Help reading reamer print

[Lynn313]

Someone knowledgeable please check to see if i’m reading the attached reamer print 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 will tell 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. Cross posted.

 

[lte82]

Why are you turning the necks?

I would call Lapua / Capstone and ask what the neck diameter is of a loaded case. My guess is that they made the brass to work with the standard reamers. I also see zero advantage to neck turning for a field gun between lost brass, extra time, and almost no advantage down range. Then you have a proprietary reamer and chamber that can't use factory ammo as well. Save yourself the time and frustration and just run the Lapua brass out of the box and don't look back.

 

[spife7980]

You seem to be reading it correctly.
If you want a tighter neck you’ll need a different reamer.

 

[Lynn313]

You seem to be reading it correctly.
If you want a tighter neck you’ll need a different reamer.

Thank you. Do you read it to be .2989?

Why are you turning the necks?

I’m presently not turning the necks. I’m thinking Having consistent neck thickness will help with consistency in my neck tension. Also, if I want a tighter chamber I will have to decide on a desired neck thickness to fit that chamber with a desired clearance. Even with a tighter chamber I should still see brass flow from case body to neck. As neck becomes thicker, the need to turn.
I reload for relaxation and accuracy. I never shoot commercial ammo. It looks to me like this reamer is designed to handle commercial ammo. Though, my knowledge of machining is almost nothing and not sure I’m reading it correctly.

 

[lte82]

Thank you. Do you read it to be .2989?

I’m presently not turning the necks. I’m thinking Having consistent neck thickness will help with consistency in my neck tension. Also, if I want a tighter chamber I will have to decide on a desired neck thickness to fit that chamber with a desired clearance. Even with a tighter chamber I should still see brass flow from case body to neck. As neck becomes thicker, the need to turn.
I reload for relaxation and accuracy. I never shoot commercial ammo. It looks to me like this reamer is designed to handle commercial ammo. Though, my knowledge of machining is almost nothing and not sure I’m reading it correctly.

I'd read it as a .298 neck, since that's the smallest diameter before the transition to the freebore.

The most I've ever done is skim-turn necks to uniform the thickness, and with Lapua you are usually only taking off a .0005 or less on one high spot. Unless you're trying to shoot benchrest or looking for that last bit of edge in an f class match, where you are already sorting cases and bullets, using a prometheus, etc, I don't think you will find any performance gains.

 

[Dthomas3523]

There’s almost zero data to show that more neck clearance over works brass enough to matter. In theory you would see split necks sooner.

But I have never seen any data to actually show this. You may need to clean a little more often.

From my experience you can definitely suffer from too tight of a clearance, but not really from too much. People used to think .001-.002 clearance was optimal for accuracy. Now the same people have realized being .006 or so is better in the same way bumping your shoulders is better than neck sizing only. Neither is more accurate, but one can definitely screw things up if tolerances are run too close.

There’s tons of people running saami reamers with handloads and have greater than .006 clearance. And I’ve never seen anyone complain about split necks from overworking brass.

 

[Lynn313]

I'd read it as a .298 neck, since that's the smallest diameter before the transition to the freebore.

The most I've ever done is skim-turn necks to uniform the thickness, and with Lapua you are usually only taking off a .0005 or less on one high spot. Unless you're trying to shoot benchrest or looking for that last bit of edge in an f class match, where you are already sorting cases and bullets, using a prometheus, etc, I don't think you will find any performance gains.

your giving me good information. So no tangible performance gains for me. I’m usually just shooting on my own range or with friends at a longer range.
what’s your opinion of extending my brass life with a tighter chamber? With out custom dies since I’m fl neck sizing with Redding type s bushing dies using a .291 bushing I am expanding my brass 8-9 thou, then resizing it back to sammi mins. I’m going to caliper my dies, but I believe even Redding resizes to sammi min specs in order to load in all commercial rifles.

 

[Lynn313]

There’s almost zero data to show that more neck clearance over works brass enough to matter. In theory you would see split necks sooner.

But I have never seen any data to actually show this. You may need to clean a little more often.

From my experience you can definitely suffer from too tight of a clearance, but not really from too much. People used to think .001-.002 clearance was optimal for accuracy. Now the same people have realized being .006 or so is better in the same way bumping your shoulders is better than neck sizing only. Neither is more accurate, but one can definitely screw things up if tolerances are run too close.

There’s tons of people running saami reamers with handloads and have greater than .006 clearance. And I’ve never seen anyone complain about split necks from overworking brass.

Thanks...... I’m thinking it would make a noticeable difference by minimizing the brass being worked. Thanks for the info from experience. It might be I keep posted chamber, but continue to move forward with the custom dies. At least I wouldn’t be squeezing it back to sammi min specs. Appreciate it.

 

[Steel head]

If you anneal that extra 2 thou growth does nothing to hurt brass life but does provide a safety margin for reliability.

 

[Lynn313]

If you anneal that extra 2 thou growth does nothing to hurt brass life but does provide a safety margin for reliability.

I don’t anneal, but am feeling better after reading the feedback on this post. The actual throat is going to be .216. It’s cut from dummy rounds I sent in. I’m also going to move forward with custom dies to minimize working the brass, but thanks to feedback I’m comfortable with chamber size. I’m thinking I wanted to go to tight.
I don’t anneal. I have looked at the AMP, but still trying to study to see if there is a real benefit if you minimize working brass. If I did it I think I would do it after every firing for consistency?
Thanks for the help from you and everyone else