OAL variation with new 550B

[ArtLan]

I have just started reloading with a new 550B and with both 9mm and 45 loads, I have a problem keeping the OAL variation small and consistent. When I run a single case through the machine, the OAL of the 9mm FMJ RN comes out to be 1.150 +/-0.003. When I have a case in each stage, the OAL will often be 1.175, with a lot of variability on the increase in length. If I run the longer cartridges through one at a time with no adjustments to the machine, they will almost always come out sized properly at 1.150 +/-0.003. The same variation in OAL variation happens with the 45ACP with cast SWC so it is not specific to the 9mm or 45ACP cartridge.

Is this variation in OAL an inherent feature of the 550B that when depriming and resizing the OAL operation becomes a bit longer because the machine is bending somehow resulting in inconsistent OAL? Or is this a setup issue or specific problem with my 550B, and if so, what should I look for in correcting the problem?

[GrumpyOne]

It's a setup issue. Always adjust your OAL with the shellplate full, a case in every station. That will take out much of the inconsistencies. There are many threads here on the forum about this. Do a search on 550 OAL and it will pull up quite a few.

[Sarge]

What he said. I run a 550 as well. Also, oal will vary if you load mixed brass. Get a hundred of the same headstamps and adjust with plate full per Grumpy and see what you come up with.

I know the mixed brass thing sounds unlikely but trust me, don't think about it, just do it!

[Singlestack]

If you are using Dillon seating dies, check to see if the profile of the seater stem matches the bullet you are using. Try turning it over to see if it helps.

[MARKAVELI]

+1 each station full will give you better results with the O.A.L and with the same brass too, mix brass can be off -/+.. Good luck..

Edited July 7, 2011 by MARKAVELI

[Bob DuBois]

+1 above, sometimes bullet shapes vary, you can mark the tip of the bullet with a sharpie or marker to see where the seating die is touching. I like to push on the nose of the bullet if possible.

I'll trash military 9mm cases because of smaller case volume, inconsistent loads and I don't want to mess with swagged primers.

Press is designed to do four things at once, best to leave it that way when you finish the session, cases in all four stations. Always push up the loading handle when you return then you know the primer is seated. Get a phone call or someone comes in the area stop, finish the conversation the start back. It's simple and enjoyable process but as humans it's easy to make a mistake.

Enjoy the 550 it will provide you with a life time of use.

[MemphisMechanic]

Also make sure your shellplate's center bolt is as tight as possible while still allowing the plate to rotate freely. Most new Dillon users run theirs too loose, and it'll cause things like this.