I was just trying to reload my 300 RUM. I did up a bunch of 165 gr XBT's and 180 Gr Nos BT's with out any problems. When I went to seat in some 180 grain Partitions the bullets seat so loose I can push the slug into the case with my thumb. I checked the XBT'S and Nos BT's and I can put a whole lot of weight on the bullets with out them moving.

Now I did get a little carried away with outside neck triming but I did all the cases at the same time. So It shouldn't effect some cases more than others, and these cases were from around the half way point of cutting incase your thinking of cutter wear.

So I figured that I would crimp the necks down a little bit and that would solve my problem. Well it doesn't the shoulders collapse before the crimp is firm enough to hold the bullets. I crimp a little bit, no change, crimp a little bit more, still no change, then the shoulder folds in.

I mic'ed the bullets and get 0.307"

So I dumped out the powder and think I am going to throw that brass out unless someone can help me figure out what is going on. I'm using RCBS dies.

Thanks Mark

I just measured the outside neck tolerance on a sized piece of Brass that has been outside turned. 0.334

An un-fired sized case that has not been turned measures 0.336-0.337

The book tolerance is 0.344 outside neck diameter.

what type of die?
You may need to take a couple thousands of the expander button due to spring back of the brass.

I neck size with an RCBS die.


I also measured inside neck tolerances on several cases.

My neck turned stuff was around 0.304-0.305"

An un-fired not neck turned case was 0.303" after being neck sized.

I'm guessing that yes it is the spring back of the brass.

I have taken just a hair too much off and now the neck has too much spring to hold the partitions for some reason. Why it doesn't effect the XBT'S or Nos B's though I couldn't tell you.

Most Partitions taper down from the bore diameter only a short distance from the base.

Shows up most when you have to seat deep.

quote:

Originally posted by markus:
I mic'ed the bullets and get 0.307"....

quote:

Originally posted by markus:
I also measured inside neck tolerances on several cases. My neck turned stuff was around 0.304-0.305"....

Hey Markus, That is an Interference Fit if it is measured accurately. And there is no way a 0.307" OD bullet will be loose in a 0.304-0.305" ID Neck.

Any chance you may have gotten distracted and just missed "Resizing" a few of them?

Anyone else have access to your Reloading Area, that might have "moved" some of your cases out of curosity or to get at something they needed and just got them out of sequence on you?

Hotcore,
Very astute observation, old man. You beat me to the suggestion!

Puncher

Unfortunately there is no chance that someone moved stuff around on me, and I resize at the sametime I deprime the fired casings. But I did everything in one sitting.

I am certain that all the cases were resized properly. I pulled apart my dies to check and make sure the expander ball was not covered in crap.

I tired 3 different Partition's (All 180 grainers) in three different cases and can't get a firm fit. I have even gone back and rechecked my inside neck diameters and I get a pretty consistant 0.305" on my outside neck tunred stuff and a constistent 0.303" on my sized, unfired, untrimmed, brass.

I do however notice that the brass I am having trouble with has alot of spring to it. More so than the fresh cases. But it will still hold Barnes bullets, and the others, which happen to mic at 0.3075" Ever so slightly larger than partitions.

I'm not sure what to think anymore.

Did you mike the expander button yet?
Peter.

I just mic'd it at 0.306"

Ok so I tossed aside the brass I am having trouble with and took out 10 pieces of fresh brass. I full length sized this stuff this time (Normally I neck size) Primed, charged and seated my partitions.

This time they seat firmer, still not as firm as other bullets seat but I can't easily push them into the case. I believe I could if I used both thumbs or really grunted alot.

I am pretty sure these would get hammered in under recoil in the mag. I can tell through the press handle they don't seat as firmly as other bullets do.


Should I undersize my expander ball a little bit? How would I do that? emory cloth?

If the neck ID is .002 or more smaller than the bullet OD, that should be tight enough.

If you are seating the Partitions too deep, they will be looser than some other bullets.

Can you seat them farther out?

Hey Markus, Grab a few of the cases you know for sure you have the "Loose match" with the Partitions. Then totally remove the Expander from the Die and Resize them once more. That should fix the problem on those specific cases.

If that does not make them small enough to hold the Partitions, you could get a set of the Redding Dies that use the swappable "Bushing" style Neck Sizers. This is probably the very best option for you since you have decided to go into Neck Turning, because you can have 3-4 of the Bushings and make the Necks as tight or loose as you like.

But, give them a try without your Expander in the Die first.

If you are using a "Factory Rifle", Neck Turning can work against you in achieving the best accuracy since you are Neck Sizing. The reason is because it will allow a bit more slop in the Neck portion of the Chamber.

If your goal is to achieve the best possible accuracy, I can recommend Partial-Full Length Resizing(P-FLR) using a Full Length Die. Just adjust it so there is a slight Crush Fit on the Case between the Boltface and Chamber-shoulder as the bolt is closed.
---

By the way, some Partitions do offer less "Bore Resistance" than other bullets. Part of it is due to their diameter and part to other design parameters. But it is not necessarily true for all Partitions.

I'd noticed this over the years that using some Partitions I'm able to use just a bit more Powder for the same Pressure and get a bit more velocity than Standard bullets.

An inexpensive way to deal with it in the short-term (before changing the expander button) is the get a Lee Factory Crimp die.

It will hold the bullets firmly for shooting.

Garrett

Thank you guys very much. I will give it a try with out the expander ball in it and see if that help, I would imagine that would tighten them right up.

I know neck turning isn't really needed with a factory chamber but I started doing it to make the cases a little bit more concentric (not that there was a problem before)

I'm not really seating them very deep in the case I could probably go a little bit longer but not very much.

Well thank you guys very much.