meplat trimming for short range benchrest........

S

scott mims

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has anyone tried it to see if it does anything for us short range shooters. the way we are so anal about everything with our loads (at least the top guys are :) ) just wondering if anyone really does it to eliminate another variable. do some do it?
 
scott mims said:
has anyone tried it to see if it does anything for us short range shooters. the way we are so anal about everything with our loads (at least the top guys are :) ) just wondering if anyone really does it to eliminate another variable. do some do it?
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I was thinking about it. I bought some .30 bullets from a well known custom maker and most of them had a "fishmouth" on the tip.People I talked to said it doesn't hurt anything, but I'm going to play with it later this spring.
 
Scott,

It may help the long range guys, but worthless for us 100/200 shooters. I've tried it and saw no improvement, what so ever!
 
As Bart said it helps the LR guys. For them the issue shows up at about 600yds and further. Doing the math comparing bullet BC and applying that to the yardage you should be able to see measurable numbers at 300 Yds. in the short range game.
 
Trimming the meplat does two things. It reduces the BC roughly 2-4% but more importantly it reduces the extreme spread. With uniform velocity that reduction of extremes decreases the vertical dispersion. I'm sure it helps at closer distances but it gets lost in all the other noise and is difficult to measure. It takes some amount of distance before the vertical dispersion shows itself on the target. Pointing on the other hand increases BC's a few percentage points and also reduces the affect of the meplat. Trim and point is good, good bullets with tips are better but more difficult to manufacture and perform at a competitive level.
 
Dave Tooley said:
Trimming the meplat does two things. It reduces the BC roughly 2-4% but more importantly it reduces the extreme spread. With uniform velocity that reduction of extremes decreases the vertical dispersion. I'm sure it helps at closer distances but it gets lost in all the other noise and is difficult to measure. It takes some amount of distance before the vertical dispersion shows itself on the target. Pointing on the other hand increases BC's a few percentage points and also reduces the affect of the meplat. Trim and point is good, good bullets with tips are better but more difficult to manufacture and perform at a competitive level.
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My understanding is that trimming actually increases BC but makes it more consistent. Pointing reduces BC.
 
The laws of physics say it's impossible to increase frontal area and at the same time decrease drag. I was the one who mainstreamed this with testing through an Oehler 43 at 300 and 600 yds. and I also did extensive testing for Sierra. Now with being said it may and I say may be possible to have such a flawed meplat that the loss of BC caused by inflight yaw maybe more than the loss from a trimmed bullet so in a sense you could increase the BC. I doubt that's possible but... In all my testing I never saw that.
 
Dave Tooley said:
The laws of physics say it's impossible to increase frontal area and at the same time decrease drag. I was the one who mainstreamed this with testing through an Oehler 43 at 300 and 600 yds. and I also did extensive testing for Sierra. Now with being said it may and I say may be possible to have such a flawed meplat that the loss of BC caused by inflight yaw maybe more than the loss from a trimmed bullet so in a sense you could increase the BC. I doubt that's possible but... In all my testing I never saw that.
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OOPS, I think that I reversed what I meant. Am I correct that trimming increases drag thus lowering BC?
 
Aside from vertical dispersion due to drag, the ballisticians say any imbalance between the outside geometry of the bullet to the axis of rotation will result in angular dispersion. (Larger group). I'm sure the closer to the axis the imbalance the less the dispersion effect. I think the question on meplat uniformity for short range becomes is it significant and how would you measure it?
 
Joe,

I never measured any BC's of bullets common to short range BR but I believe it wouldn't be hard to do. 300 yds. gave me enough resolution to see changes in LR bullets. I agree there is a difference between measuring and seeing the difference. In the short range game rifles are so accurate and the accuracy changes would be so slight that any improvement would most likely get lost in the noise.
 
Dave Tooley said:
In the short range game rifles are so accurate and the accuracy changes would be so slight that any improvement would most likely get lost in the noise.
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This points to the need to use good statistical tools on lots of samples to be certain of differences.
 
Like Dave said Long range is where it shines. I use to trim, but now all I do is point. I found I got better groups at 1000 yards and they grouped 12" higher. My next experiment is Different velocities like 400 fps difference with the same rifle.

Joe salt
 
Joe Salt said:
Like Dave said Long range is where it shines. I use to trim, but now all I do is point. I found I got better groups at 1000 yards and they grouped 12" higher. My next experiment is Different velocities like 400 fps difference with the same rifle.

Joe salt
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+12" at 1K is about what Joel got when he first tried the pointer he bought from Ferris.

400fps lower with pointed?
 
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