Dating down a grade

Posted by / 12-Jan-2018 00:40

Dating down a grade

An interesting instruction with a Purdey 50 bore rifle No 3852 of 1844 from Dallas’s book gives the charge for a round ball of .453 cal as half a dram of No 2 powder with a stout linen patch, and of a conical bullet for the same rifle as 2 drams of No 6 powder with a thin cambric patch and the hollow in the tail of the bullet filled with grease – quite a difference.The same sights were marked 50 & 100 yds for the ball and 100 & 150 yds for the bullet – illustrating the much greater drop on the ball.The trolley is now complete and I’m getting some of the BBC microbit computers sorted out as they seem just the job for the kids.Plus a a couple of school meetings this week, and two next week – being a school governor is a fairly big commitment but pretty satisfying.In fact experiments with smooth bore muskets showed that there was little to be gained by rifling below 50 yards.Once shaped bullets were introduced the ratio of mass to drag improved, so the bullets held their velocity for longer, and the longer contact of the bullet walls with the rifling meant that higher initial velocities were possible using bigger charges.30th September – Had a very nice email from the owner of the Martini Henry (see below) saying how pleased he was, and that he never expected the chequering to turn out so well! I had a recent email from the US asking about calibers of percussion rifles – a quick look at Donald Dallas’s 2003 book ‘ The British Sporting Gun and Rifle’ has interesting details.

I steamed the wood and got rid of some of the varnish and some of the dings, then wiped over with shelac and put on several coats of ‘slacum’ ( linseed oil, driers and a little beeswax).

Getting to do some gun work would be a great luxury as I seem ridiculously busy on other things – today I was working on the Geophysics Archive followed by my Stem Club – we have 11 very enthusiastic kids all making alarms to fit on to cookie jars etc…

Tomorrow is again busy with meetings but on Wednesday I will reward myself with a couple of hours clay shooting in the morning to get my eye in for driven game – update – ( ) – my next shoot is on 10th.

26th September – The Martini Henry stock and fore end are now finished and dispatched, see below.

I haven’t had a moment to do any more gun stuff as school things have been pressing – I have a new group of young children ( 6 -9) in our STEM club and Dave and I are having to reset our complexity index many steps lower.

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Much of this difficulty was caused because the rate of twist of the rifling was carried over from flintlock rifles, where the acceleration was much more gentle due to the slower burn of the powder resulting from flint ignition.