9mm Luger/parabellun

Tim Sr My RCBS 9mm dies came with a taper crimp and a roll crimp. One can over do the crimp with a taper crimp too which IS why I advised the plunk test.
 
My RCBS 9mm dies came with a taper crimp and a roll crimp.
Click to expand...

Under what circumstances would one want a roll crimp on a 9 mm cartridge? (Fairly new to reloading, so forgive me if the answer is obvious to the old hands.)
 
It's not so much that you would want to roll crimp a 9mm, but rather if a roll crimp die is all that is available, a light application can effectively result in a taper crimp.
 
Thanks, CB, that makes sense. The post I quoted sounded to me like the die set came with two different crimp dies, one for a roll crimp and one for a taper crimp. I misunderstood.
 
Yes it would seem unusual that a die set would come with both a roll and taper crimp die, but perhaps the standard seating die was the roll crimp variety and a taper crimp die was also included. Thereby you could bullet seat in one operation without using the roll crimp feature for taper crimping but then use the taper crimp die for a second application. That would make sense of the two dies.
 
Last edited:
lees 9mm factory crimp die is a taper crimp die and not a roll crimp so I see no disadvantage to using this die other than an added step if you aren't using a progressive press.
 
If the roll crimp in the 9mm dies isn't there to accommodate the 9mm revolver shooters, as noylj alluded to, then perhaps it's just a machining artifact. Once the taper crimp is machined in the die, perhaps a lip or ledge inside the die, which begins where the machining for the taper crimp ends, acts in a manner similar to how a true roll crimp acts.

I'm not a machinist, so anyone who is, please correct me if I'm wrong, but it's not difficult to imagine this happening within the die. If die manufacturers tout the feature, perhaps they're trying to convey a "we give you more for less" message to their customers? Doing so hardly seems scandalous. It'd be more in the line of making lemonade from unavoidable/leftover lemons.
 
Ok, I get the crimp part now. I like the plunk test, best answer so far. In working up my load I should be looking for the usual pressure signs, flat primers, cracked case mouths... do I really need to work up a pistol load like I would a rifle cartage? Or is their a basic go to load for hs6? the last load of 5.7 left me with sooty cases. I would assume the case isn't sealing in the chamber due to the light load like the sooty neck of a rifle load that's mild. as usual the load data sources have conflicting load data due to the differences in components and test platforms. but averaged out seems to point at about 6grns hs6 for 115gr bullet.
 
It's always best to work up, but it only takes a few rounds. Western Powders is most conservative. They say knock a maximum load down 15% for handgun cartridges and 10% for rifle cartridges. This is likely allowing that 0.1 grains is the limit most of us measure to, and that is a bigger percentage of a pistol charge than of a rifle charge. But once you have the bottom, you can work up in steps that are 2% of maximum and just fire one round at each load level, looking for a gross pressure sign. I also look at velocity over a chronograph to be sure I'm not getting way more than the load is expected to produce in my barrel length. Such would be a sign I had a "fast barrel" and was getting higher pressures than predicted by the commercial test source.

Whether to use roll or taper crimps in a revolver basically depends on its mass. For the same charge and bullet, the lighter a revolver is, the more it needs the roll crimp, as a light revolver's greater recoil causes it to smack its cylinder back against the cartridge rims (or moon clip(s)) and that has a greater tendency to dislodge the bullets from unfired rounds. I shot a lot of taper crimped wadcutter loads from my medium frame .357 and .38 Special revolvers without a problem. At the other extreme, a friend of mine who bought a titanium frame snubby in .45 Colt is unable to fire even commercial 250 grain loads without bullets pulling, and has had to limit it to 200 grain bullets even with a stiff roll crimp.
 
Forget trimming, no need for that unless your cases are way off..and they dont stretch after firing like bottleneck rifle cartridges.
Your powder charge seems a little light to me, which explains the sooty, actually surprised you got consistent function with the charge you mentioned.
Your OAL also seems a little short..at least for a Rem FMJ profile you could go longer.
Exceptions to this would be bullets with a unique profile
Such as the Hornady xtp's or very similar Montana Gold FMJ HP, which require a deeper bullet seating as seen in Hornady loading manuels
Usually 1.085-1.10( another important discussion involving bullet nose profile, chamber depth and max OAL that will function in your magazine, just rely on your MANUAL) Tip: make a dummy round to check your chamber depth then back off .015

HS-6 is what i use with various 115gr bullets.
My target loads run around 6.7gr @ 1.13 OAL

As for all the comments regarding crimp...the 9mm is actually a tapered cartridge and bullet retention is mainly a function of neck tension provided by your sizing die. Thus no need for "crimp" just use your taper crimp die to remove the little amount of bell you gave it to seat the bullet.

Forget looking for the usual pressure signs seen when using a rifle, by the time you get flat primers things will already be danger zone. Instead, just get a feel for how hard the gun is cycling, i usually start mid range and if i don't already have reliable function, i bump it up a 1/10 until i do.
 
Last edited:
You must log in or register to reply here.
Back
Top