Special throat requirements for PP?

[Dframe]

I've been wanting to try PP in my 45/70's. I have among others an original Trapdoor and an H&R. Do PP bullets require any special throating to work? Or can I just use my guns as they are.

[303Guy]

Have a look on this thread 'Paper patch bullets' by abunaitoo.

[Nobade]

Are you planning on using smokeless or BP? Quick answer, the H&R and smokeless will probably be just fine. The trapdoor ought to be shot with black, and you will probably find the throat a bit generous for bore sized PP bullets. It may work well with groove size bullets, but you'll likely have to wipe between shots to get the following round to chamber if you do that.

[docone31]

You will not need special throating. Spend some time, find the diameter, and enjoy!!!
Makes the bores shiney also.

[Dframe]

Was planning on using smokeless. I've been loading 45/70's for many years but hadn't taken the plunge going to paper. My H&R measures (surprisingly) an exact 458. I don't have the ability to accurately measure My springfield with its 3 lands and grooves, but I'm assuming it probably is oversized. Is there a good way to measure this?

[docone31]

Take the good solid performing load, and add .001.
In other words, my .308 loves paper at .309. I slugged the barrel and couldn't find the groove.
I remembered an old box of Herter's in .309 I fired in my springfield years ago. I tried paper at .309 and it was a tack driver.
I suspect, if you do something like that you will find it.

[Red River Rick]

Dframe:

Is there a good way to measure this?

Slug your barrel and do a chamber cast.


RRR

[Dframe]

I've slugged the barrel already but found the three lands and grooves to make accurate measurments difficult. I have not yet made a chamber cast.

[Lead pot]

Dframe.
You can measure a odd groove this way.
Ok if you don't have a 60 degree block you can use a 108° for five grooves or a 90 degree block.

Calibrate it with an accurate diameter pin like a drill rod and then measure the bullet and V-block with an ordinary micrometer or calipers. Then use the math below.

a = the included angle of the V-block,
t = the thickness of the V-block from the bottom of the V to the bottom,
h = the measured height of the bullet and V-block,
d = the diameter of the bullet.

For a an example using a 5 groove bullet, the included angle (a) is 108°, assume the V-block "thickness" (t) is .250" and the measured total height (h) is .5854", then
d = 2(.5854 - .250)/ (1 + 1/sin (108/2))
d = 2(.5854 - .250)/ (1 + 1/sin 54)
d = 2(.5854 - .250)/ (1 + 1/.80901)
d = 2(.5854 - .250)/ (1 + 1.23607)
d = 2(.5854 - .250)/ (2.23607)
d = 2(.3354)/(2.23607)
d = .6708/2.23607
d = .300

A way to determine the V-block thickness (t) is to measure a known cylinder and then calculate it from

t = h - (d/2) (1+1/sin(a/2) )

Or you can get some thin brass shim stock like .002 and fold it around your bullet pinching the end tight with your fingers and measure the diameter and subtract twice the thickness of the shim. This will get you close.
Or you can use paper. If you use paper just make sure you take the measurement close to the edge of the groove so you dont measure where the paper is flat over the groove.

Kurt

[RMulhern]

Buy ten moulds....and eventually you'll find a shooter!!

[Lead pot]

I*s 10 enough