Jumping the crimp?

D

disseminator

New member
Hey guys,

So I had a bullet jump the crimp in my 460 magnum and thought I'd share:

These are Doubletap 400 grain WFNGC bullets and I am working up loads to about 1650 fps or so.

The recoil is stout. I have heard of jumping the crimp but this is a first for me. The bullets are HEAVILY (.008") crimped. So much so I was worried I was deforming the bullet. I am using Starline Brass and LilGun with CCI Large Rifle Magnum primers.

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Sorry it's a little foggy, camera is wack. You get the gist of it. It DID stop the cylinder from rotating but I was able to swing it open and remove the round. It came out just as pictured.
 

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In your case. I would anneal the brass. If the bullet wont stay put after annealing. Recoil !! can be problematic with such powerful cartridges.
On such occurrences with my 25-06 due to my beyond Max loading's with a light weight jacketed bullet having no cannelure I would use a q-tip and lightly ring the case mouth with a little (liquid type) Super glue just prior to the bullets final seating & crimping. Overnight drying. Only thing that will move that bullet thereafter is its firing.
 
This is brand new never fired brass that I trimmed to uniform length before I loaded them.

I shot about 15 of them and only had trouble with the one round, that I know of......

I am surprised it jumped with so much crimp, maybe I need more.
 
Back off on your seating die, the bullet is seated too deep and you are crimping on the
full diameter of the bullet.
The crimp should be into the crimping groove.
 
I have heard of jumping the crimp but this is a first for me.
Click to expand...

That is as much jump as I've seen too (from one fired round?).
I figure you re-sized the new brass when you trimmed.
I would be tempted to measure the expanding assembly to insure that the
case has lots of tension.

If you think the expander (that you are currently using) diameter is good with your bullet diameter,
maybe order a spare and turn it down a thousandth at a time to check.
An impact puller to check bullet tension with dummy rounds would suffice to get an idea as to whether you are
gaining on the situation rather than hit the range every time until you get it solved.

JT
 
Jaguarxk120,

It doesn't look that way to me. It just looks all the way forward in the crimp groove.


Disseminator,

One problem that can arise with a stiff crimp is rolling it in so hard that the brass pulls away from the bullet below it, as shown exaggerated below. The one seating die I know of that is made to prevent this is the Redding Profile Crimp die, which has a light taper crimp leading up to the roll crimp shoulder. It makes the firmest roll crimps I am aware of.

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That said, I have a friend with a titanium short barrel revolver in .45 Colt that can't shoot 250 grain bullets without bullet jump occurring. He's a big guy with big hands, but no matter how hard he hangs on he cannot shoot bullets over 200 grains in it without them backing out. The problem is that recoil accelerates the light gun quickly and the more inertia the bullet mass has, the harder it tries to stay in place as the rapidly accelerating cylinder pushes back against the cartridge rim. It's like a magician pulling a tablecloth out from under the table setting. The quicker he pulls, the less the setting moves with it. In this case, the heavier the bullet being fired, the quicker and harder the recoil is, too, and that added acceleration to the rear combines with the greater bullet inertia to work extra hard at yanking the case off the bullet. Add to this that the sides of the case can't hold onto a lubricated lead bullet as hard as they can to a jacketed bullet, and you have a recipe for bullet jump. It may be, for equal muzzle energy, you'll find you have to use a somewhat lighter bullet.
 

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Unclenick,

I have a Redding Carbide die set for my 460 but don't always use it. The sizing die really sizes the brass down too much. I contacted Redding about this and they told me they knew it and recommended I only resize the portion of the case that will host the bullet.

I generally use a Lyman M-die for expanding with lead as it seems to work a little better than the Redding one, which I use for jacketed just fine. It is possible that I grabbed my Lyman or RCBS seater as I also load 45 Colt and Casull and Auto Rim and ACP so I have an assortment of 45 dies.

I measured the rest of the cartridges I haven't shot yet and there is no indication of a bulge from an over crimp but it seems the most likely so far.

The bullet that jumped was the last of about 15 that I shot and the last one in the cylinder so it had taken the recoil of four rounds previous.

