Taper Crimp?

PhilOhio · 05-07-2009, 12:02 PM

Sieger,

I would have to differ with you on the need for taper crimping. I think it is very much necessary, especially with a fast acting and rather violent light weight bolt assembly like that of the Luger. During feeding, that strong spring moves the light bolt forward much more smartly than in almost any other handgun design.

Even if the feed ramp geometry allows the bullet to travel freely and encounter no pressure, there may be bullet setback sometime, rarely, or almost all the time; because the bullet overcomes inertia so slowly during feeding. This leads to erratic pressures and accuracy...and perhaps jams.

Another factor is that, when reloading either jacketed or lead bullets for 9mm, it is usually necessary to bell the case mouth at least slightly. Normal bullet seating dies are not likely to remove all of this bell, and that can lead to feed problems, because the case mouth wants to "catch" any burr or roughness on the ramp.

Another problem I have run into is that of differences in case wall thickness among manufacturers; some are paper thin and some military cases are very thick. With the thick walls, the bullet might seat quite tightly without taper crimping. With thin walls, it will likely be loose and chances are high that it will be set back during feeding, perhaps only because of inertia.

So by all means put at least enough crimp on 9mm loads to ensure that the mouth belling has been eliminated and the bullet cannot be pushed inward with firm hand pressure.

And since this round headspaces on the case mouth, never ever put a roll crimp on it, or headspace won't be right and you can possibly get elevated pressures because the mouth cannot open easily to release the bullet...depending upon how your chamber has been reamed and where the rifling starts.

I reloaded for nearly 40 years before deciding that, with semiauto handgun cartridges, moderate taper crimping was the only way to go. Always. And I reload many thousands of them for handgun and SMG. For me, it eliminated a whole lot of occasionally irritating problems.

Sure, you might be able to get away without doing it much of the time. But why bother? It's no extra effort to have a taper crimp die properly adjusted at the last station on the Dillon press. That's the oly way to get a reload with the dimensions right up to factory ammo standards.

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05-07-2009, 12:02 PM	#4
PhilOhio User Join Date: Apr 2009 Location: Ohio Posts: 145 Thanks: 5 Thanked 17 Times in 14 Posts	Sieger, I would have to differ with you on the need for taper crimping. I think it is very much necessary, especially with a fast acting and rather violent light weight bolt assembly like that of the Luger. During feeding, that strong spring moves the light bolt forward much more smartly than in almost any other handgun design. Even if the feed ramp geometry allows the bullet to travel freely and encounter no pressure, there may be bullet setback sometime, rarely, or almost all the time; because the bullet overcomes inertia so slowly during feeding. This leads to erratic pressures and accuracy...and perhaps jams. Another factor is that, when reloading either jacketed or lead bullets for 9mm, it is usually necessary to bell the case mouth at least slightly. Normal bullet seating dies are not likely to remove all of this bell, and that can lead to feed problems, because the case mouth wants to "catch" any burr or roughness on the ramp. Another problem I have run into is that of differences in case wall thickness among manufacturers; some are paper thin and some military cases are very thick. With the thick walls, the bullet might seat quite tightly without taper crimping. With thin walls, it will likely be loose and chances are high that it will be set back during feeding, perhaps only because of inertia. So by all means put at least enough crimp on 9mm loads to ensure that the mouth belling has been eliminated and the bullet cannot be pushed inward with firm hand pressure. And since this round headspaces on the case mouth, never ever put a roll crimp on it, or headspace won't be right and you can possibly get elevated pressures because the mouth cannot open easily to release the bullet...depending upon how your chamber has been reamed and where the rifling starts. I reloaded for nearly 40 years before deciding that, with semiauto handgun cartridges, moderate taper crimping was the only way to go. Always. And I reload many thousands of them for handgun and SMG. For me, it eliminated a whole lot of occasionally irritating problems. Sure, you might be able to get away without doing it much of the time. But why bother? It's no extra effort to have a taper crimp die properly adjusted at the last station on the Dillon press. That's the oly way to get a reload with the dimensions right up to factory ammo standards.