Light Weight Snub Crimp Jump

[marb4]

I've been experimenting with different defensive loads for my newly aquired LCR 38 and tonight started testing Remington 38+p LSWCHP (FBI load). Online I've read a number of warnings regarding crimp jump in very light revolvers with heavy recoiling loads. My test protocol was as follows:

Measure length of round #5. Fire 4 rounds then remeasure round #5. I did this 5 times (using a new "5th round" for each test) and got a consistent 2/100ths (0.02) of an inch of "jump" each time. Nowhere near being enough to bind the cylinder but it was noticable in each test. For you more seasoned revolver shooters my question is this:

Is 0.02 inch of crimp jump something that would cause you to discount this as a defensive load in this specific snub or would it be of no concern?

 

[rcmodel]

If it didn't 'jump crimp' past the crimp groove in the bullet it wouldn't concern me.

If it straightened out the roll-crimped case to make it past the crimp groove?
It would.

rc

 

[pbearperry]

i tested the same load in my S&W 340PD, and the fifth round bullet backed out so far that it was easily plucked out of the case by fingertips. Because of that I only load 2 of them with the last three being jacketed HP's.

 

[gbran]

I've had .357 jump crimp far enough forward, the cylinder wouldn't rotate. You just have to test ammo until you find the loads that work.

 

[rcmodel]

Or, reload, and make them so they don't.

That's what I've been doing for over 50 years.

rc

 

[TimSr]

If it didn't 'jump crimp' past the crimp groove in the bullet it wouldn't concern me.

If it straightened out the roll-crimped case to make it past the crimp groove?
It would.

Dittos.

 

[243winxb]

Ammo for reduced weight revolvers-bullet jump

From S&W http://www.smith-wesson.com/wcsstore/SmWesson2/upload/other/S&W_Revolver_Manual_12-15-2014.pdf

Before placing any of these reduced weight revolvers into
service, perform the following test to determine the suitability
of the ammunition you intend to use.
At a gun range or other suitable and safe location, prepare your
revolver for firing by fully loading its cylinder with the ammunition
to be tested. While pointing the firearm in a safe direction, fire all
but the last round. Remove the empty casings and the last
loaded round from the revolver’s cylinder.
Carefully inspect the loaded round to determine if its bullet has
started to unseat (move forward) from its casing.(FIGURE 2) If it
has, you should not use the tested ammunition in your revolver.
Choose another projectile weight or brand of
ammunition and repeat this test until you find one that
DOES NOT UNSEAT under these test conditions. When you are
finished, fully unload your revolver and secure it safely.

My 10 oz M337 PD in 38 spec has a warning to use only jacketed +P ammo to avoid bullet movement. But i use home cast 100% of the time, with no problems. Neck tension with a little crimp keep bullets from moving for me.

 

[Artym]

The 5th round jumped the crimp on Rem 158 LHP in my KLCR. This is a good reason for using Speer 135Gr. Short Barrel loads, especially the 38 +p. Point of impact was too high as well with the 158 gr 38+p loads, and the 135 was right where they should be. I would reserve the LHP for heavier guns than the LCR.

 

[marb4]

One More Test

I did one more test last night with my LCR and the Remington FBI load and got basically the same result (0.015 inch "jump"). It did not appear that the bullet was pulling past the crimp groove nor did the crimp on the case appear to "open" for lack of a better term. Also, the bullet could not be pulled further or rotated in the case by hand.

I guess my question would be, should you expect absolutely zero bullet movement or would the small amount I'm experiencing be concerning?

 

[buck460XVR]

If the last round in the cylinder is not moving past the cannelure after all the other rounds in the cylinder have been shot, I would not be concerned. If I had any concerns, I would continue to keep that same round in the cylinder without firing it, while shooting several more cylinders full and see if the bullet moved any more.

A bigger concern of mine would be how accurate they are and how close to POA do they shoot with the fixed sights. It might be that there's other ammo out there that shoots better outta your gun, and does not jump crimp. There are a multitude of modern SD bullets out there with terminal performance just a good as the LSWCHP.

 

[pittpa]

It would help to clock the velocity of the one that jumped by firing it. Also, what about the third and 4th? Maybe they also jumped that amount and then jumped no further. A bit more testing would be worthwhile. I would not decide based on only 5 rounds anyway. Your LCR only weighs slightly more than my 340PD. I did not consider the other brands of 158 +P LSWCHP to be heavy recoiling. I recently clocked Winchester (new/old) as well as Federal, all 158 +P LSWCHP. They clocked 781/772/713 FPS respectively or 214/209/178 ft/lb respectively, Maybe your Rem load was hotter? Does your LCR have a 2 finger or 3 finger grip? You may be experiencing recoil differently than me if you have a short grip. I think next time I test ANY ammo in my 340, I'm going to check the length of the other rounds every shot. If nothing else, I figure any jump gets you decreased velocity. That's not good. I don't have your loading or I would clock and test it for you. You don't list your location. Location is good. I've had nice contacts and help from local folks, Maybe somebody local to you........

 

[Jim K]

My feeling is that any measurable jump in a single cylinder is too much. (I am not talking about subjecting one round to repeated cycles, as some do.)

I figure that if there is some jump there may be too much and I would not know when that would happen. So if that happened with my SD ammo, I would change ammo, even if I had to go with lighter loads. In an SD gun reliability is paramount; the most powerful gun or cartridge is of no use if it doesn't fire.

Jim

 

[pittpa]

FWIW, and to give some perspective, I tested 10 9mm rounds in a LCR 9mm revolver. The round is +P 124g, average velocity 1139 FPS, 357 ft/lb muzzle energy. Final increase in AOL was approx .025. There was no relevant change in velocity. The fifth (and longest) round in both instances of 5 was 1145 and 1141 FPS respectively. Knowing the velocity was good, I would not discount the particular 9mm loading. How this data translates to a 38 case in your situation, I do not know for sure. Maybe some experienced reloaders know how this slight increase in OAL may affect velocity/safety in your situation.