Bumping the Shoulder???

[exd3686]

I'm somewhat new to reloading. I just picked up a Possum Hollow case trimmer in .308 and it states that you must bump the shoulder before trimming. I have Forestner Competition dies with a FL sizer. I set up the dies according to the insructions. How do I know when I properly bumped the shoulder?

Thanks for the help guys,
exd3686

 

[427Cobra]

Re: Bumping the Shoulder???

Buy a headspace measuring tool from Hornady, the instructions that most fl dies come with are a waste of paper.

 

[TimK]

Re: Bumping the Shoulder???

Bolt gun or auto?

 

[Hummer]

Re: Bumping the Shoulder???

You really need two gages.
1. A MO Gage
2. A L.E. Wilson Case Gage

this will cover the whole field. The Wilson will tell you when it is back to factory dims (if it will go in a Wilson it will go in anything) and the MO will tell you exactly how much your shoulder is moved back. Typically you only need to bump shoulder .001 to .002" to get things going fine in bolt gun.

 

[223ai]

Re: Bumping the Shoulder???

What is a MO gauge? I have been looking for something to help me measure shoulder bump on my 223ai brass...

 

[RTH1800]

Re: Bumping the Shoulder???

IMO a Wilson case gauge and micrometer is all you need. Put the fired case in the gauge, mike a couple of cases, size and re mike moving the die down 1/8 of a turn until the size is .001-.003 shorter and you are there.
RTH

 

[MitchAlsup]

Re: Bumping the Shoulder???

I happen to like the RCBS case micrometers, myself. Measure before and after a trip through the sizing die, and it tells you about the case and aobut the die setup.

 

[user]

Re: Bumping the Shoulder???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">I happen to like the RCBS case micrometers, myself. Measure before and after a trip through the sizing die, and it tells you about the case and aobut the die setup. </div></div>

+1 on this and the RCBS Precision Case Mic. Thats the easy way to set up the die, if its in an available caliber. For a bolt gun I fire a fairly strong load in the chamber, then measure the case with the case mic and get a reading on the datum, and adjust die to set the shoulder back 1-2 thousands (read again on the datum, adjusting die till its where you want it). Works great for me. Fast, easy. YMMV.

 

[Dogtown]

Re: Bumping the Shoulder???

And then switch to Hornady Lock-n-Load press bushings so you can set the dies once and forget it.

 

[Hummer]

Re: Bumping the Shoulder???

A MO is RCBS gage except instead of a sharp contact point on the datum it is reamed with a chamber reamer set type set up so shoulder is angled. It also indicates case length so you can tell if you need to trim after the bump back.
MCS 166 Pocono Rd. Brookfield, Conn. 06804 is the address to get them. Phone 203-775-1013. He works most nights and Saturday mornings in his shop. Last I heard they are $50.00. All the bolt gun shooters I know use these along with Wilson gage.
I have MO for 223, 308, 30.06 and before long will have one for 300 Win Mag.