Bullet bearing surface

[SSgt G Cody]

Basically, very simply, both ends of the bullet have overall diameter reduced about 3%, and a ring of that exact diameter is forced gently onto each end of the bullet. The space between them is considered the bearing surface. It is usually 55-80% of the bullet's overall length. Longer bearing surfaces require faster twists to stabilize the bullet in flight. Use a twist chart to determine exact twist you need for your heaviest/longest bullet. It's really pretty simple.

 

[FEENIX]

https://www.mscdirect.com/product/details/16412405?cid=ppc-google-&mkwid=|dc&pcrid=&rd=k&product_id=16412405&gclid=Cj0KCQjw2eilBhCCARIsAG0Pf8tly1yftuGpzJH5dYIxkqTUoBw7A0G4MMsWHaKnDK565kq-oMbXFkMaAsr6EALw_wcB&gclsrc=aw.ds

You can kinda redneck it with a piece of sandpaper and rubbing the bullet back and forth...the bearing surface will show up but it's not very accurate and still hard measurement to get.

That brings back fond memories; early 1980s was the last time I used optical comparators.

 

[338 dude]

 

[haisardao]

View attachment 479851View attachment 479853

Thanks

 

[RichCoyle]

SSgt G Cody,

I don't want to be argumentative, but here goes.

The bearing surface does not determine the twist needed. It is overall length of the bullet.

 

[DoneNOut]

338dude posted what I was gonna say.

 

[DoneNOut]

SSgt G Cody,

I don't want to be argumentative, but here goes.

The bearing surface does not determine the twist needed. It is overall length of the bullet.

First thought is, only the length of the bearing surface would matter and not the length of the parts not touching the rifling. Do you recall why the length of the parts not touching still matters?

 

[RichCoyle]

First thought is, only the length of the bearing surface would matter and not the length of the parts not touching the rifling. Do you recall why the length of the parts not touching still matters?

Let's suppose you sharpen a 5" long pencil and try to spin it on the end. Let's suppose you sharpen a 5" long pencil from both ends so about 2" in the middle is still yellow paint while the rest is tapered wood. Now try to spin the pencil on one end or the other. Ohe has a very long "bearing" surface but the other does not.

Same concept applies to bullets.

 

[SSgt G Cody]

You do understand "Simple", and "Basic", and Conventional Bullet Shape, RIGHT??? Then add coaxial spin, longitudinal balance, and gravitational pull. Then consider release tension, friction factors, magnetism, plasma factor, and several other elements involved. And YOU want to make an argument of it??? How old are You??? I hope that soon you're old enough to know better!

 

[Rich Coyle]

SSgt G Cody,

Old enough to recognize an attempt at pedant when I see it.

 

[DoneNOut]

You do understand "Simple", and "Basic", and Conventional Bullet Shape, RIGHT??? Then add coaxial spin, longitudinal balance, and gravitational pull. Then consider release tension, friction factors, magnetism, plasma factor, and several other elements involved. And YOU want to make an argument of it??? How old are You??? I hope that soon you're old enough to know better!

That was very rude and uncalled for. If you think Rich said something incorrect, formulate your argument like an adult. It costs you nothing to be nice.

 

[Beluebow]

That escalated quickly.

 

[SSgt G Cody]

My statement was basically balistically correct, considering all the involved variables. Your argument seems to be with the barrel-makers, and their twist rate charts. Prove your point.

 

[RichCoyle]

SSgt G Cody,
So, I'm supposed to believe a 2" long bullet with a short bearing surface of 3/4" doesn't need a faster twist than a cylindrical 1 1/2" long bullet?