Need help with shoulder bumping!

TrentK16

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May 23, 2014
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35
Location
Oregon
As the title says I need help with bumping the shoulders back when resizing. Now I've been reloading for a few years now and I wouldn't consider my self a complete rookie to reloading, I also know I am no expert. I've read different manuals, watched plenty of videos so I believe I have a good grasp of reloading for precision rifles.

Alright so for my problem. I recently just resized a bunch of 300wm, 7mm rem mag, and 7mm-08. All of them my goal was to bump the shoulder back .002". So I used my hornady headspace gauge and started measuring each one and sorting them into .001" windows. In hope I could get my die dialed in for one, lock it in place and start plugging away at the rest of them that fell into that window. Then adjust accordingly to the brass that fell out of that .001" window. Well I found out fast that didn't work and ended up double and triple cycling every piece to get them just perfect. Now I've always double cycled when seating bullets. Just figured brass with the same measurement to the shoulder I wouldn't need to cycle it through more than once.

Background info:
I'm not using any competition dies, just standard rcbs FL dies.
The brass for all 3 calibers are from Remington factory rounds that have been fired through the exact same rifles I'm loading them for.
Using a hornady single stage press.
Oh and I resizing and depriming in one action, and I never got to lock my die in place cause I'm always adjust the die from case to case.

What am I doing wrong? Is it due to inconsistent powder charges from the factory so the shoulder doesn't get blown out equally shot to shot? Should I deprime then measure with headspace gauge and then resize? Or is it do to the dies or press?
Thanks for any help!

Trent
 

FearNoWind

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Jul 10, 2012
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I suspect your Hornady head space gauge is the problem. I've found that they work well to determine that there is sufficient head space but to actually adjust dies for head space - that's another story. What I've decided to do is measure the OAL the case, run it through the die and measure the difference. If it's .002 shorter than it was, I'm good. It has worked well for me ...
 

RoadKill

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Dec 17, 2010
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Caswell bush in NC
Knocking snot out the shoulder intending to shove it back but all the while watching for and working towards a .002” reduction in overall length of base of the case to the case mouth is plain wrong, everything about it is wrong, stuff don’t get any wronger kind of wrong…
 

ultraedge

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central Georgia
You need to use a bump gauge specific for the shoulder angle of the particular cartridge that you are resizing. You put them in a dial caliper and measure from the base of the cartridge to the datum line. Take a cartridge fired in your rifle, measure this length, then adjust your sizing die to move the shoulder back about .002 . If you use the cartridges in multiple rifles more shoulder bump may be required, even if they have been chambered with the same reamer, because of minute headspace differences. Also if the brass has not been annealed, you might have to leave the press ram at the top of the stroke for a longer time period to move the shoulder consistently on work hardened brass. Gary
 

TrentK16

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Joined
May 23, 2014
Messages
35
Location
Oregon
You need to use a bump gauge specific for the shoulder angle of the particular cartridge that you are resizing. You put them in a dial caliper and measure from the base of the cartridge to the datum line. Take a cartridge fired in your rifle, measure this length, then adjust your sizing die to move the shoulder back about .002 . If you use the cartridges in multiple rifles more shoulder bump may be required, even if they have been chambered with the same reamer, because of minute headspace differences. Also if the brass has not been annealed, you might have to leave the press ram at the top of the stroke for a longer time period to move the shoulder consistently on work hardened brass. Gary
I have the hornady gauge that measures to the datum lines on the shoulder. What I'm finding is that the fired brass (before resizing or depriming) when I'm measuring are different measurements from the base to the datum line from Case to case by a few thousandths. So I have to adjust the die from case to case to compensate for that.

I'm not sure if the primer in the brass is hitting my caliper?
Should I try to just deprime, then measure and adjust the die?
 

barefooter56

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Nov 10, 2014
Messages
913
I have the hornady gauge that measures to the datum lines on the shoulder. What I'm finding is that the fired brass (before resizing or depriming) when I'm measuring are different measurements from the base to the datum line from Case to case by a few thousandths. So I have to adjust the die from case to case to compensate for that.

I'm not sure if the primer in the brass is hitting my caliper?
Should I try to just deprime, then measure and adjust the die?
trentk16,
Fired brass does not expand at the same rate. So try this. If you can , remove the firing pin assembly from your bolt and try to find a couple pieces of brass fired IN THAT RIFLE that when you close the bolt on them you get no resistance through the first 2/3rd s to 3/4 of the bolt throw with some closing resistance during the last 1/3 to 1/4 of the bolt closure. Measure these cases with your Hornady Bump Gauge system and note the length. Now we adjust the full length , body or bump die. There are couple ways we can do this by either adjusting the die in the threads of the press or using the Redding Competition shell holders. The first way is to adjust the die in the press using a standard shell holder to what the factory calls for then turning the die up about 1- 1 1/2 turns. Run the brass up into the die and remeasure. If the case is still the same OR GETS LONGER (due to the die sizing the case body and no contact of the die on the cartridge shoulder) adjust the die down a small amount, run the brass through the die and re-check length. Follow this procedure until you get the shoulder bump you want/need. General rule of thumb is .001-.002 for target, .002-.003 for hunting, .003-.005 for semi-auto, pump or lever action rifles.
With the REDDING Competition shell holders. Adjust the die in the press per the instructions using a STANDARD REDDING SHELL HOLDER. Starting with the .010 thick shell holder run the the pre-measured brass through the die and check shoulder bump. If none or not enough go to the .080 thick shell holder and so on until you get the shoulder bump you want/need. I do this after I have decapped all the brass using a dedicated de-capping die like the RCBS that ONLY DE-CAPS AND DOES NO SIZING. That way I don't have to worry about a high primer. To re-cap, use the rifles chamber as a gauge to find the cartridge (s) case to use to set up your dies. Measure these cases with your bump gauge tool so you have a NUMBER to refer too. Then do your die set up to get the shoulder bump you want. IF you cannot remove the firing pin assembly from the rifle take a few cartridge cases and fire and neck size them until they chamber hard then measure and start from there. Hope this helps get you going!
 

