The idea is to get a more uniform pressure rise by increasing neck tension. It's essentially the same effect as placing a bullet into the lands (as practiced by bench rest shooters). Placing the bullet into the lands is not something you want to do with most applications.

Since almost all crimping deforms the bullet, it must reduce the maximum accuracy potential. Nevertheless, the real world accuracy often increases because crimping increases the uniformity of the load more than the bullet degradation decreases the accuracy. HTH, Dutch.

I believe that it depends on the particular firearm. Some like the crimped and some don't. Some like the bullets close to the lands others touching. It would be something that you would have to try in your particular setup to get an answer for yourself but, to say that crimping will help accuracy in all rifles is just simply not true.

I like the Lee Factory Crimp dies for all of my hunting ammo.

One thing I dont like about not crimping is sometimes you get a loose fit. Not real loose but, the bullet moves if slightly bumped.

Good Luck!

Reloader

I have RCBS dies and a good source for RCBS products (cheap). Do they make crimping dies?

No one on the benchrest circuit uses a magazine, either. Or opens the action to extract an unfired cartridge with the bullet jammed into the lands. In the real world, the Lee Factory Crimp will usually produce a small but noticeable improvement in accuracy.

I use no more than .003" neck tension. This is right at or into the lands. I don't crimp bullets and won't.

no-one on the benchrest circuit does,..and that is the proving grounds for accuracy.

I like the Lee Factory crimps also, for the money it is well worth it. (some will argue I'm sure) I have found better results in my loads by at least using a light to medium crimp.

This is the test result using the Lee Factory Crimp Die. See for yourself. The Lee Factory Crimp Die can and does increase accuracy. Run a test of your own. Load some with the Lee Die and some without. The Lee Die costs less than $10. If you don't like your results, you can sell it on Ebay for $20.

http://www.accuratereloading.com/crimping.html

Please don't take bench rest shooting as your guide. That group routinely loads into the 75,000 PSI range, and they would sell their soul for a reduction in group sizes of .05".

Very little of the "super accuracy" techniques used in 100 and 200 yard benchrest translate into field rifles. That includes neck turning, primer pocket uniforming, weighing brass, loading into the lands, etc, etc. JMO, Dutch.

I've fired thousands of reloaded rounds thru semiautos chambered in .223,.308 and 30-06 and bolt rifles up to 30-06.
Never crimped the first round, never had a problem.

Wouldn't crimp anything that wasn't extremely heavy recoiling,required a crimp to make the powder work(such as .44 mag) or was being used in a tubular magazine.
JMO

Covey16

I like the Lee Crimp die, mainly because I target shoot, plink, and hunt all with the same loads in my rifle. If I'm out varminting or plinking, I tend to shoot 2 or 3 rounds, then top off the magazine. Having the crimp at the bullet's cannelure stops the bottom bullet from shifting in the case neck.

"If you don't like your results, you can sell it on Ebay for $20."

ROFLMAO.... Isn't that the truth? Idiots will buy used bullet molds that they know nothing about, for almost DOUBLE the cost of a brand new mold of the exact same bullet.... BUT THEY WON THE AUCTION!!! what a hoot..

I think that the fact that benchrest shooters do not crimp should answer this question.After all they want every last bit of accuracy that they can get.

The real answer to the question of whether Crimping increases accuracy is sometimes it does and sometimes it doesn't. It is often worth experimenting to find out.
The Lee Crimp die works well and I greatly prefer it to a roll crimp on rifle cartridges that require one. For Semi-Auto's like an AR-15 I prefer a taper crimp.
But for most rifle reloading my experience has been that proper loading density and concentric bullet seating will result in more accurate and consistant loads than relying on a crimp. And in pure accuracy terms the fact the no benchrest shooter crimps is telling.........DJ

stubblejumper,..EXACTLY my point.

If you aren't after the best you can get,..WHY BOTHER. And the 100 and 200yd example is mute,..the LV and HV class is wayyyyyyy different than the 400-?yd classes. If you want to be sure you can take a long shot,...them make it accurate!!!! If you are only shooting 100-200yds,....then why bother worrying about the difference a crimp makes