Chamber dimension specs - Source?

[Little Al]

Anyone know where to get specs on chamber dimensions?

I am dealing with a Perdretti Sharps 1874 that it seems like a previous owner (not the one I got it from) tried to turn into a 45-90 or 45-100 and didn't do a very good job. 

On the advice of Delmonico and others, I am casting the chamber tonight with Cerrosafe but don't know where/what to compare with my casting measurements...

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Stuff I already tried....

I bought some 45-90  and 45-100 cases and:

45-90 - Fit in the chamber but would not seat (about 3/8" sticking out) with a bullet in case

45-100 - Empty case would not fit in chamber (about 1/32" of base stuck out)...same 3/8" stuck out when case was tried with bullet.

[Fox Creek Kid]

I am going to give it to you straight: oustide of Pedersoli all Italian Sharps clones are hit & miss with many just plain crap. Their specs are anyone's guess. Chamber specs are meaningless as each gun can vary. The easiest way to determine chamber length is to take a case too long and slowly trim it back until the block just closes. You will have to drive the case out with a rod and the case mouth will then show a slight crimp which is the chamber leade. You will then need to trim the case a few 0.001's back BEHIND the beginning of the chamber leade. This will shrink back some after fire forming and then keep your eye on the length after every firing.

[Dick Dastardly]

Let me know how the Cerosafe chamber casting comes out.  If it measures anywhere near where you want to be, yer good to go.  If not, send the chamber casting along with about Five fired brass from that chamber to Reddington Die Specialists.  They will want about $100 for a custom sizing die made to your exact chamber specs.

Then, you can find the nearest size brass and run it thru the custom die and trim it to exact length and enjoy all the benefits of a custom rifle.

I've done it a number of times on Mauser K98s of different wildcat calibers and chamberings, namely .25 Gibbs, 6.5mm Gibbs, .257 Durham Jet, 8mm-06 and others.  Done right  you end up with a die set that matches your gun so well that you hardly move any brass when you re-size.

Go for it.

DD-DLoS

[Wills Point Pete]

The .45-70 camber dimensions is in the back of the NRA Handloading guide. My issue is the 1989 print and have tooth marks from growing puppies. The chamber is supposed to be 2.1099 long before the lede, I believe. The case is 2.105 long.

 Take a look at http://stevespages.com/page8d.htm This page has cartridge dimensions for just about everything.

[Little Al]

I did the chamber casting last night and the chamber is about .035" short of the 45-100(2.6) case with the chamber diameter (at the case mouth) being .005 or so wider than the case with a bullet seated...I can seat a 45-100 case if I tap it in and, as Fox Creek Kid says, there is a slight chamfer on the case mouth.

I have found a local gunsmith who will ream the chamber to fit and I think I will go with that...since it's so close, I figure that may be easier than working up custom brass...

I didn't start out looking for a 45-100 but it is kinda unique...I'll work up some loads once I can actually chamber a round and see what kind of accuracy I can get...maybe I'll play with some paper patch rounds...I did make a lace-on recoil pad already though!

Like they used to say in Navy Dive School - "If it was easy, anybody could do it."

Fox Creek - Don't sugar coat it - how do you really feel about Pedretti rifles?   

[Delmonico]

I think that will explain a lot of the problems you had.  I figured all along there was more than just using the wrong weight bullet as so many said.  As Atlo said "you we're being brave and honest." when you wondered if it could be you and not the rilfe, I have seen that problem more that a few times with folks with deer rifles that had a problem.

As one also not to sugar coat things unless you can eat it, I wonder since most folks thought it was a load problem how much lead you'd a flung downrange and how much powder you's a burned "workin' up the right load."

Least we know now if someone else would have shot the rifle they wouldn't a done squt either.