Meplat Uniformers.
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Richard338
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- Joined
- Aug 22, 2003
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Whether or not you notice a difference depends on your rifle and the distance you are shooting. With a good target rifle at 1000 yards you should notice a slight difference (especially with the SMK).
I got mine from Dave Tooley (Tooleycustomrifles)
I got mine from Dave Tooley (Tooleycustomrifles)
Buffalobob
Well-Known Member
Here is a thread from ABINOK on a homemade meplat trimmer. I built a couple of them and it was a fun thing to build but am using non-hollowpoints bullets so they just sit in the box with some other reloading tools.
How to have fun on a rainy day
How to have fun on a rainy day
Yep, they are worth it, in my opinion. I still like Kevin's model best, and results will be visible closer than many believe.
This is how the whole thing started -- Larry Bartholomew & Dr. Oehler set up a model 43 at 1,000 yards, and took a bunch of measurements of different chamberings and bullets. The raw data - about 100 pages worth - was never published, but it was circulated among many industry insiders and top 1000yd benchrest shooters. One thing that was quickly noticed is that the variation in BC of bullets from the same box was significant. On the data from the 43, you get extreme spread (ES) and standard deviation (SD) of ballistic coefficient, just like ES and SD for velocity with any chronograph. It was remarkable the number of bullets which had an ES for ballistic coefficient of .020 or greater - both bullets from a green box and bullets from a yellow box. The bullets which had the lowest ES for ballistic coefficient were the Hornady A-max, in a number of calibers. That doesn't mean the A-max are better bullets overall, just that they, with their plastic tips, had a low ES for BC variation.
It is very easy to check on whether or not an ES of .020 for ballistic coefficient matters at 1,000 yards. Simply use a ballistics program, and enter all the numbers for a bullet. Let's say the velocity is 3,000 fps and the ballistic coefficient is .540. Run the program, and look at the total drop for the bullet at 1,000 yards-- you'll see a number, something like 240 inches.
Now change only the ballistic coefficient; instead of .540 use .520, and run the program again. You'll get a different number for total drop, something like 246 inches.
That means that for a change in BC of .020, you get six inches difference in drop -- practically speaking, you have 6 inches of vertical when everything else is perfect.
You can also run the comparisons of the variation of wind drift with that same .020 ES. Most match bullets will have about 2.5 inches of wind drift more for the lower bc bullets.
From this data we can determine that it is mechanically impossible to get production bullets to shoot samller groups than 6"x2.5" groups at 1000yds due to these variations.
Dave tooley was one of the people who saw the Bartholomew data, and it lead to the meplat trimming tool as a part of his study on what makes for good bullets. He eventually got a 43, and initial testing showed that trimming the meplat COULD reduce variations in BC. The tool is not a panacea - if you trim too much of the meplat, you can dramatically reduce BC. And not every bullet shows a significant reduction in ES when the meplats are trimmed - there are other factors that lead to variations in drag, but generally good bullets did show a reduction in ES for BC when the meplats were trimmed slightly & uniformly; not quite as good as using plastic tips, but good enough to remove about half that 6-inches of vertical, and half of the 2.5-inches of horizontal. Futhermore tests have shown the uniforming the meplats on match bullets and weighing them virtually eliminates the usual weight variance encountered in non-uniformed bullets.
Most tool designers and shooters today recomend removing somewhere between .003, and .010 from the meplat, with a small number going as far as .012. Bullets trimed to these dimentions typically loose 2%-3% of their rated BC in trimming, but often show extremly low BC variation. It should be noted that the more material that is removed, the more the BC will be reduced, and perhaps the best option is to remove only enough to produce the same measurement.on a batch of bullets. Many top shooters including G.David Tubb have reported identical retained velocity readings for strings of bullets.
My groups at 1350yds shrank from 16-21 inches of vertical to between 10-14 inches of vertical when sorting bullets by bearing surface length and uniforming meplats on my 220SMKs. Some groups have shown significantly less vertical. I removed (depending on the specific bullet) about .006 from the meplat.
While I don't think that meplat uniforming is mandatory for closer range shooting, I can say that it seems to reduce vertical in my 400yd groups, and I uniform just about all the bullets I load these days.
So... to me yes its worth it.
