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Crimping for an AR and accuracy

I have started reloading not long ago. i heard you are going to want to crimp your bullets if you are shooting them through a semi auto. Ive heard how important neck tension is when shooting for accuracy.

I am reloading with Lee pacesetter dies and using the Lee factory crimp that came with the set.

I am trying to figure out how important it is to crimp for my AR and if i must be crimping them how tight should i be crimping them, and how to make sure i am doing it consistantly.

P.S. i know this post has a fair amount simular with the "crimping for 30-30" and "reloading .223 match ammo" but i didnt want to do any hijacking. 8)
 
I haven't crimped any of my bullets for self-loaders in either 223/5.56 or 308/7.62 calibers. The better bullets for these calibers lack cannelures in most instances. I've not had issues with bullets "telescoping" on feedramp contact on several rifles in either caliber. And, yes, I've measured cartridges before and after feeding--sometimes after 4 or 5 cycles. The most setback seen is .010" after 4-5 cycles.

Ya want a masochistic exercise? Try balancing neck tension vs. roll crimp depth with a tiny-necked casing like 7.62 x 25 Tokarev or 7.65 Luger. Just the slightest over-crimping, even into a cannelure, will cause the case neck to spring away the bullet sidewall and enable it to spin freely in the crimp/cannelure.
 
I have been crimping the bullets for my 30-06 semi auto for some time now, and can't really notice any difference in accuracy if I crimp or if I don't, with an exception being that in a few cases it has improved the accuracy of a load. I also use a Lee factory crimp die, which doesn't need a cannelure. And as long as you don't go crazy and crush the case into the bullet, you won't lose any accuracy.

I just like the security offered by crimping my bullets in place, even though they may not "need" it. I would rather crimp than have a bullet stuffed into the case, which I am sure can cause some overpressure issues. And I also use this rig for hunting, and I would be PISSED if I had a failure to fire because I didn't crimp and a bullet was stuffed into the case or some other anomaly happened.

As for how much crimp, that's something you will need to play with and adjust to be sure you aren't affecting your accuracy. But just a light crimp is usually sufficient. Though it's like anything else, you should do a bit of accuracy testing and go with whatever proves to be most accurate.

I would load groups of 10 rounds and start with a very light crimp, and add maybe 1/8 to 1/4 turn to the crimp die and load another 10 rounds, and do this until I had a good firm crimp on a set of ten. Then go to the range and shoot two 5 shot groups of each amount of crimp and see what is best.

As far as consistency is concerned, you need to set the lock ring on your crimp die so you screw it in the same amount every time you install it in the press. The lock rings made by Forster are very good, as they clamp onto the die and will not move unless you loosen the cross bolt. The Lee lock rings have the rubber O-ring and are not the most consistent, as you can compress the O-ring different amounts and affect the position of the die in the press. I flip mine upside down if I am going to use them, so the flat aluminum side of the ring is against the press. This way there is nothing to compress and the O-ring will still keep the lock ring from rotating a bit as well.

Forster Lock rings: http://www.sinclairintl.com/.aspx/sid=62853/pid=38303/sku/FORSTER_Cross_Bolt_Lock_Ring

If you have a press such as the Breech Lock Challenger made by Lee, just leave the die in the breech lock bushing so it's installed the same way every time. If you don't have a press with quick change inserts, the Forster lock rings are your best bet for consistent die positioning.

Good luck, I hope this helps and isn't too confusing.

Kenny
 
I used to crimp some of my 'blasting' loads, but only because they utilized el cheapo 55 FMJs with a cannelure. In over 25yrs. of shooting M1, M1A, AR15&10 rifles, I've never had a problem due to a bullet telescoping back into the case, and that includes 30,000+ rounds of 223 shot in various AR service & match rifles during load development, practice, & match shooting.

Be aware - if you do decide to crimp, you've got to have all your cases trimmed to uniform length (within .001"-.002", which takes some effort to accomplish), because even a taper crimp die (or factory crimp, whatever the various die makers are calling it) is going to give widely varying neck tension if you don't.
 
I didn't mean to state "DON'T CRIMP" in my earlier text--only that "I don't crimp", unless their is a mechanical necessity to do so in a given caliber or system (revolver ammo, lever rifle ammo in tubular magazine). Much of the accuracy chase is an elimination of variables in the internal ballistic equation, and a crimp ADDS a variable that can be a PITA to manage, as noted by Flatlander. So, I don't go there unless/until there is a genuine need.
 
Well its good to hear it isnt a necessity to crimp them.

Im am using ALL Lee stuff right now because i picked up a lee anaversary kit for 80 bucks on craigslist (and luckily didnt get stabbed when i went to pick it up).

and for the whole consistancy thing. It seemed my crimping pressure would fade away the more i would crimp. I would have a crimp i could just start to see then after about ten rounds i wasnt crimping them very much if at all.

I will deffinatly be crimping my hunting rounds, i always manage to end up in one type of storm or another... Creeping through pouring rain, crawling in the mud or rolling around in the snow. Oh well thats why i make sure most the stuff i buy has life time warranties!

Thanks a lot for the help. I will just have to test it out to see what my rifle likes.
 
