Hey fellas, I just started reloading so I still have a ton to learn yet. I've started out reloading 9mm, and I'm having trouble seating with a crimp. I'm almost positive it's because I don't have my brass trimmed all the same size? So my question is, What is the best way to do this? Do I need to measure all my cleaned brass and trim them all to the same length? And then set my seating die to that? Also the Hornady manual tells me the case trim length is 0.749, a lot of my case's are only measuring 0.740 or a little more. Can I even use them? I realize that may sound stupid because I just fired them, I'm just confused! Thanks for the help.

Lesson #1; Never crimp pistol rounds that headspace on the mouth. never. not needed. I have never trimmed a piece of 9mm brass either; they don't stretch much, and you will lose it long before it gets too long. Yes, use that brass no matter how short it is. So, you are wasting a lot of time on a couple of levels. That is the way I do it, since 1968.

Holy crap! thank you for telling me!

Some guys will taper crimp rounds for rimless ammo for autoloaders; another useless exercise in my opinion. Your bullets won't move if your expander plug is right.

So as long as they feed through my gun ok, I shouldn't worry about it?

Hello Turner:

There's a lot to be said for "leaving it alone if it works", but stuff you haven't yet experienced can cause intermittent problems. DPCD doesn't believe in taper crimping and I have no problem with that. I do taper crimp--primarily because I reload my pistol ammunition on a Dillon and I get the T/C operation for free, timewise.

Where not crimping can become a problem is if the case mouth is flared a little too much and doesn't roll back almost straight when the bullet is seated. If a remnant of the flare protrudes to a point that it interferes with feeding, you will have a problem. Crimp or don't crimp as you will, but if you don't be sure your flaring operation is only enough to allow the bullet to seat without shaving lead or gilding metal.

Regards,

Dave Manson

I am starting with a Hornady lnl ap. So I also can seat and crimp at the same time. I just have so much to learn, it's a lil overwhelming rite now. But I really appreciate all the help!

Hello Turner:

If you do decide to taper crimp, be sure to do so in a separate operation, after seating the bullet to the proper depth. Seating dies that seat and crimp simultaneously produce less-than-ideal results.

Dave Manson

While I don't crimp my 9mm 45acp etc. I do set the seating die to the point that I remove and case mouth flare. I also flare the mount only enough to allow me to start the bullet.

Dave I have used my seating crimp die for years with no issue. What problems have you had?

I lightly crimp for 40S&W and 45 ACP

Never had a problem

I used to apply a light roll crimp, just enough to remove the bell and to make sure the round would chamber. Then one day I measured the outside diameter of the end of a 45 acp round and found they varied up to .005 of an inch.
Next step was to buy a Redding taper crimp die and now all the rounds measure the same with just a slight amount of crimp.

Did not do any scientific testing but the rounds with the consistent crimps and all measuring the same should be more accurate.

Of course you have to make the mouth bell straight again, but that is not crimping.
If your brass is not uniform in it's mouth wall thckness, and you apply a taper crimp to it, you have automatically introduced a variable bullet tension/pull. Since the expander plug acts on the inside of the case, when you seat the bullet, the neck tensions will all be the same but if you then squeeze the variable ODs onto the bullet, well, that will result in different force being applied to the bullet; hence the reason I see taper crimping as not only useless, but a step in the wrong direction. Sorry for complicating what you need, at this stage in your education, to be simple. I know others will disagree with me, but my logic is sound.

I really appreciate all the help from everyone. I'm sure I'll have more questions soon.:-)

I like the 4 pc Lee dies for pistol

Case trimming is counter productive to crimping, but it is definatly something you have to do...Most spin case trimmer are inaccurate in regards to crimp, anyone with a set of calibers or mics knows that..The best solution is the file trim die IMO, its slow but accurate and keep all crimps equal..I use them on rifles with tube magazines, most pistols, and all double rifles..

As to the 9mm a proper taper crimp dies work well, but if the chamber is correct then probably unnescessary..A roll crimp can be used with any pistol round, but its tricky for a number of reasons so I don't recommend it...