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Technical question

 
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  #15  
Old 01-01-2004, 10:00 AM
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Join Date: Nov 2003
Location: La Grange, TX
Posts: 222
Re: Technical question

So lets toss this out for consideration of bullets "going to sleep-or not"

Shooting VLD bullets for the prone slow fire stages of matches I see in almost all of my barrels accuracy that hovers around the .5 to .8 moa mark at 100-300 yards. Yet once we pass the 300 yard mark that ammo will, most times, get accuracy from .4 to .5 moa.

Transferred to inches I'm not at all worried when I see 3 inch groups at 300 yards with VLDS because when I take that ammo to 600(double the distance) I'm often seeing groups in the 2 to 4 inch range.

One normally assumes that the accuracy would be equal to or worse than the distance. IE 3 inches at 300 would be 6 at 600.....

Any thoughts on this one?

Jeff
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  #16  
Old 01-01-2004, 10:17 AM
 
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Re: Technical question

rost495, looks like your bullets get tired after about 300 yards. I have seen some of my bullet loads seem to have a lower moa after 300 yards.
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  #17  
Old 01-01-2004, 10:24 AM
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Join Date: May 2001
Location: Urich, MO
Posts: 838
Re: Technical question

GonHuntin,
No I don't think the longer barrel stabilizes the bullet more. The twist rate determines stabilization, not barrel length. A 1 in 10 twist is still 1 in 10 in a 10 in where the bullet make 1 turn before exiting or a 20 inch where the bullet makes 2 turns before exiting. Do the math, it all comes out the same.
If a bullet started crooked but would straighten out more in a longer barrel then we all use 40" barrels like DC [img]images/icons/grin.gif[/img] , however due to the drag DC mentioned and the fact a short barrel is stiffer (less whip) long barrels are not practical with some calibers.
The only reason for 30" barrels on guns like Palma rifles is for a longer sight radius using iron(aperture) sights. Since most of us use optics now that long sight radius is not needed.
There's just no reason to believe a longer barrel stabilizes a bullet better.
As a general rule of thumb, I would use the shortest barrel I could to obtain the desired velocities in the caliber of choice.

Rost,
I mentioned the answer to your question in my first post as to why you are seeing your groups tighten up at longer ranges. I truly believe it has to do more with sight resolution than anything else. Try experimenting with different shapes and sizes of targets, even at 100 yards. It will make a difference in groups. That why the 100 yard, 200, and 1000 yard benchrest targets are not the same. Look at a couple of good target companies, Sinclair carries one brand in particular that I am thinking of but can't remember the name, they have different targets for the same distance but different magnification levels of scopes.
Play around with it, you might be suprised by the differences.
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  #18  
Old 01-01-2004, 10:52 AM
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Join Date: Jul 2003
Location: NY
Posts: 168
Re: Technical question

Happy New Year,

Question: For some of these Ultra Mags, etc. Isn't the longer barrel used to burn the powder more efficiently?

Even the 26" tube is too short for a .300 RUM. If you were to shoot thru a sheet a few feet away you would see all the wasted unburned powder from the shorter barrel splattered on the sheet.

Is there some accurate way to calculate barrel length for maximum powder efficiency?

Thanks
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  #19  
Old 01-01-2004, 01:06 PM
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Join Date: Jan 2003
Location: The rifle range, or archery range or behind the computer in Alaska
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Re: Technical question

Just another thought to chew on. I have used loads in a given rifle that had a fair but semi low BC (168 SMK) and more twist than needed. This one load would shoot 3/4" at 300 yards. This would = .25 MOA. The same load would open up to .4 MOA at 400 yards. By 600 yards it was 1.000 MOA. This is clearly a bullet that has not gone to sleep.

On the other hand, that same rifle with a heavier bullet (175 SMK) would shoot .25 MOA from 100-1000 yards. This is clearly a bullet that has gone to sleep. Or as some agree, being stabilized properly.

Regards
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  #20  
Old 01-01-2004, 01:11 PM
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Location: The rifle range, or archery range or behind the computer in Alaska
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Re: Technical question

Agunner012,

I personally am not aware of the calculations for your question. Usually you have to experiment with different bullets and powders and charges while shooting through cardboard 10' away. I had the same problem in my old 30-378 w/a 26" barrel. I tried the 180 XBT and 107 grains of RL-25. It stopped shooting unburned powder out the barrel and the velocity got a lot more conscistent. The easiest is just experiment with a few powders. Faster powders generally burn all the powder, but ya have to be carefull not to use to much in a case that big.

[ 01-01-2004: Message edited by: meichele ]
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Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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  #21  
Old 01-01-2004, 01:27 PM
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Join Date: Sep 2003
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Re: Technical question

Gonhuntin,

As far as I can see, if each bullet leaves the muzzle at the same velocity (and therefore same spin rate) the only difference will be that the bullet from the 18inch barrel will start 'free-flight' 4 inches closer to the target than that from the 14 inch barrel.
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