Shoulder bump tolerance

[Greasegun]

Curious what you long range guys consider acceptable shoulder bump variation.

I was able to get my spread down to .001" by switching to a different sizing lube. My sized shoulders now range from .001"-.002" shorter than fired dimension. I do notice a bit of sooting beyond the neck, partially up the shoulder on some cases after firing, but most seal off good. I do not anneal my brass, although I wish I could. I use this wilson gage with a .0005" test indicator to measure (see pic)

 

[Plowboy85]

I also bump back for 0.001"-0.002" delta from fired to sized, I try to stay on the lesser side. I had problems a while back with inconsistencies in my shoulder set backs and noticed what I would describe as a "blotch" of imperial wax on the shoulder. I cleaned the dies well and at that point stopped applying lube to the shoulder and only on the case body. Since then it helped me as well.

I'm not familiar with that gauge, is it essentially a chamber to measure case length with?

 

[Greasegun]

I'm not familiar with that gauge, is it essentially a chamber to measure case length with?

I went away from imperial wax and switched to a spray on lanolin based lube, and my shoulder lengths became much more consistent. Even without lubing the shoulder with imperial, it would build up eventually in the die shoulder area.

It is an LE wilson case gauge. Yes its basically a chamber to measure shoulder length with. The body and neck area are oversize so only the shoulder makes contact. Not real useful without an indicator to check with though, as caliper measurement doesnt really work.

 

[Mikecr]

Your bump sounds right. The sooting is from high neck clearance and high chamber end clearance. Did you by chance trim them all to the shortest OAL?

 

[Greasegun]

Your bump sounds right. The sooting is from high neck clearance and high chamber end clearance. Did you by chance trim them all to the shortest OAL?

I used brass from loaded ammunition, which was already trimmed to the short end. Also, I made a plug gage to measure my chamber length, and it measured .01" over max saami case length, so there is about .015"-.020 clearance in there. Its a factory chamber so there is plenty of clearance around the neck as well.

 

[Mikecr]

So a bit of sooting can be expected there as normal.
Just be sure to clean chamber end with barrel cleaning, to mitigate a carbon ring formation.

 

[Beluebow]

I went away from imperial wax and switched to a spray on lanolin based lube, and my shoulder lengths became much more consistent.

This^^
Sorting by bump length also helps eliminate the "big jump" from shortest to longest sized cases...consistency is always a good thing.

 

[Greasegun]

So a bit of sooting can be expected there as normal.
Just be sure to clean chamber end with barrel cleaning, to mitigate a carbon ring formation.

Glad to hear that sooting on the shoulder is normal.

If I am cleaning the bore with solvents and a bronze brush, will that mitigate the carbon ring, or should I be using an oversize brush in the neck/throat area?

 

[Mikecr]

Glad to hear that sooting on the shoulder is normal.

It's not desirable as the blow-back gasses mess with neck expansion/sealing timing, increasing velocity spreads. The gasses move carbon with momentum to pile up where it's stopped (building a ring).
It's YOUR norm with the brass/chamber you're using. I get it myself with some factory chambers and available brass.

If I am cleaning the bore with solvents and a bronze brush, will that mitigate the carbon ring, or should I be using an oversize brush in the neck/throat area?

No, the carbon ring I'm referring to is before the bore, at chamber end. Right in front of loaded case mouths.
I use a bronze brush, pulling it from muzzle back to the chamber neck (setting bristles forward), where I spin it. Then I push & leave a patch ~1/2 way down the bore and spray the gunk loosened by the brush down toward the patch, with carb cleaner. Then remove it all with std. barrel cleaning.
I spot check it with a bore scope now & then.

 

[Greasegun]

It's YOUR norm with the brass/chamber you're using. I get it myself with some factory chambers and available brass.

Yes I should have worded it that way. It does make sense that the sloppy neck dimension in the factory chamber would lead to those issues.

 

[Greasegun]

No, the carbon ring I'm referring to is before the bore, at chamber end. Right in front of loaded case mouths.
I use a bronze brush, pulling it from muzzle back to the chamber neck (setting bristles forward), where I spin it. Then I push & leave a patch ~1/2 way down the bore and spray the gunk loosened by the brush down toward the patch, with carb cleaner. Then remove it all with std. barrel cleaning.
I spot check it with a bore scope now & then.
View attachment 167424

Thanks for the input!