Base to datum inconsistent with ADG brass after FL sizing

[steffen707]

So I've got a whidden full length 7rsaum sizing die with 0.313 bushing.
Im using twice fired ADG brass, use imperial sizing die wax on my rcbs summit press. I had to turn the die all the way down so it's touching the shell holder to get enough bump.

The shells come out of my gun with a 1.582" base to datum.

After running through the press I get anywhere from 2-10 thousandths bump on the shoulder.

Why isn't it consistent? Because the die is hitting the shell holder? I don't remember this kind of variation when I reloaded 7rm Winchester brass with a forster die on the same rcbs summit press last year.

I have not annealed the brass. Is that it?
I have a mitutoyo 6" caliper with a ogive and shoulder comparator, I think it's Sinclair brand.

 

[CharlieNC]

That's a lot of variability. What sized length are you trying to get, you could have some brass which are shorter and therefore not sizing. Measure 10-20 unsized brass, then size them to compare before:after in order to start ruling out factors.

 

[steffen707]

1.580" is what I'm going for.

 

[divingin]

If it's inconsistent coming out of the die, you need to look at how much of a gap you're getting between the shellplate and die bottom while sizing. Most presses will flex or stretch a bit when the case is run into a sizing die; differing amounts of friction will cause differing amounts of flex or stretch. Verify first that it's actually happening, then look at figuring out why (I'd be tending towards lubing practices, but who knows?)

Giving the brass several seconds under pressure while in the die may improve consistency as well.

 

[JFrank]

using twice fired ADG brass, use imperial sizing die wax

I’m not that familiar with ADG ..Twice fired may not be enough to have all them formed yet hence the variations.

 

[Bill Norris]

using twice fired ADG brass, use imperial sizing die wax

I’m not that familiar with ADG ..Twice fired may not be enough to have all them formed yet hence the variations.

Seems like twice fired should be enough to get better numbers. Take a look at how much sizing wax you are applying and keeping it off of the shoulder area of the brass.

 

[JFrank]

Seems like twice fired should be enough to get better numbers. Take a look at how much sizing wax you are applying and keeping it off of the shoulder area of the brass.

Sorry Bill I copied and pasted the op question I then put a thought out there. My apologies

 

[mikecr]

A 10thou difference would have to mean some of the cases are not formed to stable yet.
It's just too much to be from a die/setup.

 

[XTR]

yes, you need to anneal. Spring back is different case to case. I figured this one out a long time ago and saved myself a lot of running in circles; however, short cases indicate the brass isn’t fully formed to the chamber yet if they were short before sized.

 

[steffen707]

yes, you need to anneal. Spring back is different case to case. I figured this one out a long time ago and saved myself a lot of running in circles; however, short cases indicate the brass isn’t fully formed to the chamber yet if they were short before sized.

hmmm. I think ADG brass is supposed to be pretty good stuff https://atlasdg.com/
I would imagine their cases were consistent (wish i measured all of them and wrote it down now) I have 3 more unopened boxes, so maybe i'll open one up and test them.

Anyways, I took one of the pieces of brass and made a dumby round to send to Whidden Gun Works for them to chamber my Proof barrel and put it on my Tikka action. I asked them to make the chamber 2thousandths longer than the dumby round. I remember when I measured the first fired case I was like, YEP, its exactly 2thoughsandths longer after I shot.

So i'm pretty sure all the cases are coming out of the rifle at 1.582" to the shoulder.

So I put the FL sizing die into the press and screwed it down until it touched the shell holder, backed it off 1/4 turn and sized a piece. When I measured it, it was longer than 1.582". I heard this can happen if you are sizing the bottom of the case, but not bumping the shoulder back. (don't know if that's true or not)

So I turned the die down and tried another. It was again, longer than 1.582", but not as much as the first one.
So I turned it down until it was touching the shell holder, still long.

Turned down a little farther and I was getting no bump, but no lengthening either.

A few more tweaks and it was bumping 2thousandths for a few cases in a row, so I did like 30-40 cases and when I got done I started checking and they were all over the place.

I guess when i get home I'll measure all the cases and write down the values reload them, shoot them, then re-measure each case to compare.

 

[Zero333]

Equal amount of sizing lube on each case always helps. Also the first few will come one a little shorter since the inside of the die is still dry and inconsistent.

 

[K22]

hmmm. I think ADG brass is supposed to be pretty good stuff https://atlasdg.com/
I would imagine their cases were consistent (wish i measured all of them and wrote it down now) I have 3 more unopened boxes, so maybe i'll open one up and test them.

Anyways, I took one of the pieces of brass and made a dumby round to send to Whidden Gun Works for them to chamber my Proof barrel and put it on my Tikka action. I asked them to make the chamber 2thousandths longer than the dumby round. I remember when I measured the first fired case I was like, YEP, its exactly 2thoughsandths longer after I shot.

So i'm pretty sure all the cases are coming out of the rifle at 1.582" to the shoulder.

So I put the FL sizing die into the press and screwed it down until it touched the shell holder, backed it off 1/4 turn and sized a piece. When I measured it, it was longer than 1.582". I heard this can happen if you are sizing the bottom of the case, but not bumping the shoulder back. (don't know if that's true or not)

So I turned the die down and tried another. It was again, longer than 1.582", but not as much as the first one.
So I turned it down until it was touching the shell holder, still long.

