CRIMP JUMP

[crazyphil]

Conflicting comments here and on other forums lead me to a unique idea:
Why not read the instructions?

So I found Smith & Wesson's Safety & Instructions manual for modern revolvers.
Particularly the part under the heading "Ammunition selection
for Ti, Sc, & PD Series revolvers". (Ti for titanium and Sc for scandium).

Paraphrasing S&W's WARNING to be brief: Before placing any of these
reduced weight revolvers in service perform the following test to determine
suitability of the ammunition:
Load 5 in the cylinder.
Shoot 4.
Take #5 out and compare to a fresh round.
Crimp jump (S&W calls it UNSEAT rather than crimp jump) should be
visible. If there is crimp jump do not use the selection. Choose another
weight or brand. Test until you find a load that does not unseat.

As an aside I was conversing with Roy Huntington about this subject.
His advice was to use jacketed bullets weighing around 135-Gr. Lead
bullets are slicker so they do not crimp as well.

A totally separate WARNING: Do not use magnum loads with bullet
weights less than 120-Gr. to reduce the possibility of premature
erosion in titanium cylinders.

Ruger advises basically the same test for crimp jump in their LCR .38 Sp.
The LCR has a stainless steel cylinder so erosion should not be a concern.

 

[gwpercle]

As I said I have never experienced crimp jump, but I have never tested
the 100 Gr. & 110 Gr. loads that I mention above. I'll try them and see
what happens.

I have had an Airweight J-frame in 38 spcl (model 637) since 2005 , it goes to the range every trip and is my main walk out the door with gun. Never experienced any crimp jumping , with factory or handloaded ammunition, with bullets from 105 to 170 grains , standard velocity and +P , in the past 10 + years of shooting.
My experience shows me that it's not common....You can never say never on things like this, an improper crimp on tired brass, reloaded too many times and some expert will be screaming "crimp jump" all over the net.
Best course of action is what you are going to do.....Test it and see ! Let us know.
Gary

 

[crazyphil]

gwpercle that speaks highly of your 637. I believe your 637 has a stainless
steel cylinder (?), same as the 642. That is probably a good thing. They
seem to be getting a little bit too light weight with the titanium and the
scandium which if causing some of the problems.

 

[BigBill]

Does using a two hand hold gripping the revolver right handed with your left hand pulling the muzzle down pressure wise eliminate the muzzle jump? I gather the light weight revolvers can't be shot one handed. Don't limp wrist them.

 

[crazyphil]

BigBill in many instances they need to be shot with one hand. Many
self defense shootings are from arms length to 5 feet or so. The left
hand/arm (if you are right handed) would be busy blocking, parying,
or whatever is necessary to ward off the gun, knife, club, fist, or whatever.

 

[Bastogne71]

crazyphil,
Sorry it has taken a few days to answer your questions. The 360Sc was bought used no box or papers. Likely the prior owner only shot it 2-5 times as well. It didn't go back to S&W because the pistol was in good mechanical condition and functioned OK. I'm sure they would have said it was an incompatible ammo problem not a warranty issue.

My problem was it just hurt too much to fire the thing. Hold your hand out palm up and I'll smack it hard with a baseball bat so you can have the experience without a trip to the range! It has been replaced by a model 640 Pro that I can shoot without pausing to get feelings back in my hand.

The problem with the very light weight revolvers is a combination of the high recoil velocity with the high inertia of the 158 gr bullet causing the jump. Just my experience. Your results may differ.

 

[Captain]

In my experience(25 years in the Ammo industry) I have found crimp jump to be most prevalent in lightweight revolvers with heavy bullet weighted Ammo. In 38 Spl that woul be the 158 gr +P loads in any lightweight snubby.

 

[crazyphil]

Captain I wonder if that is because of the weight or perhaps because most
of those 158-Gr. loads tend to be lead, and as Roy said lead is slicker and
less able to hold the crimp.

 

[Captain]

It's the recoil with the lightweight guns. The gun is moving to the rear instantly as the round is fired. Lead bullets may be more prone to this phenomenon because it is softer and may not hold the crimp as well.

 

[Paul105]

It can and does happen for various reasons in both factory and handloaded ammo. Just make sure to check ammo that is intended for serious use.

Testing is imperative in light weight guns (340s, 396s, 329s) and big bore revolvers (44 Mag w/heavy bullets, up thru various 500s). It has happened to me with handloads in all of the above -- which were subsequently fixed after testing. Every bullet/load combination introduces a new variable, so test before using.

It has happened to me with Remington Factory 158gr 38 Spec +p LSWHPs in a 340 PD (these chroned 750 fps from the 1 7/8" 34o).

Also happened with factory Magtech 158gr JSP .357 Mags (picture below) don't remember gun I was shooting. Reseated these bullets and recrimped -- fixed problem -- ran the rest of the box thru same procedure.

FWIW,

Paul