Variations in 1803 Harper's Ferry Bores

[Skirmisher]

File this under the heading "useless trivia". However, just for grins I did some measuring of some original Harper's Ferry rifle bores and was surprised at the variation.  Slip gauges were used to measure the actual bore, while land to groove measurements were made with calipers.  All had 7-groove rifling and all had a twist of 1 turn in 47" to 48".
First, an 1804 dated specimen.  This had a bore diameter of .536", and a land to groove measure of .565", meaning that the .10" wide grooves had a depth of .029".
Next, an 1815 dated rifle that had a bore of .530" and a land to groove measure of .550".  Groove width at .10" and had a depth of .020".
Finally, another 1815 dated rifle had a bore of just .524", with a land to groove measure of .540", making a groove depth of .016".  Groove width again was .10".
Supposedly, the government ball was .525" to be loaded in a linen patch.  This would have been about right in one of the 1815 dated rifles but about impossible in the other.  It would have made a sloppy loose fit in the 1804 rifle.  I conclude from this that each rifle must have been originally issued with its own mould, cut to fit, as was done for civilian rifles in that period.  I have never read that this was the case but I do recall that Army riflemen were responsible for casting and "smoothing" their own ball.  It gives you some notion of the logistical issues that must have been encountered prior to perfection of interchangeable parts.

[WESTbury]

Moller reports on pages 337-338 of Vol II, that in the third quarter of 1807, HF produced 4015 Bullet Molds and Chargers. No rifles were produced during this quarter. I do not think that the molds were sized for any particular rifle based on this production number being all one calendar quarter.

[LynnC]

Of the 4015 ball molds produced does it specify the cast ball diameter?  Or do you think they could have varied somewhat in diameter to be chosen for fit to a particular rifle?

Just a thought.......Lynn

[Skirmisher]

Beats me.  I never imagined this degree of variation in bore sizes. 
Fitting all three with a single ball size would be tough.  Of-course over 200 years the 1804 dated rifle could have been freshened.  I just thought this was sufficiently interesting to share.

[WESTbury]

LynnC-- The chart in Moller's book does not specify the ball dia.

My personal SWAG is that the molds were possibly made to produce the smallest ball dia based on the tolerances used at HF for drilling the bore in the barrels before they were rifled.

Like I mentioned above, that's my guess. I've never owned one of these rifles or even discussed them in depth with someone that had any.

The dearth of info available,to researchers of Harpers Ferry arms is staggering.

[mr. no gold]

To add to this, a large number of Harper's rifles were smooth bored later on. (1) Was this done at the factory, or contracted out; do we know, and (2) were the smoothed bores all the same size? I have an 1819 smooth bored HF rifle, but have not measured the bore. These findings make me wonder.
Dick

[Skirmisher]

I have had five that were bored smooth, including one that is restocked and mounted as a typical Ohio or Indiana halfstock percussion smooth rifle.  All were roughly .58, which is about what you get when the rifling is reamed out.  I think most we're bored smooth in the Civil War period for militia use at the time that they were also percussioned.

[mr. no gold]

Thank you for your reply. Makes sense that the smooth bored guns were going to militia use. I have always taken it as fact that if one is bored smooth it was converted to percussion at the same time. While mine is flint, I suspect that it was changed back. Also read once that a number were sold in St.Louis by the government, but now can't recall where I read it. The late 1820s or 1830s come to mind for that disposal.
Dick

[Longknife]

Skirmisher. I have an unpublished manuscript from a noted firearm historian and he goes into great detail in his research of the 1803 "short" rifle. He was able to source original guns from many collections that had excellent original bores. His findings are that the rifles barrels were made with a 1-56 twist and the lands were .530 with the rifling .015 deep. Also he was  able to inspect and mic. many original military short rifle bullet molds and they were all cut to mold a .520 ball. I do not own or have I ever inspected the bore any short rifle, . Ed

[Longknife]

Henry Dearborn specified in a letter to Perkins May 25, 1803. """"should be calculated for carrying a ball of one thirtieth of a pound weight.""" I have looked at many gauge charts and they vary in size of ball for 30 gauge. An original set of bore gauges found in England presumably from the 19th century measure a 30 gauge ball at .517..... close enuff???,,,, Ed

[Belleville]

Prior to interchangeable parts, when initially boring a barrel they would try for the smaller end of bore tolerance, when making to a standardized size. If bore did not clean up i.e. there were defects in the bore, they would bore it slightly larger to see if defect would clean up, etc. If they exceeded the high end of the tolerance, the barrel was junk. So that explains the differences in bore dia. There was also tolerances for the ball dia.

[WESTbury]

Belleville--That is all great information. What is the source (sources) you used for references? It somewhat fits in with my "SWAG" post on May 17th.

[Top Jaw]

On a related topic....Anyone know of an original parts source?   Need a lock tumbler for my 1819 HF.   The hammer post is sheared off.  Or Perhaps it could be welded and repaired. 

[Longknife]

That would be a hard original part to come by! Take the tumbler out and compare it to other tumblers in TOTW catalog, start with their 1803 lock first, it just might fit!?