what difference in the point of impact does a cannelure make

[Chris338378]

A friend of mine asked me what difference in the point of impact does a cannelure make in two of the same bullets, say for an example a Nosler .338 caliber 210 grain Partition that's fired out of the same rifle. I know the purpose of the cannelure but never thought about his question. I also never fired or even loaded the same bullet with and without a cannelure so I have no experience with this. I understand every rifle is different and it comes down to the specific rifle but I'm looking for a general answer. My thought is if it had any affect it would be minimal.

 

[FOTIS]

Got to shoot both and see. My guess is minimal to none in sight in ranges. At longer range that may indeed change.
A good example is when Barnes employed the grooves on the TSX bullet the BC values came down a bit (to a lot) due to air drag.
Hence te great BC's on the Etip

 

[SJB358]

I haven't seen a difference in the 210 PT with my 338 Win Mag. Matter of fact, I haven't seen much difference with any of the crimping grooves that were put on the 2nds menu..

Fotis nailed it though, try it out. The only sure fire way you can know.

 

[JD338]

You will need to shoot them to see.
FWIW, the 210 gr PT's shot to the same POI in my 338 RUM but the 250 gr PT's were almost 1" different.

JD338

 

[Horsethief]

By itself, I don't think the cannelure makes any difference. I've fired a wide variety of calibers and weights within those calibers and never been able to pinpoint a cannelure or lack thereof as effecting accuracy.

If you crimp into a cannelure, you could over crimp and cause undue tension and cause pressures to rise. For a bolt action rifle, I see no need to crimp anything smaller than a 9.3x62mm Mauser and even that might not be necessary.

 

[kraky]

I can't believe it would make a difference BUT......
To be fair you should run both bullets past a comparator to be sure they have the exact same profile. It wouldn't be out of he question that different lots of bullets could give different jumps to the lands at the same seating depth.