Ammunition safety by velocity and bullet weight

[filmmaster]

Everyone knows that the barrel cut on the K frame AND high velocity 110 and 125 grain bullets and the muzzle flash helped kill the magnum K frame for a long time.

We also know that the high pressure gas jet from these loads will help cut the top strap...

SO the question I have is, what is the gas pressure doing to the inside of the CHAMBER?

https://www.shootingtimes.com/editorial/38-special-treasury-load/389102

the CFE pistol charge of 7.0 grains in a 38 special case IS .3 grains LESS then the starting load of 7.3 grains in a magnum case generating 23k psi per

Shooter's Reference Load Data for


IF the 110 grain load in the magnum case has enough gas pressure to cut the top strap, WHAT will the same pressure / powder charges do in a magnum chamber?

I ask because I occasionally use a 357 that was shot with remington 110 and 125 grain sjhp loads that seems to have flame cutting erosion right at the spot the specials case mouth is in the chamber.

 

[Scharfschuetzer]

I used the issue 125 grain pills for several years on the PD. My Model 65 does show gas cutting on the top strap and some erosion in the forcing cone, even though I only used them at the end of quarterly qualification prior to the issued of new ammo.

By the way, I was issued the +P+ Treasury (the link in your post) load in 1980 while on the USBP. I didn't care for the round, but as I shot it through an issue Colt BP revolver (Really a Trooper MK III) I didn't worry about gas cutting as it was a pretty heavy-duty revolver. Thorough cleaning always showed smooth and clean charge holes in the 357 chambers after firing these hot little rounds, sometimes a couple hundred in a week during training.

I've never noticed any gas cutting in the chambers or the cylinder face in any of my magnum revolvers. The gas cutting seems to occur when the high-pressure gas (35K or so in magnums) hits the angle of the forcing cone or the 90-degree impact on the top strap.

Is what you are seeing if front of the 38 Special case lip in the chamber fowling? I clean thoroughly and I've never noted any issue like this in my 357 chambers.

 

[filmmaster]

what i am seeing is in the chamber, right at the spot the special case mouth is,

its like someone took a paper clip, stuck a piece of chalk in a pipe, and traced a line around the piece of chalk, but in reverse. its very shallow, but its there. builts up junk so bad its not funny

 

[Scharfschuetzer]

That's certainly an unwanted condition and it does sound like you've got erosion rings in the chambers.

From reading the link in your first post, it looks like those +P+ loads are running about 27,000 psi. The milder magnums of today, are generally about 35,000 psi, but back in the day they ran hotter than that. Still, I've never seen your condition in something like 45 years with revolvers on police and USBP pistol teams as well as several years as a firearms training officer.

When I get build up from 38s in a .357 magnum chamber. I use a power drill with a short cleaning rod inserted and run a bronze brush and solvent at fairly low RPM in each chamber. That cleans the ring out very fast.

As I noted above, I never liked that round. It seemed to be a fish out of water with a too light bullet and too much noise and muzzle flash from a 38 Special round. I hate think what a steady diet of those would do to a Model 36 or Detective Special. I never used them on the two-way range, but my experience there definitely favors heavier bullets.

 

[stansdds]

The offending loads in the magnum revolver calibers is usually maximum velocity/pressure loads using light weight bullets and spherical (colloidal ball) powders like H-110/W-296 and the equivalent bulk powders used by ammo manufacturers. The forcing cone erosion gets a lot of attention and I suspect we see forcing cone erosion first due to the 90 degree edges on the end of the forcing cone. These relatively sharp edges are going to erode before the parallel surfaces of the cylinder throats and inside the forcing cone. I would think it is possible to develop some erosion in the cylinder throats if a lot of full power, lightweight bullet ammo was used and especially if there is significant rapid firing. All of this erosion is mostly avoided by using ammo with heavier bullets, 158 grains for 357, 240 grains for 44 Magnum, and the use of loads that are less than full power.

 

[Hair Trigger]

Everyone knows that the barrel cut on the K frame AND high velocity 110 and 125 grain bullets and the muzzle flash helped kill the magnum K frame for a long time.

We also know that the high pressure gas jet from these loads will help cut the top strap...

SO the question I have is, what is the gas pressure doing to the inside of the CHAMBER?

The 38 Special +P+ Treasury Load - Shooting Times

the CFE pistol charge of 7.0 grains in a 38 special case IS .3 grains LESS then the starting load of 7.3 grains in a magnum case generating 23k psi per

Shooter's Reference Load Data for


IF the 110 grain load in the magnum case has enough gas pressure to cut the top strap, WHAT will the same pressure / powder charges do in a magnum chamber?

I ask because I occasionally use a 357 that was shot with remington 110 and 125 grain sjhp loads that seems to have flame cutting erosion right at the spot the specials case mouth is in the chamber.

The reason the 110 and 125 loads flame cut is not because of the pressure, per se, but because of the length of the bullet, relative to heavier bullets. Chamber pressure with these light loads may actually drop off faster than with heavier bullet weights for the same reason.

Think in terms of milliseconds and even microseconds here. The shorter 110/125 bullet does not fully bridge the end of the charge hole to forcing cone during the ignition and burning time of the powder load, essentially opening the cylinder/FC gap while the powder is still in full ignition and pressure. This releases a hot flame jet as the rear of the bullet leaves the front of the cylinder, circumferentially. The top strap is the closest portion of the gun's frame to this flame jet, so of course it bears the brunt of damage. The gas ring can potentially receive a part of this jet as well. The remainder of the gas jet is dispersed and you get the larger flash, both through the muzzle as usual, plus around the front of the cylinder.

A longer bullet can bridge the gap long enough for complete powder burn, and you will still get hot gases through the gap, but not a flame jet. You might say the difference could be like a torch set up to heat something, vs. a fine flame tip made to cut.

And I believe what you've found inside the chambers is a carbon ring from a whole lot of .38 Spl loads, rather than erosion, unless the gun is very old and/or poorly cared for. This carbon ring can be pretty difficult to clean out, much more so than typical residue from shooting.

Flame cutting might be very noticeable in a gun after hundreds of light bullet loads, but rarely is it consequential to the strength of the top strap. My M19-3 had a palpable cut line when I bought it, you can see it clearly when the strap is clean, but I shoot full power magnums most of the time from this gun, and I'm not worried about the strap breaking.This isn't the best picture of the flame cut, it's more pronounced than the picture shows, but you can clearly see it:

 

[filmmaster]

it is noticable, and it fails the "paper clip case head seperation test" for each chamber,, in that same spot.

It DOES suck up lead, i last used it about 9 months ago for 2-3 cylinders of 158 swc over 13 grains 2400 in magnum cases, then ran some 148 grain hbc in magnum and 38 special cases to clean the barrel.
cleaned the gun GOOD.. but now notice i have SOME crud on those lines