Case neck shoulder change after fire forming

Vern

Vern

Morethan1waytoskinacat
Case neck shoulder change after fire forming 6PPC

I usually fire form without bullets however I am going to try it the conventional way this time.

My question is when we trim the cases and turn the necks down to the junction of neck and shoulder.
How much does the junction and which way?
Does the case shrink or grow after blowing out the shoulder?
 
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On my rifle, I have to make a full width track on the shoulder (not so deep that it is easy to catch with a finger nail) with the lead chamfer on the cutter of a Sinclair neck turning tool, for the bolt to be able to be closed with the correct feel. If I do not, excessive pressure is required to close the bolt. I do this on the first cut. The second cut is with a K&M and less than .001 is removed. After firing, the cases will be shorter. To get the shortest ones to square up, I trim to 1.495. It sounds to me like you are overly concerned with the location of the neck shoulder junction after fire forming. Since most short range bullets don't seat anywhere the base of the neck, I don't think that it really matters whether the junction moves one way or the other. As I said, where I stop is determined by what I desire for bolt close feel when chambering a round to be fire formed. If I went any farther, there would be no feel. If I stopped shorter, the force needed to close the bolt would be excessive.
 
When outside neck turning my Lapua 220 Russian/ 6ppc for the .262" necked chambers I want to just see the Sinclair 30 degree cutter blade touch the shoulder, where it meets the neck. As stated by Boyd I want to be able to run my fingernail over the neck/shoulder joint and not feel any ridge at that location. If there is a ridge I'll feel resistance when closing bolt.
 
I understand where we are suppose to turn it to prior to fire forming.
What I am trying to discern is where that point (neck shoulder junction) ends up after fire forming.
 
I was taught by a prominant shooter to fire form without bullets and we will not go into the do's and dont's of that. The shooter that taught me this has won more than their share of wood.
I always liked the concept because when I actually trim to length and actually turn the necks I am turning the necks based on where they really are.
When we turn necks on unfired cases we are turning it to the bottom of an/or very slightly past the shoulder/neck junction. HOWEVER I was just wondering where that original junction that we are turning to ended up.

I know that because most people turn before fireforming and looking at the results in matches it probably does not matter but I am just curious.

The real reason that I am going to turn necks the traditional way for now is that I dont have a spare barrel right now and dont want to burn out a good one with bullseye.
 
I have played with shooting a .22 bullet to fire form. I got the idea from James Mock. My variation is to turn to .0010 (at .22 cal.) before fire forming, so that the amount of expanding to do after fire forming, for final turning at 6mm, is reduced. I have a fire forming barrel, but I have done 35 or so rounds in a good barrel, and saw no evidence of damage, or unusual jacket fouling. This method produces very straight brass as compared with other methods that I have used. I may also try turning at .22 before non bullet fire forming with bullseye. This is all for a .262 neck. The .22 caliber turn thickness would be different for a different neck diameter chamber. Typically I have used some scrap Benchmark, to the base of a .22 cal 55 gr. BT seated well into the neck. The BT makes seating easier with a 6PPC seater. They are pretty straight.
 
Boyd when I usually do mine I do it inside the house.
I fill the case with bullseye and cap from a sheet of 1/16 thick bee's wax
Put the barrel of the gun into a roll of insulation and fire.
All you hear is a thud.
Then when I take the brass and trim and turn I am turning to the exact junction of the neck/shoulder.
AND BEFORE ANYBODY POSTS
I have heard all of the dont do thats. I have been doing this for years and it works just fine, but I am not going to do it anymore until I have a scrap barrel to shoot out of.
It has been eating at me what bullsey might be doing to the barrel.
This after someone answered my question as to "Why doesnt anyone shoot ball powder anymore?" They said the ball powder would burn up the barrel quickly....sooooooooo
As Paul Harvey used to say Now you know the rest of the story.
Sure do miss his programs.....
 
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