Seating Depth issue

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PepNYC

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Hey all. So I'm having a weird issue when seating my bullets. I set my die to my desired depth on the first round. Seats spot on. As I seat the rest the OAL starts to vary. For example, I set it to 1.150 for a 9mm. First one seats at 1.150. Next will be 1.147, 1.153, 1,144, etc. Even had one off by as much as 1.156. I put the exact same amount of pressure on each one when lowering the ram. Any suggestions?

BTW it's a Lee Breech lock press and Lee die set.
 
You will have some variance due to variances in bullet ogive, more pronounced with cast, with HPs due to variances in cavity/meplat formation, and also brass alloy, thickness, and hardening which effects spring back. If compressed loads that can also make a difference. They will never be identical. +/- .006 is way tighter than I'd worry about.
 
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I got cheap $10 ebay chinese junk. If you have two showing same issue thats not the problem of course.
 
I had a large box of bulk Remington jacketed soft points for a 223 and had problems with seating depths. I started comparing bullets from that box and found a good bit of variation among them. Some were visibly quite different. They also did not shoot worth a hoot.
 
I use Lee taper crimp dies on my Dillon 650 for 9mm. Of course the length of the case can determine the amount of crimp that is put on the bullet. It seems to me that a longer case which will have a slightly tighter crimp seems to push the bullet down a little farther. Not enough to be any concern, but I did notice it when loading some Lehigh bullets that are longer and I was watching the seating depth closely because I didn't want compressed charges. I noticed then that the OAL length varied a tad due to the case length. Its not a issue either way.
 
I load 9mm on my Dillon 550b. When I set the seating die up, there is only one cartridge in the press. I start long, then "sneak up" on the COL I want. Once I lock the die down, I can consistently get within .001 or .002 COL when there is ONLY that ONE station occupied. When I begin a run with all stations occupied, and all four operations happening with every pull of the handle, checks of COL might be .004 or .005 off from where I set the die, but they are consistent as long as all 4 stations are in operation. As the last 3 rounds progress through the remaining operations, COL tends to wander back to whatever I set it for when just that single station was occupied.

I usually set COL to what I want, then once full operation begins, I'll check a finished round and might make a very slight adjustment to the seating die, so the bulk of the batch is as close to the COL I want. Periodic spot checks prove to be quite consistent.
 
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