Case Neck/Chamber Neck Relief Question

[LeeSpeed]

I have a Husqvarna M146 9.3x57 with a groove depth of .369. I cast bullets using the NEI 175C mold and have sized them to .370. Loaded, the case neck mikes .390-.391 across.

Fired cases mike .391-.393 depending on where they are miked {rotating the case and taking measurements yields different results}. There may be some springback of the case neck, but short of doing a chamber cast, I am not sure.

I am thinking the loaded round might be a bit too thick at the case neck and this might generate excessive pressure.

I have not fired any rounds yet. I'd prefer not to have to size more, but in the interest of safety I am thinking I might have to.

What say ye?

Comments?

[felix]

Always plan on enforcing 0.001 minimum total clearance (0.0005 per side), by either neck turning (BR guns only) or by sizing the projectile down. For military guns, it definitely won't hurt matters if you had a minimum clearance of 0.002. Any scraping on a paint job around the loaded cartridge neck with a magic marker after the cartridge is gently inserted into the chamber, and the bolt is closed gently, and the cartridge pull gently back out, is too tight. ... felix

[S.R.Custom]

... Loaded, the case neck mikes .390-.391 across.... Fired cases mike .391-.393 depending on where they are miked {rotating the case and taking measurements yields different results}. What say ye?

Sounds... perfect. :drinks:

[Larry Gibson]

Sounds pretty good to me too.

Larry Gibson

[Andy_P]

A chamber cast is the definitive way to determine neck clearance, but based on what you've stated, I'd say that's neck clearance to die for. If you decide to try 0.371" or larger, I'd recommend outside neck turning though.

[LeeSpeed]

Thanks for the posts.

I have tested the bullets in fired case mouths.

They can be slid in but only just, and with pressure, as the bullets hang up at each bearing ring. The problem seems to be that with this rifle, even though the groove depth is .369, CHAMBER NECK DIAMETER is only .391 or so, in other words, what you would expect for a .366 groove 9.3.


Part of my problem is that the Lyman M die doesn't work properly at all, and leaves case mouths unevenly expanded which results in a bulge caused by the misaligned bullet. this is what appears to be scuffing on the chamber neck in the rifle.

I think I'll get a Lee Universal flare die and give that whirl.

Thoughts?

[Pepe Ray]

You may be getting off center results in your case neck expanding, but it's not the "M" dies fault.
I've never seen any die that isn't completely worn out, give those results.
In 99'999% of instances like this it's because of the brass.
Unless brass is neck turned or reamed, it will be uneven and be thick/thin around the circumference. Some are worse than others. Can't help it. It's the nature of things. Mass production and economics demand it.
Pepe Ray

[LeeSpeed]

You may be getting off center results in your case neck expanding, but it's not the "M" dies fault.
I've never seen any die that isn't completely worn out, give those results.
In 99'999% of instances like this it's because of the brass.
Unless brass is neck turned or reamed, it will be uneven and be thick/thin around the circumference. Some are worse than others. Can't help it. It's the nature of things. Mass production and economics demand it.
Pepe Ray

Brass certainly could be a compounding problem. The flare is oblong {case thickness variations?} and it is impossible to start the bullet accurately. Jacketed bullets seat OK because they start deeper in the case due to being .004-.005 smaller. The flare is weird and with this particular die the "step" common to M dies doesn't show up at all. I read somewhere that others have had trouble with this .366 M die also, so I wonder if they just messed up when they designed it.

I'll do some more investigating...

[LeeSpeed]

I don't know why I didn't think of this before, but part of the bullet seating problem is the fact that a .370 diameter bullet is being seated in a case sized for .366 bullets. This amounts to a grossly oversized condition. The base of the bullet must move alot of brass out of the way as it settles into the neck.

I need to get a larger expander ball, like a .375 cal and then grind it to the right dimension.

[looseprojectile]

Did you make the cases from once fired or new, something else?
I would try annealing one and try it with a little bell at the mouth. I have had good results by just chamfering the inside of the mouth using soft brass. Soft brass don't spring back as much.
I have a case turning gadget that I have never used, but it may be necessary with your setup just to make the necks uniform. If you are forming cases I would form it first and then anneal it and after annealing run it through the sizer one more time.
Sounds like you have most all the bases covered with the information given by these folks.

[leftiye]

Soft steel will expand a lot of cases before it wears small enough to cause problems. Make (or have made) an expander ball that will fit in any expander ball die (any you want to use). To make it live longer, make it overly long in the part that is the O.D. you want. Then it will wear on the end first, but still open the necks to the desired size before they hit the flaring cone.

As you say, the expander ball you're using is most likely undersized. Your sizer is probly sizing down too far too (they almost all do), and this will/is cause(ing) problems. But you still might want to outside neck turn just to get a little more neck clearance as well as garnering some more co-axial straightness.

[runfiverun]

that .004 neck tension is a lot and is probably not doing your boolit alot of good
sounds like you necked up. winchester brass would be my guess ?
if i really liked this rifle i would see how the cast holds in just a fired case or do the
math and order an inside neck reamer from forster
you just outside neck size and cut the inside to the tension diameter that you want