375 CT neck help

Goin'Hot

Gunny Sergeant
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I have 100 pcs of Bertram 375 brass. I have a set of Applied Ballistics and PTG FL dies.

I have one piece of Peterson brass for comparison. The neck diameter of a loaded round in Peterson brass measures 0.405". Loaded neck in Bertram brass is just under 0.400".

My AB dies size the Bertram brass to 0.402". I can actually drop a bullet into my resized case with no neck tension.

I know Lee makes collet dies but not for the 375 CT. What are my options here?
 

xdeano

Sergeant
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So whats your neck thickness on your bertram brass vs peterson?

My bertram 375 brass fired neck thickness is .0135. Which should be close to yours.

My loaded ammo is 0.399

0.0135x2= 0.027+.375= 0.402
0.402-0.399= 0.003 neck tension.

Im using AB dies also.
Id contact AB to see if you got a Friday die set.

Xdeano
 

Geno C.

Dirty Carnie (ICLASA)
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Wait, what?!

You say your loaded ammo is .399” but you also say your neck thickness is .0135”. I’m just a carnie but that math don’t work🤔

And you equation of .402-.399 for a .003 neck tension only works if your loaded round is .402 and your dies or bushings size down to .399”.
 

Goin'Hot

Gunny Sergeant
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I have no way to pull a 375 bullet from a case. All I can do at this point is measure the o.d. of the brass that has a bullet seated.

The one piece of Peterson brass that I have, has a Berger 379 seated to get the oal I desired. When I measure the o.d. of the neck, where the bullet is located, I get 0.405".

Same thing with my Bertram brass. Measured the same way. I get a loaded dimension of 0.3998". Of course I realize that my Starrett dial indicator does not have that resolution but it's better than "less than 0.400".

When I run a piece of my fired Bertram brass, through the AB resizer die and measure the o.d. of the neck, before I attempt to seat a bullet, I measure 0.402".

When I put a bullet at the case mouth, it passes through the open hole with no tension.

I can read a dial...
 
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xdeano

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I was referring to @xdeano i went through this with my 375 snipetac because I’m running Bertram brass also
[/QUOTE}

Yeah Shit! It was a late night, early morning! Trying to get it typed out while thinking of something else.

My fired unsized brass is 0.4100
My fired resized brass is 0.3975
My loaded round is 0.3990
0.3990-0.3975= 0.0015" neck tension (on my brass).

Your dies are messed up. call AB it should be resizing down more.

Xdeano
 
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Goin'Hot

Gunny Sergeant
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As a public service announcement...

I called Whidden to inquire about their FL sizer. It was stated that the neck dimension is 0.395". I purchased one and measured the neck dimension on my brass after sizing at 0.3985". Not a slam against Whidden but this is the dimension of their FL die.

It's on the way back to them to be exchanged with a bushing die. I normally don't use bushing dies because I want the entire neck sized and bushing dies have a little extra "error" built in since the bushing needs to slip in and out of the body.

The best solution would be a custom die but at this point, I don't have the time to go that route.
 

918v

Manipulated by Variables
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It’s .001” if you FL size an annealed neck. A hard neck springs back more.

Where on the neck did you measure?
 

Goin'Hot

Gunny Sergeant
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Once fired, factory annealed. I measured from the mouth, down a couple .100". I spun the case while measuring and applied firm pressure to the calipers. Thre same amount of pressure that I use to verify the dial is at 0.000" initially.
 
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Tokay444

I like to go fast.
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Sounds like you’re squeezing the mouth closed.
I’d load and shoot some ammo before anything else, or better yet, run a mandrel through them, load them and and shoot them.
 

Tokay444

I like to go fast.
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Ah, yeah. Spring back. Anneal better.
Can I blame lack of caffeine?
 
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