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A number of guys I know who shoot .338 Win. Mag. and load for it here, do not crimp. Pretty sure the .338 Lapua guys do not crimp either.

I certainly agree with the .458 needing to be crimped, but that is a different ball of wax and there are multiple reasons to crimp that one & other straight or almost straight cased rounds.

Virtually all straight case heavy recoiling rounds should be crimped just to improve powder burning, let alone any other reason. If recoil seats the bullet deeper, then yes, need a tighter neck fit, or crimping to hold the bullet against recoiling into the magazine front end and pushing the bullets deeper.

I had to neck my .458's (.458 Alaskan, and pair of .458 2") just to get good ballistics.

The heaviest recoiling necked cases I have ever used was the 9.5x68 and .375H&H. My current .375/06IMP about duplicates actual .375H&H ballistics (up to 4,200fpe) and it does not need crimping.

The light recoiling 6.5x54 does not have a recoil problem that will seat bullets different, as far as I know. Even my .264 Winchester did not need to be crimped.

I crimped, that is I had to crimp the .22Hornet and .218Bee just to get consistent ballistics due to bullet movement prior to powder ignition. In these two cases, crimping was necessary just for ballistics reasons.

None of my standard dies taper crimp. They all roll crimp.
I agree with the use of Lee crimp dies as the bullet does not need a cannelure for crimping as those dies use a collet system and do not push the case up against a smaller interior ring in the die as normal crimp dies perform.
A taper crimp die is a die that has a gentle taper inside, not a crimping ring.
Most taper crimp dies are made for Semi-auto rim that headspace on the ctg. mouth. These dies press the case neck onto the bullet, increasing bullet pull strength, yet leave the case neck's mouth for proper headspacing.

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