More About Case Trimming

[Diesel9]

I've following some of the case trimming threads here recently, and it reminded me of a question I've had for awhile.

I have a couple or AR-15's (.223) and I pick up a lot of range brass that I reload. I'm mostly a pistol reloader, but as a reloading addict I just can't stand to see good brass go to waste.

I sort these .223 cases by headstamp. I find that after sizing the cases, some of them exceed max length and require trimming, while others are shorter than max length. I have only a LEE trimmer so I can only trim to the length that its pilot allows. This is basically max length (1.760"). Since the Lee trimmer won't do anything to a case that is already shorter than the pilot allows I end up with cases that vary in length from max (1.760") down to about 1.750". Because of this length variance, when I seat the bullets the bullet cannelure ends up in a different position relative to the case mouth even though the C.O.L. is the same for all rounds.

I crimp with a Factory Crimp die, so I don't think this variance affects my crimp.





I have been considering getting a more sophisticated (and expensive) case trimmer to help alleviate this problem but I am only shooting these bullets out of a couple of M4's (factory peep sights, short barrels, so not really long range rifles) and they seem to do OK for the kind of shooting I do.

I was doing some load work-up the other day and shot this group from 25 yards with a Colt M4.



I load mostly pistol cartridges. My dad and I used to do a lot of pistol and shotshell reloading back in the day and he taught me a lot about that. We didn't do much with rifle cartridges though, so I've had to learn it on my own.

Should I worry about the variance in cannelure position or not?

[theshephard]

I'm gonna go out on a limb and say, "No".

Do the rounds work? Check
Are you trying for the utmost in accuracy? No

The thing you're sacrificing here, IMHO, is consistency from round to round, so if you're working on your own marksmanship or trying to test the limits of the gun, you've introduced a variable that's going to hinder such efforts by bringing questions into your mind. e.g. was it the gun or was it that round? Did I flinch, or was it that round? etc.

I sympathize with being OCD on reloading, and when it comes to testing my abilities or the equipment's, I firmly believe you have to eliminate as many variables as possible. Based on what you've written - i.e. mostly shoot pistol, shooting at 25yrds - you're not reloading for LR accuracy anyway. I believe you're in the "go with what works" category, and what you've got works.

If you want to be OCD, sure - the answer is easy - dump the short brass into a different bucket and strive for consistency if that's what's important.

[rebs]

I have the Lee case trimming tool and it trims to 1.750 every time unless the case in under 1.750 to begin with.
I believe you could grind off a small portion of the gauge tip if you want to go shorter than 1.750. Just be careful not to grind off or file off too much.

[Diesel9]

Thanks for the replies.

I have to admit I kinda feel stupid because it never occurred to me to shorten the length of the pilot on my Lee case trimmer. I guess that would do the trick.

[zxcvbob]

The short ones are all FC headstamps, aren't they? Just separate those out and load them as a different batch.

[Diesel9]

Most recently I've been working with a batch of 2 or 3 hundred PMC's. I have noticed that F.C and IMI brass tends to be on the short side of max spec though and L.C. tends to be at or above max length after sizing.

[moxie]

That's normal for your purpose. Your group looks good. Shoot 'em up. If you ever go for longer range tight accuracy, then start worrying about matching headstamps and case lengths. For now, you're cool!

[the led farmer]

if you are a "type a" sort of guy and want to get extreme then separate by headstamp, then by weight, they by case length (and make sure you reset your seating and fcd to compensate for the varied length). total pita.

for and ar and especially plinkers then i would't worry that much. it's really up to you however you won't really see the extra work pay off in an ar like you would a bolt action precision rifle/round

my $0.02

[Slamfire]

I think you have introduced more inaccuracy with your Lee Factory Crimp Die than with any other procedure you are following.

My LFCD instructions are as follows:




Here the instructions tell you to form a cannelure if the bullet does not have one:

And this is what you will get if you follow factory instructions.:


Swaging a bullet in the middle deforms the soft lead core and it does not spring back. Just press a thumb nail into dead soft lead to understand that. The jacket may spring back a bit, but underneath is a deformed core. Moving the center of gravity from the axis of rotation will decrease accuracy, the further you get out the more inaccuracy you will see. Crimpers typically show their 100 targets, which can be quite good, but you never see these guys shooting, or winning, at 1000 yards. The more oscillation you induce in your bullets the worse it gets with range. I was talking to a F Class champion this weekend, he said, as other 1000 yard shooters say, everything effects everything at long distance. (I had case neck cracks at a 1000 yard match and my shots were everywhere)

Lee's claim that crimp is the most critical factor to accuracy is bogus, for them it is critical that you believe it, so you will buy one of their dies.

I do not recommend crimping cartridges for the AR15, good case neck tension is all you need.

As for trim length being critical, maybe for Bench rest, , you would have to be pretty good to see error associated with trim length. These long range guys do see things with seating depth, but I doubt anyone shooting military surplus bullets out of a military type AR15 will the variance due to seating depth.

Trim length is safety critical because you don’t want a long case neck pinched in the throat. I have trimmed some brass way too much, loaded the stuff, and in the Garands I used it in, heck if I could see anything at the distances I shot. I really don’t know what short does except increase bullet jump. Depending on the bullet, bullet jump is important. I use 69 SMK which are jump insensitive and I shoot good groups out to 300 yards. I replace barrels when the barrel is too worn to cluster at 600 yards. Jump makes a difference at long range.

[Diesel9]

I appreciate your input. I'm here to learn.

I'm not clear about why you think the FCD is causing inaccuracy in my bullets. The bullets I'm using have a cannelure, and I'm only giving them a minimum crip. I doubt if I'm crushing the lead core of the bullets, although it can probably be done.

As I said earlier in this thread I'm no expert at reloading, especially in regard to rifle cartridges. I've read a lot of info on the subject and the general consensus seems to be that in order to prevent bullet setback, ammo used in magazine fed semi-autos should have a crimp (Lee FCD or otherwise). AR's with M4 feed ramps like mine are specifically pointed out as needing crimped ammo in a lot of what I've read.

Have I misunderstood something about this?