conventional wisdom and shooting to 1000 yards

M

MichaelMarc

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Not having any experience in this area, i would appreciate some insight into one peculiar 'rule' I have heard many times. I have been told that for consistent accuracy in shooting at 1000 yards, it is neccessary to keep the bullet moving at 1.2 mach -- that the region in which the bullet goes transonic negatively affects its accuracy.

I have looked at JBM trajectory charts for the various .308 loads I shoot, and while I rarely venture past 200-300 yards, I see that 800-825 yards seems to be the maximum distance before the sub 1.2 mark is hit.

How do people who shoot .308 competitievely deal with this?
 
I'm tempted to write far too many words in response. Shooting in the transonic range is something I know a bit about. However, I decided to spare y'all the boredom.

Since I'm not a rifle shooter of any note, I'll defer to people with actual experience in the specific discipline about which you've inquired. I think you might find this link useful as a starting point: http://riflemansjournal.blogspot.com/2011/01/cartridges-1000-yard-308-load.html
 
Not all bullets react the same when they enter and exit the transonic zone. If they did we would not be able to shoot the smaller cartridges out to and beyond 1000 yards. But we do. The 168 grain and 175 grain SMKs are a good example. The 168 grain was designed for 300 meter International shooting and it does quite well out to 600 yards in a 308W size case. The 175 grain was designed for 1000 yards and it does quite well in the same case. There's only 7 grains difference between the two but the bullet shape makes all the difference in the world.

And, that's how it's done. :)

Ray
 
MichaelMarc said:
Not having any experience in this area, i would appreciate some insight into one peculiar 'rule' I have heard many times. I have been told that for consistent accuracy in shooting at 1000 yards, it is neccessary to keep the bullet moving at 1.2 mach -- that the region in which the bullet goes transonic negatively affects its accuracy.

I have looked at JBM trajectory charts for the various .308 loads I shoot, and while I rarely venture past 200-300 yards, I see that 800-825 yards seems to be the maximum distance before the sub 1.2 mark is hit.

How do people who shoot .308 competitievely deal with this?
Click to expand...
You're taking the statement out of context and applying it to all 1K shooting. Most likely you heard this from someone who shoots 1000 yard BR, and in that context, it is true. That is a very different game than Palma, with different goals.

When the game you play restricts you to using a 308, you find a bullet that best suits the purpose. You also compete against other people with the same cartridge restriction. If you shoot 1K BR, you are allowed to shoot anything you like. Obviously then, handicapping yourself with a cartridge that can't propel the best-for-caliber bullets is foolish. In that context, if you don't maintain mach 1.2 or thereabouts, you're going to loose.

In 1KBr, you don't have a foot of wind drift to give up to the guys who are already shooting groups of 3 or 4 inches, sometimes, in considerable wind.
 
Don't forget, Palma not only restricts the case you can use (308W) it also limits the bullet weight to no more than 155 grains. So, Palma shooters have a doubly difficult chore in trying to stay above trans-sonic. (And they are further handicapped because they assume the un-gentlemanly position of shooting laying down in the mud. ;) ;))
 
MM
You need to consider that the Palma Game is shot with various bullets, however the 155SMK shot at the speed of 2975 to 3000 or so out of a 30" barrel with STAY supersonic to 1K and a bit further and will shoot into the Xring easily (if one can read the wind)
 
Staying super sonic at 1000

MichaelMarc said:
Not having any experience in this area, i would appreciate some insight into one peculiar 'rule' I have heard many times. I have been told that for consistent accuracy in shooting at 1000 yards, it is neccessary to keep the bullet moving at 1.2 mach -- that the region in which the bullet goes transonic negatively affects its accuracy.

I have looked at JBM trajectory charts for the various .308 loads I shoot, and while I rarely venture past 200-300 yards, I see that 800-825 yards seems to be the maximum distance before the sub 1.2 mark is hit.

How do people who shoot .308 competitievely deal with this?
Click to expand...

Michael:

This is the reason most of the best FTR shooters shoot 185-210 grain, high BC, .308 bullets out of 30-34" .300/.308 bore, 1:10-1:12 twist barrels barrels.

Just look at what Jeff Rorer, and James Crofts are shooting.

These bullets may only start off at 2650-2800 fps but they retain their velocity down range better.
Nat Lambeth
 
4Mesh said:
You're taking the statement out of context and applying it to all 1K shooting. Most likely you heard this from someone who shoots 1000 yard BR, and in that context, it is true. That is a very different game than Palma, with different goals.

When the game you play restricts you to using a 308, you find a bullet that best suits the purpose. You also compete against other people with the same cartridge restriction. If you shoot 1K BR, you are allowed to shoot anything you like. Obviously then, handicapping yourself with a cartridge that can't propel the best-for-caliber bullets is foolish. In that context, if you don't maintain mach 1.2 or thereabouts, you're going to loose.

In 1KBr, you don't have a foot of wind drift to give up to the guys who are already shooting groups of 3 or 4 inches, sometimes, in considerable wind.
Click to expand...

Excellent point and info. Has anyone actually figured the standard deviation when a bullet enters the transonic range? What I am looking for here would be empirical data to suggest a maximum deflection based on bullet length, speed, weight, etc.
 
I doubt if you'll find data such as that outside the manufacturers, and I doubt if they would share much of it with you. The chances are that it's mostly proprietary. But, you could call them and ask. Anything that you'll get from shooters will be mostly anecdotal and we all know how much that is worth.

Ray
 
MichaelMarc said:
Excellent point and info. Has anyone actually figured the standard deviation when a bullet enters the transonic range? What I am looking for here would be empirical data to suggest a maximum deflection based on bullet length, speed, weight, etc.
Click to expand...

You need to go & read McCoy on Dynamic Stability. Anecdotally, we do not even know the cause. It can be calculated only after the fact. But read McCoy, because I'm just a shooter.
 
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