Guys,

I remember seeing some rules of thumb (heuristics) for the reloading of double rifles posted here some time ago. I simply cannot find them with the search function. I remember it covering things like increasing/decreasing the velocity and barrel residence time to change crossover and impact point.

I'd VERY much appreciate someone reposting them or providing the link to the original post.

Thank you all VERY much,

nopride,
Theoretically true, but practically not observed. Perfection requires perfect velocity control of the ammo, an impossibility.

The regulation aims to find the crossing point of the X pattern at a given range, either 50 yards or 100 yards, crudely put.

Or, one could try to regulate to two groups, one from each barrel, printing 1" apart at 100 yards, with the line between centers of the groups being horizontal and exactly bisected by the POA.

Then I want you to tell me how many angels can actually dance on the head of a pin, please.

I would suggest that you look through Old "Rifle" magazines for Articles by Ross Seyfried. I think they even have them on CD. Ross has written quite a bit about doubles etc. Of course double gun journal is required reading in your research.
The only thing I can remember is that Ross suggest RL-15 as THE powder to use in the old cordite rounds. He has a formula for charge weight that you might check into........DJ

Good on the X pattern. Poor on crossing point. A theoretically perfectly regulated double has no crossing point. If the muzzle centerlines are an inch apart, the bullets are an inch apart at any range.

Dave

I have been thinking of getting a Merkel or Kreighoff double in 500NE for a fun gun. I was wondering if it was regulated with 570gn bullets at around 2050 fps, I should be able to work up a lighter bullet load at lower velocities and get it to regulate?
If lighter bullets cross over earler and lower velocity causes it to cross over later, then I should be able to work up a light load which will work?

I tried this "regulating' business with a .54 Koddiak double using Swiss FFg. With a 90-grain charge, (too fast) the barrels crossed with about 6" total divergence at 100 yards. With an 80-grain load, they diverged about the same amount (too slow). With 85 grains, both barrels shot into a 2 & 7/8" pattern @ 100 yards, R then L barrel. I think this is acceptably small for a ML double rifle.

I have looked all around for XMR5744 ,but its not available in Australia. I would have to work up a load with a lighter charge and pufflon. Either that or go through the process of importing some XMR5744 for myself and others. I think a 500 NE would be a good fun gun if I can get some lighter loads to work in it.

When the right barrel is fired, the rifle muzzle moves upward and kicks out to the right, since it is right of the long axis of the sighting plane, etc. ... The left barrel muzzle moves upward and to the left when it recoils, so ...



Since the regulated set of sxs barrels has the bores set to converge and point below the POA when the sights are on POA ... Voila!:



Muzzle velocity too slow, barrel dwell time too long (left barrel shoots left and high, right barrel shoots right and high):



LL...........RR

...............

...............

...............

......POA......



Muzzle velocity too fast, barrel dwell time too short (left barrel shoots right and low, right barrel shoots left and low):



.......POA.......

.................

.................

.................

RR.............LL



Muzzle velocity just right, L and R converge on point of aim, the crossing point:



.....L...R....

......POA.....

.....R...L....



Well, that's a start! Need to know any other rules of thumb? I am mostly just bolt action trash, myself, but I am sure the uppity-double crowd will be able to help.