Shoulder bump

[AlNyhus]

Nothing good comes from extreme minimal shoulder push back. -Al

 

[Wild Bill IV]

Nothing good comes from extreme minimal shoulder push back. -Al

A universal statement Al!!! Tell me, why can you still get neck size dies today? What is it purpose? A FL die can be set to mimic a neck size die! A single loading rifle loves minimal bump!!!!!! After all, pressure, volume, and heat are directly related to each other!!!! Change one ever so slightly, effects the other two!!! I've learned, to achieve a long range, single shot hit, you have to have minimal bump with a round warmed kept in a shirt pocket!! Minimal change in length of the chamber round minimizes the volumetric change of the case under pressure, while the steady state of initial powder temperature (measurement of heat) results in a more consistent pressure curve!!!!

And, most factory rifles have a long throat!! To squeeze accuracy of this rifles, the over all cartridge length may exceed the box magazine or clip lengths!!! Might as well go for minimal bump in this case, single shooting the near max pressure node load, and extending maximum effective range for hunting purposes!!!

 

[Steve Donlon]

I just got done reloading for one of my AR 15 rifles that is very accurate for what it is. I reload it as if it was a bench rifle. I have been using paper shims for a long time for all of my rifles but finally got some steel shims. They work good but I still like my paper ones better. I needed to just go down a little bit to get just the right amount of bump. With my steel shims, I did not have a thin enough one, so I went back to paper. I agree that just the right amount of bump does make a difference no matter what rifle you are using. Just one more variable to deal without having to buy special dies.

 

[JFrank]

If you’re reasonably consistent with sizing I wouldn’t think a guy would see any variance in performance from either .001 or .003 set back that would affect the target.
In all fairness I have tested about every thing I can think of but testing set back on paper hadn’t crossed my mind.
Jim

 

[Wild Bill IV]

If you’re reasonably consistent with sizing I wouldn’t think a guy would see any variance in performance from either .001 or .003 set back that would affect the target.
In all fairness I have tested about every thing I can think of but testing set back on paper hadn’t crossed my mind.
Jim

Good point Jim!!! But what about the slight energy lost due to the case base slamming or hammering the bolt face and working the stretch area? Hunters want to get just as much brass life as they can with high pressure loads. They are not going to last as long as a middle pressure load! The hunter does not want case head separation out in the field or back county! Plus, I was at silhouette shoots were a 7mm Mauser and 7-08 had cases head separation from too much bump with high pressure, high energy loads!!! I set my 7-08 bump 0.001" too avoid working the stretch too much with those near max loads!!!

 

[Kracken McGraw]

Me too, it’s tough enough to get all my rounds down range before a condition changes , fighting a bolt open and upsetting the rifle in the bags is an absolute killer.

This kind of corresponds with Alex Wheeler’s video on sizing and seeing the bolt fall.

 

[JFrank]

But what about the slight energy lost due to the case base slamming or hammering the bolt face and working the stretch area

To be honest Bill, if I had a week to think up weird stuff to go wrong this wouldn’t make the top ten.
Additional point to offer here is that what’s important to a BR guy might not hold as much value to a hunter with magazine fed firearm.

Jim

 

[Wild Bill IV]

To be honest Bill, if I had a week to think up weird stuff to go wrong this wouldn’t make the top ten.
Additional point to offer here is that what’s important to a BR guy might not hold as much value to a hunter with magazine fed firearm.

Jim

You got a point!!! However, some of us hunters try to achieve high accuracy too, using bench rest methods at higher pressures!! Some of the Old BR methods from 50 years ago can still work for the LR hunter today!!! Neck sizing only (no bump) from that era is a prime example!!! I still neck ream too!!! The fastest, easiest, and cheapest way of trueing a fire formed neck and trimming at the same time!! This increases the bullet alignment with the rifling when using minimal bump!!! Sometimes, the most accurate loads will not fit in the magazine due to near jam!! Those hunters can single feed if the so chose!! Higher pressure with too much bump can lead to case head separation!!! I have no need to shoot 1000!! However, I shoot targets that can move at 600 and only get one shot!! And those targets do not have an "X" with circles around it!! That is the maximum effective range for two of my 26" target/varmint barreled big game hunting rifles!! And, there are accurate shooter hunters too on this website!!! Not just target and bench rest shooters!!

