Shoulder bump FL sizing and measurements

[Mram10us]

To help with measuring on the fl die, I put a sharpie mark on the body lining up somewhere on the nut. Easy way to adjust for small amounts. When you find the magic setting, write the comparator number on the side of the die and your good to go. I'm sure there's better ways, but this works for me

 

[MNbogboy]

To help with measuring on the fl die, I put a sharpie mark on the body lining up somewhere on the nut. Easy way to adjust for small amounts. When you find the magic setting, write the comparator number on the side of the die and your good to go. I'm sure there's better ways, but this works for me
View attachment 164778

Exactly the way I've done it for over 50 years....easy & simple.

 

[Tac-O]

I want to update this thread as I made a discovery recently and think this information would be helpful to others. I was attempting to use my FL sizing die to bump the shoulders back 0.002". I found that my fired cases would max out at about 1.742 for base to datum (I think... I can't remember exactly off the top of my head). Chambering a case of this size starts giving resistance through the full length of closing the bolt, so this is the length of my chamber for fired cases. No matter how I set up my FL sizing die, it would cause my base to datum measurement on the case to increase! If it was a 1x fired case and was only 1.740, after sizing it would be 1.742. If it was a 2x fired case and measured 1.742, then after sizing it would measure 1.743! I could set my die up to the manufacturer's instructions for a SAAMI spec FL resize and I'd still end up with bolt resistance when closing the bolt after a 2 or 3 firings.

I happen to find this article the other day:

http://bulletin.accurateshooter.com/2010/09/bedeviled-by-bump-when-full-length-dies-dont-work/

After reading that article, I determined that my die was just a little bit too long on the inside. So here's what I did:

- put a sheet of 400 grit sand paper on a very flat surface (stainless top table)
- put some cutting oil on the sand paper
- sanded down the bottom of my FL sizing die by 0.004-0.005".

Now when setting up my die, I can set it up to have just a slight bit of cam over and it will bump my shoulders back from 1.742 to 1.740.

From what I've found reading, there's other ways of accomplishing this; grinding down top of shellholder, etc. Each have their own merits and drawbacks. In my case, if I get a different rifle of same chambering or have a new barrel put in, then my customized die might not work anymore. Or maybe it will. No need to worry about that since Lee dies are affordable and now I can actually size my cases the way I want!

 

[338 dude]

Thanks for the link!

One piece of info I left out is that they are once fired brass, with a 150gr bullet and a low-mid range powder charge. So, I probably didn't even completely fire form the brass yet! I'll have to pull out some older cases this evening and check those.

Usually 2or3 firings for me until I need to bump

 

[338 dude]

I want to update this thread as I made a discovery recently and think this information would be helpful to others. I was attempting to use my FL sizing die to bump the shoulders back 0.002". I found that my fired cases would max out at about 1.742 for base to datum (I think... I can't remember exactly off the top of my head). Chambering a case of this size starts giving resistance through the full length of closing the bolt, so this is the length of my chamber for fired cases. No matter how I set up my FL sizing die, it would cause my base to datum measurement on the case to increase! If it was a 1x fired case and was only 1.740, after sizing it would be 1.742. If it was a 2x fired case and measured 1.742, then after sizing it would measure 1.743! I could set my die up to the manufacturer's instructions for a SAAMI spec FL resize and I'd still end up with bolt resistance when closing the bolt after a 2 or 3 firings.

I happen to find this article the other day:

http://bulletin.accurateshooter.com/2010/09/bedeviled-by-bump-when-full-length-dies-dont-work/

After reading that article, I determined that my die was just a little bit too long on the inside. So here's what I did:

- put a sheet of 400 grit sand paper on a very flat surface (stainless top table)
- put some cutting oil on the sand paper
- sanded down the bottom of my FL sizing die by 0.004-0.005".

Now when setting up my die, I can set it up to have just a slight bit of cam over and it will bump my shoulders back from 1.742 to 1.740.

From what I've found reading, there's other ways of accomplishing this; grinding down top of shellholder, etc. Each have their own merits and drawbacks. In my case, if I get a different rifle of same chambering or have a new barrel put in, then my customized die might not work anymore. Or maybe it will. No need to worry about that since Lee dies are affordable and now I can actually size my cases the way I want!

First I would try a different shell holder after that I would grind or sand down the shell holder they are cheaper and easily replaceable much more so than a die

 

[Tac-O]

First I would try a different shell holder after that I would grind or sand down the shell holder they are cheaper and easily replaceable much more so than a die

That's true with most dies. In the case of my Lee die, which is $15-20, it would only take buying two shell holders to hit that number, so I figured I'd go with the method that would definitely work.

 

[Mram10us]

I always take .010" off my shell holders. I used to trim the bottom of the die but then had to worry about polishing so it wouldn't scrape the brass

 

[MNbogboy]

Usually 2or3 firings for me until I need to bump

Agree 2 to 3 firings to reach full length then I anneal and bump every cycle. I also measure each case before & after bumping. Some cases often are a little different than the others and I make slight die adjustments to compensate. Ideally my goal is .0015 to .0025 bump.

Lots of good advice on this thread.