Was wondering what would be the weight limit for the 43 Spanish

[brstevns]

Just how heavy of a bullet can be used in the 43 Spanish Rolling Block? 450-500gr?

[fouronesix]

Well it would depend on the nose shape/diameter. Most all of them have a generous and fairly long throat. But it is a little deceiving because most of those throats are a simple taper from leading edge of the chamber case mouth end into the bore.

No doubt you could design a bullet with a shank diameter proper for the bore/chamber and a long bore riding nose- so the sky would be limit for weight. I have no idea the stability/accuracy implications of a long heavy in the 43 Span with a nominal twist of about 20".

[Don McDowell]

You'ld be lucky to keep anything heavier than 460 stable past 800 yds.

[brstevns]

Then a 430 gr would not be to heavy?

[JSnover]

Then a 430 gr would not be to heavy?
Nope. Your main concern would be pressure. If you stick with black you should be safe. At what distance and for what purpose are you shooting?

[Don McDowell]

Then a 430 gr would not be to heavy?
Probably not, but it will depend entirely on the barrel twist rate.

[Nobade]

And keep in mind that loads too far from the originals won't hit to the sights on a military rifle.

-Nobade

[EDG]

The rate of twist and the lenght of the bullet affect the stability the most.

If you have the rate of twist you can calculate the rest of the information with one of the on line calculators.

[Don McDowell]

In the 44-77 Shiloh's with their 19 inch twist, a bullet 1.3 inches long is as long as will stay stable to 1000. 1.35 will make it to 800 but start having tons of trouble after that especially in the wind.
Assuming that roller has the 20 inch twist as stated in some of the books, a bullet at 430 grs or about 1.25 is going to be at the top end of what will stay stable. Then as Nobade has brought up, the sights as marked may be problematic.

[Ballistics in Scotland]

The last post (Don McDowell's if I type slowly) sounds about right. People promote modern formulae for calculating this, but a pretty good rule of thumb for a bullet with flat base, not an unduly sharp point and density conventional for lead alloy, is Greenhill's formula. Multiply the bullet length in calibres by the rifling pitch in calibres, and you will be fine with an answer of 150. In practice 200 will often stabilize a bullet.

A given point on the bullet's surface will describe a faster-pitch spiral at long range than short, because the bullet loses longitudinal velocity faster than it does rotational velocity. But that doesn't matter for this purpose. It is the actual rotation in RPM that stabilizes a bullet, and I think there is a good chance of the 200 bullet becoming unstable at long range.

[JSnover]

Lee says you can load smokeless under 475 grain boolits to 1000-1400 fps. Their charts list boolit weights up to 500gr.
Assuming you are just punching paper, what range are you shooting?

[brstevns]

Just punching paper and no more the 200 yards at that. Was just playing with the idea of sizing down a 45cal bullet that I load for my cousins 45-70. Bullets made from WW come out at 420 gr.

[Don McDowell]

Depending if you don't have to size those down so far as to all but eliminate the grease grooves, that should work.

[fouronesix]

As I mentioned in my post the standard twist for the 43 Span in the Rem RB contract rifles was 20". I measured mine and it is 20". Now, whether or not that is across the board for all of them… I have no idea. It is very easy to accurately measure the twist in one of those.

The question of absolute or ideal stability of any one bullet out of XYZ twist rate is purely academic and the twist to bullet length formulas and tables, like the Greenhill, are likewise very general in nature and don't always work in reality.

Sizing a 458 +/- bullet down to 440 +/- may be a trick- that's a lot of sizing!

I just use a conventional tangent ogive, small meplat type GG GC 380gr bullet in mine and have excellent accuracy and stability to out as far as I shoot which is commonly 50 yards to 300 yards.

Of course a 43 Span Rem RB rifle is capable of much longer ranges with reasonable POI accuracy if the load and bullet are reasonably stable and accurate. You can put a really big target out or put a big flat piece of steel out at much longer ranges and randomly splatter lead on it.

[JSnover]

420 is plenty safe. You can load them to fairly mild pressure and still have plenty of room to tweak the data for targets at 200.

[ascast]

sizing 458 down to 440 ain't gon'a work, sides, you probably want a .445 or 6 anyway. Slug your bore. Both Lyman and RCBS make molds in
this size, 439 up to 448 in rifle weights, say 370grns or more. I shoot the biggest I can chamber. If you have dies, they are probably wrong in that they expand for a 439 bullet. You might try the bullet swap board to see if anybody has some boolits on hand. I would send you some if I had them made up.

[EDG]

Greenhill's formula does not work quite as well as one of the newer calculators developed with imput from the 1000 yard BPCR shooters.


The last post (Don McDowell's if I type slowly) sounds about right. People promote modern formulae for calculating this, but a pretty good rule of thumb for a bullet with flat base, not an unduly sharp point and density conventional for lead alloy, is Greenhill's formula. Multiply the bullet length in calibres by the rifling pitch in calibres, and you will be fine with an answer of 150. In practice 200 will often stabilize a bullet.

A given point on the bullet's surface will describe a faster-pitch spiral at long range than short, because the bullet loses longitudinal velocity faster than it does rotational velocity. But that doesn't matter for this purpose. It is the actual rotation in RPM that stabilizes a bullet, and I think there is a good chance of the 200 bullet becoming unstable at long range.