Bore ride diameter

LBD
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Bore ride diameter

Postby LBD » Tue Aug 27, 2013 11:26 am

Mtngun,

What would be the tolerance on the bore riding diameter of a 215 grain .35 caliber bullet (casting with a 3-cavity XL aluminum mold and approx. 650F WW metal)?

In your app, the label associated to the bore ride pull-down menu is "nominal". Are you saying that the bore ride diameter can go either way (±) of one's selection and if so, by how much?

Thank you,
LBD

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mtngun
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Re: Bore ride diameter

Postby mtngun » Tue Aug 27, 2013 12:20 pm

"Nominal" mean there are no tolerances and no guarantees. :(

In other words, I am not encouraging people to use the program to design bore riding rifle bullets. My bore riding option was originally intended for revolvers and lever actions where nose tolerances are not critical.

BTW, most CBA competitors who shoot bore riding bullets use a "bump" die to guarantee the nose diameter. The beauty of a bump die is that any bullet can be swaged to fit your barrel perfectly. If the bullet diameter is too small, the bump die will bump it up. If the bullet diameter is too large, the bump die will swage it down.

At one time the Hanned Line offered bump dies, but they seem to have closed their doors. Don Eagan used to offer tapered nose dies to fit tapered throats, but he passed away. I am not sure if there is anyone still selling bump dies or nose dies at this time ?

In the future, I may be offering a few nose dies that allow sizing bore riding noses, i.e., perhaps a 0.360" x 0.351", or a 0.312" x 0.301". I don't have any plans to offer bump dies yet, but wouldn't rule it out if the market is there. I would have to charge enough to make it worth my time and I'm not sure that people would be willing to pay.

LBD
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Re: Bore ride diameter

Postby LBD » Tue Aug 27, 2013 1:38 pm

Are you indicating, if I were to specify a bore ride diameter of .351" and length of .06" on a 215 grain .35 caliber rifle bullet (I'm trying to modify RCBS 35-200-FN to fit my .358 and .357 somewhat better) that it (the bore ride diameter) could end up .349" in diameter or smaller even when cast under optimal conditions from your 3-cavity XL aluminum mold?

LBD

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mtngun
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Re: Bore ride diameter

Postby mtngun » Tue Aug 27, 2013 3:55 pm

I'm saying I'll try to hit your specified nose diameter, but there are no guaranteed tolerances on the nose.

Re: a 0.06" bore riding length. I consider that more of a "step" than a bore riding nose because you can't even measure it very consistently when it is that short. It would have to be about 0.100" long before I would even take it seriously.

What firearm were you planning to shoot this in ?

LBD
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Re: Bore ride diameter

Postby LBD » Tue Aug 27, 2013 5:30 pm

What firearm were you planning to shoot this in ?


As many .35's as possible.

Imagine RCBS 35-200-FN without a crimp groove but with a forward driving band .160" long to accommodate various seating depths and a "Lee Factory Crimp" for revolver use. Also, instead of the deep 1/2 round lube groove I want two square grooves with 55 degree bevels. The function of the "bore ride" is to allow the bullet to be seated out in my .358 Winchester and .350 Rem Mag so the two narrow driving bands (approx. 0.07" long) and lube grooves are contained completely in the cartridge case neck.

LDB

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mtngun
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Re: Bore ride diameter

Postby mtngun » Wed Aug 28, 2013 9:30 am

LBD wrote: a forward driving band .160" long to accommodate various seating depths and a "Lee Factory Crimp" for revolver use.

FWIW the "factory crimps" for revolvers will squash the bullet. I am not a fan of them.

The function of the "bore ride" is to allow the bullet to be seated out.... so the ... lube grooves are contained completely in the cartridge case neck.


Right. Traditionalists like bore riders because they believe that terrible things will happen if a cast bullet is seated deep.

Please provide proof that terrible things will happen if a bullet is seated deep ? :?:

In any event, I fail to see how your bore ride dimension is critical since it is so short.

A SAAMI 350 mag chamber has 1/4" freebore followed by a short 5 degree leade.

A SAAMI 358 chamber has no freebore, just a 3 degree leade that begins immediately after the case.

If your rifles have SAAMI chambers, most likely the front band will make contact with the leade before the bore rider makes contact with the lands. However, the short bore rider would help support the bullet once it starts moving down the barrel, assuming the bore ride diameter is big enough to engrave the rifling.
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LBD
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Re: Bore ride diameter

Postby LBD » Wed Aug 28, 2013 6:29 pm

With all due respect, it is not my intention to enter into a debate on cast bullet design, I simply want to understand your capabilities. What I've gleaned from this discussion is that you do not have the capability to hold a bore riding section to plus or minus .001" of the dimension selected in your "Bore Ride Diameter" pull down menu unless the bore ride section is at least 0.1" long. Is this an accurate statement? I may be able to work with a 0.1" long bore riding section that falls somewhere within a diameter of .350-352".

Thank you,
LBD

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Re: Bore ride diameter

Postby mtngun » Thu Aug 29, 2013 9:42 am

LBD wrote:With all due respect, it is not my intention to enter into a debate on cast bullet design, I simply want to understand your capabilities.

It is not a question of capability, it is a question of what I choose to specialize in, which is plainly stated on the Mountain Molds home page.
Image

What I've gleaned from this discussion is that you do not have the capability to hold a bore riding section to plus or minus .001" of the dimension selected in your "Bore Ride Diameter" pull down menu unless the bore ride section is at least 0.1" long. Is this an accurate statement?

No. I make NO GUARANTEE ON BORE RIDE DIAMETER, PERIOD. As I have stated previously, the online design program was intended for revolvers and lever actions -- 357 mag, 44 mag, 45/70, 444, etc.. The only bolt action rifle molds I make are for high velocity, which means loverin designs, not bore riding designs.

If you are looking for a traditional 2-diameter mold for bolt actions, there are other makers who cater to that. Please use them.

Conversation over, thread locked.


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