Comments on: TECH Tip: How to Set Your Dies for Correct Shoulder Bump

By: Ralph D

Ralph D — Sat, 30 Sep 2023 21:18:44 +0000

Complete fire forming BEFORE bumping back shoulders will insure consistent HS measurements.

By: Dasher

Dasher — Tue, 23 Oct 2012 09:31:31 +0000

Agreed, you have to look at it case by case in those situations. I’m working with barrel and dies made off my own reamers. Taking a remmy700 and RCBS sizer may not be as good a match to blindly size the case. However, in that situation most folks size as the manufacturer tells them to, which is always excessive. This article describes that there is more in between “manufacturer setting” and “pure-bred BR”.

By: Boyd Allen

Boyd Allen — Tue, 23 Oct 2012 01:43:13 +0000

Setting dies by feel is based on an assumption that the die is small enough that it will size the back of the case when set for the correct amount of shoulder bump. When shooting rifles with generous chamber dimensions, and using standard factory dies (that tend to size cases more than absolutely necessary) this is generally the case, but these are not the only rifles out there, and if you have ever had a die that would not size the back of a case when the shoulder was bumped correctly, you know what I am writing about. In the latter case, setting by feel, will guarantee that bump is excessive. This is why I think that it is not a good thing to give the blanket instruction to set a die by feel. Also, if a die will not size the back of a case without excessive bump, a different die is needed. This can not be solved with an adjustment. Bottom line, there are advantages to measuring, and some potential disadvantage to not measuring. If you have been getting good results for umpteen years setting dies by feel, all that this means is that all of your dies were dimensioned to allow this approach, not that everyone’s will be.

By: tenring

tenring — Mon, 22 Oct 2012 23:39:54 +0000

Initially, I use the bolt feel down method with FP removed. About half way down the bolt will encounter very slight resistance. This means the shoulder has met the chamber. With very little effort, the bolt will easily close. That means the HS is correct. If not, case needs to be bumped.
After turning the die down very little and resizing until bolt closes lightly, I put it in my Redding Instant Indicator, set the dial to zero, and use that tool to check every case. Some cases will not need to be bumped.

By: Dasher

Dasher — Mon, 22 Oct 2012 15:12:53 +0000

You can set the die up initialy to bump too much and then add shims to get the exact bump required. That way you are not guessing with “turn in a little” but adjusting with .001″ accuracy. Takes a little fiddling for the first setup removing and re-inserting the die into the press, but easy to remove the Die afterwards and then get the same setting again because of the shims.

You’re trying to get the case as close to the headspace of the chamber, so as not to size too much to stress the brass, but also to not size it enough and get jams.

I did a write up here, but it’s in dutch, but the photos show what I mean though.
http://www.vuurwapens.net/forum/index.php?action=articles;sa=view;article=55

By: Editor

Editor — Mon, 22 Oct 2012 13:41:28 +0000

Dasher wrote: “The bolt-feel may be “legacy” but I have yet to find 20 cases that are all the same size. You can set back 0.002″, but in reference to what? One of the 20 cases you measured? Did you measure the right case, or the long one, or the short one.?”

NOTE: We refer to shoulder bump in terms of .001, .0015, .002. But Dasher is correct that the actual amount of headspace reduction (i.e. shoulder bump) may vary slightly among cases in a batch (particularly if they were fired with different loads).

But in reality, where the cases start, is not so important as where they END UP dimensionally. That’s why we use a tool to measure off the shoulder. In a good press, with the die set up correctly, your brass, even if it starts with different base to shoulder measurements, will end up with the same base to shoulder dimension. That’s what we’re looking to hold constant! We do recommend measuring each of your cases after full-length sizing.

By: JDeUgarte

JDeUgarte — Mon, 22 Oct 2012 12:43:21 +0000

The article still does not explain how to set up your die for shoulder bump like the title implies, just explains why.

EDITOR: OK, perhaps we missed the obvious point. For more bump, screw the die down (a very little bit at a time). For less bump, screw the die up. When you get to the point where bump is starting to be achieved, a very small rotation (a few degrees of rotation) can make a big difference. You’ll need to set the lock ring as you change settings.

By: Dasher

Dasher — Mon, 22 Oct 2012 11:55:59 +0000

The bolt-feel may be “legacy” but I have yet to find 20 cases that are all the same size. You can set back 0.002″, but in reference to what? One of the 20 cases you measured? Did you measure the right case, or the long one, or the short one.

The “legacy” aproach let’s me set up the FL-sizer to within 0.001″ using shims. 90% of the cases could fit with 0.002″ less, but 5-10% need a little more to set them back to a good fit. Slight resistance on the bolt when closing (without pin).

I’ve been shooting this for over 10-12 years and have never had case defects as you describe. Some cases were resized 30-40 times this way, no issues.

If this were the case, all the plain-jane reloaders out there would be having case problems non-stop with the “turn in all the way and add 1/4 rotation” setup for their FLs

By: fdshuster

fdshuster — Mon, 22 Oct 2012 00:21:27 +0000

I take my dimensions off the fired case, after cleaning, before sizing & record those numbers for each chambering.

Use the Stoney Point gauge to verify that the shoulders are being pushed back .001″ to .002″ with each sizing with the Redding Type S FL neck bushing dies.

Case trimming is seldom required & when it does, it’s only a few thousandth’s. I’ve never had to throw away a case for incipiant case head seperation.

Talking about 6ppc & 6BR chamberings, not factory.

By: Only Measure

Only Measure — Sun, 21 Oct 2012 21:22:03 +0000

IMO – the bolt drop method is a legacy approach before decent tools were readily available. It is way too easy to over size by many thou and cause early head separation. Measuring the set back is the only way to go safely.