By the way, I big game hunt and varmint hunt, single feeding those long cartridges with Sierra Gameking SBT that are very accurate at near touch!!! I have that much confidence in the loads, the guns, and my type of shooting skills!! All one shot kills in over 40 years of big game hunting!!!

 

[precision1]

It depends on what type of shooting sport you are into!!!!!!!
I'm a cold barrel shooter!!! I do once and done high pressure fire forming!!! I bump back right at full chamber length or -0.0005" (just enough for slight compression of the case in the chamber with slight heavy bolt drop very near full bolt lock)!!!

I have found out that lubricity is the key to bumping back this tiny bit!!! A thin film lube is essential!!! Lanolin base lubes (animal fats used mainly for skin hydration) don't provide for a thin film!!! The high pressure oil lubes (derived from crude oil) provides that thin film!!! Those tiny molecules (from long term heat and pressure) act like tiny ball bearing!!!! I've also noticed that lube pastes, waxes, and sprays require a little more force on the press handle!!

At my bench, I periodically check (1 out of 10-15 FL sized cases) the bump compared to a set aside full fire formed case (black brass patina)!!! Plus, I periodically check the cases in the rifle itself!!!

What do you use for case lube?

 

[Wild Bill IV]

What do you use for case lube?

I use Bonanza case lube from 45 years ago! Still have a 1/3 bottle full after reloading around 15000 cases!!
Forster and RCBS still make the high pressure oil lubes!!! A lube pad is needed for this type of lubing the cases! And, after getting a good thin coat in the die, you can alternate a dry case and lubed care through the die!! If the cases are clean enough, I have gone 3 dry to 1 lubed case!!! But you have to learn the feel of the press to do this!! Especially on the upward stroke!! Otherwise, you can end up with a stuck case in the die!!! After 45 years of reloading with the old Bonanza press, you can feel that slight change and know when to run a lubed case!!! I've only had one stuck case!!! What a mess!!!

Then, I wipe the oil off an give the cases an alcohol bath!!!
DM me if you want to get into this!! There are other little procedures for effective and efficient use of the pad and the oil!!!

 

[D-4297]

Maybe I’m just getting too old but I can’t seem to understand the obsession with setting back a shoulder at such razor thin margins. Has anyone discovered some benefit on paper at any distance ?
I have only seen problems with fired brass cycling freely.

Jim

Yes . I have seen a improvement in both scores , and X-count when I began "Bumping" the shoulder to a .001 requirement . I think it is all part of the "Process" of creating consistent , repeatable ammo , reducing the variables to the lowest common denominator . I think that if more people were as concerned about creating consistent Brass , they wouldn't spend so much time fretting about inconsistent S/D numbers .

 

[gmr4]

I’ve adhere to .002 and wont except more than .0005 variance. I’ve been told the main reason to be consistent is ignition timing. Same for primer seating depth… need to be consistent. I have tested various primer seating depths at 1000 yards and it does matter. Shoot 10 at distance with all different shoulder bumps vs 10 with consistent.. test it…

 

[Wild Bill IV]

I’ve adhere to .002 and wont except more than .0005 variance. I’ve been told the main reason to be consistent is ignition timing. Same for primer seating depth… need to be consistent. I have tested various primer seating depths at 1000 yards and it does matter. Shoot 10 at distance with all different shoulder bumps vs 10 with consistent.. test it…

gmr4: A reloader, shooter that is going far from his testing!!!!!

