+- Historic Shooting Forums (http://historicshooting.com)
+-- Forum: General (http://historicshooting.com/forum-1.html)
+--- Forum: The rifles (http://historicshooting.com/forum-2.html)
+---- Forum: Single shot centerfire (http://historicshooting.com/forum-14.html)
+---- Thread: hepburn 40/2.5 (/thread-1657.html)
hepburn 40/2.5 - bruce moulds - 12-12-2015
a friend recently acquired an original hepburn 40/70 straight.a chamber cast reveals some interesting things, although it is only an assumption that the chamber is still original.
base diameter is 0.462, which seems a little larger than expected, but not overly so. bore and groove diameter have yet to be established, due to an odd number of lands and grooves.
rim thickness seems to be about 0.070, again a little thicker than expected.
the chamber has what appears to be between 7 and 4 degrees transition which is also the leade angle.
neck diameter is 0.426 at the front, and has no parralell section, the case being tapered right to the front.
assuming cases with 0.010 thick necks, this would allow finger seating of a bullet 0.406 in unsized cases.
this would suggest a pp chamber, to be used with sized cases and possibly tapered bullets, or a bigger bore than 0.400, or a chamber modified but still too small for groove diameter bullets.
I will patch some bullets to different diameters, and use them like pin gauges using a breech seater to establish a correct bullet diameter.
a most interesting project for a lucky guy.
keep safe,
bruce.
RE: hepburn 40/2.5 - Don McDowell - 12-12-2015
Interested to see how this comes out for you. That chamber sounds an awful lot like the one C Sharps cuts. I have not had the opportunity to try my Canoe paddle and it's plethora of test loads yet, but maybe one of these days the weather and spare time will all come together..
RE: hepburn 40/2.5 - bruce moulds - 12-12-2015
don,
since the original post some research into cerrosafe has revealed that after 200 hours a cast is 0.0025" larger than the actual chamber.
this would bring the case mouth of the chamber to 0.426 minus 0.0025 = 0.4235".
if we call that 0.423, and assume a case wall thickness of 0.010, then a fired case would have 0.003 clearance on a bullet patched to 0.400.
0.423 - (2 x 0.010) = 0.423- 0.020 =0.403"
this chamber has not had a heathen gunsmith pollute it into a greaser dimension.
never thought I would have the luck to see something like this down under.
keep safe,
bruce.
RE: hepburn 40/2.5 - Don McDowell - 12-12-2015
Something as pristine as that is a rare find for sure.
RE: hepburn 40/2.5 - Kurt - 12-12-2015
Bruce.
The use of a lubed ring bullet was in use during that time period. They used a thick skirted hollow based bullet the same diameter as the patched bullets.
I have tried it and it works quite well.
RE: hepburn 40/2.5 - Kurt - 12-12-2015
By the way, I have a friend that collects the old vintage Remington rifles and hand guns. He has several Hepburns a couple complete in a wood case with loading tools, breach seater and cases with bullets in new conditions or almost new used for the Creedmoor matches. Also the one has a heal sight and tang with the spirit front sight.
On this side of the pond I cant afford one of his rifles unless I take out a mortgage loan. You have a good find.
Kurt
RE: hepburn 40/2.5 - bruce moulds - 12-12-2015
kurt,
I am just helping the owner, as he has no experience with pp bullets. he is a greaser man.
your friends collection must be wonderful to see.
what is interesting about those rifles is the inclusion of breech seaters in the creedmoor kit.
yet more evidence for the dinosaurs who bury their heads in the sand at the mere thought of such things.
keep safe,
bruce.
RE: hepburn 40/2.5 - Kurt - 12-12-2015
Yes it is interesting Bruce. And they all are palm seaters similar to what Pope used.
RE: hepburn 40/2.5 - bruce moulds - 12-12-2015
absolutely interesting kurt.
the reason for palm seaters is that they are all you need for bore diameter or a little larger pp bullets.
those leverage seaters are needed for groove + 0.001 bullets as sometimes used in scheutzen.
keep safe,
bruce.