Thanks Paul! I'll take all the knowledge you want to give on reloading for a double. The biggest issue I'm having is finding bullets and powder here in the states. Thanks to our President Obummer, both are scarce even for the .470. I have quite a bit (5lbs) of IMR 4350 and a pound or so of IMR 4831. What's your thoughts on these two?
BB, spare a thought for us Down Under !
We are only just now begining to get a trickle of dribs and drabs of powders and projectiles.
Prices have sky-rocketed !!!!
Both powders you mention are listed by Graeme Wright in his 3rd Edition Shooting the British Double Rifle as useful powders for loading traditional for caliber .474 bullets.(you'll find this book a wealth of vital information)
IMR 4350 in particular is similar in burning rates to R 15, another useful powder, and our own locally manufactured AR 2209.
The greatest "baggage" that goes with reloading for your double is the requirement to get the new load regulated.
If your Sabatti is anything like my buddy Sam's it will love the C.E.B bullets as well as Nth Forks and it will love them at extreme velocity.
Two good freinds have put A LOT of top end loads through Sam's Sabatti and it has taken it all in it's stride !!!
Select a projectile you want to use long term, a powder that is suitable and plan to stick with that combination.
KEEP ALL OF YOUR BRASS IN THE ONE BRAND.
In the larger calibers such as .470 and .500 there is a great deal of variation in case capacity between various brands of brass.
I have 7 different makes of .500 brass here at home, they have 5 gns of capacity difference between the least and the most.
If I were running a load near the threshold of pressure based on the case with the least capacity, then the cases with the greatest capacity would be over max.
What I've found recently is that when begginging to handload for a double there are two indespensible tools that are a must have;
* digital micrometer (caliper)
* chronograph.
Record keeping is also crucial.
Keeping note of expansion in the base of cases and monitoring the point of diminished return between load and velocity are two, of many, ways of reading pressure in your double.
I and a few of my buddies are now trying to correlate the expansion of the case base to pressure. We will certainly know more soon but at this stage it is safe to say that any case that expands to more than .003 greater than its pre-fired measurement is too hot for a double.
Note;
* measurement is taken .335 up from the rim
* cases will expand more on their first firing than their second.
Above notes on case head increase are for second firings.
Also, learn to look at your brass and be able to identify unusual wear marks, shiny banding around the pressure point noted above, keep an eye over appearance (and size) of primer pockets etc etc.
Another well known method of watching for pressure is how the shells "release" from the chamber after firing.
Open the gun ever so slightly and make sure the cases are well free of the chamber after firing. Obviously anything that "sticks" in the chamber is too hot.
People with a lot more knowledge than myself are telling me that a load that makes a double stiff or difficult to open is WAY too hot and well over maximum.
I have been told that this traditional method for gauging pressure in a double is unreliable and not precise enough.
Hope some of this helps.
Cheers,
Paul.