When you indicate the Redding Profile Crimp die as being superior, does that include the seater and crimp in my carbide set or only the stand alone profile crimp die? I have a stand alone profile crimp die by Redding for 45 AR but that may be too short for this application?

Thanks Reloading Wizard, I mean Unclenick.

;)
 
An impact puller to check bullet tension with dummy rounds would suffice to get an idea as to whether you are gaining on the situation rather than hit the range every time until you get it solved.
Click to expand...

Interesting idea, I don't have a kinetic puller, but may try it if I have the issue again.

Thanks.
 
Back off on your seating die, the bullet is seated too deep and you are crimping on the full diameter of the bullet.
The crimp should be into the crimping groove.
Click to expand...

It is in the groove. It just looks that way in the picture.

Truly, these have a DEEP groove, I doubt I got all the way down which probably contributed to this as well. I'll back off the OAL a wee bit next time and try your advice, cant hurt.
 
RCBS suggests a method of crimping big boomers like that by crimping twice, resetting the crimp the second time around to make the crimp even heavier without bulging the brass, as shown in Unclenick's post. The second time around you are just working the crimp and not the case neck. That said, your crimp in the first pic showing the good cartridge does not look like a heavy for .460 caliber crimp. It in fact, does not look any heavier than the crimp on the jumped bullet. Could be just the pic tho. Still, life of .460 brass used with stout loads is short, don't be afraid to crimp more than you are doing. Believe me, the cases themselves will split long before the necks crack from being overworked. Part of the problem with big boomers and lead bullets is that the lube will rub off on the inside of the case neck when being seated and make the case neck slippery, thus reducing neck tension and bullet hold. Also, sometimes folks will overbell so as not to shave lead when seating, which also reduces neck tension. Sometimes, big heavy bullets under stout recoil just jump. Seems to be more of a problem with lead than with jacketed.

One more suggestion. Dump the Lil' Gun and go with a different powder. It is well known for eating .460 forcing cones in a relatively short time.
 
RCBS suggests a method of crimping big boomers like that by crimping twice, resetting the crimp the second time around to make the crimp even heavier without bulging the brass, as shown in Unclenick's post. The second time around you are just working the crimp and not the case neck. That said, your crimp in the first pic showing the good cartridge does not look like a heavy for .460 caliber crimp. It in fact, does not look any heavier than the crimp on the jumped bullet. Could be just the pic tho. Still, life of .460 brass used with stout loads is short, don't be afraid to crimp more than you are doing. Believe me, the cases themselves will split long before the necks crack from being overworked. Part of the problem with big boomers and lead bullets is that the lube will rub off on the inside of the case neck when being seated and make the case neck slippery, thus reducing neck tension and bullet hold. Also, sometimes folks will overbell so as not to shave lead when seating, which also reduces neck tension. Sometimes, big heavy bullets under stout recoil just jump. Seems to be more of a problem with lead than with jacketed.

One more suggestion. Dump the Lil' Gun and go with a different powder. It is well known for eating .460 forcing cones in a relatively short time.
Click to expand...

So with this helpful advice from all you guys I went back to square one and looked at what is different with these loads vs others I was also testing. ( 300 Cast Performance WFNGC )

I decided to pull a bullet and lengthen the COAL a tiny bit and re-crimp with my Redding Die. I was very surprised how easy it was to pull the bullet. Much easier than a jacketed bullet for sure. I see now why such a heavy crimp is needed with hard cast.

I was worried about going too far on the crimp as I've crushed cases with Jacketed bullets but I see now it's not to worry about that with the hard cast. I think my COAL was ok with the original loads. I did lengthen the one a bit and then went as far as a .015" crimp where I felt it was crimped enough. With that in mind I ran the remaining rounds I had loaded through the crimp and they too took a .015" crimp without issue.

I measured for bulging and there is none. I chamber checked them in my XVR revolver and they slide in like a vault door, smooth as can be.

I greatly appreciate all your advice.
 
