possible chamber spec problem--- or fl die problem.

[Catbrain]

Shooting an interarms X in 30-06. Older gun - maybe 1970's or 80's
Finaly gotten around to shooting it some after owning for about 20 yrs.
Been shooting a few handloads through it. Shot a barns tsx through it.
(just one). when I examined the brass-- the neck had not one- but TWO---zig-zaggy rips midway on the nick. They were open pretty far. It had the look like the neck expanded so much that it just tore..
I shot several other loads - including some factory PMC fmj--- and did not see any abnormal splits.

So tonight -- I was wanting to try a new bullet-- so I was trying to make a case to allow a sliding bullet so I could measure the max oal to the lands.
I took a fired case--- the bullet just fell through. So I gave it a little nudge on the resizing die to shrink the neck a bit. when I looked at the neck-- I could see an obvious step-down in the neck where the die worked it. The step was .009 smaller than the fired case neck.

My first thought was that the chamber in the neck area is somehow too large--- and allowing the neck to expand way too much---and due to the neck wall being stretched-- that tore the brass there.
But then I thought about the possibility that the resizing die could be too restrictive in the neck....

I have looked on line and can't find a spec for the chamber in the neck area. Anyone know what that should be ? im going to try to comapre a fired case with the same factory load unfired and see what the difference in outside neck dia. is. I woud'nt expect it to be more than .002 or .003 difference ----- ( or should it be less ?) hoping this will tell me if its the chamber or the FL resizing die.

does anyone know what the neck dia. is supposed to be inside the chamber ? Couldnt find it anywhere ...... I guess it could vary- depending on the reamer used.......

The outside of the necks of fired cases are about .343 to .344 inches. A bullet will just drop through freely-----

 

[Southpaw Tikka]

What is the I.D. of a sized case? If it's a few thous tighter than caliber then you know it your chamber for sure. If its sizing the neck down way past .305" then you know its your dies or brass

 

[ShtrRdy]

Follow this link and click on Z299.4. Go to the cartridge drawing for 30-06 to see the chamber and cartridge dimensions.

SAAMI Standards - SAAMI

Note: New & Revised Cartridge & Chamber Drawings not yet included in the standards can be found HERE. American National Standards Published by SAAMI The SAAMI Standards are published to provide safety, reliability, and interchangeability standards for commercial manufactures of firearms...

saami.org

 

[Catbrain]

iD of sized cases is about 304-305. that seems reasonable.
fired case neck OD is about 344 --- sized neck OD is 333.
loaded neck OD is 333. factory loaded neck OD is 336-337.
These are RCBS dies with the roll crimp type crimper.
I normally use lee with the factor crimp dies.

I compared the necks on some shot 308 with the necks on my shot 30-06---- i get about the same ID and OD. That makes me think the chamber is OK. Im thinking that the sizing die maybe is a little too small in the neck area.
Im getting .009 between loaded round and fired round on the neck OD. That seems like a lot------

Just checked some 308 for the savage 10FP. 333 vs 344.
about the same difference. Still don't understand why I got a double ripped case neck on the barnes bullet.......

Is it normal to get a .010 diameter change on the neck when you size ? seems like that's working the neck too much.....

 

[RegionRat]

Is it normal to get a .010 diameter change on the neck when you size ? seems like that's working the neck too much.....

This depends on the condition of the brass when fired, and the diameter of the chamber neck, but your numbers are not unusual or abnormal for a typical chamber.
If you really want to know your chamber dimensions, you either trace them back to the manufacturer or you chamber cast and inspect.

With the very long history of the cartridge, folks have tailored many reamer designs that made all sorts of custom changes to the original SAAMI dimensions above, so I would either research the chamber reamer they used or inspect.

Don't let the SAAMI numbers throw you off track. Those values represent what happens when too many folks get on a committee and all sorts of factions get a vote. Some of the most popular old cartridges have the worst specification drawings as a result.

As for the case neck in your first post that failed, what was the history of the ammo/brass?
Is there anything in the history of that brass that could explain the issue?

ETA: here is the Serengeti version

 

[Catbrain]

I loaded those about 10 years ago. I THINK i remember using new brass. But I looked at the case heads-- and on the other in the same box- most have a little bevel on the outer edge of the rim. Like a little wear or maybe where they hit the action on the way out. So it could be just a bad case. I loaded 10 solids and 10 hornady interlocks with that brass. I might try shooting 2 or 3 of the interlocks just to see what the brass does. I talked to a Tech at Hornady and he thought the sharp edges of the relief grooves could have tried to grab the case neck. But it doesnt look like that to me---

as an artifact---- there are two vert. cracks in the neck. Each of the cracks-- at it's top and bottom-- there is a little round hole--- all most like the hole was gas cut. What is that telling me ?

The dies are rcbs--- and I just dont like them. I think I will order a set of lee dies withe the collet crimper. im used to them and have had good luck using them. Never had this kind of crap before-----

as an aside---- I have seen brand new factory brass exhibit a lind of slot down the side like the metal got a pleat or fold in it during one of the forming steps--- then it went through a couple more pulls and the defect area got ironed flat--- but still there.

i have a split-ball type internal hole gauge-- I may try to
directly measure the neck area inside the chamber. see what I see.

i compared the inner and outer diameters to some of my 308 brass and got just about all the same measurements.
I just don't like how that rcbs die is working. i don't think I trust it.

 

[Catbrain]

pS--- thanks for the diagram R-Rat !

I did a length test with a sliding bullet-- a 165 a-max--
and it was just touching the lands when the base of the bullet was in the case about 3mm. so it must have the WW1 style throat to accomodate the big 220 grain blunt bullets. But it seems fairly accurate----
so about any reasonable projectile will be way back off the lands a mile----

 

[RegionRat]

Just food for thought...
For the cost of the bullets, and the trouble of your time, you owe it to yourself to start with some known good brass.

 

[243winxb]

Is it normal to get a .010 diameter change on the neck when you size ? seems like that's working the neck too much.....

Yes, to much. To control the neck sizing, buy a Redding type S full length sizing, bushing die. You may need more then 1 bushing.

loaded neck OD is 333.

Start with a bushing size of .331" OR, First find the loaded round with the smallest OD & get the bushing .002" smaller. It may be different.

https://www.midwayusa.com/product/1018049293?pid=699314

 

[Rosebud]

For what it's worth, I've had to toss more Barnes once fired brass away than all others I've ever reloaded. Got to the point where if a guy brought Barnes brass in for reloading I'd say find some other brass. If the split necks were Barnes brass that explains a good amount of the problem.

 

[Catbrain]

I only shot one of the barnes that I loaded. I thought I would test the other in the box that had the same brass but with speer conventional projectiles-- to see if it a brass problem.

Seems like the sizing die is closing the neck down firther than needed when the expander blows most of that compression back out as the ram comes up. Seems like needless work hardening----

I will look at the redding type S you left the link for.

seems suspicious that is the only brass I can ever remember ripping open like that. Never liked the idea of a solid copper bullet from the very onset of that invention. Too much to force down the throat. asking for trouble. If they had installed plastic bands to Engauge the rifling--- that would have seemed much better. Like artillery shells.