Bumping The Shoulder .002 Rifle Reloading

[NA Woody]

Where is Guffey when we need his expertise?

 

[J_idaho]

The whole point of fl sizing and setting shoulder back .002 is to get consistent and functioning rounds without over working the brass. Once fired brass could have already moved .010” before you bought them. Every chamber and cartridge has different specks but the best you can ask for in a factory rifle would be min. Saami chamber and and max saami brass.

 

[JFrank]

Where is Guffey when we need his expertise?

Right here.

Bumping shoulder back

I may be a little long winded, but bare with me. I just put together a sweet little 6.5x47 with a .290" neck. In every one of my rifles when I bump the shoulder back the bolt cams down effortlessly. I cannot get the 6.5x47 brass to size without a little "bump/hickup" while camming down. I...

forum.accurateshooter.com

 

[WinterRanger]

It can take multiple firings to get brass shoulders to expand to the full length of the chamber. While you can play it (very) safe by bumping them back to their original length as-new brass, the point of bumping the shoulders back .002 is based on the brass being fully expanded such that the brass is .002 shorter than the chamber from base to brass shoulder.

Easiest way to get there quickly is to take tiny squares of scotch tape on one piece of unloaded brass and add one on the bottom of the brass and chamber it. If it chambers easily, add another, etc until you find the point where it's snug or hard to close the bolt. Now measure the base to shoulder using your comparator and take off .002 if it was just a snug fit or .004 or .005 if it was a hard close. This is the value you want your brass to be each time.

Now for the second phase: keep firing that brass and let the brass grow until it reaches that length. Now you can set your die to achieve this length after sizing. It's not really possible to set the die for correct shoulder bump until you have brass that's longer than the chamber.

I had no idea it took multiple firings to get the brass to fully expand. Thanks for the info.

 

[WinterRanger]

Out of curiosity, where did you obtain Lake City virgin brass?

Sorry my bad. Thinking of my 5.56 brass. This is virgin Star.

 

[WinterRanger]

Great info. Thanks to all who replied. Just what I was looking for.

 

[Webster]

I end up using a Go-Gauge to set up my FL die. If the Go-Gauge measure 1.6185" from base to datem.,. I size the brass to 1.6165"-1.6175" and call it a day. Anyway I look at it, the brass end up being bumped anywhere from 0.001" to 0.003".

However, before doing so, I measure the brass and chamber to verify it has a true Headspace of no more than 0.0035".

I read on this website that go/no guages can vary several thou from manufacturer to manufacturer. Measurements after firing in your chamber and setback are all that matters. Do you see a difference in groups with different bumps?

 

[Zero333]

I read on this website that go/no guages can vary several thou from manufacturer to manufacturer. Measurements after firing in your chamber and setback are all that matters. Do you see a difference in groups with different bumps?

NO,... but I do set my own headspace on the barrels and I always measure the fired brass to see the difference between go-gauge and the actual fired brass.
To be completely honest,. I use the go-gauge specs when I'm sizing brass for semi-auto duty. Otherwise I just aim for 0.002" bump.

 

[JB1970]

I’m a noobie so others may want to refute this - which is perfectly ok. I found it really fiddly trying to bump shoulder and came across the video below that accomplishes the same end with varying thickness Redding shell holders. Might be worth a watch OP.

 

[Dave M.]

It's all about how you set up the die.

Hence why we use headspace comparator to compare fired and sized brass. Everything else is not very relevant.

I have some FL dies that when they're set up to cam-over, they push the shoulder 0.006"... which is not ideal, and that much shoulder bump will result in headspace separation sooner than later.
0.002" shoulder bump is a sweet spot for brass concentricity and decent life span.

Personally, if your sizing is done very accurately, I personally think .002” bump is way too much for a custom bolt action rifle. I have been bumping .0005-.001” for two years now and my scores have shown this is the correct thing to do. But to each their own I suppose, I’m just saying .002” bump is a lot for a custom chamber and precision reloading.
Dave

 

[Zero333]

Personally, if your sizing is done very accurately, I personally think .002” bump is way too much for a custom bolt action rifle. I have been bumping .0005-.001” for two years now and my scores have shown this is the correct thing to do. But to each their own I suppose, I’m just saying .002” bump is a lot for a custom chamber and precision reloading.
Dave

And I agree.. However I reload a few of the same cartridges for more than one rifle and prefer the ease of mind. Some of my rifles are PRS while others are for range duty only. Thus 0.002" shoulder bump satisfies all the rifles.

 

[marine52]

The go gage is actually short in your rifles chamber. Possibly a couple thou. Not what I would use to setup(adjust) my FL die.

Yes, a go gauge is usually at SAAMI min but can be used effectively to set bump. I use a go gauge and then use aluminum foil on end with a smidge of paste to find exact headspace (reg foil is about .0004 - .0006” and ” and heavy foil is right at .0008”). I do this on a newly chambered barrel and then I have a set target number for the rest of its life. If I want .002 bump, all I do is index off of the go gauge. I do confirm case fit in chamber during sizing using the tape method. It’s generally spot on.

 

[Dave M.]

The E-Z Chek'r lands tool works great for determining shoulder bump IN YOUR CHAMBER. I'll post a link to the thread here and instruction sheet. You just need a fired case that will chamber easily, just drop in fully and then size the case to the bump you want. Super easy and precise.

What accent? Lol!

Link to discussion

Finding the lands...Tool!

This is a tool I've used for years for different things, from finding the lands, checking shoulder bump, chambering barrels and even cutting cone depth with an attachment I have inside that contacts a "datum" or reference point from an old bbl that transfers to the new one when cut. Super simple...

forum.accurateshooter.com

Instruction sheet below

Works super easy (EZ, pun intended). Love it.
Dave