550 bullet seating depth variance

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Has anyone noticed this or is it just my reloader? after I initially set my bullet depth for my OAL at a certain depth, Ex. 1.140, on just my initial single bullet, I will start to reload a batch but as soon as my shell plate gets full and all 4 stages are going at one pull, my OAL will change to 1.145 or longer. So if I want to seat a specific OAL i have to initially set it up with a shorter length. What gives?

[Alan550]

When setting the seating AND the crimp dies, the shell plate must be full. Otherwise there is some "play" in the shell plate that must be there in order for it to be loose enough to turn. With a case in only one station, the shell plate will tilt slightly and give you the incorrect result that you're getting once the stations are loaded. In fact, it's really best to set all 4 stations with the plate loaded.

Alan~^~

[BMartens]

I generally do the initial set up with one round in the press. Much easier to do it that way. You will be very close to your final set up with a single round.

Then load up the shell plate and start checking and measuring each round coming off. Do the touch up settings for bell, seat and crimp until you have exactly what you want.

[calishootr]

+1 to what has already been said, there is a certain amount of flex to the system, that will even itself out oncethe plate is full, also whatyou can try is to shim the toolhead to take out the little bit of play that it has, but to be honest the variations are going to be there because of brass(is it new??? mixed headstamp, many times fired etc...)

[GentlemanJim]

You can also put set screws in the press frame to take all the slack out of the tool head.

A small variation in oal for pistol is usually not a problem

For rifle however...it can be a very big deal

A drill a tap and 4 10-32 setscrews is a cheap fix

Jim

[Sarge]

I generally do the initial set up with one round in the press. Much easier to do it that way. You will be very close to your final set up with a single round.

Then load up the shell plate and start checking and measuring each round coming off. Do the touch up settings for bell, seat and crimp until you have exactly what you want.

+1 Exactly how I do it.

[JThompson]

It's all about the amount of pressure... with a single bullet, you have little pressure. Just get it close and tweak it with all dies full.

JT

Edited November 13, 2009 by JThompson

[Quigley]

Do yourself a favour and buy the Redding Competition seating die. It's money well spent...and the micrometer adjustment for OAL is great!

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thanks guys. i appreciate everyone's advice.

[Graham Smith]

This is what I understand...

When setting the dies, you need to start with the sizing die and get that right, it should just touch the shellplate when the plate is fully raised. Then check to see if you still get a full stroke when there is a case in station one - if not you may need to adjust the die. The point being, if you don't get a full stroke every time, then none of the rest of the stations will be consistent.

After setting station one, you should be able to get the other stations pretty close doing them one at a time. After they are all done, start running some actual rounds through until you have all stations full, then start pulling out cases and checking them. You'll be able to dial things in pretty quickly. Then periodically, spot check things.

As to the Redding die, I didn't feel like spending that much but did buy a Hornady seating die and a micrometer adjustment knob. It sure makes tweaking the seating length a lot easier.

And I encourage you to find a copy of Brians Competition Reloading DVD - there are some great tips in there about making adjustments.