A 1911 idea. Will I be banned for this?

[1911Tuner]

I dunno, owen. I've seen some strange things happen with extra-light bullets. Had a stock Combat Commander that short-cycled with an early lot of Glaser Safety Slugs until I dropped the recoil spring a couple pounds.

If memory serves me, that was...what...a 130-grain bullet at about 1400 f/s?

 

[Owen]

Tuner, its straight up math.

Impulse = momentum

Force x Time = Mass x Velocity

 

[1911Tuner]

I understand that, owen, but like our old friend Yogi mentioned:

"In theory, theory and practice are the same. In practice...they ain't."

Sometimes...there's somethin' that we fail to plug into the equation.

That 130-grain slug at 1400 fps should have had more than enough impulse/momentum to run that stock Commander...but it didn't.

 

[Owen]

It's not theory, its law. the law of conservation of Momentum.

A heavy bullet and a light bullet leaving the barrel with the mae momentum both experienced the same impulse. The impulse on the bullet is equal to the impulse on the slide barrel assembly. This is High School physics stuff.

 

[1911Tuner]

Not arguing that, owen. I said that I've seen strange things happen with light, high-speed bullets.

F'rinstance...

An Officer's Model that short-cycled with 185-grain hollowpoints, but didn't with 230 hollowpoints. According to the chronograph, the 185's impulse/momentum was higher than the 230's...but I still had short-cycle failures to eject with the 185s. When I went to 230s, the problems went away. When I went back to the 185s, they came back. Lather, rinse, repeat.

 

[Jim Watson]

High school physics is not adequate.

You not only have momentum, mass times velocity, you have acceleration. I am not qualified in Davis Mechanics but there is a school of thought that the rate of change in acceleration - fourth derivative - has physical significance.

And you have empirical observations from Tuner, but also from the people who have put 7.62 barrels in their .38 Supers and found the guns to function even with the light fast bullet.

 

[1911Tuner]

Jim, I have a couple of theories as to why I had the problems that I did. I won't throw'em out here, though. No sense in starting an argument. One of the things that crossed my mind is the difference in powder burn rate in the 185-grain round. There's impulse and there's impulse. Even with like muzzle velocities, the way those velocities are developed can produce some different results on the back end.

There's also the equal momentum thing. In theory, momentums are equal. In reality, they're only equal in the absence of outside force, or in the presence of equal outside force. With an autopistol, there's never an equal outside force. You can get close by removing the recoil spring, but the hammer or striker spring is still in play.

 

[buckskinbob]

I love my 1911s have a pre-war ACE that has a lightened slide and is recoil operated, not really a 1911 lock up. Ditto my series 70 service ace. both are to valuable for me to mess with. I had one in 9mm and traded it for another in 45, the several that i own
in 45 are either collectors or shooters. Thouhg none are sacred and get shot occasionally. I have yet to own a Super 38, I was close but this orphan bromhandle came along. the adooption papers were expensive so the super is on hold. 20-20 hindsite says if I'd kept the 9 I could have just swapped the bbl.
will the Tok head diameter be close enough to use that slide ? I sure hope that you build it and more important Enjoy It !!!

 

[Owen]

High school physics is not adequate

Yes it is. Verified with High Speed Video.

 

[grendelbane]

Remember, the bullet is not the only thing being ejected. The burning powder produces a gas which still weighs as much as it did when it was a solid. And, it is moving fast, faster than the bullet does.

Some cartridges are louder than others. Because the pressure of the burning powder is higher than in other cartridges. Or, in shorter barrels, the same thing holds true.

7.62 Tok is a loud cartridge, those gasses are moving quickly when they leave the barrel.

 

[1911Tuner]

Yes it is. Verified with High Speed Video.

And yet, I still had short-cycle problems with light, screamin' velocity bullets that should have produced greater impulse and momentum than the heavier, slower ones. That's evidence that there's a little more in play here than simple action and reaction.

 

[barnbwt]

You not only have momentum, mass times velocity, you have acceleration. I am not qualified in Davis Mechanics but there is a school of thought that the rate of change in acceleration - fourth derivative - has physical significance.

It's called "jerk," and I believe it affects how energy is dissipated through heat when metal deforms ("elastically" or plastically). I think (very vague memory here) that it can affect spring stiffness(that may only be in large springs, though). There's also friction forces that are harder to pin down; in a larger-caliber platform (like the 1911) there may be more friction going on with the (larger) bearing surfaces than in a lighter-built gun.

Most likely, though, it's all pressure-spike distribution; if the Tok round burns it's juice off while the gun is in lockup, a larger share of it's energy is spent pushing metal into metal, when the mechanical advantage of the recoil is low. A longer duration burn (like the .45) gives enough boost to unlock the action, plus some residual pressure to push the action back when mechanical advantage is a bit better. Obviously this effect would vary greatly from pistol-model to pistol-model, and would be much more pronounced with a lower recoiling, faster round like the Tok. That could explain the mixed results people report.

TCB

 

[Jaymo]

I'm with Tuner and Barnbwt on this one. In theory, different weight/velocity rounds with equal recoil impulse will work the same.
In practice, they don't.
Not only do you have different burn/recoil durations due to bullet weight and powder burn rate, you also have increased friction with the longer/heavier bullet. That increased bearing surface also increases the pressure duration and recoil impulse duration.

Did I explain that well enough? I had a pretty bad wreck today, at work, and the pain meds are kicking in. Explaining things is not my strong suit, while under the influence.

Anyway, recoil energy is only part of the equation. Much like how gas pressure is only part of the equation in reliable cycling of gas operated autos.
Like how you can have two different loads with the same peak pressure, but one can be safe in a given gun and the other can be unsafe in the same gun, due to the difference in how fast they build pressure.

I have this nifty theory that recoil and blowback operated guns are actually gas operated, because it's the gas pressure that propels the bullet and creates the recoil impulse and blowback. According to my theory, the bullet is a gas piston.

We good?

BTW, my buddy and I have been talking for a good while about converting a .10mm or .38 Super EAA Witness and/or Para Ord into a Hicap 7.62x25.

 

[Swampman]

I know this is kind of an old thread, but in the interest of safety I wanted to address 56hawk's statement about the Privi Partizan claim of 1722 fps velocity for the 7.62x25.
Be advised that this is their claimed velocity from a 250 mm (9.84 inch smg) barrel.
Toks and CZ52s are generally good, safe weapons, until handloaders start to chase after velocities and power levels they were never designed for.