RoadKill

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Dec 17, 2010
Messages
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Location
Caswell bush in NC
It might take the firing of a couple or three full power loads before the brass expands on firing and then after it has relaxed, it’ll nearly or completely be filling the full length of the chamber from the bolt face to the shoulder datum. At this point is where I want to take a measurement (get a number) representative near as practicable of the bolt face to shoulder datum length of that chamber. Knowing that brass measuring at or longer than my number gets crushed to some extent on closing the bolt, I adjust the die so it’ll minimally bump back the shoulder ~ .001” or .002” (bolt gun, for use only in that chamber). With shoulder bumped and pushed fully forward butted against the shoulder end of the chamber, there will be at least some clearance between the bolt face and cartridge base up to but not greater than .002”. I’m thinking some variance in but not exceeding .002” bolt face to case base clearance should mean less potential for squirreling how well the thing could shoot than would a varying amount of case crush on every closing of the bolt.
 

TrentK16

Active Member
Joined
May 23, 2014
Messages
35
Location
Oregon
trentk16,
Fired brass does not expand at the same rate. So try this. If you can , remove the firing pin assembly from your bolt and try to find a couple pieces of brass fired IN THAT RIFLE that when you close the bolt on them you get no resistance through the first 2/3rd s to 3/4 of the bolt throw with some closing resistance during the last 1/3 to 1/4 of the bolt closure. Measure these cases with your Hornady Bump Gauge system and note the length. Now we adjust the full length , body or bump die. There are couple ways we can do this by either adjusting the die in the threads of the press or using the Redding Competition shell holders. The first way is to adjust the die in the press using a standard shell holder to what the factory calls for then turning the die up about 1- 1 1/2 turns. Run the brass up into the die and remeasure. If the case is still the same OR GETS LONGER (due to the die sizing the case body and no contact of the die on the cartridge shoulder) adjust the die down a small amount, run the brass through the die and re-check length. Follow this procedure until you get the shoulder bump you want/need. General rule of thumb is .001-.002 for target, .002-.003 for hunting, .003-.005 for semi-auto, pump or lever action rifles.
With the REDDING Competition shell holders. Adjust the die in the press per the instructions using a STANDARD REDDING SHELL HOLDER. Starting with the .010 thick shell holder run the the pre-measured brass through the die and check shoulder bump. If none or not enough go to the .080 thick shell holder and so on until you get the shoulder bump you want/need. I do this after I have decapped all the brass using a dedicated de-capping die like the RCBS that ONLY DE-CAPS AND DOES NO SIZING. That way I don't have to worry about a high primer. To re-cap, use the rifles chamber as a gauge to find the cartridge (s) case to use to set up your dies. Measure these cases with your bump gauge tool so you have a NUMBER to refer too. Then do your die set up to get the shoulder bump you want. IF you cannot remove the firing pin assembly from the rifle take a few cartridge cases and fire and neck size them until they chamber hard then measure and start from there. Hope this helps get you going!
I have been doing that process with my rcbs FL die and measuring and remeasuring till perfect like you were saying (without decapping first and and removing the firing pin). So maybe that is my problem? I will have to give that a try. Thanks guys!

Trent
 

Mikecr

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Aug 10, 2003
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5,311
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NC, oceanfront
+1 Roadkill
Removing the pin allows the bolt to turn freely, allowing you to find a case with .000 headspace. Once you have this with your tool, log it, adjust your die w/resp to this.

Some die/chamber combinations are difficult when it comes to bumping. Another thing that matters is very very consistent application of lube.
I use separate Redding body dies and store the die with shellholder in a box for each chamber. The cost of an extra shellholder is far cheaper than the aggrevation of finding logged setting every time otherwise.
 

RoadKill

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Dec 17, 2010
Messages
39
Location
Caswell bush in NC
If you use a completely gutted bolt body for feeling out case fit then you’ll not have to determine if all the resistance you’re feeling is from closing the bolt on brass completely filling the base to shoulder length of the chamber, or whether maybe some or even all of it is from battling the geometry and spring loaded mechanicals going on within the cocking and/or ejector mechanisms.

Find what number your implements will give you checking brass that’s right at zero clearance in your chamber. Knowing that, now you can adjust the die to size the brass to just under that number so it’ll give you at least some clearance on up to .002”, or thereabouts. A cheap calculator will tell you quick how far one turn or a fraction of a turn will move a 7/8”-14 threaded die in or out of the press. One turn moves the die ~ .071”, 1 turn / 14 threads per inch = .0714”. One eighth of one full turn will change the die’s adjustment by ~ .009” or 1/14/8 = .0089”. Using this calculator math you can easily cipher for any fraction of a turn, 1/4th turn does 1/14/4 = .0179”, 1/8th turn does 1/14/8 = .0089”, and if you want to adjust the die by only one measly thousandth of an inch, all you got to do is crank it exactly 1/64th of a turn or 1/14/64 = .0011”. Redding’s Competition Shell Holder sets are workin’ real good, easy die adjustments in .002” increments.

Any case crush on closing the bolt is induced stress I’d rather avoid.
 

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