Range Report Effect of crimping canlure on long range performan

[wadcutter]

Given two bullets that are very similar. ie, the Hornady SST and the Hornady Interbond bullets

They are almost identical in 225 grain .338 calibre except for the canlure on the SST bullet. The B.C. for both is listed as .515.

In .308 calibre, the canlured 165 grain SST and the smooth sided Interbond are both listed with a B.C. of .447.

I was wondering what effect on exterior ballistics that the canlure must have?

Hornady list the two bullets as having the same B.C. but I can not see how this is possible given the extra drag induced by the canlure on the SST projectile.

Anyone have any data on just how much effect a canlure has on B.C.

 

[Grump]

Re: Effect of crimping canlure on long range performan

I think it's the laminar air flow effect. What's right next to the shank and hits the groove is "passing" much slower than the rest of the air. That tends to smooth things out a bit.

OR...

Small differences elsewhere, such as meplat, ogive, boat-tail angle and length, and radius of various bends, cancel out any cannelure effects.

 

[Rovieairto]

Re: Effect of crimping canlure on long range performan

A cannelure should have very little effect if it is aft of the ogive (which it always is).

As long as it doesn't add to the cross sectional area, the B.C. should be close enough.

Subsonic, the air moves out of the way before the body arrives.
Supersonic, the body moves the air out of the way.
(Mostly true)