This is how the whole thing started -- Larry Bartholomew & Dr. Oehler set up a model 43 at 1,000 yards, and took a bunch of measurements of different chamberings and bullets. The raw data - about 100 pages worth - was never published, but it was circulated among many industry insiders and top 1000yd benchrest shooters. One thing that was quickly noticed is that the variation in BC of bullets from the same box was significant. On the data from the 43, you get extreme spread (ES) and standard deviation (SD) of ballistic coefficient, just like ES and SD for velocity with any chronograph. It was remarkable the number of bullets which had an ES for ballistic coefficient of .020 or greater - both bullets from a green box and bullets from a yellow box. The bullets which had the lowest ES for ballistic coefficient were the Hornady A-max, in a number of calibers. That doesn't mean the A-max are better bullets overall, just that they, with their plastic tips, had a low ES for BC variation.
It is very easy to check on whether or not an ES of .020 for ballistic coefficient matters at 1,000 yards. Simply use a ballistics program, and enter all the numbers for a bullet. Let's say the velocity is 3,000 fps and the ballistic coefficient is .540. Run the program, and look at the total drop for the bullet at 1,000 yards-- you'll see a number, something like 240 inches.
Now change only the ballistic coefficient; instead of .540 use .520, and run the program again. You'll get a different number for total drop, something like 246 inches.
That means that for a change in BC of .020, you get six inches difference in drop -- practically speaking, you have 6 inches of vertical when everything else is perfect.
You can also run the comparisons of the variation of wind drift with that same .020 ES. Most match bullets will have about 2.5 inches of wind drift more for the lower bc bullets.
From this data we can determine that it is mechanically impossible to get production bullets to shoot samller groups than 6"x2.5" groups at 1000yds due to these variations.
Dave tooley was one of the people who saw the Bartholomew data, and it lead to the meplat trimming tool as a part of his study on what makes for good bullets. He eventually got a 43, and initial testing showed that trimming the meplat COULD reduce variations in BC. The tool is not a panacea - if you trim too much of the meplat, you can dramatically reduce BC. And not every bullet shows a significant reduction in ES when the meplats are trimmed - there are other factors that lead to variations in drag, but generally good bullets did show a reduction in ES for BC when the meplats were trimmed slightly & uniformly; not quite as good as using plastic tips, but good enough to remove about half that 6-inches of vertical, and half of the 2.5-inches of horizontal. Futhermore tests have shown the uniforming the meplats on match bullets and weighing them virtually eliminates the usual weight variance encountered in non-uniformed bullets.
Most tool designers and shooters today recomend removing somewhere between .003, and .010 from the meplat, with a small number going as far as .012. Bullets trimed to these dimentions typically loose 2%-3% of their rated BC in trimming, but often show extremly low BC variation. It should be noted that the more material that is removed, the more the BC will be reduced, and perhaps the best option is to remove only enough to produce the same measurement.on a batch of bullets. Many top shooters including G.David Tubb have reported identical retained velocity readings for strings of bullets.
My groups at 1350yds shrank from 16-21 inches of vertical to between 10-14 inches of vertical when sorting bullets by bearing surface length and uniforming meplats on my 220SMKs. Some groups have shown significantly less vertical. I removed (depending on the specific bullet) about .006 from the meplat.
While I don't think that meplat uniforming is mandatory for closer range shooting, I can say that it seems to reduce vertical in my 400yd groups, and I uniform just about all the bullets I load these days.
So... to me yes its worth it.
Richard338
Well-Known Member
- Joined
- Aug 22, 2003
- Messages
- 126
Sorry, I wasn't clear, I bought the meplat tool from Tooley. My rifle is a PGWDTI Timberwolf in .338LM.
Living in Canada its probably a pain to bring one across. Tooley is VERY well respected for his benchrest rifles though.
I notice that his prices havn't really gone up with his recent success. I'd love to have him build one.
Steve Shelp from Benchrest Central has experience with the Yogi, and is friends with Tooley.
I just use the standard 338LM. I'm actually quite happy with the standard round. I get 2800 fps using 300SMK, and outstanding accuracy.
My 600 yard groups (three shot) are often under 2"!! Best one 0.92!!
Living in Canada its probably a pain to bring one across. Tooley is VERY well respected for his benchrest rifles though.
I notice that his prices havn't really gone up with his recent success. I'd love to have him build one.
Steve Shelp from Benchrest Central has experience with the Yogi, and is friends with Tooley.
I just use the standard 338LM. I'm actually quite happy with the standard round. I get 2800 fps using 300SMK, and outstanding accuracy.
My 600 yard groups (three shot) are often under 2"!! Best one 0.92!!
Jimm
Well-Known Member
Sinclair Int'l has a new meplat tool in their latest catalog.
Jim
Jim