I ordered rcbs 7mm mag small base crimp dies for my friends browning bar. I did not realize about the crimp. With it not set right i got a few cases where there was deformation at the base of the shoulder and some with deformation at top of the shoulder. Needless to say i dont like crimp dies. I would not buy crimp dies for myself.
 
Flatlander, in case you haven't seen the factory crimp die and how it works, it's basically a collet that squeezes the neck around the bullet, and because of the way it works trim length is not critical. The shoulder of the case actually actuates the crimping die, and not the neck as in other types of crimping.

As long as your cases are within a few thou of each other, they will all be crimped the same amount. It doesn't mean you shouldn't be trimming your brass, as I still feel it's an important step in brass prep. But it doesn't need to be as critical as with other styles of dies.

As for the die not crimping after 10 rounds or so, I would be checking on the lock ring as it may be backing off a bit. Flipping it so the solid side is against the press will help, as you can tighten it right down and it will basically lock itself in place, and it will lock down much tighter than it will against the rubber O-Ring. And since you should have the Breech Lock Challenger press, just leave the crimp die in the bushing and keep it set the same way all the time.

The Forster lock rings are still the way to go, as they are the best lock rings made and will never move once tightened down. This allows for very repeatable die settings, which is very important to consistency. I have replaced most all my lock rings with Forster's, you should do the same.

Good luck

Kenny
 
Robbor, your RCBS small base dies have a very different crimping method which is built into the seating die, as most seating dies have some type of crimping stage built into them anyway.
The Lee factory crimp die makes it impossible to collapse a case from excessive crimp, it just can't happen. This is why the Lee FCD is such a good die, as it operates completely different than any other "crimping die". It's actually a collet that squeezes the case neck, where as other crimp dies just use a tapered section at the top of the neck area, hence the reason they can and will crush your cases if not adjusted properly, and also why trim length is so important with standard crimp dies.

You would be surprised at how many seating dies actually have a crimp stage machined into them, as most all standard dies have it.
 
I taper crimp my 'blasting' loads as well, they're 62 FMJ with canellure - I load them up to 3100 FPS as M855 clones. They're the only ones I crimp though.

The stuff I use for high power for mag length (68 Hornady BHTP) I don't, that wouldn't serve much good.

i heard you are going to want to crimp your bullets if you are shooting them through a semi auto.

Nothing wrong with jamming them for single feed at the long line. I jam 75 Amaxes and VLDs .010" for that.

Wayne
 
Yeah Tango i plan on testing stuff that wont fit in my mag at all and test some stuff i can only fit into my mag if i remove the front section. in the last couple days i have put 120 rounds together 100 of them the same and another 20 to test powders and primers. This weekend, if the weather holds up, there are some local guys shooting on saturday and holding a non registered competition on sunday. So this will be my first competition! for whatever its worth.

The 100 rounds i am using for sure are all based off a crudely done test i did a couple weeks ago with the first batch i ever reloaded. 24.8gr varget 69gr Sierra match kings. i switched to CCI BR4 primers from CCI 400 because they all flattened at light loads and ive got 80 of the 100 rounds made with vergin Lapua brass and the others are Hornady.


But Kenny i have actually crushed my first two cases with the Lee factory crimper.... dont ask my how i did it but they were toast.
 
Rock,

24.8 of Varget under a 69 SMK sounds about right to me. Don't try to crimp those though, it won't do you any good and when you're slinged up recoil is so low that there's no way that your bullet depth is changing and it can hurt your accuracy. 24.8 of Varget's crunching pretty good under a 69 SMK seated to mag length. If you desire more speed and not so much compressing give R15 a try - keep in mind it's temperature sensitive though. R15 has given me a 100 FPS gain over Varget with less pressure with 68-75 grain bullets in .223.

A huge priority out on the line is making sure your rifle and ammo is reliable and this business with one brand running well for you and another not makes me wonder what is going on with your dies. Do you have a FLS die that you're sizing with? Are you camming over? I've never found a use for those small base dies and all I've ever used to size .223 is a FLS die camming over. Having a jam while doing your rapid string can ruin your day.

Good luck with Sunday, the grass is under about 2 feet of snow here so I'm jealous.

Wayne
 
Yes i am using a FLS i havent had any jamming problems but i have only shot about 60 hand loads.

A huge priority out on the line is making sure your rifle and ammo is reliable and this business with one brand running well for you and another not makes me wonder what is going on with your dies. Do you have a FLS die that you're sizing with? Are you camming over? I've never found a use for those small base dies and all I've ever used to size .223 is a FLS die camming over. Having a jam while doing your rapid string can ruin your day.

Im not quite sure what you mean by having problems with one brand and not another. Maybe when i said i was using fresh lapua brass and some hornady, im doing that because i didnt have enough hornady to make it through the weekend so i got 100 lapua.

i plan on testing stuff that wont fit in my mag at all and test some stuff i can only fit into my mag if i remove the front section


When i said that i meant the OAL and not by brand. But what ever

Hey Tango we have no less snow than what you say, but you gotta do what you gotta do. I was lucky enough to find some guys that care about the snow as much as i do, just go and shoot. My next problem is going to be chacing my new lapua brass around and not losing it in the snow. :'(
 

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