Shoulder Bumping

[rickp]

I measured the head space on few rounds I shot this past weekend and I'm getting between 2.640 to 2.655 so I set my die to bump the shoulder back to about 2.630 to 2.635.
That gives me about as low as .001 1/2 to 002 1/2.

That sound about right to you guys? I'm just making sure I'm on track. Some of you guys know more about this than I do.

R.

 

[427Cobra]

Re: Shoulder Bumping

What Caliber?

 

[rickp]

Re: Shoulder Bumping

.308

 

[targaflorio]

Re: Shoulder Bumping

Your numbers don't look right to me. 2.4 to 2.655?? 308 win?
Are you using a bump gauge and caliper set up? I prefer the rcbs precision mic because there is no wobble to deal with. The key is to measure the headspace of your fired case and bump the shoulders of your new brass back about .002" for bolt action and .004" for semi autos. My dillon 550 gets me within .002-003" spread on win brass, my redding big boss is right on every case.

 

[rickp]

Re: Shoulder Bumping

Shit my bad. I meant 2.640 to 2.655
I'll edit the original post.
MY BAD

 

[427Cobra]

Re: Shoulder Bumping

Your measurements are off, no way in hell can the Headspace meaurement be 2.6 anything, but that really doesn't matter, decap your fired brass, if you have 50 pieces good, the longest ones need to be used to set up your FL die, using the headspace gauge, screw the die down until the gauge reads .001-.0015 less, lock your die in place and call it a day.

 

[rickp]

Re: Shoulder Bumping

I know the head space isn't 2.6" long (that number includes comparator and bump gauge).What I'm asking is the thousands of an inch difference between the 2 shoulder measurements.

 

[427Cobra]

Re: Shoulder Bumping

Its the brass, that why I said to set up your die on the longest headspace reading fired brass, and decap the brass before taking the reading, because the primer flows backwards and gives erractic readings

 

[harley_jeff]

Re: Shoulder Bumping

Take a look at the sticky at the top of this page.

Hand loading for Long range 1: brass case prep
I think your question is answered there in the first post

 

[rickp]

Re: Shoulder Bumping

I'll take a look at that.

thanks

 

[FLIGHT762]

Re: Shoulder Bumping

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">Its the brass, that why I said to set up your die on the longest headspace reading fired brass, and decap the brass before taking the reading, because the primer flows backwards and gives erractic readings </div></div>

This is important ^^^^^^^^^^^^^^^^ I agree with decapping the brass before measuring, primer cratering and flow back will give false readings What you can do is take your measurement off the shoulder of your fired brass with your bump gauge and then ZERO out your digital caliper. This should give you a reading of 0.00 on your the shoulder of your fired brass. You then set your F/L die to resize to a reading of -(minus).001"-.002". It can make it easier reading the numbers .

Just remember, different brands of brass can resize and spring back differently. Also, the type and amount of resizing lube can change the readings.

After I set my F/L dies, I use a set of "Skip's" shims, if I want to adjust the amount of resizing with different brands of brass.

 

[rickp]

Re: Shoulder Bumping

that's a good idea.

Yeah it never occurred to me that the primer would give me a bad reading.

again thanks guys.

 

[lonely_wolf]

Re: Shoulder Bumping

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FLIGHT762</div><div class="ubbcode-body"> After I set my F/L dies, I use a set of "Skip's" shims, if I want to adjust the amount of resizing with different brands of brass. </div></div>

Alos take a look at Redding's "Competition Shell Holders." They made my life a lot easier.

 

[rbeckwith]

Re: Shoulder Bumping

I use a universal decapper...works great when you need to take readings on fired brass to accuartely set up your dies.

They are really cheap, everyone should have one for this purpose.