Need help: erratic shoulder bump on progressive press

[Hengehold]

BLUF: shoulder bump on Dillon 750 is erratic and not maintained at the initial shoulder bump setting.

I decided to get a progressive to do several steps of brass prep at one time (FL size with Type-S die, prime, and uniform the NK dia with an expanding mandrill). I just bought a Dillon 750 and am setting it up to bump the shoulder about .002-.003”. After I have the FL die adjusted for the desired setting I begin cycling the press to process brass. When using the press in full operation (size, prime, NK uniform at the same time) the shoulder bump goes from .003 to .006 of setback.

I readjust the die and it happens again.

-Armanov tool head is screwed firmly into place.
-FL die lock ring is used as a standard lock ring and not used in the “floating” configuration. Lock ring was initially used on top of tool head with minimal die thread access so moved it to the bottom of the die. (See pic)
-.020” taken off bottom of FL sizing die to ensure it is not contacting the Dillon shell holder. (See pic)
-case holder has no play or rocking to cause variance. It is solid.
-brass used was once fired Lapua 308 Win.

On a single stage press I might have a max of .001” variation in shoulder bump based on the number of times brass was fired.

Is anybody able to get similar shoulder bump consistency between a single stage and progressive or is my experience of inconsistent shoulder bump with a 750 just par for the course?

 

[K22]

.020” taken off bottom of FL sizing die to ensure it is not contacting the Dillon shell holder. (See pic)

All the following comments are based on my experience with bolt action rifles.

Why did you modify the F/L die? While I never use a Dillon or any other progressive press, in my experience, in order to bump the shoulder, the F/L die needs some amount of cam over (contact with the shell holder) in order to bump the shoulder due to the mechanical play in most presses under F/L sizing force. The case has to make full contact with the F/L die (shoulder area of the die) otherwise the case will be extruded.

However, by shaving off the F/L die, you changed the relationship between the F/L die and shell holder increasing the bump. The condition may be aggravated since although it may be an optical illusion in the picture, the F/L die appears at an angle to the shell holder. When the F/L die is not set leveled against shell holder inconsistent sizing can result.

Another issue is that often it takes a few firings before the brass is fully fireformed in the rifle chamber. Therefore, the cases may not need bumping at this stage since you stated they have only been fired once. Measuring fired cases (primer removed) with a bump gauge to obtain a baseline of case head space and checking the fired cases for chamber fit will reveal if you need to bump. In my experience, you will not need to bump the shoulder for several firing. You can still use the F/L die, just set for a zero to .001" bump.

 

[Shooter13]

Brass new or old? Trimmed? Annealed? Just some factors that may affect the bump. I have a 650 and the shell plate does move, wouldn't use it for accurate reloading, .223s, .308s, hunting or pistol or plinking, sure but not for competition rounds. Just my thoughts, that (my thoughts) and $2 will get you a cup of coffee at Micky Ds.

 

[Hengehold]

.020” taken off bottom of FL sizing die to ensure it is not contacting the Dillon shell holder. (See pic)

All the following comments are based on my experience with bolt action rifles.

Why did you modify the F/L die? While I never use a Dillon or any other progressive press, in my experience, in order to bump the shoulder, the F/L die needs some amount of cam over (contact with the shell holder) in order to bump the shoulder due to the mechanical play in most presses under F/L sizing force. The case has to make full contact with the F/L die (shoulder area of the die) otherwise the case will be extruded.

However, by shaving off the F/L die, you changed the relationship between the F/L die and shell holder increasing the bump. The condition may be aggravated since although it may be an optical illusion in the picture, the F/L die appears at an angle to the shell holder. When the F/L die is not set leveled against shell holder inconsistent sizing can result.

Another issue is that often it takes a few firings before the brass is fully fireformed in the rifle chamber. Therefore, the cases may not need bumping at this stage since you stated they have only been fired once. Measuring fired cases (primer removed) with a bump gauge to obtain a baseline of case head space and checking the fired cases for chamber fit will reveal if you need to bump. In my experience, you will not need to bump the shoulder for several firing. You can still use the F/L die, just set for a zero to .001" bump.

Progressive presses can’t use a stepped shell holder so removed a few thou to allow enough room to bump shoulder adequately and not contact shell holder.

 

[David Christian]

Have been using 2 different 750s for over 5 years to produce match level rounds. The machine can do it with a few fine tunings.

Have you ground the bottom of the shell plate to level it? Both of mine had several high and low spots. Are you using a thrust bearing on the center bolt holding the shell plate down? Without these 2 mods there is likely slop under pressure.


My guess is that this slop is giving you one measurement on the initial brass sizing, then when you have multiple stations full of brass the press is exerting different amounts of force across multiple dies, hence uneven sizing. The shell plate is basically rocking back and forth under pressure.

