Shiloh Rifle Forums

Was out shooting yesterday and noticed something I had not seen before, but I’m betting some of you have.

Extracting the fired case, I see a thin “layer” of lead around the perimeter of the case mouth. Maybe 1/8” wide at the most but erratic and not the entire perimeter. You can scrape it off with your thumbnail.

It’s a Model 74, 40 cal 2 1/2, 416-grain Paul Jones 20:1 greaser, 68.0 of OE 1 1/2, CCI BR2. 1 poly wad. The only difference in the load of yesterday and all previous loads was I used 0.002” neck tension.

Any idea what would cause this?

Thanks!

Tom

Just a question. Have the cases been trimmed lately? Uneven case length or case mouth?

These cases don’t seem to grow. I’ve been using them since 2010 and have only trimmed them once in that time frame. But I will check the lengths later today. Hornady 405 Winchester cases.

Thanks!

Possibly the cartridges are a bit short and a little lead is shaved as the slug is making the transition from the cartridge into the barrel. Try to find someone that can stretch 3 or 4 cartridges, load them up with powder and a wax slug, and light them off. They should fireform to your chamber and one can then trim/camphor to precisely match his chamber dimensions.

1minute wrote: ↑Sat Sep 03, 2022 4:34 pm Possibly the cartridges are a bit short and a little lead is shaved as the slug is making the transition from the cartridge into the barrel. Try to find someone that can stretch 3 or 4 cartridges, load them up with powder and a wax slug, and light them off. They should fireform to your chamber and one can then trim/camphor to precisely match his chamber dimensions.

If their to long this can happen also . And if their to long and shooting paper patch they'll cut paper rings also .

When the loaded cartridge is seated in the chamber, does the lands in the barrel engrave the contact driving band about 30 thousandths?

Some brass history…

I bought (300) Hornady 405 Winchester cases in 2010. For my shooting I left (150) in their original boxes and used the other (150) for shooting. I checked my max. case length and trimmed them @ 2.510”. A check of a random (25) cases Saturday showed most in the 2.502 2.508” length. There were a few shorter than 2.500” with the shortest @ 2.495”. Since 2010 there have been 2,826 rounds through the gun. With the (150) round batch of brass that’s about 18.8 firings per case. I have (139) cases that I’m using with the missing (11) due to “operator error” @ the loading press, etc. At the end of the year they all get cleaned and annealed.

If the slight reduction in length is not a good thing, instead of trying to stretch them, I could retire them and start using the new, unused batch of (150) cases. Obviously I don’t shoot as often as most of our forum readers.

My “theory” on the presence of lead @ the case mouth….it just started appearing on the cases that are sized to produce 0.002” neck tension. I just started doing that this summer. Maybe the case holds onto the bullet just a bit longer than it does when an as fired case is used, to make the bullet stay put and shed some lead as it finally escapes the case,

The target results were not very good with the added neck tension so I’m going back to using the as fired cases.

My cartridge OAL is just long enough to require me to push with my thumb the case into the chamber, so I suspect the bullet is engraving the rifling a bit but I have not measured it to see if it is about 0.030”. But I am curious if the asked about 0.030” is a desired amount or too much?

Tom

in my Shiloh 40 70 ss, three years old and shot weekly. 1/16 twist, usual for Shiloh I think .
my reg weight bbl gets hot and I fit a water bottle to the blow tube and lit it drain and cool.
one wet, one dry every 5 shots. 3 inch or under at 100 yds.
I show NO leading in the bbl. a turpentine wash shows nothing there.
I am shooting a 410 408 GG 330 , cast 1/16.

I trim my cases, (BA 30 40 Craig ) to 2.495 or a little longer.
I show no leading in the cases, never have. very little stretching . trim very seldom but measure and do it when necessary.
the cases have been shot hundreds of time. still going strong.

SPG lube, hand dipped, shot as cast. weighed inside of 1 grain usually. any more than that I recast.

Tom,

What I think is your seeing a collection of lead rings that build up at the chamber end where the 45º transition is.
You will hear that some will say they never get lead or paper rings but they are there.I have one of my Shiloh's that has been fired so many times that it washed a groove between the end of the case and the 45º transition and it collects lead or paper forming a ring that will stick to the end of the case mouth or it gets wiped out when wiping the bore between shots fired.'Most of my chambers are of the original transitions of 4º to 12º and I don't get the rings that I do with the 45º . Most are with a 5º transition. Orville's 7º that Shiloh will use with a request is a very good transition that works very good in one rifle I have. Some call it a PP chamber but I call it a lead bullet chamber, it works for both.
Below is a photo of my .40-70 chamber that has that wash in font of the transition. There is no case in this chamber and you can see this wash and you can see the build up of lead that did not wipe out during cleaning. My borescope will reach in 42" so I can run it in from the muzzle down to the breach block and I left a fired case in the chamber to see what is going on and I could see paper in my case with the PP bullets I shoot stuck between the end of the case and the 45º transition that rifle has.
If the case is to long for the chamber it will get pulled up into the throat and form a reduced inside edge on the case mouth and it will strip the lead or paper, also if the case is too short it will cut the paper or lead between the case mouth and 45º transition. I seen this in my rifles scoping them after shots fired.

Kurt,

That explanation and especially the photo are very insightful. Thank you!

I need to pay better attention to case length. Shooting is a never ending learning lesson and that’s what makes it so rewarding.

Tom