case stretched

[kenny s]

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OK....look at the stretched case mouth.
40 70 SS
30 40 Craig cases BA and fairly new.
67 Swiss 1 1/2
215 reg match primers
one poly one veggie wad
1/8 inch compression
360 custom two diameter PP bullet, 1 in 20 cast
cases trimmed 2.499 for 2.5 inch case , no overlap in bore I'm aware of.

dead on and accurate at 100 yards. wet and dry wiped between shots. 4 of those 10 shots are in one hole.
chamber swab dry....(could I have miss doing this once?)

This has happened once before and is not usual.

I will not use the case again, just wondering.
I did have a case separate a couple of weeks ago, but came out OK.

so....Ideas?? Ken

[bobw]

1st off I make damn sure the inside of my case necks are polished clean. I do this before priming with a 20v Dewalt drill driving a brass brush with a wisp of 4 ought steel wool wrapped on it. Absolutely no fouling residuals in the case neck. try something else besides poly wads, they didn't need them in the 1870's either. bobw

[kenny s]

Bob, the cases are tumbled in ceramic and are clean inside and out.
The cases are unsized always and the PP bullets are hand seated with a slight touch with the taper crimp die to hold the bullet in place.

I will check the necks next time.....tks....Ken

[bobw]

Time to pole vault, change the poly to a card wad. and see if that don't cure it. bobw

[longshot10x]

That's the curse of the 40-70 2 1/2" straight!!!! Ask me how I know. Went to 40-65 RL and never looked back.

[mike herth]

Bobw,
Now that raises another question. After using ceramic media and Shiloh’s solution in a tumbler, the inside of my cases is never shiny like the outside. Does this make a difference in case life or accuracy? I too have used a bronze brush to polish the inside but quit due to not seeing a difference on the target. Bullets are only seated about .13 deep anyway.
Mike

[Kurt]

I use the .30-40 brass from BA and the necks get thin from their stretching. My .40-70 Shiloh has the 45 degree chamber end and I had this going on when I first got the rifle. Some shots would pull the neck off.
What I found out going on after changing the loads/wads/lube/and case prep. I did not use poly wads Bob just OZ+J carton or fiber gasket materials, but my problem started when I trimmed my fired brass to the chamber end because I was getting paper rings so I trimmed them close. Shooting bore diameter PP bullets I had to size the neck down a little or just put a slight taper crimp on the neck to hold the bullet. The taper crimp had a long taper and this sized more of the neck down making the cases a little longer and I think this when the round fired up the expansion and powder friction would pull the case past the 45 degree chamber end and the bullet obturation before it cleared the case neck was enough to pull the soft cases into the throat. I trim the cases for this rifle with a 45 degree .005" short and make sure the case mouth is chamfered so nothing grips the bullet and the problem stopped for me.
Also I use a mix of ceramics and SST pins and this seems to get the inside of the cases and primer pockets cleaner.

Now with mt .44-2-5/8 BN I will get 7 out of 10 cases pulled off loading a PP with out a lube wad. Too much friction from the missing lube wad not lubing the inside of the case neck ?????? My straight wall cases don't have this problem......

[Maj. Forrest Smith]

Possibly as simple as changing to two veggie wads and not using the poly wad. Sometime, the poly can "grab" the sides of the case walls and stretch the case out, I have heard. There is not much "give" to the poly wad over the veggie wad. At least that is and easy thing to check with out changing anything thing else to start.

[kenny s]

two veggie wads from now on, but I'm all loaded up for this week.... one each. so we'll see.
I don't think the straight case is the cause. It would happen with all the rest of the straight cases.
I'm thinking of trying some with NO grip on the case, just hand set.
being careful to push them in before chambering...


Ken

[rdnck]

longshot 10x has it figured out. So does bobw. Shoot straight,rdnck.

[bruce m]

this cartridge was gold standard in the day because it delivered the goods in accuracy and reliability.
it was also known to deliver good accuracy when shot dirty.
everyone chambered for it.
paper patch bullets were the standard load.
so if today the win 40/65 works and the 40/2.5 won't, there must be a reason.
nail that reason - problem solved.
i have shot my 40/72 many times and never had this problem, and it is basically the same case but a bit longer.
that in a 40 degree transition and a 7 degree transition.
could be wads, although I mainly use plastic.
kurt's description sounds a good possibility.
bruce.

[rdnck]

Bruce--what is your parent case? rdnck.

[bruce m]

Hornady 405 win.
bruce.

[Coltsmoke]

Why use two wads?

[Kurt]

Most likely to keep this from happening. Gas cuts.

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