Neck Turning Brass Question

TXCOONDOG

TXCOONDOG

Well-known member
I have an X-Caliber barrel chambered in .243 (AR 10). I full length resized the Lapua brass and seated the bullet (87gr VMAX) with a light crimp (.003" neck tension). The dummy rounds would not chamber fully. I checked with a bore scope and didn't see any burrs, tooling marks, etc. I colored the case with lip stick so I could see where it was hitting. It was the case neck so I turned the brass down .004" and it chambered fine (pushing the BCG closed by hand).

Should I turn the case neck down an additional .002"-.003" to ensure the case neck opens up fully and releases the bullet consistently or will that make the case necks too thin?

The case neck wall thickness before turning varies between .376"-.380" using a digital micrometer. The cases have to be turned down to .374"-.375"before the BCG will close with no drag.
 
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Not a gunsmith, but according to Sierra & Nosler manuals, loaded case neck of 243 Win. should be .276". Subtract .243" bullet dia. leaves >.033" divided by 2 = neck wall thickness of .0165". Unless the chamber is undersized you should be OK w/.276" OD @ neck on your loaded rounds.

Regards,
hm
 
It's been a long day, I'm tired and didn't have my glasses on and had the micrometer set to MM instead of inches.

It's mainly the brass, with a bullet seated, the OD of the brass measures .280" which makes sense why turning it down .004" (.276) let them chamber. From what I've read, depending on what the reamer cut,you want your loaded rounds to be .002" to .003" under the chamber's neck diameter. Ideally, the case neck wall thickness of .013"-.015"

I'm going to cast my chamber as that should give me the exact dimensions, and I'll have an idea of how much more I need to turn down (if any).

I appreciate the response.
 
Sounds like a plan.

I checked the thickness on several .308 & 30-06 cases and most ran .015" but 6mm Rem. were about .013". I used to turn my long range 30-06 match brass but only cleaned 'em up to be concentric and never measured the thickness.

Regards,
hm
 
Me too so this is something new to learn. I didn't even think about neck turning or checking the brass for centricity being an AR barrel and Lapua being known for consistency. It appears that X-Caliber runs tight tolerances on their barrels.

You bet I will be checking brass, etc from here on out (lesson learned).

Thanks for taking the time to check.
 
Only similar issue I have witnessed is one competitor started blowing primers on his Garand. I checked his ammo and found that he had reloaded his brass numerous times without trimming cases and after ?? reloadings the brass had grown to the point that cases were not releasing the bullets.

Never personally encountered a tight chamber on a new barrel, but it could sure cause problems. Have you fired any factory ammo in that barrel? Let us know what you find out.

Regards,
hm

 
Originally Posted By: TXCOONDOGI'm going to cast my chamber as that should give me the exact dimensions, and I'll have an idea of how much more I need to turn down (if any).

A chamber cast is the best way to know exactly what you're dealing with.
 
I ordered a 1:10 twist which is what is stamped on the barrel. I checked using the cleaning rod method and it's a 1:8 twist.

Anyway, It's being returned for a replacement.


They agree with me that the chamber is too tight, and the twist is all wrong. At this point, I feel confident that they will make things right.

PS: Brownell's is replacing the Lapua brass.

hm1996,

I don't have any factory ammo for the .243. I haven't bought any factory ammo in 5 plus years.
 
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I often buy one box of factory to get a base line for a new cartridge, but load everything after that. I was just curious if factory would fit that chamber.

Glad you have things figured out. As my FIL used to say, sounds like that barrel was made on a Monday in a union shop, wrong twist & tight chamber.
lol.gif


Regards,
hm
 
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