.375 Cheytac brass vs reamer base dimension

[flyfisherman246]

Peterson brass measures .633 at the .200" mark at the base and my reamer is about .6395 at the .200" mark. There seams to be different specs on the Cheytac all over the place. Is this .0065 bigger base going to cause issues with brass expanding that much at the base? What are you guys using for reamer base size and are you getting this kind of expansion?

Thanks,
Zack

 

[badassgunworks]

Peterson brass measures .633 at the .200" mark at the base and my reamer is about .6395 at the .200" mark. There seams to be different specs on the Cheytac all over the place. Is this .0065 bigger base going to cause issues with brass expanding that much at the base? What are you guys using for reamer base size and are you getting this kind of expansion?

Thanks,
Zack

Not only is there a difference at the base but there is a headspacing difference about.015 standard sammi braass spects for cheytac brass at the .200 mark should be .637 so the reamer is correct. peterson brass is not cheytac it's a metric variant that has a different ring diameter and datum a different headspace my suggestion is to return the Reamer and have a custom one made from the Peterson brass. .0035 larger in all areas. The reason I suggest this because Peterson build the best available brass but it's not really CheyTac brass but your chamber reamer that you have is. It's better to have a custom chamber than try to fire form that brass to fit . please note reamer at 200 mark should be about . .6375 to .638 did you measure reamer with calipers? If so thats part of the problem

 

[flyfisherman246]

Measured with a micrometer. It is PTG, so there is that. If I get the reamer reground to Peterson brass specs, what do I do for headspacing? Is .015 an exact difference between Peterson and cheytac? Should I cut .015 short of a cheytac go guage? Thanks for the help.

 

[badassgunworks]

Get with dave kiff at ptg send him a one of the peterson cases . Along with the reamer he can re grind. optimum is .003 clearances in body and neck .001 headapacing .

 

[timintx]

I agree , get with Dave Kiff. In my experience , your reamer is for the Jamison brass, and .6395 is way too big for Peterson brass. With Peterson brass I used .636.-.637 at the base . New Peterson brass I had varied .008 head spacing before it was fired so that is a flip of the coin ,but I used the Kiff min CIP head space go gauge and have had no problems feeding new brass or bumping shoulders with the dies. The AB dies match up well with the .636 reamer . I have cut 5 chambers and they all fed well and resized well with my .636. Dave stayed late to get me mine because it was a emergency and I was so thankful for what he did . The reamer cuts really well and the chambers have worked perfect with the dies, never had a feeding problem or sticky extraction . I Tried a .639, .640 and had all kinds of problems. They would not even go in my dies because the base or the case was too big . but .636 has worked flawlessly in 4 barrels so far. Good luck