modern ??? big bore bullet design...

Magnum Wheel Man
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Joined: Wed May 27, 2009 3:21 am

modern ??? big bore bullet design...

Postby Magnum Wheel Man » Wed May 27, 2009 4:05 am

1st off... I found the bullet calculator very interesting...

I'm trying to build a "poor mans" big bore double rifle... based on the 577 Snider case ( since I can easily get brass & loading dies )... I found a strong exposed hammer side by side Husqvarna 12 ga triple lock with rebounding firing pins, & a nice pistol grip stock in very good condition to use as an action... the barrels have been cut to 22" & are of light weight thickness... my local builder has come up with a unique way to regulate the gun, using liners made of chrome moly steel... over all weight & balance should end up typical of a traditional double rifle... I'm currently looking at Krieger barrels, as they can do the 58 caliber barrels, & I can adjust the twist rate

my original thought was to use a 58 caliber minnie ball rather than the $2.00 a piece 577 Nitro bullets,but the thin skirt with medium heavy loads that I could load in the Snider case would likly over flair the skirt after leaving the barrel... I happened onto your website, & played around with the bullet calculator a while yesterday ( I found the suggested twist rate window of particular interest, since I've been getting mixed suggestions for the twist rate of my rifle )

so... fo a 58 caliber medium velocity bullet, any specific suggestions??? any definate "no no's" ???

I guess I'm looking at 2 molds... one as a "stopper" for bear size animals at shorter distances, & one taylored to shoot further ( I know... it's a 58 caliber bullet coming out of a Snider case ) but I'm looking at traditional 3 leaf safari sights, which I'll regulate after developing a load... but "distance" will likely be either 75 or 90 yards ??? & I'm hoping for as flat a "rainbow" as possible

the "stopper bullet" came out looking like this... 550 grains, wheel weights, SEC nose profile, .585 diameter, .100 front band length, .420 nose length, 65% meplat, plain base, .090 length of base, 1.0 G to B, & 45* groove angle

the "distance bullet" came out looking like this... 550 grains, wheel weghts, SEC nose profile, .585 diameter, .100 front band length, .420 nose length, 35% meplat, bevel base, .100 length of base, .8 G to B, & 45* groove angle

how did I do ??? any suggestions to improve either bullet

how about lead times or anything special on the molds ???

I'm waiting on my dies to get here, for final measurements & will decide the twist rate of the barrel based on the bullet, & right now I'm leaning towards ordering a couple dies here...

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mtngun
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Re: modern ??? big bore bullet design...

Postby mtngun » Wed May 27, 2009 6:01 am

Magnum Wheel Man wrote:so... fo a 58 caliber medium velocity bullet, any specific suggestions??? any definate "no no's" ???

I've never shot a Snider, so I can only offer vague advice for cast bullets in general.

....the "stopper bullet" came out looking like this... 550 grains, wheel weights, SEC nose profile, .585 diameter, .100 front band length, .420 nose length, 65% meplat, plain base, .090 length of base, 1.0 G to B, & 45* groove angle

I presume you will need to crimp the bullet, to keep the bullet from "walking out" under recoil ? That means you will not be able to adjust the bullet seating depth to fit the throat. That means you need to choose a nose that fits your throat when seated for crimping. It should chamber easily, yet it should not have to jump a long way before it contacts the rifling.

You did not tell us anything about the rifle's throat dimensions, so we can't say whether or not your proposed design is a good fit in the throat.

....the "distance bullet" came out looking like this... 550 grains, wheel weghts, SEC nose profile, .585 diameter, .100 front band length, .420 nose length, 35% meplat, bevel base, .100 length of base, .8 G to B, & 45* groove angle

I never recommend a bevel base. There is no known advantage. The bevel is too small to have any impact on the ballistic coefficient.

In general, I never choose a cast bullet based on ballistic coefficient. That's just not what cast bullets are about, to my way of thinking.

any suggestions to improve either bullet

It has to fit your throat. The throat should be cast-friendly -- do not assume that it will be. Do not assume that your gunsmith knows what a cast-friendly chamber is.

There is some debate about what constitutes the ideal cast bullet throat, but we can agree that long jumps to the rifling, and grossly oversize throat diameters are not ideal.

We can agree that rifling which starts abruptly, without a tapered entrance, is not ideal.

A general rule of thumb is that cast bullet diameter should be 0.002" larger than groove diameter. There are many variables, and the only sure way to determine the ideal diameter is to experiment with several different diameters and see which one shoots best.

You didn't say what velocity you have in mind, but since gas checks are not available for 585, this might be a good excuse to play around with paper patched bullets.
how about lead times

Estimated lead time is always posted on my home page.

Good luck with your project.

Magnum Wheel Man
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Joined: Wed May 27, 2009 3:21 am

Re: modern ??? big bore bullet design...

Postby Magnum Wheel Man » Wed May 27, 2009 6:28 am

thanks for the reply, & suggestions... we will be custom cutting a reamer & my builder is all about cast bullets ( he's a retired tool & die guy thats been casting his own bullets & building rifles that shoot cast bullets for well over 40 years... ) I'm going to build the gun around the bullet ( seems like how it really should be done ) I'm locked into the bore dimensions, but can adjust the twist ratio, as well as chamber & throat yet... still waiting on a set of Lee dies, to see if we can use them as is, or if we need to re-make the expander or ???

so you offer beveled base bullets only to apease the customer, or to ease in seating in the cases ??? either way, I'm trying to limit the ranbow effect of a 550 or 600 grain 58 caliber bullet, but still want an effective mad animal stopper

I'm not sure if I need / want a crimp groove or not yet, I'm looking at molds for my single shot 45-70, & a single shot 50-70 ( both built on Martini actions ), & likely a mold for my 32-40 single shot ( built using a faser twist 8mm barrel & on Remington #1 Rolling Block action )

the 577 Snider will be a double rifle, & I'm unsure if a tight taper crimp will be good, or if I'll need to roll crimp ??? heavier rifle, & realitively mild loads ( compared to a 577 Nitro ) ???

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mtngun
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Re: modern ??? big bore bullet design...

Postby mtngun » Wed May 27, 2009 7:14 am

Magnum Wheel Man wrote:thanks for the reply, & suggestions... we will be custom cutting a reamer & my builder is all about cast bullets ( he's a retired tool & die guy thats been casting his own bullets & building rifles that shoot cast bullets for well over 40 years... )

That's very helpful to have a gunsmith who knows his way around a cast bullet.

so you offer beveled base bullets only to apease the customer

Pretty much.

the 577 Snider will be a double rifle, & I'm unsure if a tight taper crimp will be good, or if I'll need to roll crimp ???

I would definitely not crimp a single shot, but since it is a double rifle, the 2nd cartridge will experience recoil forces. You'll have to decide if it should be crimped. Taper crimps are not desirable for cast bullets -- anything that squashes the outside of the cartridge is also going to squash the bullet inside the case. A roll crimp into the crimp groove is the way to go.


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