Primer ignition timing is very critical in the pressure curve!! I have not done your testing of variations in bump to consistent bump. However, I use a set aside fire formed case as a master for comparing die formed cases!!!!! But, I have found, in the primer punching process, irregularities in the base around the primer pocket (slight mounting, slight depressions, or totally flat on rare occasions) which affects primer seating depth slightly!!!! I lightly file the bases flat, until I see a consistent removal of brass around that primer pocket area before I uniform the primer pocket itself!!!!!!!!! Now, the primer will be at a much more consistent depth with uniform pressure crush on seating the primers!!!!!!!! AND, IT MAY AID IN MORE CONSISTENT SHOULDER BUMP WHICH THIS THREAD IS ABOUT!!!

Before you start filing on new brass, use scrap brass to practice on!!! I use a broken file and place in and old rectangular serving tray that has the small ribs!! Holding the case down and flat with the file, stroke it into the file cutting ribs about 1/2 to 3/4" stroke forward while giving it a slight twist!!! Twisting and holding down in the stroke keeps it from UNWANTED chattering or bouncing which can cause unwanted tapering or angle deflection of the wanted 90° flat surface!!! Then, draw straight back that distance with lighter force but firm squaring force!! Go be the case some rotation, and repeat the both and forth stoke! After a few cycles, inspect the case and look for brass removal around the primer pocket and well into the base itself!! This has been one of my case prep procedures for the past 40 years!!!! This tightened group sizes from my prior 5 years of no bump reloading!! IMO, this could benefit the BR reloader in getting slightly better primer seating and a more consistent case geometry in FIRING and FORMING!!!!

Most accurate reloaders worry about the shoulder (BUMP) and the neck (Thickness and potential TENSION acting against the bullet COMPRESSION) and forget the A$$ END (Base flatness and truer primer pocket uniformity)!!! CONSISTENT ALL AROUND CASE GEOMETRY IS KEY TO NEAR PERFECT ACCURACY!!! THE CASE IS THE FOUNDATION OF AN ACCURATE CARTRIDGE!!!!!!!!!!!!

 

[6.5 forever]

To be honest Bill, if I had a week to think up weird stuff to go wrong this wouldn’t make the top ten.
Additional point to offer here is that what’s important to a BR guy might not hold as much value to a hunter with magazine fed firearm.

Jim

or a PRS run and gun guy

 

[gmr4]

or a PRS run and gun guy

If I was invested in winning at PRS I would adhere to F Class reloading practices. Looking at PRS scores it looks like one hit or one miss can make a big difference in where you place over an entire weekend. I know a winning PRS shooter who is really meticulous with his reloading and never says “its PRS I dont need to do that”. Set tight tolerances for primer seating depth, shoulder bump, neck tension, seating depth … SORT BULLETS (out of 500 Bergers I always find 4-5 that are off).

 

[6.5 forever]

If I was invested in winning at PRS I would adhere to F Class reloading practices. Looking at PRS scores it looks like one hit or one miss can make a big difference in where you place over an entire weekend. I know a winning PRS shooter who is really meticulous with his reloading and never says “its PRS I dont need to do that”. Set tight tolerances for primer seating depth, shoulder bump, neck tension, seating depth … SORT BULLETS (out of 500 Bergers I always find 4-5 that are off).

My thought was a PRS shooter NEEDS to make sure he gets a good shoulder set back. No tight or hard chambers needed in that game.

 

[Wild Bill IV]

Off the subject with bad news!!

My hometown of Grinnell, Kansas was hit by a tornado late last evening!! It snaps power poles, ripped houses total off their foundations!!! Knocked over head stones in the cemetery!!!!! Rolled trucks and cars off I-70!!! Even a Porsche!!!

God was there, Nobody was seriously injured or killed!!! God was there, the Catholic Church roof was ripped from the rafters, but all the candles were still burning inside!!! They say strange things happen in wild weather, but candles still burning????? THE LIGHT IN THE DARKNESS!! God was in Grinnell!!!!!!!!!!!

 

[gmr4]

My thought was a PRS shooter NEEDS to make sure he gets a good shoulder set back. No tight or hard chambers needed in that game.

Yes that is correct, good shoulder bump and consistent.