6 br shoulder bump question

[Falfan2017]

I have a 6 br criterion barrel on savage target action. I've been loading for it and always read while using a fl sizer to set it so it bumps the shoulder back .0015. Well if I do that the bolt is extremely stiff. I need to get it bumped back .005 until it closes with just a bit of resistance. Anybody know what's going on here?

Also today I shot a 4 target 5 shot per target match. I had 2 targets with once fired brass I'd resized and 2 with new lapua brass that I'd not resized. Both groups with new brass was significantly better making me think I'm not resizing right.

 

[rocketron]

was primer removed from fired case before you measured?
was the fireing pin and ejector removed from the bolt?

 

[sidecutter]

wheeleraccuracy | Videos

sizing brass

 

[boltfluter]

Measure the brass diameter at the neck/shoulder intersection and see if the body diameter has expanded. If so , your die may not match your chamber. Good luck.

Paul

 

[fayettefatts]

What are you using to measuring shoulder bump?
How do fired cases chamber before sizing? easier...same...harder?
Are you feeling the stiff closing bolt before seating a bullet?

 

[RonS]

What is a "FL seater"?

 

[Falfan2017]

What is a "FL seater"?

Edited to say sizer

 

[Falfan2017]

What are you using to measuring shoulder bump?
How do fired cases chamber before sizing? easier...same...harder?
Are you feeling the stiff closing bolt before seating a bullet?

Fired brass before sizing hardly chambers very stiff bolt. I'm using a piece of .284 brass. Not ideal but it's giving me very consistent measurements. I'm getting a stiff bolt before and after seating a bullet

 

[fayettefatts]

Fired brass before sizing hardly chambers very stiff bolt. I'm using a piece of .284 brass. Not ideal but it's giving me very consistent measurements. I'm getting a stiff bolt before and after seating a bullet

Then I would follow Paul's suggestion that your die and chamber may not be a perfect match. Measure as best you can the case diameter at the neck shoulder junction as well as diameter just above the case web. Compare fired and sized to new brass measurements.

 

[Falfan2017]

Then I would follow Paul's suggestion that your die and chamber may not be a perfect match. Measure as best you can the case diameter at the neck shoulder junction as well as diameter just above the case web. Compare fired and sized to new brass measurements.

Do you know what new brass measures? I don't have one on hand

 

[fayettefatts]

I don't have any new brass to measure. I did try to compare brass fired in my chamber vs. sized brass. The body at the neck shoulder junction is being sized approx. .0005" and the body just above the web is being sized less than .0005". Hard to measure tapered case, especially since my micrometers have only .001 increments.

I did have .284 Win brass on hand and I looked at using it to measure bump. It seems like it may not be quite large enough. May be resting somewhere on the neck shoulder junction rather than on the shoulder. Not sure about this, but would suggest you try something a bit larger, like a .30 cal, or invest in a dedicated tool. Hope this helps.

 

[KenOath]

My current batch of virgin Lapua 6BR Brass measures 1.100”,

In my experience with the BR I have not seen any loss in accuracy bumping shoulders back .002” to .0025”..

Cheers Rushty

Edit: Using a Sinclair insert on a caliper.

 

[foxguy]

New Factory Lapua

Neck Shoulder Junction - .459

.200 above the Base (above case web) - .467

 

[Falfan2017]

I don't have any new brass to measure. I did try to compare brass fired in my chamber vs. sized brass. The body at the neck shoulder junction is being sized approx. .0005" and the body just above the web is being sized less than .0005". Hard to measure tapered case, especially since my micrometers have only .001 increments.

I did have .284 Win brass on hand and I looked at using it to measure bump. It seems like it may not be quite large enough. May be resting somewhere on the neck shoulder junction rather than on the shoulder. Not sure about this, but would suggest you try something a bit larger, like a .30 cal, or invest in a dedicated tool. Hope this helps.

You were right. The .284 wasn't big enough. I used a 9mm which sits about 2/3rd the way down the shoulder and found out the shoulder was not being moved at all. Set my die so it was actually moving back .002 and what do you know perfect chambering. This is a great forum haha.

 

[6ShotsOr5?]

I’ve got a hunch that’s too much shoulder bump.

 

[dkhunt14]

I’ve got a hunch that’s too much shoulder bump.
View attachment 1048513

.002 is not too much. Lots of match shooters bump the shoulder that much. Matt

 

[6ShotsOr5?]

.002 is not too much. Lots of match shooters bump the shoulder that much. Matt

I take it BACK. It was only a HUNCH.

 

[pat fulghum]

Make sure bolt face is clean, no primer, etc

I deprime one and make sure boltface and bottom of brass are smooth and then and try to chamber. I set the amount of bump until there is ever so slight resistance.

Try this experiment on a nice hot day.... in a 20 shot string where you eject the brass immediately, leave the last spent fired brass in the chamber for 20s and measure it compared to the others. I bet it doesn’t require the same amount of bump.

Also unless anneal you will get different spring back from the die