Shoulder bump

[Thompsonj]

The reason I ask this. A friend of mine has a 300RUM that was built. Someone out of state worked up the load for the rifle. He was running low on ammo, I have the supplies and the dies he used to develop the load. When I put the resize die in, the shell holder gets doesn't touch the resize die when cycled up. I don't know if he used a different press than what I'm using, or if that's how he set the resize die to work

 

[SSG Graybush]

The reason I ask this. A friend of mine has a 300RUM that was built. Someone out of state worked up the load for the rifle. He was running low on ammo, I have the supplies and the dies he used to develop the load. When I put the resize die in, the shell holder gets doesn't touch the resize die when cycled up. I don't know if he used a different press than what I'm using, or if that's how he set the resize die to work

Don't follow rcbs instructions that say cam over, that's wrong. Use a headspace guage on a caliper, measure some fired brass. Get an average and set sizing die up to only bump 2 thou from fired. Before you load throw a few in the chamber and make sure it's bumped back enough, and adjust as needed.
edit- you only want to bump enough to chamber reliably, excess is just overworking the brass, affects accuracy, and way too much headspace can cause a catastrophic failure.

 

[Thompsonj]

Don't follow rcbs instructions that say cam over, that's wrong. Use a headspace guage on a caliper, measure some fired brass. Get an average and set sizing die up to only bump 2 thou from fired. Before you load throw a few in the chamber and make sure it's bumped back enough, and adjust as needed.

Sounds like another rabbit hole that I'm going to need to explore

 

[VinceMule]

Got to love it when a plan comes together!

 

[SSG Graybush]

Sounds like another rabbit hole that I'm going to need to explore

it's super ez, learn what/where a datum line is(Lee manual has it in the specs, I believe, but only use it as a reference), measure fired brass from base to datum line using the correct collect in the headspace guage in a caliper, get an average of fire brass, start with die loose, too long not bumping, run it down on a fired case, in 1/8 or less turns run die down till it bumps shoulder back 2 thou. you need to tighten the die in-between each test. It's a pain but only done once if done correctly.

 

[VinceMule]

Just because you bump the shoulder back .002 does not mean the web of the case has been sized enough to chamber the round smoothly.

 

[Thompsonj]

it's super ez, learn what/where a datum line is(Lee manual has it in the specs, I believe, but only use it as a reference), measure fired brass from base to datum line using the correct collect in the headspace guage in a caliper, get an average of fire brass, start with die loose, too long not bumping, run it down on a fired case, in 1/8 or less turns run die down till it bumps shoulder back 2 thou. you need to tighten the die in-between each test. It's a pain but only done once if done correctly.

Since the seater die is in there as well. If I seat a bullet in the case that's been resized, and come out with the same dimension as what they wrote down, that should mean the resize die is correct for the load right? How much the shoulder being bumped would be unknown until I get some gauges

 

[Montana'eer]

This guy over at LRO has a great vid on proper resizing and it's what I use on my .280AI brass/rifle

 

[SSG Graybush]

Just because you bump the shoulder back .002 does not mean the web of the case has been sized enough to chamber the round smoothly.

True but 9.5x out of 10 it's fine. I've never had to worry about it in anything I load for, belted or not. Am sure there's rifle chambers out there it might be an issue with, but let's not confuse this guy more, he can cross that bridge if needed later in the rare case that's an issue.

 

[Thompsonj]

This is the information I have, does include headspace info. Be nice to know what gauge he used

 

[SSG Graybush]

This is the information I have, does include headspace info. Be nice to know what gauge he used
View attachment 616262

My headspace inserts are numbered by the orfis size, that's looks like a "E" insert and length. Find out the brand and opening size for your info. But really you should take fired brass and work it yourself.

 

[memtb]

SSG Graybush mentioned to "NOT" use the "cam over" technique recommendation by RCBS….. I assume this would be the same for other press manufacturers use similar design.

So, my question, if the case was measured after each "cam over" until the desired setback is achieved, and the die is "locked-in"……should it not repeat on all of the following cases?

If it's a very small difference in setback, assuming the case chambers properly…….will that setback difference have any measurable difference to the hunter and his equipment? That hunter that doesn't have multiple thousands of $ invested in his/her equipment?

Will these near immeasurable differences going to matter…….or is he/she putting Formula1 tires on his/her box stock LTI Camaro thinking it will be competitive on the F1 circuit? I think that many other limiting factors will become apparent! memtb

 

[SSG Graybush]

And while you buying Headspace guages get bullet comparators as well and start measuring cbto instead of coal. Much more consistent. I use Hornady's. Their caliper is ok as well.

 

[Beluebow]

This is the information I have, does include headspace info. Be nice to know what gauge he used
View attachment 616262

It really doesn't matter what gauge he used....You have your buddy fired brass and loaded ammo and your own tools.....knock the primer out and measure several fired pieces. With the loaded ammo pull a bullet, dump the powder and measure the shoulder bump on the unfired...reassemble and make it a fouler/sighter....set your sizing die up accordingly.