Turned down a little farther and I was getting no bump, but no lengthening either.

A few more tweaks and it was bumping 2thousandths for a few cases in a row, so I did like 30-40 cases and when I got done I started checking and they were all over the place.

I guess when i get home I'll measure all the cases and write down the values reload them, shoot them, then re-measure each case to compare.

The lengthening is caused by the case being extruded in the die. This can happen when the die does not touch the shoulder of the case.

I would stop at the point where you "turned down a little farther and I was getting no bump, but no lengthening either." Then I would check the chambering in the rifle for fit.

This may be all the sizing that you need. Don't forget that you are also sizing the radial dimension of the case when you full length resize. Many times, it's not necessary to bump the shoulder back to promote chambering.

 

[steffen707]

I would stop at the point where you "turned down a little farther and I was getting no bump, but no lengthening either." Then I would check the chambering in the rifle for fit.

This may be all the sizing that you need. Don't forget that you are also sizing the radial dimension of the case when you full length resize. Many times, it's not necessary to bump the shoulder back to promote chambering.

Alright, after I fireform the cases again and measure each of them after firing, i'll try this. I thought if you didn't bump the shoulder back in a hunting rifle, you run the risk of debris causing it to not chamber.

 

[K22]

Alright, after I fireform the cases again and measure each of them after firing, i'll try this. I thought if you didn't bump the shoulder back in a hunting rifle, you run the risk of debris causing it to not chamber.

If you get debris in the chamber it's going to cause chambering issues whether you full size or neck size. The only reason to bump the shoulder is when the case has lengthened to a point where it creates difficult chambering which does need to be avoided especially for a hunter.

If you full size the case back to the fired case head space and it chambers without issue, then that's enough sizing at this point. Eventually you may have to increase the sizing (i.e., shoulder bump). By monitoring fired case head space, you will be able to determine when additional sizing is needed. The first goal should be to establish some sizing consistency to the point where the cases chamber without difficulty,

As cases harden from repeated firings and work hardening from repeated sizing's, some sizing adjustment will be necessary. The standard rule of thumb of a .001 to .002" shoulder bump is an effective guideline and works most of the time but it's only a guideline. Sometimes you have to tailor the sizing to a specific rifle and lot of cases. Since in your situation, turning the sizing die down too far has created erratic sized case head space, a sizing adjustment is needed to restore sizing consistency. I would be more concerned with over sizing and sizing consistency than getting debris in the chamber.

 

[steffen707]

If you full size the case back to the fired case head space and it chambers without issue, then that's enough sizing at this point. Eventually you may have to increase the sizing (i.e., shoulder bump). By monitoring fired case head space, you will be able to determine when additional sizing is needed. The first goal should be to establish some sizing consistency to the point where the cases chamber without difficulty,

Awesome. I really appreciate everybody's replies and suggestions. Can't wait to work on this again this Saturday.

 

[Dave M.]

Seems like twice fired should be enough to get better numbers. Take a look at how much sizing wax you are applying and keeping it off of the shoulder area of the brass.

I agree. Twice fired really should be enough to fully form the brass. Minimize amount of wax used (a little goes a long way) and finally, you could be seeing some inconsistent results due to varying hardness of the brass but I don’t use ADG brass and I’m not sure if that has been an a issue. Certainly, proper annealing of the brass prior to sizing could not possibly hurt. Does the dwell time when the ram is at full up have any bearing with the amount of shoulder bump? I’d suggest backing the die out until you are no longer bumping the shoulders, from there mark the die and lock ring with a sharpie marker stripe. From there, turn the die back in approx 5 degrees. This should be approx 1 thou. There should be no need to bump the shoulders more than 1-1.5 thou max.
Dave

 

[steffen707]

I loaded up 29 rounds fired them cleaned them and measured with my shoulder gage.

5 - 1.5815"
20 - 1.5820"
3 - 1.5825"
1 - 1.5830"

Is this normal or could this be a sign of overpressure? I think I felt increased effort to eject a few of these cases.
Federal 215 primer, 59gr of imr 4831, 154gr SST, 2820fps MV out of 18" barrel

So now should I reset my die to just not touching the shell holder and size 1 of the 20 - 1.5820" cases?

 

[Dusty Stevens]

Youre within .001. Your calipers cannot actually read to the .0005 so its making it look worse than it is. Case lube application can account for more than .001

 

[Ccrider]

No need to move the shoulders back until you feel them touching the chamber after firing. If you pay attention, you should be able to feel this when chambering the fired case whe they get long enough.

Measure your case at that point and and adjust your die enough to set the shoulder back .002 or so. That will free up your bolt again.

Some cases may take sizing more than once to get it to .002. Annealing makes the process more consistent but is not mandatory.

Also, some will tell you to get more (.003) or less (.0015) clearance. Others will tell you the want to feel a little pressure but not enough to upset the gun in the bags when cycling. Decide for yourself what you are comfortable with.

Last, your fireformed brass is pretty consistent and in the range I look for.

 

[rebs]

How can you tell when your die is wore out?