Cast 550 grain 458 Win Mag

kencolamarino
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Joined: Sun May 29, 2011 11:37 am

Cast 550 grain 458 Win Mag

Postby kencolamarino » Sun May 29, 2011 12:45 pm

Have strived mightily to get standard 458 mold bullets to shoot less than an inch or so in my Win 70 Super Express and have managed to do it only with very light loads of Unique or 2400. The problem is the cavernous tapered 1.1 inch freebore (standard SAAMI chamber) and 3.4 in limitation on OAL. The heavier cast bullets (425 grain max) shoot smaller groups the farther I seat them out but the exposed grease grooves are not practical.

To make a long story short, using your program, I've designed a 550 grain gas checked bullet about 1.3 inches long with a 0.8 inch nose with 0.4 bore bearing length and .460 diameter and .450 diameter nose. Crimped in the crimping groove I should get a 3.3 OAL which is a 0.3 jump but the best I can do. The .460 diameter should help center the neck and is the largest sizing die I have.

A couple of questions.

1. I'm given a choice of one large or two smaller grease grooves, the two smaller hold a little more lube. Is there any reason to prefer one over the other? Oviously the bands are smaller with the two grease grooves.

2. If I extended the front band (it's now 0.1) farther to maybe 0.4 (groove riding nose), the .460 diameter would center sooner or maybe touch (I'll have to calculate) the freebore. Would that much over groove diameter bearing length without lube be a problem?

The SAMMI freebore on a 458 Win Mag I do not understand except maybe to act as additional powder space to get more velocity with top end loads with jacketed bullets.

Thanks,

Ken

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mtngun
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Re: Cast 550 grain 458 Win Mag

Postby mtngun » Sun May 29, 2011 5:34 pm

I think you are on the right track to reduce the jump to the rifling.

Dangerous game rifles often have humongous throats, to ensure reliable chamber when a buffalo is charging you, or some such thing.

The problem with a 0.400" long front band is that when it is engraved by the rifling, the displaced lead has nowhere to go. This increases bullet distortion and can hurt accuracy. It would be better to have grooves out there. You don't have to fill the exposed grooves with lube.

I assume you will be crimping to prevent bullet jump in the magazine, so if you go with exposed grooves, then you'll have to plan a way to crimp in a lube groove. The planning part is hard because the design program isn't set up to figure on crimping in a lube groove.

Regarding two lube grooves or one, I think lots of little bands and grooves tend to shoot better, however, big bands fill out easier, especially on a heavy bullet.

If your 0.450" bore riding nose contacts the rifling when chambered, that is the main thing for accuracy. You may be able to make the nose 0.001" larger than the bore so they will engrave slightly.

kencolamarino
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Joined: Sun May 29, 2011 11:37 am

Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Mon May 30, 2011 4:54 am

With a 2.5 inch case and 1.1 inch throat, I'll not get close to the leade with a 3.4 inch LOA limitation. I guess I'll go with the 0.8 inch nose for a 3.3 LOA, nice bore ride nose, and fat .460 diameter with two lube grooves. Can do this with a 550 grain bullet. The potential is there, as it shoots 405 jacketed really well at 3.3 LOA. Thanks for the insight regards the lube grooves. I guess I've got my project for the summer. 12.5 bullets to the pound will go through my WW stash in a hurry.

turbo1889
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Re: Cast 550 grain 458 Win Mag

Postby turbo1889 » Mon May 30, 2011 2:35 pm

kencolamarino wrote:. . . 550 grain bullet . . . . 12.5 bullets to the pound will go through my WW stash in a hurry.


You think that is bad try 880gr. (a 73-cal mold I use - not a MN mold since he don't cut calibers that large) that is less then 8 boolits per pound of lead. :o :shock:

kencolamarino
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Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Sat Jun 04, 2011 9:46 am

I just ordered a 550 grain, .460 band diameter, .4 inch .45 bore ride, .8 inch nose gas check bullet for my 458 Win Mag. As designed, it had two grease grooves. When I went back to the program after ordering, it showed the one grease groove version. Could you confirm that what you received was the two grease groove version? Have I made any obvious goofs for its intended purpose?

Thanks,

Ken

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mtngun
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Re: Cast 550 grain 458 Win Mag

Postby mtngun » Sat Jun 04, 2011 11:22 am

This is what you ordered.
kens45.jpg
kens45.jpg (70.34 KiB) Viewed 6705 times


No goofs. Always more than one way to skin a cat, though.

If the rifling is 1" away from the case mouth, then why not go slightly oversize on the bore rider ? Say 0.451" or even 0.452" ? Chambering is not going to be an issue because the nose is not going to touch the rifling until the bullet starts moving.

kencolamarino
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Joined: Sun May 29, 2011 11:37 am

Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Sat Jun 04, 2011 1:19 pm

I thought about doing that, and I guess it would not displace that much material. OK, I agree go .451 on the bore riding portion.

Thanks,

Ken

kencolamarino
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Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Sat Jun 04, 2011 1:29 pm

Oh, and yes, I realize the weight will be slightly more to retain the two groove design.

kencolamarino
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Joined: Sun May 29, 2011 11:37 am

Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Sat Jun 04, 2011 1:37 pm

Just went back and plugged in .451 for the bore ride portion and still did it at 550 grains with two grease grooves....go figure.

Ken

kencolamarino
Posts: 14
Joined: Sun May 29, 2011 11:37 am

Re: Cast 550 grain 458 Win Mag

Postby kencolamarino » Sat Jun 04, 2011 1:57 pm

This time the program also let me use a 0.055 crimp groove with the .451 nose diameter and still retain 550 grain weight. To be clear, the design you sent back is OK with the change to a .451 bore ride diameter and a .055 crimp groove. Sorry for all of my confusion.

Regards,

Ken


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