 

[Fire Dog]

Brass new or old? Trimmed? Annealed? Just some factors that may affect the bump. I have a 650 and the shell plate does move, wouldn't use it for accurate reloading, .223s, .308s, hunting or pistol or plinking, sure but not for competition rounds. Just my thoughts, that (my thoughts) and $2 will get you a cup of coffee at Micky Ds.

Coffee? Is that what they call the horrible, burnt, sour black stuff they serve out of long over due for a cleaning machines at Macca’s…?

 

[Hengehold]

Have been using 2 different 750s for over 5 years to produce match level rounds. The machine can do it with a few fine tunings.

Have you ground the bottom of the shell plate to level it? Both of mine had several high and low spots. Are you using a thrust bearing on the center bolt holding the shell plate down? Without these 2 mods there is likely slop under pressure.View attachment 1726496
View attachment 1726495

My guess is that this slop is giving you one measurement on the initial brass sizing, then when you have multiple stations full of brass the press is exerting different amounts of force across multiple dies, hence uneven sizing. The shell plate is basically rocking back and forth under pressure.

Thanks for the advice.
Yes I have a thrust bearing installed.

No, have not ground the shell plate. Where can I send the shell plate to get this done?

 

[David Christian]

Thanks for the advice.
Yes I have a thrust bearing installed.

No, have not ground the shell plate. Where can I send the shell plate to get this done?

First one I did by hand over a few hours with sand paper on a flat surface. Using a marker to color the plate, reinstall it with pressure, and rotated it around to find the wear marks. 2nd one a buddies machine shop had a high tech belt sander.

 

[243winxb]

erratic

If each station of the shell plate is the same? Use a Lee dead length seat die, as a stop for the press linkage.

BUt if the shell plate is a different thickness, at each station, it will not help.

The base plate flexing, can be another problem.

This Dillon shell plate gives 4 different shoulder bumps. On 5.56/223.

 

[charlie b]

I've had 3 Lee progressives but never measured bump. I'd set the dies based on trying the cases in the chamber. Once I set the size die, then I'd set the others. It was a fine balance to get the seat and size die set perfectly to each work properly. That was one of the reasons I stopped using the progressives for rifle loads.

 

[Hoser]

Having a machine shop use a surface grinder on the bottom of your shell plate should help, if not fix things.

 

[243winxb]

Deck height of shell plate or shell holder should be the same. If any die is making contact with it.

.125" +/- .001"

 

[mgunderson]

Yes. I have observed the variation and it will change from lot to lot and your annealing regime. Watch for die contact like people suggest. That cost me a match as well.

Single stage is the most precise. Progressive is an exercise in patience and tolerance.

Are you running more than one barrel.. that can get exciting as well with a progressive.

I tend to run a little more shoulder clearance with the progressive.

 

[D-4297]

From the FWIW Dept : You have to many moving parts , clearances and other "issues" to deal with in a Progressive press . There was a discussion about this issue one day in the Pit at Ben Avery and guys were going back and forth about the Pros and Cons of each . There was a slight break in the debate , and "Mid" ; in his usual manner spoke . "Anybody trying to use a Progressive Press to create Match Ammo is wasting their time" ! It won't be consistent .
So why would anyone listen to this guy about this ?
Because he has more Titles and Championships , than most people have letters in their name ! I do all of my loading with a single stage RCBS Press !

 

[Rewinder]

 

[Rewinder]

 

[makethemdead]

#1 de-prim before you measure fired brass headspace to remove any variables from the fired primer, and then check the fired de-primed brass in your chamber to find out if/or how much you need to set back headspace, bunch of youtube videos on setting up your die headspace bump. Best results usually requires annealing before you size.
I know most likely you know these steps but best to make sure before you throw money away chasing a ghost of your own making.

 

[Shooter13]

Have been using 2 different 750s for over 5 years to produce match level rounds. The machine can do it with a few fine tunings.

Have you ground the bottom of the shell plate to level it? Both of mine had several high and low spots. Are you using a thrust bearing on the center bolt holding the shell plate down? Without these 2 mods there is likely slop under pressure.View attachment 1726496
View attachment 1726495

My guess is that this slop is giving you one measurement on the initial brass sizing, then when you have multiple stations full of brass the press is exerting different amounts of force across multiple dies, hence uneven sizing. The shell plate is basically rocking back and forth under pressure.

Work arounds to make it do what it wasn't designed to do, not being a wise guy but putting lipstick on a pig doesn't make it pretty (did help miss piggy) LOL I think it was fclass john that had one running doing just that and you long range guys do it differently. I guess if it works it works.

 

[358WCF]

Just a thought...

It says "-brass used was once fired Lapua 308 Win." in the OP.

Are you sure the brass has all expanded equally? Maybe nothing to do with progressive press, maybe due to not fully formed brass?

Just for shits & giggles I wonder what the brass measures before sizing?

 

[FTR_Mojo]

I dont use a progressive.
But are you giving enough dwelling time?