Bullet Nose setback not slump.

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mdeland
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Re: Bullet Nose setback not slump.

Post by mdeland »

I agree as well about the difference between pressure from both ends (extrusion) as opposed to pressure from the base ( bump up) being able to be uniformly measured without firing the slugs. I think that oiled saw dust is the best way to capture them with the least amount of and most consistent distortion.
bruce m
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Re: Bullet Nose setback not slump.

Post by bruce m »

there is in a sense pressure from both ends, even though the hit comes from the rear on firing.
this is because of inertia in the nose resisiting the bang in the butt.
something has to go somewhere, so it goes sideways.
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Distant Thunder
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Re: Bullet Nose setback not slump.

Post by Distant Thunder »

To measure nose set back and the effect of differ alloys on that set back you're probably going to have to shoot actual cast bullets with noses into some sort of recovery media and compare a lot of bullets. Pretty much what Kurt has been doing for years.

Some set back is going occur even with the harder alloys and like so many other things in this game if you go too far in one direction trying to avoid a perceived problem and you start to have problems elsewhere. As long as set back is consistent and not excessive I think things are as good as they are going to get. I try to stay somewhere about in the middle! :lol:
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bruce m
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Re: Bullet Nose setback not slump.

Post by bruce m »

so jim, arnie, and I take an interest in this.
what we have in common is that we shoot dual diameter bullets, patched to bore mostly, and patched to internal fired case size in the case as well.
fired in greaser chambers, these bullets barely have to bump up in the case at all.
we have already put thought into this.
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powderburner
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Re: Bullet Nose setback not slump.

Post by powderburner »

The lasa website has a formula to determine min pressure for obduration.
Basicly bhn x 1422 this is the min pressure to bump the base of the alloy
The file is too big to attach
The site is the los angles sillouette assn
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bruce m
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Re: Bullet Nose setback not slump.

Post by bruce m »

just to complicate things, I remember reading a thing about bullets of the same bhn, one of lead/tin and the other lead/tin/antimony, and bumpup.
apparently the lead/tin/antimony alloy will bump up more easily.
reason being that antimony is crystalline within the allow, as opposed to how tin combines with lead.
for the same bhn, there is more lead in the bullet, and the crystals flow with it.
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mdeland
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Re: Bullet Nose setback not slump.

Post by mdeland »

But is not bullet bump up on a taper from the base to the nose, rather than symmetrical of it's contact length? The farther forward portions of the bullet has much less mass inertia squashing it outward to the bore wall.
mdeland
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Re: Bullet Nose setback not slump.

Post by mdeland »

The best way I can think of( but totally impractical if not impossible) to capture a fired bullet with the least deformation, is to fire it vertically and catch it in a shallow water pond. Gen. Hatcher talks about doing this if I remember correctly, at I think Aberdeen proving grounds, in his book. They were testing how lethal a falling projectile was if memory serves.
Kenny Wasserburger
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Re: Bullet Nose setback not slump.

Post by Kenny Wasserburger »

I agree that the cylinder is perhaps the better way to test.

How about a fixture the you put the bullet in point down and compress the bullets base?


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Orville
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Re: Bullet Nose setback not slump.

Post by Orville »

A simple way to measure the difference upset with different alloys, take the cast cylinders of different alloys, use a standard hydraulic press with pressure gauge, applying the same pressure to all the cylinders then measure them.
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martinibelgian
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Re: Bullet Nose setback not slump.

Post by martinibelgian »

I recently recovered a CBE bullet fired from my 45-70. This one has a boreriding section on the nose, style Lyman 457125. The surprise was that the boreriding bit on the recovered bullet seemed to have upset completely to groove diameter, this with a 30:1 alloy. Load was 66.7 grs of Swiss 2fg. I might need to try the same bullet with my harder alloy - 16:1. It already is groove diameter, so...
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desert deuce
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Re: Bullet Nose setback not slump.

Post by desert deuce »

The question is: how accurate is that load in your 45-70 and for what type of shooting is it purposed?
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martinibelgian
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Re: Bullet Nose setback not slump.

Post by martinibelgian »

How accurate? too early to tell, it shoots nice groups for the moment, but more than 1. And it is destined to be a target round, so the only requirement is accuracy.
BFD
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Re: Bullet Nose setback not slump.

Post by BFD »

Orville wrote: Sun Dec 15, 2019 6:51 am A simple way to measure the difference upset with different alloys, take the cast cylinders of different alloys, use a standard hydraulic press with pressure gauge, applying the same pressure to all the cylinders then measure them.
No, you will need some measure of time as well. If you apply the same pressure continually, it will continue to smash the cylinder shorter as long as the pressure is on.
Glen Ring
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Re: Bullet Nose setback not slump.

Post by Glen Ring »

Dang fellas...I bought a BPCR rifle..a couple of Lyman molds and just started shooting.
I appreciate the research , quantitative analysis, opposing theorems and even the novellas...but doesn't it all boil down to what a particular rifle likes?
Don't get me wrong..I Like reading anything technical concerning shooting and Jeanne caught me down loading Pellet rifle trajectory and wind drift tables., but doesn't it all boil down to buying a rifle, and seeing what THAT particular rifle likes and how it behaves dirty and clean ??
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