Pedersoli chamber length question

[DIRT Farmer]

I'm slowly creeping into B/P cartridge and have a Pedersoli Rolling Block and Sharps carbine both 45-70 I have just bought the Lyman 457-132 that mesures .459 to 460 on my discount mike. I loaded 70 grns of Goex ffg in RP cases that were neck sized and a fiber wad 0.30 from the top of the case for an overall length of 3.25 in the RB or 2.58 from the first driving band to the base of thr rim.

The same set up in the Sharps requires the powder to be compressed 0.50 from the mouth of the case to the wad to chamber in the rifle.

#1 do these mersurements seem reasonable?
#2 what should the chamber length be for 45-70?

[Tom-ADC]

Chamber length for 45-70 should be 2.10
For my roundnose bullets, I drop the boolit into the chamber and then measure from the end of the chamber to the base of the boolit ussing the depth portion of my calipers, I then subtract that number from 2.10 and that tells me how deep to seat the boolit, I usually allow for a few more thousands to make sure the cartridge chambers okay.

[DIRT Farmer]

Tom that is how I did it. I found the differance between the Sharps and the RB was 0.20. I was wondering as they chamber the RB in 45-90 also I was wondering what the length 45-90 was. I don't think the space in front of the case will work when I try paper patch.

[powderburnerr]

sounds like you have a short transition from chamber to rifling in the sharps and a longer transition from bore to rifling,in the pedersoli .. you judt have to set the bullet to where you want them in the different chambers......Dean

[montana_charlie]

Chamber length for 45-70 should be 2.10.
You would probably be amazed to learn that is only rarely true...

DIRT Farmer,
The chamber in your Pedersoli Sharps should be 2.129" if it was built after about 1999.
But, there is still the 'throat' out ahead of the chamber to account for.
That includes a low-angled chamber 'step' which occupies .0613" and a freebore that is an additional .236".
I don't know how the chamber is shaped on rifles built prior to 1999.

The Pedersoli rolling blocks (at least the older ones) are also shaped differently, but I don't know in which ways.
A chamber cast is your best bet, there.

For more on the (current) chamber in their Sharps, this thead has more than you probably want to know.
http://castboolits.gunloads.com/showthread.php?t=83951

CM

[DIRT Farmer]

Thanks CM for the link. I have never made a chamber cast, one more danged thing to learn. At the present I have three bullets I can load for the 45-70 The Lyman 457-124 385 grn, Lyman 457-132 535 grn (Postell) and just for kicks the 451-114 450 grn Volenteer bullet that I tried PP on. It has to be seated deep to chamber like a wad cutter but it shoots stright at 100 yds.
So just keep playing with it and make notes?

Thanks

[montana_charlie]

At the present I have three bullets I can load for the 45-70 The Lyman 457-124 385 grn, Lyman 457-132 535 grn (Postell) and just for kicks the 451-114 450 grn Volenteer bullet
In those images created by Tom, you see how well the PGT bullet fits the throat of the Pedersoli Sharps. That's because it was designed specifically for that chamber.

The three bullets you currently have can all probably be useful in one way or another. The Postell is such a good bullet, you can probably get it to shoot well for you.

But, if a Pedersoli Sharps owner only wanted to own one bullet mould...and needed to know which one would be most guaranteed to shoot...that would be the 460-550 Pedersoli/Gunn/Trenk (PGT) bullet.

CM

[kennisondan]

In those images created by Tom, you see how well the PGT bullet fits the throat of the Pedersoli Sharps. That's because it was designed specifically for that chamber.

The three bullets you currently have can all probably be useful in one way or another. The Postell is such a good bullet, you can probably get it to shoot well for you.

But, if a Pedersoli Sharps owner only wanted to own one bullet mould...and needed to know which one would be most guaranteed to shoot...that would be the 460-550 Pedersoli/Gunn/Trenk (PGT) bullet.

CM

that is the first one I will buy then... it will be a while before I shoot up all I have coming but, heck guy has to have a plan, right :
dk

[montana_charlie]

that is the first one I will buy then... it will be a while before I shoot up all I have coming but, heck guy has to have a plan, right :
dk
Dan,
Although any mould maker can cut this design, Paul Jones is the only one who has it as a stock item. You can see it at http://www.pauljonesmoulds.com/45_caliberpage2.htm where he calls it the 'Pedersoli Chamber' #45021.

If you know a mould maker, or have experience with one, you can ask him to cut you a mould in the PGT design. He can get the detailed drawing here http://bpcr.net/site_docs-results_schedules/documents/pedersoli_gunn_trenk_bullet.htm

CM

[John Boy]

In words, here are the chamber dimensions of a Pedersoli 45-70 from Dick Trenk:

Following is dimensions from our chamber reamer blueprint for 45-70 caliber. These are the nominal dimensions given to each rifle, with a mfr. tolerance of unspecified fore and aft change due to the obvious differences in how far the reamer is actually moved into each barrel. I would guess we control reamer depth by +.003" and -.000" .
Rim Dia. .618"
Rim width .070 (depth of rim seat)
Case dia at rim base .508
Case length 2.129 (includes .070 rim thickness)
Length of 45 deg angle .060
Diameter at rear of throat (at 45 deg angle) .4598
Length of throat .236
Diameter of throat at front .4578
Leade angle 1 deg. 30 min
Bore dia, .4500"
Groove dia .4580"
Leade length and distance is not quoted and the leade angle will control that.
Remember that when the reamer is used a bit deeper or more shallow it not only changes the rim seat depth but affects the leade start and end locations as well.
Dick T.

[montana_charlie]

Length of 45 deg angle .060
John Boy, that chamber step does not have a 45 degree angle.
You can prove it by doing the math.

Chamber diameter is about .482".
Groove Diameter is .460"
That's a difference of around .012"
The length of barrel used by the 'step' is .060".

Conctruct a right triangle on which one side is .012" in length and the other is .060".
Solve for the hypotenuse and you'll find that angle to be very close to 10 degrees.

If your math skills are as rusty as mine, you can use this online 'calculator' http://www.1728.com/pythgorn.htm .

Here is a cut and paste of the email I got from Dick back in 2005.

"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.
From the above you can make a drawing.
Cheers,
Dick T"

In this email he calls it the 'transition' and states the actual angle...along with the same length you posted.

Tom Myers made up a drawing based on Dick's email to me, and put the PGT bullet in it.
It looks like this...

http://i684.photobucket.com/albums/vv203/montana_charlie/45-70_Govt__PedersoliwithPGTBullet.gif

Notice the 'step' (or transition) angle.
Also notice that the actual chamber depth (of a 45/70) is 2.129"...almost 30 thousandths over nominal.

I don't have a factory chamber in my rifle. So, you (or somebody) will have to make a chamber cast to see if a 'real gun' matches the dimensions in the drawing.

CM