6mm vs 7mm in the wind - Am I missing something?

macguru · Post by **macguru** » Sun Sep 08, 2013 8:43 pm

It posted twice for some reason :?:

RAVEN · Post by **RAVEN** » Sun Sep 08, 2013 9:04 pm

Its relative to the BC (6mm=0.5, 7mm=.65), not the calibre, or we would all be shooting 8mm

If you shoot a 6mm and learn the wind drift then you allow for that if you shoot a big 30 the same applies so it relative to what you are shooting.
Or you could shoot a 50 I know what I would prefer :idea:

Yes I agree Matt
IMO some seem to think it's all about the maths.

It’s the whole delivery system and you could have the best on the line but if you can't read the wind it's not worth a piece of Shizer.
For most club shooting the 6.5X47 would be one of the best all rounders
Superb accuracy good barrel life.

RB

Post by **AlanF** » Sun Sep 08, 2013 9:24 pm

RAVEN wrote:Yes I agree Matt
IMO some seem to think it's all about the maths.

It’s the whole delivery system and you could have the best on the line but if you can't read the wind it's not worth a piece of Shizer.
For most club shooting the 6.5X47 would be one of the best all rounders
Superb accuracy good barrel life.
RB

I for one certainly don't think its all about the maths Richard. But I do think that ballistics calculations are an excellent tool for illustrating what is important with regards minimising wind drift. All else being equal, the shooter whose bullet deflects less in the wind can reasonably expect to get a higher score. If you think that wind reading is everything, and ballistics are nothing, then you're doing yourself and your scores a disservice.

Alan

macguru · Post by **macguru** » Sun Sep 08, 2013 9:42 pm

I agree with you Alan, there seem to be many situations where its really hard to pick the changes, and if you can shoot a caliber that holds the 6 , you will get the scores. Of course when its really blowing hard, any caliber we are allowed to shoot will be messed up.

I am continually amazed by the skill of the top fullbore shooters to hold it together and read conditions. I know they have a bigger aiming mark but even so its very impressive.

Bindi2 · Post by **Bindi2** » Sun Sep 08, 2013 10:24 pm

macguru wrote:I agree with you Alan, there seem to be many situations where its really hard to pick the changes, and if you can shoot a caliber that holds the 6 , you will get the scores. Of course when its really blowing hard, any caliber we are allowed to shoot will be messed up.

I am continually amazed by the skill of the top fullbore shooters to hold it together and read conditions. I know they have a bigger aiming mark but even so its very impressive.

I just shows that their aiming system has a larger built in deflection margin. Their ammo has the same accurracy.

DaveMc · Post by **DaveMc** » Mon Sep 09, 2013 7:17 am

I am afraid I am one of these people that subscribe to the laws of physics. They have not been proven wrong on too many occasions!!! Those that want to try - be my guest...... But I would like to point out that winning an individual prize shoot or even a single Queens does not prove anything.

The issue, (if any) lies in our scoring system, The large rings can be very forgiving on accuracy and wind reading errors. Peter Smith has written several articles on this. If you truly wish to delineate between shooter and rifle skills then 10 ring targets with more (finer graduations) rings would be required. Our system means the scores can be closer despite a significant advantage. This means a bit of luck can swing it one way or the other. Where you get a great number of good shooters and or calm conditions and or short ranges then the little guns can do it occasionally - but the averages will win out in the end.

The only argument in which a 6 or 6.5mm is better for you on average and over time is purely as Matt and Chop have pointed out - do you shoot it better (due to less recoil and torque) or is it more accurate??? You don't magically turn into a 20-30% better wind reader simply by picking up a different caliber (unless you are so concentrating on pulling a good shot that you forget about the wind). You might have some successes but the average result will even out. What has really changed over the last few years is the accuracy of the 7mm. These things can now compete with 6BR's at 300m!! (on our target at least) and most people are shooting them well with a little practice.

The future for 30 cal will be interesting (and exciting). There is no doubt if someone can tame them then they will be hard to beat. In most likelihood in certain situations they will dominate and in others they may lose some ground. They were not as dominant in Raton as promised because there was a need to rattle off a few shots between condition changes but if you were shooting bisley style or indeed a condition that was regularly returning then it may be a different story.

BISLEY STYLE IN RATON WOULD HAVE BEEN REALLY INTERESTING!!!????

macguru · Post by **macguru** » Mon Sep 09, 2013 7:51 am

I agree Dave, I have not seen anyone using a 6mm whose wind reading skills are SO good that it can cancel out the BC advantage , the changes would catch them out eventually and over a long enough time the scores would reflect that...

