1871 Springfield

Topics related to Pre - 1898 Remington Rifles
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varsity07840
Posts: 9
Joined: Wed Apr 27, 2016 8:26 am

1871 Springfield

Post by varsity07840 » Fri Jan 11, 2019 11:24 am

I have an 1871 in nice condition that is a shooter. I recently slugged the bore out of curiosity. Surprisingly, at least to me is that the bore is the usual .500 or so, but the groove size is a bit over .524. I was expecting it to be around .515. I have been shooting .517s in it. Has anyone run into this besides me? The slug was measured with an anvil mike.

wlw-19958
Posts: 77
Joined: Sun Sep 18, 2016 7:21 pm

Re: 1871 Springfield

Post by wlw-19958 » Sat Jan 12, 2019 4:23 pm

Hi There,

The Springfields of that era had (I thought) 3 groove/land
rifling. What model micrometer are you using to measure
the groove diameter? I bought a Starret model 483 mic for
this purpose. Rolling Blocks usually have 5 groove/land rifling
and I got a Starrett 485 to handle those. Both of these mics
are calibrated in tenths (.0001").

Good Luck!
-Blue Chips-
Webb

varsity07840
Posts: 9
Joined: Wed Apr 27, 2016 8:26 am

Re: 1871 Springfield

Post by varsity07840 » Sat Jan 12, 2019 4:58 pm

The Springfield version does indeed have a three groove barrel. I didn't measure the slug myself. A gentleman who has done a number of other odd number slugs for me measured this one.

wlw-19958
Posts: 77
Joined: Sun Sep 18, 2016 7:21 pm

Re: 1871 Springfield

Post by wlw-19958 » Sat Jan 12, 2019 7:19 pm

Hi There,

After consulting my book Trapdoor Springfield by
Waite and Ernst
, the 1868 board designated that the
rifling be .0075" deep. This would create a difference of
.015" between the bore and the groove diameters. Un-
fortunately, the bore is designated as .50" (notice that the
bore is only specified to two digits) and I lack experience
to know how much variation exists in bore diameters of
Springfield Trapdoors of the period.

Assuming that the bore is held to the nominal .500" diameter,
the groove diameter should be .515". Of course there would
be a manufacturing tolerance of about 1 or 2 thousandths of
an inch so the range could be anywhere from .513" to .517".
Even allowing for wear in the bore, the .524" seems greater
than one would expect from a barrel in "good" shooting condition
(at least from what I would expect). You may wish to ask your
guy to double check his findings.

There would be a certain amount of obturation involved with
a soft lead projectile. A hollow base bullet would expand more
and seal the oversized bore. Another possibility may be to go
with a paper patched bullet. If you "roll your own," you can make
bullets of the diameter you desire.

Paper patched bullets were very popular during the later half
of the 19th Century. Of course, the eclipsing of black powder
by smokeless powders doomed the paper patched bullet and
ushered in the bullet jacketed with gilding metal.

Anyway, I hope a Trapdoor enthusiast will contribute and add
to the discussion.

Good Luck!
-Blue Chips-
Webb

varsity07840
Posts: 9
Joined: Wed Apr 27, 2016 8:26 am

Re: 1871 Springfield

Post by varsity07840 » Sun Jan 13, 2019 8:04 pm

He did three measurements on the slug and between the three there was only .0005 difference.I'm inclined to accept his numbers. The bore diameter is .5012, meaning that the groove depth is what's unusual. My 1868 TD is .515 groove. I have a mould that casts .526 bullets that I have been able to squeeze in to the cases. I'll see how they shoot in 20/1 alloy.

wlw-19958
Posts: 77
Joined: Sun Sep 18, 2016 7:21 pm

Re: 1871 Springfield

Post by wlw-19958 » Sun Jan 13, 2019 10:04 pm

Hi There,

If the bore is .5012" and your groove is .524" that
is giving a mean groove depth of .0114". That is
much greater that the Springfield Armory specification
for rifling depth (which was .0075"). Of course in
the nearly 150 years since it was made, who can say
what has happened to it and why.

Just to be on the safe side, have you made a chamber
cast and/or measured the chamber diameter in the
neck area? You should check this so that your cartridges
won't be too tight with the larger projectile.

Good Luck!
-Blue Chips-
Webb

varsity07840
Posts: 9
Joined: Wed Apr 27, 2016 8:26 am

Re: 1871 Springfield

Post by varsity07840 » Mon Jan 14, 2019 1:04 pm

I didn't do a chamber cast, but loaded rounds drop in easily. Haven't shot it yet.

wlw-19958
Posts: 77
Joined: Sun Sep 18, 2016 7:21 pm

Re: 1871 Springfield

Post by wlw-19958 » Mon Jan 14, 2019 2:03 pm

Hi There,

Okay, but you indicated that you were using .517"
projectiles and you are planning to move to a larger
projectile. If the new rounds with the larger bullet
are not tight in the chamber, then you will probably
be alright. You just don't want to raise the chamber
pressure to an unsafe level.

Good Luck!
-Blue Chips-
Webb

varsity07840
Posts: 9
Joined: Wed Apr 27, 2016 8:26 am

Re: 1871 Springfield

Post by varsity07840 » Mon Jan 14, 2019 4:25 pm

Agreed. They drop in easily and extract smoothly. By the way, using a digital caliper to measure, the difference between outside of muzzle to land, and outside of muzzle to groove is around .011.

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