PP Barrel Dimension info...

[rbertalotto]

Today I decided to inventory the various 45-70 rifles I own with regard to their internal barrel dimensions


Measuring "bore" diameter proved to be difficult because of the various number of lands and grooves and the twist on the driven slug.


I ordered a set of precision ground pin gauges .250 to .500 (negative ground)





Using these pin gauges and verifying the numbers with an expandable Ball Type Hole Gage I was able to arrive at relatively accurate numbers.





Once I knew the bore, I wrapped various pin gauges with two layers of #9 Onion paper that I sourced through Buffalo Arms


Using this method I arrived at the exact diameter I needed for a bullet if I wanted the bullet and the paper to ride on the lands. To this number I'll add X inches to arrive at the casting mold dimension I'll need.


I'll then turn a "D" Reamer on the lathe and proceed to cut a paper-patch bullet mold.


Does this sound like I'm headed in the correct direction?


45-70 Rifle Barrel Dimensions
Paper Patch #9 Onion / 25% cotton = .0016” (Double Wrap = .0064”)




RIFLE BORE GROOVE BULLET FINAL
PEDERSOLI
Rolling Block (Pistol Grip) .4500 .4570 .4450 .4513
PEDERSOLI
Rolling Block (Straight) .4500 .4553 .4440 .4504
PEDERSOLI
1874 Sharps .4490 .4575 .4430 .4488
H&R
1884 Trap Door Officers .4490 .4575 .4430 .4488
WINCHESTER
1886 (Japan) Take-Down .4500 .4563 .4450 .4513
WINCHESTER
1885 BPCR (Badger) .4500 .4560 .4450 .4513


“BORE” measured using negative gauge pins
“FINAL” is negative gauge pin wrapped twice with patch paper and a tight fit without paper tearing.


3-21-15

[Lead pot]

Pin gauges are a good way to get bore and also groove dimensions. If you don't have a V anvil micrometer for getting a odd number groove depth you can use a pin gauge with a good lead core to get the depth using a quality certified caliper. Or something simple like using a brad nail, core and a mic.