For me this is just a mental exercise, as I currently don't have a double. But maybe again someday. While riding the mower today, I was thinking about reloading for doubles and wondered if you had a double that was regulated for a lighter bullet, perhaps you could apply the seventy-five percent rule in reverse. Say a 9.3x74R regulated with 232 grain bullets. Would you expect it to regulate with 300 grain bullets and the same charge? Or say a 500 BPE that was regulated with 350's. Would it regulate with something close to 460 grains? It seems to me it should work, but as Einstein once said, "In theory, theory and practice are the same. In practice, they are not." Just wondering.
Bfly

Black Fly:
I have used the 75% rule both ways. Using 75% of bullet weight and full charge of powder seems to work the best for me. However, that said, using the full bullet weight and 75% of the powder charge also works well but (in my limited experience) seems to group a bit larger.

One more thing--the larger the bore the more forgiving as to regulation. In other words, I get more variation in group size with the smaller double rifle calibers than with the larger calibers. Less so in the .600 and even less when I get to 8s and 4-bores.
Cheers,
Cal

The 75% rule in reverse will not work if the lighter bullet is loaded to the full chamber pressure, as the heavier bullet would cause a LOT more pressure.
Reducing the powder charge 25% in a small bore double could also lead to SEE problems.

In the case of your 9,3 I would just get some 286gr bullets,a suitable powder, and do regular load development, shootng a right and a left, and a right and a left, as you go up in powder charge.

You might find a load the rifle regulates good with.

My 9,3 shoots several different 286gr bulleted handloads and factory ammo with 286 gr bullets AND 323 gr bullets into acceptable groups at 100 yards suitable for hunting.

I also agree with Cal as it seems the larger bores are easier to get to shoot different weight bullets in the same place with very good regulation.

I found the OP's post a bit confusing as to
what he was describing.

9.3 and 375's seem to be those calibres that
just regulate with multiple bullet weights,
al be it with a little playing around.

Agree, big bores are more forgiving.

Thanks guys.
505G, sorry about not being clear. That confusion was what I was having the problem with. It seems straightforward to lower projectile weight, but keeping powder type and charge the same. When I tried to think it through in reverse, it seemed that a full charge of powder for a lighter bullet would not be appropriate for the heavier bullet, because of either too fast powder or too much pressure. I could imagine it working with black powder in the express cartridges, but to go to smokeless, seemed a bit more likely to be a problem. I just don't have the experience to be satisfied with my conclusions.
My only double experience has been with 9.3x74R doubles. Mine were all regulated with the 286 grain bullets. I shot a number of different bullet weights with a number of different powders to try to learn how things changed with the different components. I just never got around to trying the process with heavier bullets in my guns. My drillings and combinations don't seem as sensitive to changes in components, so my own experiments will have to wait until I get another double.
Thanks
Bfly

No worries.

Not a huge need to go heavier than 286gn anyway
in a 9.3 but they do tend to be forgiving and you an often get a way with a slightly heavier bullet.

As you know with DR's, what happens with one gun might not happen with the another double
and some doubles are more sensitive to changes in components than others.

500 there is one reason to go heavier than 286gr in the 9.3 and that is bullet performance. I remember Michael458 mentioning in his terminals testing that the big long woodleigh 320gr RN was one of the few RN bullets (of any caliber) to track straight in his test box. I sent him some 285gr 9.3 FMJ bullets I have, to test for my own peace of mind. Damn things went every which way but straight once they entered the test medium. Plenty of lighter bullets out there that work well in a 9.3 though as you say.

On a side note. Didn't Holland regulate their 375 FL Mag double to shoot all three factory loads 235gr, 270gr & 300gr to point of aim in the same gun? Or near enough to hunt with. I don't know how they managed this but very handy if you can get it.

Rhodes

Black Fly don't forget what NE 450 No2 says above, when you increase bullet weight and keep powder charge the same you increase chamber pressure.

There's an old german proofing method, and some gunsmiths use it, where you take the max powder charge for a given load then increase bullet weight by 10% and fire this as a proof load to test the weapons integrity. As you know proof loads aren't meant to be used as regular loads. By using the 75% rule in reverse and increasing bullet weight by 25% while keeping the powder charge the same you are in effect creating a very intense proof load.

Rhodes

Rhodes

Yes, the 320gn tracks straight and penetrates.
I found it hard to keep it in Buffalo to get recoveries.

It works in the 7 but from having shot a lot
of Buff with the 9.3 x 64 as a test bed at all velocities (to simulate 360 No 2, 9.3 x 74 and
9.3 x 62), the 286 does 95 - 98% of what the
320gn will do.

Re 375, my gun will regulate all 3 to the same point.

quote:

Originally posted by 505G:
Rhodes

Yes, the 320gn tracks straight and penetrates.
I found it hard to keep it in Buffalo to get recoveries.

It works in the 7 but from having shot a lot
of Buff with the 9.3 x 64 as a test bed at all velocities (to simulate 360 No 2, 9.3 x 74 and
9.3 x 62), the 286 does 95 - 98% of what the
320gn will do.

Re 375, my gun will regulate all 3 to the same point.

Which 286gr bullets have you found that worked for you on buffalo?

Personally I am a RN man, and like the Woodleigh's
as they always worked for me in any gun I have used. Please note that the testing I did was for Woodleigh and that was because I had a '64 which meant we could get enough speed to test them.

So to me, Woodleigh RN, 286gn is fine, 320gn just keep going.

Having now fired a couple of Woodleigh Hydro's,
(in 375H&H and others but not 9.3) I wouldn't hesitate to use Hydro's either.


What have you or do you use ?

9.3x74R which is regulated for RWS 285gr RN loads. I only hunt wild boar with it so the softs with plenty of lead showing work fine. I have a soft spot for RN bullets as well. I don't get out much anymore but we are playing with different lathe turned bullets at the moment to see how they go.

Your stint testing bullets for woodleigh was a great opportunity. Did you try the 9.3 softs on water buffalo or only the solids?

quote:

Originally posted by Rhodes:
Your stint testing bullets for woodleigh was a great opportunity. Did you try the 9.3 softs on water buffalo or only the solids?

Only softs from memory. I can't remember shooting a solid but I probably had some in the mag as at that stage I normally did.

Softs were the RN and the PP's. It was the PP's I was testing to work out the Recommended Impact Velocity an we used the RN as a control as we knew how they performed.

It was interesting, especially the very low and very high velocity.

I shot an elephant one time, with the 9,3x74R, side brain, at five yards.
The bullet, a 286gr Woodleigh Solid, went completely through the elephants head...

How much more penetration do you need???