Design Parameter Recommendations for a 45 Colt Mold

Racer X
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Design Parameter Recommendations for a 45 Colt Mold

Postby Racer X » Sat Apr 17, 2010 8:51 am

I am new to this site and am considering buying one of your molds and wanted to get your recommendations on a mold design. My gun is a custom Ruger Bisley in 45 Colt with .453" throats and minimum-spec chambers (.481 @ the base & .480" in the leede). The gun has a custom 7-1/2" barrel with a 1 in 18" twist.

I would like a plain-base bullet that casts from WW metal at 280 grains. I also want the biggest meplat that will still give me excellent accuracy, even when started at low as 900 - 1000 FPS. The bullet should retain its stability beyond 100 yards for recreational rock busting if driven to higher velocities (1200 - 1300 FPS).

Although I understand buyers are on their own for designing a mold, I would greatly appreciate your recommendations regarding profiles that are most likely to be accurate, as well as recommended design parameters (nose length, mepat %, crimp groove size, lube groove shape, bullet size to order, sizing, etc.) that will meet my requirements stated above.

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mtngun
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby mtngun » Sat Apr 17, 2010 4:24 pm

Racer X wrote:I am new to this site and am considering buying one of your molds and wanted to get your recommendations on a mold design. My gun is a custom Ruger Bisley in 45 Colt with .453" throats and minimum-spec chambers (.481 @ the base & .480" in the leede). The gun has a custom 7-1/2" barrel with a 1 in 18" twist.
Sounds like you can't go wrong with a well made gun like that.

I would like a plain-base bullet that casts from WW metal at 280 grains. I also want the biggest meplat that will still give me excellent accuracy, even when started at low as 900 - 1000 FPS. The bullet should retain its stability beyond 100 yards for recreational rock busting if driven to higher velocities (1200 - 1300 FPS).
:lol: Ya, and I'd like a new 1 ton 4wd pickup truck that gets 100 mpg, seats 4 NBA players comfortably, and rides like a Cadillac.

A few random thoughts:

-- 280 grains is on the light side for a 45 colt.

-- big meplat, slow speeds, and accuracy ? Might happen, but probably wishful thinking.

-- long range stability ? More likely with a modest meplat and 300 grain bullet, if not heavier.

I'm not a 45 colt shooter so I can't offer any personal experiences and specific examples, just that short stubby bullets are seldom a recipe for sure fire accuracy, especially at long ranges.

Racer X
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby Racer X » Sat Apr 17, 2010 5:21 pm

Ok, then limiting my requirements to short-range (< 75 yards) hunting accuracy, can you recommend an accurate design with a good hunting meplat? I don't need a 300 grain bullet to shoot scawny deer and even decent-size hogs. I was thinking of having a shorter nose and longer shank to increase bearing surface.

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mtngun
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby mtngun » Sun Apr 18, 2010 6:20 am

Racer X wrote:Ok, then limiting my requirements to short-range (< 75 yards) hunting accuracy, can you recommend an accurate design with a good hunting meplat? I don't need a 300 grain bullet to shoot scawny deer and even decent-size hogs. I was thinking of having a shorter nose and longer shank to increase bearing surface.

A 75% meplat is a good place to start. Sometimes it needs velocity to stabilize, sometimes not.

Short nose/long shank is a good idea, too, especially for a light bullet. :)

True, you do not need a 300 grain bullet to shoot deer, that is why I hunt deer (and bear, and elk) with a 357. But ..... you chose a 45, not a 357. It seems to be human nature to chose a big bore gun and then try to use it to shoot little bullets. 8-)

Racer X
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby Racer X » Sun Apr 18, 2010 6:59 am

A 75% meplat would be about a .340" meplat, which using LBT profiles as a comparison, falls between a LFN and WFN.

I am thinking about a Truncated Cone with a 75% meplat at around 280 grains. A couple more questions to narrow my design criteria:

1) Is the Truncated Cone typically an accurate profile?

2) What Nose Length would you recommend for adequate bearing surface on a mid-weight bullet such as a 280 grain with this profile and 75% meplat?

3) With the minimum spec chambers, .453" throats, and .451" groove, what bullet diameter do you recommend I specify?

4) In respect to question # 3, what should diameter should I size my bullets to?

Thanks.

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mtngun
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby mtngun » Sun Apr 18, 2010 9:38 pm

Thank you for asking specific questions. When someone asks a vague, open ended question about bullet design, I assume they really want someone else to design a bullet for them, which is not what we do here.

Is the Truncated Cone typically an accurate profile?
It is neither inherently accurate nor inherently inaccurate.

Think about what purpose a nose serves on a revolver bullet. It helps quide the cartridge into the chamber. It improves aerodynamic stability. That's about it. If we didn't need help guiding the cartridge into the chamber, and if the bullet didn't need aerodynamic stability, we'd all be shooting full wadcutters in our wheelguns.

The TC can serve those two functions. Other types of noses can serve those two functions, also.

What Nose Length would you recommend for adequate bearing surface on a mid-weight bullet such as a 280 grain with this profile and 75% meplat?
There is no right or wrong answer to that question, except that a long unsupported nose is always a bad thing. Ask yourself how the nose length affects the two functions of the nose -- guiding the cartridge into the chamber, and aerodynamic stability. Since this is a light-for-caliber bullet, I'd go with just enough nose to serve those two purposes -- maybe 0.300", maybe a little less. But that's just me.

With the minimum spec chambers, .453" throats, and .451" groove, what bullet diameter do you recommend I specify?
I don't understand the 453/451 combination, but that's another story. I'd size 0.453" - 0.4535". Personally, I like bullets to drop out of the mold about 0.002" larger than the sizing diameter, but not everyone sees it that way.

jbquack1
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Re: Design Parameter Recommendations for a 45 Colt Mold

Postby jbquack1 » Sat Apr 24, 2010 7:39 pm

i got a 275 grain mold from dan about 6 months ago,i used the bore riding secant nose profile.At 25 yards out of my 4 5/8 inch ruger i get groupd around 1 1/2 inches off a rest and i use a 75 percent meplat.my nose legth is .350,being a bore rider with a .120 front driving band i have plenty of bearing surface.my reason for a big front bad is chamber fit, not to gain powder space as with a bullet this light that is not a problem.The bore rider concept in handguns allows you to get the slug right where it needs to be for minimal jump to the throat.also the bullet is centered better which can help.jim


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