6BR vs 30BR

[Edward]

My range is 100, 200 & 300yds We shoot for score. I've noticed in windy conditions 6BR wins and in mild conditions 30BR wins Is there a rule of thumb as to wind conditions between using a 6BR instead of a 30BR (under10mph 30BR over 10mph 6BR???)

 

[TonyinKY]

Do you score by best edge scoring? If so the 30BR will win because of the bigger bullet hole. Other than that I think the 6PPC and 30BR are the same. I like the 30BR because I get a MUCH longer barrel life. My current barrel has 4000+ rounds and still bores a hole when I do my part. My $.02 on the 6PPC and 30BR debate. I'm not sure where the 6BR compares but I'd be surprised if it is as consistent as the 30BR.

 

[Link]

following.

 

[Laurie]

The 6BR beats the 30 hands down in any wind change at 300 yards. That might not matter for BR comps in stable conditions, but if constantly changing, the 30BR sees just too much wind drift.

My interest isn't BR, rather F-Class, and having just had an old 'Target Rifle' Paramount (ie Fullbore / Palma job) rebarrelled to 30BR as a (hopefully) accurate and cheap to run pensioner's plinker, I had hoped it might be competitive in 'F' at 300, the shortest distance my main club shoots this discipline over. So yesterday evening, I ran the numbers as following:

125 Sierra HP Match @ 2,900 fps MV (30BR) ....... 9.3"


224 80.5gn Berger @ 3,000 fps (223 Rem) ......... 6.35"

224 90gn VLD @ 2,850 fps (223 Rem) ............... 5.55"

243 108gn Berger BT @ 2,750 fps (6BR) ............ 5.99"

7mm 150gn Scenar L @ 2,800 fps (7-08) ........... 6.03"

7mm 160gn Sierra TMK @ 2,825 fps (7-08) ........ 5.09"

(10 mph 90-deg wind, so for each equivalent 1 mph @ 90-deg divide by 10.)


Apart from the 30BR where I have yet to run the barrel in never mind work up loads, these are all cartridges available to me in existing F-Class rifles with proven track records and a good idea how they perform in the wind, also what sort of groups they can produce in still conditions at 300 yards and up.

The range I shoot over will likely see nil to 1.5 mph 90-deg equivalent changes between shots at this distance (actually much larger in gust mph terms, but the prevailing wind is from 5 o'clock reducing lateral effects).

so an equivalent 1 mph wind change between shots would see the 30BR moved nearly an inch, the 160gn TMK in the 70-08 not much more than half that. Were the 30BR shooting into 0.1-MOA at that distance windage aside and the 7-08 into 0.5-0.75-MOA, the 30 might still have a chance, but the seven reliably shoots into 0.3-0.4-MOA (managed 0.6-MOA in a 1,000 yard BR match a couple of weeks ago on a day when the small group for all classes was 4.47").

The 30BR v a mild 6BR load sees 0.93" v 0.6" respectively per 1 mph change, the 30 seeing a 50% increase in wind effect and unlikely to give greater precision all other things being equal.

One benefit is as per BR for score - although there is a '30-calibre' scoring rule in F-Class (ie the shot hole edges should be adjusted as if it were made by a .30 bullet when smaller calibres are used), in practice the butts crew will almost invariably score the shot on whether it breaks the line or not - this disadvantages the 6mm even more so 223. In the case of the 223, occasional shots are 'lost' too on heavily patched targets where the bullet slips under the edge of a patch without leaving a hole.

I do shoot on another 200+300 yard range in a deep and very sheltered valley that only sees light breezes in most wind directions, so I am still hopeful that the 30BR will be competitive at this distance - it'll be interesting to see.