There are posters on the Shiloh forum that have pictures of bullets with nose slump, that they have fired into sawdust or snowbanks and recovered.  The slump occurs in the barrel, as the burning (or, in the case of black powder, deflagrating) powder charge accelerates the rear of the bullet while inertia momentarily keeps the nose static.  Depending upon the strength of the alloy, the nose will be pushed to one side of the barrel or the other, while the body of the bullet either moves forward into the rifling or slugs up to fill the rifling grooves.

Typically, one sees a bullet with the nose visibly off-center, and the rifling marks higher up one side of the bullet body than the other.

I don't have snow or sawdust to confirm, but the targets i have shot indicate that 25: to 20:1 alloy is fine for grease groove bullets and 16:1 is indicated for paper patch bullets.  Or, in modern measuring terms, a BHN of 5-7 is fine for grease groove and black powder, 8-11 for paper patch and black powder.  The one study with lead:tin alloys I did with smokeless powder in a .32-40 indicated 20:1 the best over all.

Muzzleloading slug gun shooters use a 2 piece bullet with the front portion harder alloy and the rear softer alloy to upset and take the rifling.  The 2 part
bullet is swaged together in a special die.  Has anybody tried that in a breech
seated bullet?  Seems like a lot of work but could cure the nose slump problem.

Probably another factor in nose slump is the torque when the driving bands hit fast twist lands and the nose gets whipped around trying to catch up. Guys shooting supersonic bullets to near rock throwing distance of 200 yards have it easy and can even get away with spitzer bullets. Actually didn't Mann's testing show that as long as the base was good the nose didn't matter that much. BPCR and BPTR is a whole different world of transsonic and subsonic flight that requires entirely different nose profiles (which don't include spitzers!) on the very long heavy bullets required to get the BC up there and the very fast twists required to stabilize them.

Once the nose slumps over it is like having an unbalanced drive shaft and it only gets worse as it continues down the barrel. A 32-40 bullet is typically turning at 74,000 RPM's and the fellows shooting spitzers at 200yds benchrest cannot get around the ill effects. They might not seem as bad but they sure indeed are if one is trying to achieve extreme benchrest match accuracy Oneatatime. I think most just have a tendency to blame some of those off shots somewhere else. If shooting offhand one would never notice the difference nor would someone who has yet to establish day in, day out and all year long consistency in their bench rifles. They are also typically the same ones who would also freely state I have never seen a difference based on my own personal experiences and they are indeed correct and probably never will. More than half a bullet out is one point lost and one half the bullet diameter in is one point gained. They all add up and they are either for you or against you and that is where the real difference comes into play if one wants to consistently place in the top three in benchrest matches.

Seems to me that about all the bench shooters I know are shooting spitzers and are shooting 250's and half inch groups, so shouldn't we just let them slump. With all the varibiles we have in this game, rifle,power,primer,WIND, and the human element etc. how can the flier be caused by nose slump, as opposed to all the other problems we have.  Ledball

I have to agree with Joe. 

My thesis to the matter is:

Those that shoot well with spitzers, don't get nose slump but, those that don't do well, with spitzers, do developed nose slump. It seems fairly easy to understand, now.

Frank

firstly, spitzer bullets are superior to some others at the supersonic speeds used by some.
for bpcr bullets which start their journey at the top of transonic, elliptical and metford noses have greater stability and less drag.
horses for courses.
while we have been talking of nose slump, we have all neglected that there are 2 types of it.
one where the nose goes off centre, which could be referred to as slump.the other where the nose stays centre, but sets back.
let's call it setback.
the former can and will destroy accuracy.
the latter can still be accurate, but will reduce b.c due to increased nose drag.
both conditions are more prone with bpcr due to the greater "suddenness" when the fire is lit.
setback is a thing that pp people must come to grips with, so that bullets are patched far enough forward but not too far.
studying confetti negates the need to recover fired bullets
bore riding noses so popular now can be problems due to setback, as the bore ride is forced into the rifling causing leading.
the modern trend to long ogives could very well be self defeating due to setback.
my own experiments suggest that there is no use having a nose longer than 1.5/1.6 calibres long when shooting black powder.
even with 12:1 alloy any longer will suffer from slump, and any setback will reduce nose length to about 1.5 calibres anyway.
keep safe,
bruce.