Thinking about Taper crimping for .300 mag

[sam700]

I recently tried roll crimping for my .300 win mag and was surprised to find it cut my groups in half!! The gun went from shooting 1.5 moa to 0.5 to .75 moa. Not bad for a sub 7 lb hunting rifle! The one problem is that I obviously have to trim all cases to exactly the same length to roll crimp.

Just curious if there is any range in case length with crimping that produces a minimal effect on accuracy.

Also, I thought about taper crimping instead. Is it correct to say that with a taper crimp, a variation in case length of .005 or so is not as critical?

Basically, I’m thinking about picking up a taper crimp die, but am wondering if I would be any better off that I am with the roll crimp. I am aware that I don’t need the crimp groove with the taper crimp

 

[Stinger]

Your findings run contrary to what benchresters have been doing for decades. They NEVER crimp. Ever.

Of course, internet commandos all shoot 1/2 MOA with the Lee FCD.

 

[brasskeeper]

I cant say which provides better accuracy but the only rifle cartridges I crimp are 45-70.

 

[rcmodel]

If you want to crimp uniformly without trimming, the Lee Factory Crimp Die is the only way to do it.

But all you are accomplishing by crimping is a more uniform bullet pull to get the powder burning before the bullet starts moving.

You could accomplish the same thing by seating the bullet out closer to the rifling, or reducing the diameter of your reloading dies expander button to increase case-neck tension.

Regardless, you will still need to trim your .300 Mag cases occasionally, or they will eventually get too long to release the bullets because they are jammed into the end of the chamber throat, and pressure may become a problem.


rcmodel

 

[sam700]

I looked into the Lee Factory Crimp die and it looks like the way to go. I'm not looking to get away from trimming entirely, but just trying to minimize it as it is one of the more time consuming s teps for me.

 

[steve4102]

Your findings run contrary to what benchresters have been doing for decades. They NEVER crimp. Ever.

It's true that BR shooters choose not to crimp. They do things like seat the bullet so it is pig jambed into the lands. This technique improves accuracy because pressure must build to a higher level before the bullet begins to move. This higher start pressure insures a more uniform pressure curve and less velocity variation. Seating bullets jambed into the lands is usually not possible with a hunting rifle.

So, How can we accomplish this in our hunting rifles? You guessed it, We CRIMP with the Lee Factory Crimp Die. The LFCD will improve accuracy because pressure must build to a higher level before the bullet begins to move. This higher start pressure insures a more uniform pressure curve and less velocity variation.

There are countless handloaders on these forums that have found the use of the LFCD to improve accuracy. Many of the naysayers go by what the BR crowd is doing and have never even tried it.

 

[Wildfire]

Crimps

My .223s are very accurate with one hole or clover leafs at the 100 meter.
These are Rem. 700s Heavy guns. I never crimp. My bullets are .012" off the rifling. I shoot with a good bench shooter and his are always .010" off the rifling. His are one hole at the 200. He shoots better then I do.
I can not give a good arguement agains crimping but can say that crimpnig is not some chiseled in stone requirement for accuracy. My .308 Rem 700 PSS has a very long free Bore. .250" You can not seat near the rifling with 168 gr NM. Never crimp that one. One hole gun. The idea of crimping for that start up PSI may have some merrit. But again as far as accuracy goes,,,, Not chiseled in stone.
Also many bench shooters use custom made barrels, 1 in 18" twist with .30 cal 112 grain bullets. Not much hold back from the rifling, and PSI is usually not an issue. The .30 BR. good example.
I load for a lot of .300 wm. never crimp. All have been 3/4" to 1/2" loads. Hunting rounds or target.