Since I shoot mostly single shots I don't worry much about crimping. I do have a 38-55 for my Contender tho that was leaving abit of powder in the bbl. (H4227) I found that giving the case a slight crimp gave a better burn.
I always put a slight crimp on my auto or revlover ammo.

One way to check a crimp is to measure your OAL, take the cartridge in hand, place on bench or other solid surface and try to push the bullet into the case. Usually if you have no crimp you can see the bullet move into the case, otherwise remeasure and see if your OAL has changed slightly.
Or, make up a dummy with no powder and place in your bullet puller, you can usually 'feel' the resistance of a bullet in a tightly crimped case.

If you fully load the mag. of your 243, and fire two or three shots, check the remaining cartridge(s) in the mag. In some rifles, the bullets can move forward and slam into the wall of the mag when the gun is fired. That can deform some bullets, and even shove them back into the cartridge case if not crimped. If none of that happens, don't bother crimping for your gun.

The onlything that I have found that I have to crimp is my 338 RUM. Dont really know why but the bullets do move from where I have them at after I reload them.

I dont know if it is becouse of the recoil or if it is becouse the bolt when chambering them, pushes the bullet up.

I have never had this problem until I started reloading for my 338 RUM.

hunter338

hunter338,

Are the loads for your 338RUM compressed loads? I remember reading somewhere (in the Speer manual I think) that heavily compressed loads can actually expand inside the case enough after the bullet is seated to push the bullet back out a little bit. If I remember correctly this could be tested by loading up some rounds with the bullets seated at the desired depth and leaving them to sit for a couple days. After they sit for awhile you measure the COL again to see if the bullets got pushed out any. If they did they suggested trying to crimp like you did, or using a more dense powder that doesn't fill the case as much.. If they didn't move then the compressed load is good-to-go.

Mike

Depending on what powder your using for magnum rifle loads a crimp may be necessary to help achieve a complete burn. Thing is you have to really be consistant with the crimp.

Yes... I read the same thing but it was in Nosler i think, or maybe Lyman, they said to load em up and mike them...let them sit overnight and measure again.. if there is any "growth" crimp them in the future.

First, let me say there are other reasons to crimp.....crimping actually gives you better start pressures, therefore, more accuracy. Have you ever seen a factory load that wasn't crimped? I purchased the Lee factory crimp die, and after trying it, now own one for every caliber I shoot

I have a question for you .300 ultra mag shooters out there. Do you crimp or not? And if you do, do you use a special crimping die? Just wanting to know if I should or should not for my .300 Ultra Mag. Also my wife's .208 is a Rem auto so I should crimp right?
Thanks.

idahoe, I'm a 300 UM shooter and have never crimped. I get excellent accuracy and have never had a problem with bullet shift. It goes without saying, I don't shoot any compressed loads either. Don't know why you'd need to either, you're already dropping anywhere from 88 to 100+ grains. If you need to load the big 300 to compressed, you should probably buy a larger caliber, IMHO. Several years ago, while working up loads for my 7mm Mag, I did experience (over compressed loads), some bullet slide. In that particular situation, I did put a very slight crimp on. Again IMHO, crimping = pressure, and deserves all the extra care you can muster.

I don't crimp my RUM. All of my loads are less than 1 MOA. Factory original.