Note also that I am convinced velocity is also important, not just BC. I think a warm load that groups well will shoot inside a mild one with respect to wind. And a 6x47 will beat a 6BR IF it can group as well (thats the catch, and keeping it from wearing too fast also in the case of the 6x47) The same holds true say a 22-250 will beat a 223 IF it groups, UNTIL the barrel wears out (not long until that happens)....

bruce moulds · Post by **bruce moulds** » Mon Sep 09, 2013 8:06 am

the 6.5/284 is as good in the wind as the 284.
less b.c., but more speed balances out.
it is easier to shoot.
but 900 to 1200 shots barrel life make it expensive, and also difficult to get a load for, as this reduces useable barrel life percentage even more.
one other issue with smaller calibres is markers not using a gauge when they should. electronic targets help here. this could rob points occasionally.
one other thought.
could someone like Corbett score as well with a 6mm as a 7mm. fclass wind reading skills have a long way to improve yet world wide. it will be interesting to revisit wind reading in 10 and then 20 years time.
keep safe,
bruce.

DaveMc · Post by **DaveMc** » Mon Sep 09, 2013 8:12 am

Richards comment about us not being able to determine between a 284 and SAUM is fair. our 284's (and Shehanes) were running 2820-2950 and the SAUMS 2950-3000. The bulk of the winds were 0 to 3 minutes and twitchy tailwinds the difference only accounted to 1 * 1/8 click most of the time and we could certainly work off each other easily.

DaveMc · Post by **DaveMc** » Mon Sep 09, 2013 8:14 am

James Corbett would probably beat us with a 6mm Bruce but this does not mean he wouldn't FLOG us with a 7mm!!!
His wind reading skills will not change whether he picks up a 6mm or 7mm - that is the point.

DaveMc · Post by **DaveMc** » Mon Sep 09, 2013 8:16 am

The 6.5*284 loses out on another front Bruce. I had a few of these and cannot for the life of me get the same velocity spread or long range vertical I can with the 284, 284SH or SAUM.

Quick · Post by **Quick** » Mon Sep 09, 2013 8:32 am

Gents,

That's the sorta answer I was looking for, I was sure I was missing something and this thread has answered a lot of questions that stem from that. Very interesting indeed.

Personally, I think my rifle set up is decent and should so the job, it's simply my wind reading and cal choice which will let me down. I know 6mm is a disadvantage, but given that data I collected, I was wondering where else that disadvantage is and know I have learned more about it. I just have to get a 7mm barrel and choose what case to use.

You learn something new everyday

that's why I love this forum. Sorry to anyone who doesn't like seeing questions such as this. I just try to learn and this is the best place to ask such questions.

IanP · Post by **IanP** » Mon Sep 09, 2013 9:01 am

Reading thru these posts really highlights the difference between those who understand ballistics and those who do not. Experience is a great teacher but without knowing the theory you place yourself at a great disadvantage.

I think the days are gone when you decide on a new F-Class project rifle and make your decision solely on calibre. I always look at the available bullets and their BC then enter them into my spreadsheet which calculates ballistics, side by side for comparison. I know their wind drift and velocity at 1000 yards and also the calculated free-recoil for the barrel length and weight in my stocks.

The days of selection based solely on gut feel, guessing or claibre alone are gone but you need to understand long range ballistics and why the G7 drag model is essential to use. I recommend to every long distance shooter to buy Bryan Litz's books and DVD's and then actually read them and do some simple calculations for yourself to gain some understanding.

Its not difficult to understand, if it was I would be in trouble! We live in a age of computer modelling and its an asset for the shooter to model the ballistics of his future F-Class rifle. Its fun to do, but you need understanding gained by reading books like Bryan Litz has made available.

To those that doubt the worth of modelling all I can say is summed up in that disparaging cliche, "ignorance is bliss".

Ian

Seddo · Post by **Seddo** » Mon Sep 09, 2013 9:26 am

macguru wrote: The same holds true say a 22-250 will beat a 223 IF it groups, UNTIL the barrel wears out (not long until that happens)....

Mac,
I should be in a position to put that to the test soon. I have started neck turning brass for my 7 twist 22-250AI and i can run it against my 7 twist 223.

How many people are running 2 rifles? Say a 6mm for the shorts and a 7mm for the longs? To me it seems like the ideal situation.

bruce moulds · Post by **bruce moulds** » Mon Sep 09, 2013 9:27 am

it is all about the bullet, either for hunting or target shooting.
then you select a system to deliver it.
this includes rifle and cartridge.
then you look at other factors like recoil and availability of components, and of course barrel life.
one further consideration is such things as will it foul out in the length string fired, and what cleaning regime is required.
keep safe,
bruce.