Setting up sizing die - Wide range of BTS measurements on fired brass???

[fguffey]

USA military arsenals spec'd bullet release or extraction forces for all small arms ammo back in the 1950's. What's in a name? Whatever your want it to be. But the process is the same.

You had bullet grip up to 500 pounds and then there was that boring run on about bullet weld and no one on the forum was any better off after than they were when the question was asked.

What's in a name?

If it was not very important to you we would not be having this conversation. We had a member that was not happy when another member did a search on terms. It seems out of vanity he insisted he invented the term. The skilled researcher did the search and assured the vain person was not going to be happy with what he discovered.

F. Guffey

 

[Eddie Harren]

I understand everyone reading this thread believe you but me. I have said forever I am the fan of 'the bullet jump' I want my bullets to have that running start; I do not want my bullet setting at the lands trying to decide if it is going to make it past the rifling. What does that mean? If I have spike it will be when the bullet hits the rifling meaning when the bullet passes the rifling the pressure starts to drop. And then there was that thing about magic, a smith in Iowa Park, Tx blew the end of barrels put on a regular bases.

Serious spikes: A shooter in central North Texas took a rifle to the range with a new box of ammo. The rifle did not belong to him. He chambered a round from a newly purchased box of ammo, he pulled the trigger and then headed to a gun smith. The shooter purchased 308 W ammo for his friends 25/06. The shooter was going to sue all involved. It was not possible to read the head stamp on the 308W case.

F. Guffey

I just cancelled my subscription to the funny papers!

 

[Brians356]

If a 30 caliber bullet needs 80 pounds of force to push it out of the case and into the rifling, pressure in the case will have to be almost 1100 psi.

Yep, close to 1074 psi. But how much of that is required to push it out of the case vs push it into the bore (assuming there is significant bullet jump)?
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[Brians356]

I just cancelled my subscription to the funny papers!

The Katzenjammer Kids. Ah, youth!
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[Bart B.]

Yep, close to 1074 psi. But how much of that is required to push it out of the case vs push it into the bore (assuming there is significant bullet jump)?

You could put known forces uniformly on the bullet back in noting the amount to fully engrave the bullet with the lands, then less would be needed until bullet exit.

Then there's the groove diameter issue. Some 30 caliber bullets are .3092" diameter. Some 30 caliber barrel groove diameters are .3065".

Bullet jackets vary in how soft or hard they are.

I don't know how to calculate the force required to push a given bullet through a given barrel so it leaves at some speed.

It may be as easy to calculate force on the bullet incremental across a pressure transducer's psi curve to see the force at those points. But that curve accelerates the bullet up to some speed. If peak pressure is 60,000 psi, there's about 4400 pounds of force on the back end of a 30 caliber bullet when it's 5 to 7 inches out of the case. About 740 pounds when it leaves the muzzle from a 24" barrel.

How much force is needed just to keep it moving a couple fps?

I've pushed 31 caliber lead bullets through 30 caliber bores to measure them for the barrel's groove diameter. Once they're past the throuat, probably 15 pounds of force to push 'em out the muzzle.

Good barrels require uniform force to push the bullet the same speed out. Bad barrels with loose and tight spots are a different story; as well as different forces when bullets are in different places. Gotta pay match barrel makers extra shekels to lap them to near zero diameter tolerances.

 

[spife7980]

I have said I have tensions gages; none of my tension gages measure tensions, all of my tension gages are calibrated in pounds. I also have a deflection gage, it measures deflection in thousandths and inches.

So get out those tension gauges that measure in pounds. Now take two cases from the same batch and size one case down with a bushing and then size another with a bushing that is .001" smaller. Measure the force (in pounds you idiot) and compare between the two. Does the one thats .001 smaller require more force (pounds) to move? Exactly. Smaller diameter requires more force because there is more tension. Call it tension pounds interference fit or whatever you care to call it.

Are there other variables such as cleanliness, thickness, hardness etc that change the actual amount of force? Yes. Does that change the fact that all other things aside the smaller one will require more force? No.

Quit being dense.