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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles

Tatume
.400 member

Reged: 09/06/07
Posts: 1091
Loc: Gloucester, Va USA

Re: cast loads in 458WM
09/03/10 11:12 PM

The crimp in a straight-sided case serves two purposes. One is to prevent bullet migration, either due to recoil (outward movement, as in revolvers), or magazine pressure (inward movement, as in tubular-magazine lever action rifles). My 458 Win Mag is a Ruger #1, so I have no concerns about migration.

The second purpose is to increase bullet pull, so as to ensure proper combustion. If insufficient pressure builds in the case, combustion will be incomplete. The shoulder of a bottle-necked case provides this function. In a straight-sided case the increased bullet pull caused by the crimp raises pressure long enough to aid combustion. This is easily observed with slow powders. With the same load, but with and without crimp, a considerable difference in muzzle velocity can be measured. With faster burning powders the effect is less obvious, but present.

The only accuracy deficit I have observed that may be attributed to the crimp involves an improper crimp. If the bullet seating die is adjusted to seat and crimp at the same time, shaving occurs. I have seen this with cast and jacketed bullets. This is detrimental to accuracy, markedly so. The crimp should be applied in a separate operation, either with a special-purpose die or by readjusting the seating die.

--------------------
Take care, Tom
NRA Life Member

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Subject	Posted by	Posted on
cast loads in 458WM	mauserand9mm	07/03/10 09:00 PM
Re: cast loads in 458WM	bonanza	30/04/10 12:49 AM
Re: cast loads in 458WM	mauserand9mm	30/04/10 08:41 PM
Re: cast loads in 458WM	mauserand9mm	17/05/10 01:29 PM
Re: cast loads in 458WM	mauserand9mm	05/11/10 07:59 AM
Re: cast loads in 458WM	DarylS	05/11/10 11:49 AM
Re: cast loads in 458WM	mauserand9mm	05/11/10 09:57 AM
Re: cast loads in 458WM	DarylS	06/11/10 03:32 AM
Re: cast loads in 458WM	VonGruff	06/11/10 05:58 AM
Re: cast loads in 458WM	mauserand9mm	07/11/10 08:39 PM
Re: cast loads in 458WM	Tatume	07/03/10 11:01 PM
Re: cast loads in 458WM	bonanza	08/11/10 03:17 AM
Re: cast loads in 458WM	mauserand9mm	08/03/10 10:30 AM
Re: cast loads in 458WM	Tatume	08/03/10 11:35 PM
Re: cast loads in 458WM	mauserand9mm	09/03/10 11:31 AM
Re: cast loads in 458WM	450_Ackley	09/03/10 04:28 PM
Re: cast loads in 458WM	Tatume	09/03/10 11:12 PM
Re: cast loads in 458WM	DarylS	10/03/10 03:26 AM
Re: cast loads in 458WM	450_Ackley	10/03/10 07:38 AM
Re: cast loads in 458WM	mauserand9mm	10/03/10 11:52 AM
Re: cast loads in 458WM	Tatume	11/03/10 12:24 AM
Re: cast loads in 458WM	DarylS	11/03/10 12:40 PM
Re: cast loads in 458WM	450	11/03/10 04:39 PM
Re: cast loads in 458WM	mauserand9mm	11/03/10 10:19 PM
Re: cast loads in 458WM	DarylS	12/03/10 01:49 AM
Re: cast loads in 458WM	mauserand9mm	12/03/10 11:29 AM
Re: cast loads in 458WM	DarylS	13/03/10 04:00 AM
Re: cast loads in 458WM	Tatume	13/03/10 06:45 AM
Re: cast loads in 458WM	gwindrider1	16/03/10 12:28 PM
Re: cast loads in 458WM	mauserand9mm	18/03/10 11:44 AM
Re: cast loads in 458WM	450_Ackley	18/03/10 07:04 PM
Re: cast loads in 458WM	450	23/03/10 08:24 PM
Re: cast loads in 458WM	DarylS	24/03/10 07:12 AM
Re: cast loads in 458WM	mauserand9mm	24/03/10 01:50 PM
Re: cast loads in 458WM	DarylS	24/03/10 11:19 PM
Re: cast loads in 458WM	mauserand9mm	25/03/10 09:58 AM
Re: cast loads in 458WM	eagle27	25/03/10 05:29 PM
Re: cast loads in 458WM	DarylS	26/03/10 01:00 AM
Re: cast loads in 458WM	greenshoots	26/03/10 06:08 AM
Re: cast loads in 458WM	86thecat	29/03/10 12:55 PM
Re: cast loads in 458WM	mauserand9mm	29/04/10 08:51 PM
Re: cast loads in 458WM	DarylS	29/04/10 10:00 PM
Re: cast loads in 458WM	mauserand9mm	14/03/10 08:43 PM
Re: cast loads in 458WM	eagle27	14/03/10 09:09 PM
Re: cast loads in 458WM	Tatume	14/03/10 10:57 PM
Re: cast loads in 458WM	DarylS	15/03/10 02:52 AM
Re: cast loads in 458WM	mauserand9mm	15/03/10 09:54 AM
Re: cast loads in 458WM	DarylS	15/03/10 10:22 AM
Re: cast loads in 458WM	9dot3x74R	15/03/10 12:19 PM
Re: cast loads in 458WM	DarylS	15/03/10 12:59 PM
Re: cast loads in 458WM	mauserand9mm	15/03/10 02:10 PM
Re: cast loads in 458WM	450_Ackley	15/03/10 06:14 PM
Re: cast loads in 458WM	450	12/03/10 04:56 PM
Re: cast loads in 458WM	DarylS	10/03/10 12:25 PM
Re: cast loads in 458WM	86thecat	10/03/10 05:18 PM
Re: cast loads in 458WM	450_Ackley	08/03/10 02:22 PM
Re: cast loads in 458WM	DarylS	08/03/10 03:25 PM
Re: cast loads in 458WM	mauserand9mm	08/03/10 06:07 PM
Re: cast loads in 458WM	450_Ackley	08/03/10 08:44 PM

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