Resizing question?

[Andouille]

...So measuring a factory round at the datum line and adding a piece of scotch tape won't give you an accurate enough measurement to tell you if the chamber is in spec or not. You need to use a gauge to be sure.

I somewhat disagree because go-no-go gauges just do what the name implies, without providing a measurement of chamber headspace. I believe that the scotch tape test does provide an indication of sufficient headspace for safe firing in my case, because I had easy bolt drop/lift with factory ammo, and a stiff bolt with 2 layers scotch tape (0.003" added). I had consistent results with trying the test 10 or so times with three different Federal cases from different ammo batches. This is the same method many competition shooters use to determine shoulder bump for resizing cases.

The only thing I can think of with the shoulder issue is that if it is in fact changing the shape, that is changing the contact point of the bullet insert, and therefore the perceived measurement. You may not be actually bumping the shoulders back .007". I'm perplexed as to why the shoulders are changing shape though, might be worth having a gunsmith gauge and scope it.

It's combination of shoulder deformation (rounding) and bump by over 0.002" (0.007" measured with comparator) because I'm turning the die about 1/8-1/6" extra turn beyond where 0.002" bump should be. 1/6-1/8" turn on a 14 TPI die is about 0.012-0.009", so the die is definitely doing more resizing than optimal. But consider that it is the resizing with the die and not the chamber that is causing the shoulder deformation, so scoping the chamber is unlikely to show a funny-shaped chamber, especially given that this is a Tikka factory barrel. But a true headspace measurement by a Gunsmith could be helpful in determining whether I need a different thickness shellholder.

I think my options now after getting similar shoulder bump issues with Lee, LE Wilson, and Hornady dies are to try a shellholder with different thickness (more or less?) and different brass.

 

[Harvey_NW]

I somewhat disagree because go-no-go gauges just do what the name implies, without providing a measurement of chamber headspace. I believe that the scotch tape test does provide an indication of sufficient headspace for safe firing in my case, because I had easy bolt drop/lift with factory ammo, and a stiff bolt with 2 layers scotch tape (0.003" added). I had consistent results with trying the test 10 or so times with three different Federal cases from different ammo batches. This is the same method many competition shooters use to determine shoulder bump for resizing cases.

I understand that, but that only tells you those Federal cases are dimensionally optimal in your chamber, it does not tell you if your chamber is within spec or not.

It's combination of shoulder deformation (rounding) and bump by over 0.002" (0.007" measured with comparator) because I'm turning the die about 1/8-1/6" extra turn beyond where 0.002" bump should be. 1/6-1/8" turn on a 14 TPI die is about 0.012-0.009", so the die is definitely doing more resizing than optimal. But consider that it is the resizing with the die and not the chamber that is causing the shoulder deformation, so scoping the chamber is unlikely to show a funny-shaped chamber, especially given that this is a Tikka factory barrel. But a true headspace measurement by a Gunsmith could be helpful in determining whether I need a different thickness shellholder.

I think my options now after getting similar shoulder bump issues with Lee, LE Wilson, and Hornady dies are to try a shellholder with different thickness (more or less?) and different brass.

I'm at a loss for the cause and solution, I don't see how different thicknesses of shellholders could change what happens in the top end of the sizing die.

 

[ropeup79]

I'm at a loss for the cause and solution, I don't see how different thicknesses of shellholders could change what happens in the top end of the sizing die.

If you take a little material off the top of the shell holder then more of the case can go into the die.

 

[A382DWDZQ]

I'm having a similar issue of rounds not chambering in my 300 WSM, but to a larger magnitude. I have to full length resize rounds with 0.010 shoulder bump to get them to chamber with a couple thou clearance. This means I'm having to excessively resize my brass. For example, can take a once-fired case at 1.773 that just barely chambers, then FL resize to 1.770 and it will not chamber at all- hard bolt stop. The resizing in my FL Hornady Custom die (expander ball removed) causes a bulge in the shoulder that effectively makes the cartridge "longer" as far as chamber fit goes, so I have to resize to 1.766 to accommodate the shoulder bump plus a little clearance.

Here's some base to shoulder measurements on 2x fired brass to clarify the issue:
1.775 longest fired length, doesn't chamber.
1.773 average fired length chambers (tight)
1.771 shortest fired length chambers with 1 layer scotch tape (I should be shooting for this length).
1.768 longest FL resized round case that chambers (tight bolt)
1.766 longest FL resized round that chambers with 1 layer scotch tape (~1.7675")
Brass annealed prior to resizing. Trim length checked (still well below max).
And for reference, new Norma brass is 1.765"

I've sharpied the shoulders of fired and re-sized rounds, then spun them in a Wilson Case gauge and the buldged shoulder is evident on the resized round, whereas the fired round just shows a thin mark at the base of the neck/shoulder junction. I'm using Hornady custom dies and #35 shell holder.

I'm at a loss as to how to change my die setting to achieve 0.002-0.003 shoulder bump from 1.773 to have a cartridge that chambers with a few thou clearance to spare. Does anyone have any insight on whether I can bump only 0.002" with my FL die without affecting shoulder shape?

I want to go back to this. Why are you concluding that the shoulder is bulged from this? Is it just from seeing where the shoulder is contacting the case gauge? It could just be that the shoulder angle on the sized case is closer to the angle of gauge than the fired case?

 

[Harvey_NW]

If you take a little material off the top of the shell holder then more of the case can go into the die.

Fully understand that, don't see how that fixes the rounded shoulder and more than .007" setback problem.

 

[Pickettpuncher]

Ok my turn on resizing. 6.5 PRC, Lapua brass 1x fired, Hornady Match Grade die. Once fired re-chambers easily but neck ID is too large and bullet falls in. Set-up my die to only size the neck and measured shoulder bump at 0.000. Sized brass will re-chamber but requires effort and case head has a shiny spot. I am going to examine the depth the expander is set at and see if I can move it out into a position that will allow more of the case to be supported when the expander ball enters. Other than that I don't know what else to look at. Rifle is a Seekins PH2.

Have you fixed this issue. If your bullet is falling in on the match grade dies you need a smaller bushing. Not poking fun, but do you have a bushing in the die. I would also check the expander and make sure you have the proper sized expander, Hornady could have sent the wrong one.

 

[ropeup79]

Fully understand that, don't see how that fixes the rounded shoulder and more than .007" setback problem.

I agree that the rounded shoulder is probably a different issue. As stated before I’ve had similar issues with expander portion of de-capping pin bulging shoulders or changing shoulder angles.