared to the body diameter of the 6.5cm at the shoulder junction is your problem area. The CM is .004" larger than the AI and at a point ~.170" back from the AI body/shoulder junction.

Hope this helps...

(Edited to correct the body/shoulder junction difference)

A A Ron said:

According to the chamber prints the 6.5 Creedmore is .4709" at the widest point on the case body. The .260 AI is .4714" at the widest point on the case body.

Question, is .005" enough material to keep a reamer centered when rechambering a mass production 6.5 barrel to a .260 AI?

Would setting it back a few threads increase the margin if the factory tolerances are too sloppy?

Click to expand...

A A Ron said:

Back to the point. Is .005" enough material to properly center the chamber reamer without slop or excessive runout?

Click to expand...

You are inducing an error, making it out of tolerance, so yes, it "can" have a negative effect. Most of us keep our runout at .002" and better. However, I say go for it if you think it is worth your time, money, and effort. We are saying to do it right from the start and go with .260 AI. Good luck!

your .200 line dia. isn't your problem the shoulder dia. is. creed .463, 260ai .460 you will have to remove a good portion of the Creedmoor chamber to clean up the shoulder with the smaller 260ai reamer. if you have enough shank left on the barrel to remove the threads and start over and the barrel is a quality barrel with low round count it might be worth it, high round count or factory barrel don't waste your time just save for a new barrel

A A Ron said:

It's actually more of an investment to go 6.5 Creedmore. I have hundreds of pieces of Remington and Lapua brass that feed my .260 and my .260 AI. I have dies for .260 AI.

I have nothing for Creedmore. I also have no desire to add another caliber to the stable.

Back to the point. Is .005" enough material to properly center the chamber reamer without slop or excessive runout?

Click to expand...

I shoot High Power and own my own .260 reamer and do my own barrel work and for the same reasons you speak of, having the dies ,reamer and having shot many 10's of thousands of rounds through a 260 so load development is close to non existant, put the same load in as the last barrel and go to a match and see how it shoots chances are it will be fine so when we were allowed to have scopes I switched to a ruger precision rifle and took off the barrel and put a 260 barrel on. I have rechambered some of the original 6.5 creedmore barrels to 6.5x284 and the reamer will follow the original chamber just fine, I am quite sure you couldn't hardly get it to not follow, have you ever tryed to fix in steel a hole not drilled in the right spot and tryed to move it over with a drill bit the bit will follow the hole every time. The only chambering job I did that came out off center by about half the height of the lands I did on a barrel which had been chambered in 7 br and had the most impressive chattering marks from the reamer I have ever seen so I put a 284 reamer which waq piloted in the barrel and did not have a problem with it chattering but when all done the chamber was not concentric with the bore so my supposition was the chattering chamber was not concentric so the reamer followed the first chambering job so I don't believe you can do any thing with a reamer to make it not follow the original chamber so if your first chamber is concentric you will be fine using good chambering practices

buckbrush said:

I have both 6.5 Creedmoor and 260 AI. Juice isn't worth the squeeze in my opinion.

Click to expand...

What are the specs of your 6.5CM and loads? I agree that 100fps might not be worth a rechamber on a factory barrel. But if you start fresh with a new barrel, the ,260AI makes a lot of sense...for the handloader.

My 20" .260AI is running a 140 Hyb @ 2914fps over H4350. I hit 2964 w. H4350 or 2997 w. RL26.
My 24" .260AI is running a 140 Hyb @ 2958fps over H4350. I hit 3004 w. H4350 and the 140 Hyb. Or a 130 OTM @ 3068fps over H4350.
None of my final loads are max loads.