Thread: Need help understanding shoulder bump

I've asked about this previously but never really got my head around it. Just now I've found my .338 Lapua brass is tight to chamber after been fired and neck-sized twice, I am using Redding deluxe dies, and just measuring COAL rather than measuring from the ogive as I just anted the loaded rounds to fit in the magazine (rifle is a Savage) accuracy has been excellent but with the cost of Lapua brass I want to be mindful of brass longevity.

So, am I correct in understanding I need to get a shoulder collar to fit the shoulder angle (and maybe a better set of calipers) to measure headspace from my fire-formed cases, then play around with my FL sizing die to bump the shoulder 2 thou or so, or maybe get a set of Redding competition shell holders in 2 thou increments to do it? If I do it by just unscrewing the FL die, will it mean the necks will not be sized fully? Also, I see that standalone shoulder bump dies don't seem to be available for the .338, so could I just get an engineer to bore out the neck part of the FL size so it leaves the neck alone, and neck size with the neck size die as a separate step? Will doing the above still work the body of the case to any degree worth worrying about?

Cheers for any advice, Tom

Gunsmithing &Reloading Tools - Redding Body Dies, Dies

My 2c: Go to this site and buy this die. Put your (primerless) brass in the holder and lower the lever with no die in, then put the die in and screw down it till it touches firm. Get you rifle ready and use it to chamber the brass in question, brass that don't fit are good! They tell you that your bump die needs screwing down more.
Just slowly repeat the trial and error method by screwing down this body die 1/16th each time till one of your sizings does result in a chamber.

Now you have the choice: set that as your goto resize / bump point or make it a little more (if that result caused a sticky bolt lift by not resizing enough).

You can do it without measuring, but when it comes to reloading I measure everything...

The hornady "headspace gauge" has an insert for the caliber you use. I my case it is .400 for 308 family of brass. After firing, measure the shoulder to see what your fi reformed shoulder is. I then set up a Redding body die to reduce that by 0.002. Chamber the case to see that the bolt closes easily.

You might want to check your overall brass length as well. Difficulty chambering can be from multiple causes : brass needs to be trimmed, shoulder pushed back, or base is too tight for chamber (use small base die to fix this).

You can adjust the FL die to bump the shoulder, but unless you remove the expander ball, you are working the necks of your brass quite a bit. I am very careful with the necks of my brass, so use a body die, and then a collet neck die to reduce working the necks to a minimum.

You could bore out the neck part of a FL die, but dies are made to be incredibly hard, and are not kind on tooling, so you might struggle to find an engineering shop to do it.

Pretty well covered by ebf. What I also do is remove the firing pin/spring mechanism from the bolt - not sure whether the Savage lends itself to this. You can then try your brass for bolt closing without the influence of the firing pin spring holding the bolt hard back against the locking lugs. For hunting reloads and cartridges that stretch after only a few loadings 2 thou is good. For my target loads and the likes of my Ackley where the brass just doesn’t move after only a few firings I set the die so that I get a very very small resistance at the very last part of closing the bolt.

As always lubricate the locking lugs.

Also remember 1 full turn of a die will give 71 thou movement so gently gently only fractions required. I also find that when you have a case almost at the right setting after adjusting the die use another case to try the new setting. If you use the same case you will find due to brass hysteresis/spring back and the only small change required for that piece of brass you end up having to over adjust the die to get that last small movement. Use another piece of unsized brass to test the outcome of your last adjustment.

To get very fine movements I use either Redding Competition Shellholders of shims between the die and the press - Skip's shims. I have a mate who uses feeler gauges inserted into the shellholder under the case brass to achieve the same result. Works OK but you have to put the feeler gauge in for each case sizing. Better to find a permanent seeting on the die and lock it off.

There may be others that disagree with this but I would bump the shoulder absolutely every time you load if you use the rifle for hunting or sooner or later you will strike a sticky piece of brass that will ruin your day -your follow up shot will turn to shit in a heart beat as you wrestle with a stuck or stiff bolt and your target runs or limps off into scrub

Originally Posted by yerimaginaryM8

There may be others that disagree with this but I would bump the shoulder absolutely every time you load if you use the rifle for hunting or sooner or later you will strike a sticky piece of brass that will ruin your day -your follow up shot will turn to shit in a heart beat as you wrestle with a stuck or stiff bolt and your target runs or limps off into scrub

This the best practice for hunting rifles and target rifles if shooting long strings of shots it doesn't take much powder fouling in to take up the clearance between case and chamber in tight cut chambers,
for my .308's I have a Redding comp die set, body die and small base bushing die, the small base die gets used the most it's set to bump the case .002" I never have a problem with the bolt closing and can see no
difference in accuracy over full length sized,
You should be able to set the .338 FL die to bump the case .002" with out worrying about the neck not being sized the last .002" in fact it will help centre the case in the chamber, get a set of the Redding comp case holders
to adjust the bump or FL size dies so you don't need the change the die settings.

Some are saying to use the FL die to bump the shoulder back - i never had much luck with that. I'd just personally found that i munted far less brass just using the body die only and making sure the rifle can close the bolt on all my brass before i prime and load it.

I try to keep my measuring to a minimum - i fear there's a risk of OCD that im probably heading towards anyway. I just decided to start de-burring flashholes....Very retro i know but i'm curious to see if it does anything for Lapua brass consistency.

I got a set of the Hornady headspace gauges, from what i've read online the D 4.20' one should suit the shoulder, but it doesn't seem to give a snug fit and is hard to get a reading off as it wobbles a bit. Does the expander ball in the neck sizing and FL sizing Redding dies function the same way? It looks like Lee don't make a collet neck die for the .338, I'm wondering if there is any advantage of using a Redding neck size plus body size dies, versus a Redding FL size die if they are set up the same for minimal shoulder bump?
Cheers, Tom

The body die is mainly for when using the competition die set as the size die is a bushing neck die it would not hurt to have the body die if it does not bump the shoulder
enough you can have the die base trimmed, I did it to one of mine works fine.