Help reading reamer print

[Lynn313]

Someone knowledgeable please check to see if i’m reading this correctly. This is for a 6.5 PRC. I’m wanting a tight chamber to minimize working brass. Willing to neck turn to keep proper dimensions. I’ve been told about 12 thou case neck thickness is optimal.

ID of neck = .2989
bullet = .264 + .024 case neck thickness = .288
bullet = .264 + .026 case neck thickness = ..290

Whether I go with 12 thou or 13 thou it appears I will be overworking my brass. I have 500 Lapua cases due the 1st of Feb-2021. I will then fire form cases 3Xs neck sizing only prior to sending off for custom dies.

it appears to me I will be expanding my brass necks 10 thou if I’m reading the print correctly. I’m hoping an expert telling me if I’m reading the attached print correctly.

My goal is for the chamber to be 3-4 thou over. The rifle is a mag fed bolt. I hear the benchrest shooters use as little a 2 thou over. I‘m picking 3-4 as a compromise to minimize brass working while probably avoiding jams.

I’m headed to my reloading shop with my 1st build to measure chamber ID’s. I know that I’m currently using a .291 bushing while sizing on my ADG brass (no neck turning).

Appreciate knowledgeable feedback.

 

[Bill Norris]

I believe you are correct. With a .298 neck reamer u would not need to turn brass. My smith just built a 260AI for a friend of mine with that same neck diameter and brass fits perfectly in the chamber with Lapua and other brass as well. Loaded neck round with Lapua brass measures .2935 - .0294.

 

[Fast14riot]

0.298" is generally a no-turn neck diameter for 6.5 chamberings.

 

[Lynn313]

I believe you are correct. With a .298 neck reamer u would not need to turn brass. My smith just built one for a friend of mine with that same neck diameter and brass fits perfectly in the chamber with Lapua and other brass as well. Loaded neck round with Lapua brass measures .2935 - .0294.

Thanks Bill. I don’t have the Lapua brass to measure. It looks like if I’m reading the print correctly I would still have 6 to 6-1/2 though expansion on brass. What’s your opinion on using a reamer that only gives 3-4 thou clearance.

 

[Bill Norris]

I think that is adequate in both departments (Safety & Performance). I base that on the fact that my smith (WSMNUT) here on the site, who also competively shoots a 260AI used the same size necked reamer for his bench rifle and wins often.

 

[Fast14riot]

Thanks Bill. I don’t have the Lapua brass to measure. It looks like if I’m reading the print correctly I would still have 6 to 6-1/2 though expansion on brass. What’s your opinion on using a reamer that only gives 3-4 thou clearance.

3-4 thou clearance per side is pretty normal. 3-4 total would leave you very little room.

 

[Bill Norris]

3-4 thou clearance per side is pretty normal. 3-4 total would leave you very little room.

He could always do a slight turn clean-up on the necks (25 to 50 % touch) to buy a little more clearance if needed.