Crimping: To crimp? Or not to crimp? (kinda)

B

bhoglan

Inactive
So I finished processing my .308 brass, primed it, charged it, and seated my bullets using my Hornady Custom Grade seating die. After seating the bullets (which have a cannelure) I went to try and crimp them. I followed Hornady's directions and backed the seater screw out a few turns, raised the ram up and then threaded the die body until I got resistance. At that point I started turning the die body about 1/16th of a turn for each cycle of the ram. I inspected the bullet with each cycle. The top of the case is at about the middle of the cannelure. At no point did I see any change in the character of the top of the case to indicate it was crimping into the cannelure. On my last 1/16th turn, I lowered the ram and found that the case itself had been "crunched" down, that is to say that much like stepping on an aluminum can, the case is deformed just below where the shoulder becomes the width of the main body of the case.

Am I just continuing my idiot streak here? What should the case neck look like in the cannelure when properly crimped?


Thanks!
Brian
 
Correct me if I'm wrong but I think you should be able to take your caliper and measure the case mouth to be 0.002-0.004" smaller than the rest of the neck.
 
The idea behind the crimp cannelure is to give the brass somewhere to go as you squeeze it. So you really want the case mouth to come up as close to the top of the cannelure as you can do without getting the case mouth over the solid part. This will allow the most give space. Having the mouth level with the middle of the cannelure may be leaving too much solid bullet behind the brass. It's hard to generalize because some bullets are made with taller cannelures than others.

If you've turned the past the point where the die makes contact the mouth of the case, it is applying crimping pressure. It's just a matter of degree. If you collapse a case, clearly you are pushing too hard.

As a check, if you have a bullet puller, you can remove one of the bullets and see if you can see the cannelure knurl marks on the inside of the case mouth. If so, you had some crimp. You will get more when you seat a little deeper and get the case mouth near the top of the cannelure.
 
Neck Tension — Not Just Bushing Size is a pretty good read on the subject. You are not the first and won't be the last to crunch a case exactly as you describe. As to crimp or not crimp? I don't bother, call it neck tension, bullet hold or whatever trips your trigger but that is all I rely on. I really see no need to crimp a bottle neck rifle cartridge. If I can seat a bullet and then using moderate force push that loaded round against my bench and the bullet doesn't move I call it good.

You want uniformity with neck tension which is why I like to work with the same lots and head stamps of brass. You want uniformity in the neck thickness and inside diameters.

Some loaders like the Lee FCD (Factory Crimp Die) and while I have several which apply a collet type crimp I don't use them, for me I see no need but to each their own. I won't argue their merit one way or the other. I am not sure the crimp the Hornady Dies apply but reading your post and reading the destructions, err instructions you seem to have adjusted things correctly.

SEATING WITH A CRIMP
To begin, refer to the procedure for SEATING WITHOUT A
CRIMP. Follow the procedure throughout, however, DO NOT
TIGHTEN THE DIE BODY LOCK RING.
1. Once you’ve reached the preferred seating depth for the
bullet, back out the seater adjustment screw a few turns.
2. Raise the ram, with the cartridge, to the top of the stroke.
3. Thread the seater die body into the press until it meets
resistance (again, at that point, the mouth of the case
has met resistance with the crimper.)
4. Thread the seater die body into the press in small
increments (one-sixteenth turns) each time operating
the handle. At the completion of each stroke, inspect the
cartridge for the proper crimp.
5. Once you’ve reached the desired crimp (with the cartridge
still in the die), tighten the die body lock ring. Then, while
holding down the handle, thread the seater adjustment
screw downward until it contacts the bullet.
NOTE: On presses with a cam-over action, back out the
adjusting screw 1/8 to 1/4 of a turn to allow for cam-over.
6. Raise the handle and remove the cartridge. Check the lock
ring to make sure it’s still tight. Try another case with a
bullet. If the desired seating depth and crimp are attained,
then you can begin seating and crimping in one operation.
If not, make the needed minor adjustments.
NOTE: For uniform crimps, cases must all be trimmed
to a uniform length.
Click to expand...

My best guess is the die uses a collet to crimp and your neck diameters are already smaller than the collet inside diameter so eventually you crushed the shoulder down.

<EDIT> and as I slowly crawled along typing Uncle Nick answered the question and made a great suggestion. :) </EDIT>

Ron
 
@Unclenick - Thanks for the information. I think the purpose and positioning of the crimp were the piece I was missing. When I get home I'll seat them down to the top of the cannelure. I was hesitant to go too much farther because I'm already below the COL as specified by the Hornady manual (2.810 if my memory isn't failing me) and I'm down in the 2.780-ish range.

I checked and the rounds seem to seat in my AR chamber the same as factory rounds (though I don't recall if I measured the factory rounds for their OAL.

I don't have a bullet puller yet, but I did try to pull a bullet using a pair of pliers, I couldn't really get it to move... I'm not sure if that's a good or bad thing. I'm using almost no effort when I seat the bullets in the case.

@Reloadron - I was doing some reading last night and your opinion is not a rare one. It sounds like somewhere around half the people like the crimp, about half don't, and each have their own well-reasoned arguments for their side. At this point, I think I'll go without a crimp.
 
The 2.810" number is just the number you cannot exceed without some magazines being too short to allow the rounds to fit in and feed properly. You can always seat shorter if the bullet design calls for it. For example, with the Hornady 150 grain FMJ bullet, if you look next to the picture of it in the Hornady manual, for the .308 it says the COL should be 2.700". For the 150 grain round nose Interlock it says 2.520". Unless the bullet was designed specifically for use in a different cartridge that has an unusual chamber throat configuration or a special requirement, like the Hornady FTX .45 cal bullets requiring a non-standard shorter case in the .45-70, the cannelure will tell you where the maker intended you to seat the bullet in a standard case.
 
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