Variances in shoulder set back..

GreenBlood10

GreenBlood10

Lead Farmer
Full Member
Minuteman
Nov 27, 2012
193
14
Spring Grove, Pa
#1
I am brand new to reloading and just started prepping some brass. My set up is a Forster Co-Ax press and Redding Type-S full length sizing die with a .289 bushing installed. I am using once fired 6.5cm Prime brass. For case lube I am using imperial sizing die wax.

Before I started, I used a Hornady headspace gauge to measure from the base of a few cases to their datum line. The measurement I took, on several cases, was 1.581". Since these reloads are for a GAP-10, I aimed for a .003" shoulder set back. Once I was able to reproduce a measurement of 1.578", I locked the die down with the Forster lock ring.

I continued to measure each case after I ran them through the sizing die and noticed some variances from case to case. The cases I measured after going through the die ranged anywhere from 1.5765" to 1.578".

I made sure I was applying a thin coat of wax to just the case body and not the shoulder or neck. I believe I am being consistent on my strokes with the press. Is this normal or acceptable?
 
#2
Try some more lube and put a thin coat over the whole case. I have done extensive playing around with shoulder bump and to get consistent bump, you need to have the correct amount of lube on the cases. If a case doesn't get quite enough lube, it will not bump back properly. I always lube the entire case.

I just had it happen yesterday when I was testing out a new RCBS Precision Mic. Had a case not show the correct amount of bump, I then added a touch more lube and ran it through again and it bumped properly.

Another thing that may help is to pause for a second or two with the case fully in the die and not run the cases through the die really fast. A pause at the up stroke can help keep shoulders consistent.
 
#4
Yes, I ran them all through a Lee universal decapping die, then through the tumbler and then I took my measurements.

I think the culprit may be slightly bent rims. There is a barely noticeable wave to some of the rims I've been looking at. I'm going to go sort through all my brass now.
 
#5
GreenBlood10 said:
Yes, I ran them all through a Lee universal decapping die, then through the tumbler and then I took my measurements.

I think the culprit may be slightly bent rims. There is a barely noticeable wave to some of the rims I've been looking at. I'm going to go sort through all my brass now.
Click to expand...

definitely check for bent/warped case rims...gas guns will do it and throw off your measurements
 
#7
Nosler brass is expensive. For a gas gun I would grab some Lake City. 1/3 the price and will likely last longer. Will it take a bit more work to unify it all? Yeah. Will it last longer and tolerate more abuse? I would imagine so since thats what its original purpose was geared towards. Its hard and thick to take the abuse of rapidly firing guns.
 
#8
spife7980 said:
Nosler brass is expensive. For a gas gun I would grab some Lake City. 1/3 the price and will likely last longer. Will it take a bit more work to unify it all? Yeah. Will it last longer and tolerate more abuse? I would imagine so since thats what its original purpose was geared towards. Its hard and thick to take the abuse of rapidly firing guns.
Click to expand...

Not sure I want to spend the time converting .308 LC brass to 6.5CM.
 
#9
GreenBlood10 said:
Not sure I want to spend the time converting .308 LC brass to 6.5CM.
Click to expand...

Aw shit, I dropped the ball on that part.
The prime should be the same as the nosler brass I believe both are manufactured by norma. I think the nosler is weight sorted though.
Do your cases that measure 1.578 chamber without having to use the feed button to close the bolt up on them?

I personally would find your variance of .0015 to be acceptable though for a gas gun and manually smeared on wax. Ive noticed that a case can read .001 different depending on if I measure it dry or lubed.
 
#10
What I found out recently is that the lube used for case sizing can have a big impact on consistency of how the shoulder is set back during resizing. I was using Hornady One Shot which I believe is a wax based lube and I was have a very difficult time getting a consistent shoulder bump. I then switched to RCBS water based lube and the shoulder bump was very consistent, and the resizing force on the press was less. When I followed Hornady's instructions to allow the One Shot to dry sizing force was much higher and shoulder bump was inconsistent. When I used One shot and sized a case that was still wet with the lube it sized more easily. Now I remember why I tried One Shot years ago and it has set on the reloading bench unused for so long. Decided to give it a shot again recently and wasn't happy with the results. I'll stick with an RCBS type lube since it has worked.
 
#11
Yes, they do. I took one case that measured 1.578" and manually placed it into the chamber and closed the bolt using the bolt release button. It closed completely. My main concern now is the effect the warped rims will have on accuracy.
 
#12
I think I'm gonna pick up a box or two of Norma brass. My OCD won't allow me to sleep knowing I loaded up cases with warped/bent case rims lol. I'm fairly certain that will eliminate the variance I am seeing on my calipers.
 
