Bullet - to - cylinder -size and strain on a revolver?

[Outpost75]

Tim had it right. The basic answer is that there is no need to shoot "hard" bullets in a revolver, so the entire question is a non-issue, what we West Virginia hillbillys would call "mental masturbation." Keith did all his development in .357 and .44 Magnum with alloys which for the most part did not exceed 12 BHN.

[mdi]

FWIW; last night I watched super slow motion video of a revolver firing. The hammer falls and the bullet has exited the barrel way before any movement of the gun takes place (recoil)...

[jsizemore]

Tim had it right. The basic answer is that there is no need to shoot "hard" bullets in a revolver, so the entire question is a non-issue, what we West Virginia hillbillys would call "mental masturbation." Keith did all his development in .357 and .44 Magnum with alloys which for the most part did not exceed 12 BHN.

Check out the pressures on the Casull and 460 Ruger. Hard alloy is very necessary.

[Outpost75]

Check out the pressures on the Casull and 460 Ruger. Hard alloy is very necessary.

The Casull and 460 Ruger have no purpose in my battery and therefore I have no interest in doing so.
The locals here ate all the mastadons during trhe last ice age.

[DougGuy]

It comes down to resistance when you question pressure increases because of a hard alloy, and/or smaller throats. It's very obvious that the more the boolit has to be swaged down to go through a throat, resistance increases, which will cause pressure to increase. If a harder alloy creates more resistance than a softer boolit of the same diameter, then the harder alloy creates more pressure than a softer alloy would.

Sizing the boolit .0005" smaller than the throat diameter, OR sizing the throat diameter .0005" larger than the boolit would present the least amount of resistance and therefore the lowest amount of pressure increase from resistance in the throats since now there is very little if any.

My own personal Vaquero had very tight throats, and a .449" thread choke, I was shooting 340gr SSK truncated boolits which were BHN 22-24, over 23gr of W296 and impact was 6" higher at 25yds than Hornady 300gr XTP bullets over the same charge of W296.

After reaming throats to .4525" and using a Clymer reamer to Taylor Throat the barrel to remove the thread choke, point of impact of the 340gr SSK boolits dropped to strike the target even in elevation with the 300gr XTP.

I can safely deduce that resistance before reaming was probably extreme, and maybe even dangerous since 23.0gr of W296 was a max. load, enough resistance to slow the travel of the boolit in the bore and increase the dwell time long enough to raise the barrel more before exiting the muzzle, explaining the higher point of impact on the target.

After reaming, the SSK boolit was free to travel without resistance and it exited the muzzle slightly sooner than before, which caused the point of impact to be lower on the target. Probably a lot safer load after reaming as well.

The XTP bullets on the other hand did not change point of impact, as these are a dead soft lead core swaged into a gilding metal jacket which would easily swage down to go through the tight throats and also the choked barrel, then since this was a max. load, there was enough pressure to bump them back up to seal in the bore, and they shot to the same point of impact both before and after throat reaming and Taylor throating the barrel.

This alone shows that the resistance from tight throats is less with softer alloy, as any change in dwell time in the barrel would have changed point of impact on the target. Only the very hard SSK boolit showed change in point of impact, which would reflect enough difference in resistance to change the dwell time in the barrel, and also the resulting increase in pressure would be different pre reaming as compared to post reaming.

[tazman]

I don't worry about shooting hard alloy boolits in my guns. I never use max powder charges so the pressures never come into play. I do, occasionally, have a barrel with short height rifling. In these barrels I use hard alloy because I need all the grip I can get to stabilize the boolits.
The hard alloy has been needed in three of the guns I have in order for them to work right with cast.

[onelight]

The hardest lead alloy will be softer than a jacketed bullet.

[dtknowles]

The hardest lead alloy will be softer than a jacketed bullet.

Yes and no. They really don't compare well. The jacket is harder and will grip the rifling better but with a soft core will swage down easier than hard cast. Just look at what happens on impact a hard cast bullet will not expand but a soft jacketed bullet will mushroom.

Tim

[Larry Gibson]

For the last year or so I've been pressure testing in several cartridges [pistol and rifle] attempting to determine whether a jacketed bullet or cast bullet of the same weight gave a higher pressure with a given load.

Can't come to a conclusion because sometimes the jacketed bullet gives higher pressure [not consistent within test to test variation] and sometimes the cast bullet gave higher pressure.

The alloy used in handgun cartridge bullets does not appear to make any difference in pressure. It seems the difference in weight between different alloy of the same bullet give essentially the same pressure with a given load all other being equal. With my RCBS 44-250-K mould bullets cast of linotype weigh 245 grs, of COWW + 2% tin 251 gr and of 16-1 alloy 258 gr. It appears the softer alloyed bullets heavier weight may offset any potential pressure increase from the harder yet lighter weight bullets.

What I have concluded from my testing so far is that any increase in pressure is more a function of seating depth [not to be confused with OAL] with bullets of the same weight +/- than it is with bullet "hardness".

[onelight]

Interesting I would have guessed the jacketed would always have had higher pressure all else being equal .
The more I learn ,the less I'm sure of.

[gwpercle]

No the first thing to move is the hammer and then the primer backs out of the pocket a bit. Both of which move the cylinder forward and hold it there until the bullet moves into the forcing cone then the bullet acts like a piston in a cylinder and drives the case backward. Depending on the friction between the case and the chamber the cylinder might move backward at this point. Once the bullet is free of the cylinder the cylinder definitely moves backward. If you shoot really light loads you will see the primer protruding from the pocket as the cylinder never moved back to reseat the primer.

Tim

Tim's nailed the sequence that I've seen reported from the Speer Lab in one of the older Speer reloading manuals .
I have also experienced the very light load - primer backs out thing and at first it's confusing as to what's going on.
Gary

[Larry Gibson]

Sometimes we [myself included] over theorize what is actually happening. In the last 14 years +/- conducting serious testing internal ballistics and being able to actually measure such I've surprised myself with how many preconceived notions I had that weren't correct. Those preconceived notions were based on the writings [books, articles and internet] of many who I highly respected as "experts". What they thought and had deduced certainly made sense but actual testing with the equipment we have today which they did not have is giving us a much better and more accurate idea of what really occurs. I'm sure if they had the test equipment we have today their writing would have been much different.

[Outpost75]

^^^^THIS!^^^^

Larry has certainly educated me and corrected some pre-conceived notions I had been taught by noted "experts" in their time. But actual measurement trumps theory and mental masturbation every time.