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30br question

Kevin1990

Forgive this amateur question, or perhaps I’m not thinking/reading correctly...Or overthinking.


So I’m going to send off my Lapua 6br brass to get necked up and neck turned for 30br. I have a .332

Been reading about this, and everything I’ve read says to take a loaded round, and measure it, and then to do the math and give yourself .002 clearance?

I have hottenstien and barts bullets. But in the future I’d like to try Bibs, Ammerman and others.

So my question is.

If I don’t load a round, and I don’t know what the pressure ring diameter of a Bib or Ammerman is, how will I know what to have my brass turned to?

Also, what is yourneck clearance on your 30br?
 
It's more than just the pressure ring differences. Do your homework on the shank/pressure ring dimensions of BR quality bullets you're likely to use. Big to small, you can be looking at close to .0005 (half a thou.) difference.

If you cut the necks for .002 with a small bullet and then want to try a wide body....now you've got .0015 clearance.

Neck clearances that work in the .30s have been repeated ad nauseum by many qualified competitors and builders.
 
AlNyhus said:
It's more than just the pressure ring differences. Do your homework on the shank/pressure ring dimensions of BR quality bullets you're likely to use. Big to small, you can be looking at close to .0005 (half a thou.) difference.

If you cut the necks for .002 with a small bullet and then want to try a wide body....now you've got .0015 clearance.

Neck clearances that work in the .30s have been repeated ad nauseum by many qualified competitors and builders.
Click to expand...
Yep. Just set it up for .003 with a smaller bullet and you'll be about right for anything. I'd rather have a tad more clearance than needed than not enough. On top of that, the trend for several years has been toward a tad more clearance. I have to agree with this trend being best. Little to no downside and I do think they shoot better with around .003 min clearance anyway.

The Bibs are likely on the bigger end of what you'll see.
 
@AlNyhus @jackieschmidt @gunsandgunsmithing Thanks for all the information guys. Much appreciated!

I measured the bases on the 112 Hottenstiens and 112 Barts. They both measured .3085 with my origin calipers. I contacted Ammerman about his as I don't have any on hand.

Depending on what Ammerman says I will go .003 off of the barts/hottensteins?... in hopes that one day I will get my hands on some BIBs.
 
WSnyder said:
Calipers won’t tell you what you need to know out to the tenths. That fourth digit only displays a 0 or a 5 so you really don’t know where you’re are exactly. You need a micrometer that reads to tenths to accurately measure what you’re trying to measure.
Click to expand...
I knew that, and it didn’t register until I saw your post. I’ll just go off of barts measurement in this post and do .003. Thanks for pointing that out.
 
I have a buddy who is a machinist. He has a whole set of expander mandrels from 6 all the to 30. I’m just going to head to his place, expand one piece, and measure a seated round to get my measurement because now it’s bugging me. I’ll also get some numbers for the base of the hottenstein bullets.
 
Kevin1990 said:
I have a buddy who is a machinist. He has a whole set of expander mandrels from 6 all the to 30. I’m just going to head to his place, expand one piece, and measure a seated round to get my measurement because now it’s bugging me. I’ll also get some numbers for the base of the hottenstein bullets.
Click to expand...
Kevin, don't get too hung up on the math...neck thickness x 2 + bullet diameter = xxxx.

All you really need to know is what the neck measures when the bullet is seated. If you turn a neck to a fixed dimension, quite often the final dimension when the bullet is seated doesn't quite add up.

If you're having someone else prep your cases, just supply them with a few of the biggest bullets you'll use and instruct them to turn the necks to give you the finished dimension you want.

Just my approach to it.... -Al

PS: Verify the finished neck diameter the reamer produces prior to all of this. ;)
 
I was debating on if I should send the smaller or larger bullet between the Barts and Hottenstiens for my neck turning.

If I send Barts bullet in, and ask for .003 then hottenstien’s bullet would only have .0022 clearance With the measurement above . If I send Hottensteins bullet in and ask for .003 clearance with that measurement above, I’d be looking at .0038 for Barts, which is what I think I will do.

Does this sound like a good idea?

I now realize Al’s comment, about clearance differences. A lot more difference than I thought!
 
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