One more suggestion. Dump the Lil' Gun and go with a different powder. It is well known for eating .460 forcing cones in a relatively short time.
Click to expand...

I had thought this wasn't settled science on the LilGun, is it just with the 460? I use it in other guns as well. I do also regularly use: H110, AA #9, vvN110, 1680 but none of them match LilGun velocities with most bullets.
 
I believe there is a problem with the over crimp illustration, there is no reason the bullet to bulge, if it did bulge it would conform to the bulged in the case, A long time ago Lyman said crimping could be a bad habit because the bulge in the case would reduce bullet hold, since the invention of tension I have no ideal what it does because I can measure bullet hold because all of my gages measure in pounds, even my tension gages, none of my tension gages measure tensions.

F. Guffey
 
Neck tension keeps bullets from jumping.

Expander may need to be smaller in diameter. Measure sized brass, before and after seating a bullet. After seating, has it expanded .003" or more?
 
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Interesting idea, I don't have a kinetic puller,
Click to expand...

Yes, you do! It's your .460 Revolver!! :D

Question #1, what number was the round that jumped crimp? 2? 3? 4? 5?

#2: was it ONLY that one round, or did any others show signs, ?

#3: Have you repeated the test? Could it have been a fluke??

Is the problem consistent?? Or did it only happen the one time??

If you are shooting other rounds, with the same load, loaded the same way, and only one of them jumps crimp, write it off as a bad round, and toss the case in the recycle or in the "only use after the end of the world when all the good cases are used up" stash. (you know you have one, :rolleyes:)

IF the problem shows up regularly, THEN you need to look at doing something different with either your load, or your ammo construction.

AND, be aware that no matter what you do, there are certain combinations of things that just cannot be made to work "right", despite the fact that we think they ought to...
 
fguffey said:
I believe there is a problem with the over crimp illustration, there is no reason the bullet to bulge, if it did bulge it would conform to the bulged in the case,
Click to expand...

It doesn't bulge. Only the case does. The case sides pull away from the bullet due to the combination of the crimp shoulder pushing down on the crimp and to it bending the crimp's from a small corner radius with the case body. The bullet is simply pushed deeper into the case by all that action and that doesn't offer enough resistance to bulge. It's the resulting lack of contact between the sides of the case and the bullet that reduces bullet pull. As I mentioned, the drawing is exaggerated. I would expect that in many instances the case never leaves the sides of the bullets far enough to fail to spring back into some degree of contact with it, albeit weaker that it was before the crimp was applied. So it's possible you can't even measure a bulge, but still may have a case with a weaker grip on the bullet.
 
...toss the case in the recycle, or in the "only use after the end of the world when all the good cases are used up" stash. (you know you have one, )
Click to expand...

I LOL'ed at that one. So true! :)


disseminator (or others)-
Have you ever seen the crimps on the older .454 ammo that Freedom Arms used to sell? The crimp on that stuff was waaaaaay harder than what you're doing, so I don't think you'll have to worry about case bulging just yet.

Couldn't find a good pic, but if ya zoom in on this one, you can see that the crimp is actually concave, almost making the rounds look bottlenecked.

{edit: see the board policy on posting copyrighted materials (there's a watermark on this image) without there express permission. No hot linking to photos on other sites (we once had a guy get so mad that one of our posters hotlinked his image and used up his bandwidth that he replaced the image with a pornographic one that then showed up in the post here).}
 
Unclenick, I think fguffey doesn't see the gap between the bullet and case in your drawing because of the low contrast between the colors of the bullet and the gap. I had to go back and look at your illustration to see what he was talking about, but that is my best guess.
 
It doesn't bulge. Only the case does.
Click to expand...

Forgive: I went back and looked at the drawings again and again etc and finally I was able to see a gap between the outside of the bullet and inside of the case. That is the reason Lyman claimed crimping can be a bad habit. Back in those days no one had discovered neck tension and I have always had a problem with tension, as you know my tension gages are calibrated in pounds not tensions. The first one I used required the user to count the number of cables going up-over and down two large block of pulleys , I was 15.

F. Guffey
 
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