Nueces...Throat question

[montana_charlie]

I saw where you elected to answer Jjed's question about a smokeless load for his Pedersoli, rather than referring him to the Single Shot section.

But, in your post, you said...

After a range session, we pull some lead flakes out of the ends of our chambers, due, we think, to the lack of a decent throat. I'm about to experiment with some cut-down 45-90s to see if full length cases help. A throating reamer will be next.
That piqued my interest because, about 18 months ago, I was trying hard to discover exactly how a Pedersoli throat is shaped.

Have you cast that chamber? Do you have any dimensions/numbers? How long do you think your brass needs to be?

If you go after it with a throating reamer, what shape do you intend to cut?
CM

[Nueces]

CM,

I have not cast or slugged the chamber. Visually (no bore scope), it appears to be just a sudden transition from chamber to rifling, without any evident taper in the 'throat.' My buddy gave me some new Bertram 45-90 cases and I plan to reduce the annulus between factory 45-70 cases and the end of my chamber, by cutting them to the greatest length that the chamber will accept. I think I can measure the chamber length if it is cut the way it appears to be, then trim a little long to allow cut and try for a final length.

For a throat, which I've never cut before, my naive plan is to use a Brownell's Manson throating reamer to break the leading edge of the rifled bore a bit at a time, watching for a reduction in leading. I may get the reamer even if the longer cases work in my rifle, since both I and my friend have other 45-70s to feed and we don't want to segregate cases for each one.

Really, if we did nothing, we'd still have fine hunting performance - three together from a cold barrel, and very little lead. However, we're now retired and are having fun figuring this stuff out.

Since you've expressed interest, I'll certainly post what we find out.

Mark

[montana_charlie]

A few days ago, I had my first look into my Sharps' chamber. Like you, I don't have a borescope, but I had the gun stripped to just the barrel and receiver, so I donned a pair of magnifiers and squirmed around under a lamp until I could see down in there.

Like your experience, it looked like a sharp change from the chamber to the rifling.

However, I already know the shape and dimensions of the chamber and throat that Lee Shaver cut in this rifle, with his match reamer.
I can assure you that (in spite of 'how it looks') it is not an abrupt change in mine...and most probably not in yours.

When I was in that search mode to discover the shape of a Pedersoli chamber, Dick Trenk (a Pedersoli rep) sent me this...

"Charlie: I have no actual drawing available but will quote you all your main specs.
From the forward edge of the rim seat, to the end of the case chamber = 2.059" length and the diameter at the rim edge is .508" and at the case mouth is .481"-.482"
Rim seat itself will have a depth of .070"
Transition angle at case chamber mouth is 10 deg. 12 min. 14 seconds per side and this will have a length of .060" and a finished diameter of .4598" to .4600" where the throat starts.

Throat starting where angle ends, is straight for .236" then has a "leade" angle of 1 deg. 11 min. 37 sec. per side.
Length varies from .065" to perhaps .080"
How the reamer is handled causes a slight variation in this length of leade.

This basic chamber shape prevails on all our 45 cal chambers."

That leade angle is shallower (less abrupt) than many others.
So, you might want to think about it a bit more...before digging around in there with something sharp.
That is especially true since the .236" freebore (sic) is already more than twice as long as most others.

Since freebore has a diameter of .460", you might try bullets that size...and see if leading decreases.
And, if you set them out far enough to use up that freebore, you can probably get close to .45/90 performance from your .45/70.
CM

[Nueces]

Thanks, Charlie, that's good poop. I would certainly slug the throat before cutting on it, but, you're right, the specs sound pretty good as they are.

I'm still loading the boolits that my friend bought, thus the 459 sizing. My old Lyman blocks throw slugs a little too small; we're waiting for some GBs to come in so we can try larger sizes.

I wince when I recall all those years of cast bullet 'advice' from the print mag experts that specified groove-diameter sizing. Old Harvey Donaldson and Elmer Keith had it right many years ago and, now, the web has allowed enough current experience to get together to reach a critical mass of sound opinion.

And all this 'thinkin' is available to anyone who can type google.com. Despite scientific training, I've always been something of a Luddite. I've embraced the web, though.

Thanks again for the details, Mark