45-120 Case Cracks/Separation

[mehavey]

I've had a (Farmingdale) Shiloh Sharps 45-3¼ since `81; and over years of sporadic shooting have experienced several unexpected case separations about an inch above the head. All of these loads are Black Powder (GoEx 1Fg and/or Swiss 1½), and with both RCBS and HDS (Huntingdon) cases.

Today another case (HDS) case separated, and I can see still another loaded case that has all the signs of getting ready to go on next firing: (Bright ring partially marked w/ blue sharpie)

https://i.postimg.cc/Y9WpjrKX/45-120-Case-Crack-sm.jpg

Anyone else experienced this with long BP loads/cases such as this 3¼ ?
(I've had none w/ four other 45-70's and two 45-90s -- just this cartridge/rifle)

[M-Tecs]

My first guess would be headspace. Firing a primed but empty case with a standard size flashhole should tell the tale. The primer will back out and give you a rough idea of headspace.

[texasmac]

Here's an article that may shed some light on the subject.

http://www.texas-mac.com/Case_Stretching_and_Separating_in_BPC_Rifles.html

Wayne

[Bent Ramrod]

I’ve had several 40-90 3-1/4” cases stretch into the throat or leade, and even into the rifling. Some have separated, with the front section going clear out the barrel with the boolit. Typically, this happens with paper patch boolits and chambers that were insufficiently dried after wiping between shots. I even had one 45-70 separate in this way. Never had the problem with grease groove boolits in either caliber.

A friend with a .40-70 Sharps Straight using paper patch boolits started having this problem when he eliminated the grease cookie he was using in his loads. He went back to the grease cookie and the problem went away. He wipes the barrel and swabs the chamber. The swab no doubt gets somewhat damp in the course of shooting a match, which would leave residual moisture in the chamber.

Excess moisture condensing in a blow tube could also give a wet chamber. I haven’t seen a problem using lubricated boolits, of any type, though.

[mehavey]

OK... after much mucking around with a zillion variations that went not only nowhere, but killed three more cases (10-thou stretch&worse every shot), I went back to simplified assembly from 35 years ago:

- Annealed necks using 750 Tempilaq
- Cleaned/sonic'd/walnuted the cases
- Trimmed to 3.25" perxactly
- Used Lyman BlkPwdrGold (http://go.thehighroad.org/?id=58513X1360171&isjs=1&jv=13.23.5-stackpath&sref=https%3A%2F%2Fwww.thehighroad.org%2Findex.php %3Fthreads%2F45-120-case-cracks-separation.856795%2F&url=https%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Di%26 source%3Dimages%26cd%3D%26ved%3D2ahUKEwiDjKfp7fTkA hUOn-AKHRu6C_cQjRx6BAgBEAQ%26url%3Dhttps%253A%252F%252F www.trackofthewolf.com%252F%253Fp%253Dlube-gold%26psig%3DAOvVaw19JVdKXYy6sE4NNLuvtEyg%26ust%3 D1569806164125425&xguid=a11149d1407710763790df5bcfe2f483&xs=1&xtz=240&xuuid=32a9512cfe95f2a6302a09330618dfaf)* Lube cut as a 0.2"-thick/quartered disk as grease cookie
- Sandwich the cookie between 2 0.060" veg cards hand-pressed home
- put a "release" 0.030 card above cookie sandwich
- Shoot cases Unsized
- Hand-insert bullet: just enough friction w/ paper patch to retain
- Kicker duplex charge of 10gr 4759
- Enougth GoEX 1Fg to result in an UNcompressed charge column giving me ~⅓" shank depth (~89-90gr -- 152 volume setting on the Harrells)
- Wiped 1x-&-out Damp Patch, followed w/ 1x-&-out dry between shots . . .

* Only use I've found in the 15 years I've happened to have the tube of it -- normally use DLG in the grooved&Lubed game

https://i.postimg.cc/63Rx2snZ/Sharps450-120-1982-Paper-Patch-Load-Ld-Trgt-sm.jpg

[mehavey]

Meanwhile, back at the ranch . . .

Got my new TOY (https://images-na.ssl-images-amazon.com/images/I/81hfCU2M4lL._SL1500_.jpg) in the mail today.
Loaded a case w/ the 4759/1Fg combo noted above topped w/ a 60-thou card by hand.
Stuffed some Lyman's BlkPwdrGold into the New Toy; extruded a 0.2"x½" ribbon onto the the kitchen counter; used the loaded case to cut a grease cookie directly into case;** pushed another 60+30thou card down on top; and seated the bullet (again by hand)

Took it out late 6 Monday night drizzle/fog/failing light, front post as sight....
First/Clean/Cold/...Only... shot overlaid on previous target:

https://i.postimg.cc/4x4nq4gx/45-120-Next-Day.jpg

Leave it alone.....




** (really nifty):D

[Chill Wills]

Fast? Almost 1350 - 1400 FPS with that heavy bullet?
Just guessing.

The accuracy is there at 100y
Did you try it at 600y or 1000y? Just asking. If you have no need to, 100y is great too.

I assume that bullet is from one of Tom Ballard's molds.

[mehavey]

Roger that. Tom Ballard
1,403±5 at 8 yds (recorded May`09)

I'll have to take it out to FXRGC for 300 yds (used to run near 900yds in the desert near Edwards AFB before I ran out of sight adjustment ... but that was a looooong time ago.)

Different Time
Different State.)

[John in PA]

Here's an article that may shed some light on the subject.

http://www.texas-mac.com/Case_Stretching_and_Separating_in_BPC_Rifles.html

Wayne

Wayne, the article is excellent. Could you explain the mechanics of a moist or lubricated chamber leading to case stretch/separation? I can't quite wrap my head around that aspect of the problem.

[pacomdiver]

i had almost the same problem with my father in laws 50-70, on the 2nd firing, it would split the cases in about the same place. starline is the case maker, i was told it was because the cases arent annealed. i have annealed the bases up abt 3/4 of the case on a test lot of 20 but havent had time to try them out