#13
Something you have to be careful about is too much lube on a the shoulder. I was always taught to NOT lube the shoulder but I have to to get consistent shoulder bump. With the Imperial that you're using you shouldn't have problems with dented shoulders.
The thing that helps me get consistent shoulder bump is annealing. Making sure I get the shoulder area annealed as well as the neck. After loading a case two or three times the shoulders get pretty springy.
 
#16
Alrighty , here's a list to ensure consistency

clean and deprime cases prior to sizing
cam over
anneal cases
pause at the top stroke
*size a case, turn it 1/4-1/2 then size again (some say this overworks brass, YMMV)

lubricate cases outside and inside neck (if using a ball). If conditions are right ie:
-dry neck
-tight neck from sizing neck too much
you can pull your neck hard and cause a little stretching
 
#17
Annealing will help a ton and make sure you are measuring the case correctly and consistently every time. It's very easy to not have the case centered and completely flat every time. The base attachment for the opposite side of the caliper jaw can help if you don't have one already. I also spin the case while slightly pinched between the gauge and caliper to help center and find the smallest measurement possible.
 
#18
Juggerxxx said:
The base attachment for the opposite side of the caliper jaw can help if you don't have one already. I also spin the case while slightly pinched between the gauge and caliper to help center and find the smallest measurement possible.
Click to expand...

I was spinning the cases while measuring which is when I would see the fluctuation. That is when I started to suspect that the case rims were warped. They aren't extremely warped but definitely enough to be giving me my .001" variance. I am going to order some new brass, along with the Hornady anvil base tomorrow.

 
#19
There are all kinds of variables that would cause you to have .001 variance temperature fluctuations, amount of lube, was the die clean or dirty when you started, assuming you are using vernier mics most have a measurable tolerance of +/- .002 and that is for a good set of mitutoyo's. If you are using aluminum case gauges the mouths will bellow out causing inconsistent readings. If your camming over that will cause inconsistencies in your press. Reloading press are not fine tool machines they are not built to deliver .001 accuracy. So add all those variables up and if you are coming out with only .001 difference be happy with that only the stars aligning and mother nature blowing rainbow loads upon your equipment will improve that.

Never been a big fan of camming presses I used to do it but now that I have a lathe I just buzz what I need off the bottom of the die and don't have to stress the press and loads are more consistent. I never tried the spacers that redding sales but guess they would do the same.
 
#21
GreenBlood10 said:
I am brand new to reloading and just started prepping some brass. My set up is a Forster Co-Ax press and Redding Type-S full length sizing die with a .289 bushing installed. I am using once fired 6.5cm Prime brass. For case lube I am using imperial sizing die wax.

Before I started, I used a Hornady headspace gauge to measure from the base of a few cases to their datum line. The measurement I took, on several cases, was 1.581". Since these reloads are for a GAP-10, I aimed for a .003" shoulder set back. Once I was able to reproduce a measurement of 1.578", I locked the die down with the Forster lock ring.

I continued to measure each case after I ran them through the sizing die and noticed some variances from case to case. The cases I measured after going through the die ranged anywhere from 1.5765" to 1.578".

I made sure I was applying a thin coat of wax to just the case body and not the shoulder or neck. I believe I am being consistent on my strokes with the press. Is this normal or acceptable?
Click to expand...

might want to try this trick of imperial case wax and spray lube as in this video: https://www.youtube.com/edit?o=U&video_id=ZUhVxp1rOXs

everything is about consistency... running the ram, amount of pressure you apply at the end of the ram stroke, you name.... for the first and maybe every 30th pc of brass ish ill put the thinnest (damn near none) film of imperial wax over the entire body of the brass when I see brass being stubborn for shoulder set back... don't forget the inside of the case mouth with imperial wax with a qtip.. if you don't have imperial wax, then id get some asap... annealing the brass helps too... consistency, consistency, consistency from reloading to shooting the rifle
 
#22
While I applaud the Co-Ax press for excellent concentricity on loaded rounds, the lingering fact that the bottom of the die doesn't make hard contact with a shell holder top will make bumping consistency a moving target. A Redding Competition shell holder of the correct pocket depth used a conventional press will let you make hard contact with the bottom of your die for dead nuts consistent shoulder bumping. If you get the full set, you will have a choice of a +.002" to .010" deeper pocket that your cartridge case head sits against, while the top of the shell holder maintains hard contact with the bottom of your bumping die.
 
#24
As an update, I went out last week and bought two boxes of Hornady brass on sale. Took a few that measured longer than others on the headspace gauge and ran them through the FL sizer to bump back a thou. They all measured consistently. Appears that the issue was indeed the warped case rims. Thanks for the tips guys.
 
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