Meplat trimming by OAL or ogive
- Thread starter milanuk
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John Kielly
Shari's fan club
Monte,
I'm a lazy bugger & hate doing extra work for no benefit. I find that if I point my projectiles with the Whidden pointing tool, then trim them with his meplat trimmer, I can avoid measuring bearing surface, so i get two for the price of one.
With the projectiles that I use, I've found that there is a very good correlation between the bearing surface length & the OAL after pointing. I set the trimmer to clean up the longer projectiles perfectly with the first cut (batch one), then take a more aggressive trim (batch 2), leaving behind a few sinkers & barrel warmers.
Ok, there's probably a tad of fudge in all this, but then again, after it was suggested that most bearing comparitors have an element of inaccuracy to them (was that you, Eric Stecker), I figure that I can live with the shame of it all.
John
I'm a lazy bugger & hate doing extra work for no benefit. I find that if I point my projectiles with the Whidden pointing tool, then trim them with his meplat trimmer, I can avoid measuring bearing surface, so i get two for the price of one.
With the projectiles that I use, I've found that there is a very good correlation between the bearing surface length & the OAL after pointing. I set the trimmer to clean up the longer projectiles perfectly with the first cut (batch one), then take a more aggressive trim (batch 2), leaving behind a few sinkers & barrel warmers.
Ok, there's probably a tad of fudge in all this, but then again, after it was suggested that most bearing comparitors have an element of inaccuracy to them (was that you, Eric Stecker), I figure that I can live with the shame of it all.
John
Hi Monte, I make all my own stuff so i don't use any commercial ones but what i need to know is that each projectile has the same exterior shape.. To this end i want to qualify each from the meplat to the area on the ogive at it's barrel land dia ( in my case it's .300 for a 30 cal )and then from there to the base and from there to the boat tail break .. I batch to a tolerance of .001 or less and if i check at these 3 points then the bullets in the batch have as close as to the same shape.. JR.. Jeff Rogers.pic of the one i made with the Tubb unit underneath
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John, Jeff,
Thanks for the responses... gives me something to think on at any rate. I am kind of surprised a few other folks didn't weigh in on the matter... seemed like the perfect bait for those LR shooters stuck inside and sufferin' from cabin fever this time of year!
Monte
Thanks for the responses... gives me something to think on at any rate. I am kind of surprised a few other folks didn't weigh in on the matter... seemed like the perfect bait for those LR shooters stuck inside and sufferin' from cabin fever this time of year!
Monte
Dave Tooley
Active member
Monte
I'll jump in since I made the first meplat trimmers and I manufacture the trimmer for David Tubb. You want to reference off the ogive. The goal is to have an inflight, nose on, profile as uniform as you can get. That means all the meplats needs to be as close to the same diameter as possible. The only area that should be consistant from bullet to bullet is the ogive and the diameter. Thus my meplat trimmer mates up to a location on the ogive, not unlike the lead angle in a chamber.
What happens to a bullet that hasn't had the meplat trimmed is the nonuniform air flow over the meplat creates inflight yaw. That yaw varies from bullet to bullet thus the frontal profile varies and the BC's vary. You can get as anal as you want over things like this but you reach a point that you can't see the difference on the target. All I do is trim meplats. I have some unproven ideas about hitting a bullet on the tip and expecting it not to change along the ogive.
Dave Tooley
I'll jump in since I made the first meplat trimmers and I manufacture the trimmer for David Tubb. You want to reference off the ogive. The goal is to have an inflight, nose on, profile as uniform as you can get. That means all the meplats needs to be as close to the same diameter as possible. The only area that should be consistant from bullet to bullet is the ogive and the diameter. Thus my meplat trimmer mates up to a location on the ogive, not unlike the lead angle in a chamber.
What happens to a bullet that hasn't had the meplat trimmed is the nonuniform air flow over the meplat creates inflight yaw. That yaw varies from bullet to bullet thus the frontal profile varies and the BC's vary. You can get as anal as you want over things like this but you reach a point that you can't see the difference on the target. All I do is trim meplats. I have some unproven ideas about hitting a bullet on the tip and expecting it not to change along the ogive.
Dave Tooley
G
Greg Culpepper
Guest
Dave and Monte,
Since I shoot in both worlds (F-Class/Palma and 600/1k BR) I'd like to add the observation that the goals of bullet prep across them are not identical.
BR holds a greater reward for very small bc variation as a predictor of minimum vertical.
Conversely, long range with its much longer strings of fire, slower shot cadence, consequently much greater variation in condition over time and lesser precision in target alignment holds a greater reward for higher bc.
If you can improve both bc and consistency without compromising one or the other the same prep will serve both arenas.
Greg
Since I shoot in both worlds (F-Class/Palma and 600/1k BR) I'd like to add the observation that the goals of bullet prep across them are not identical.
BR holds a greater reward for very small bc variation as a predictor of minimum vertical.
Conversely, long range with its much longer strings of fire, slower shot cadence, consequently much greater variation in condition over time and lesser precision in target alignment holds a greater reward for higher bc.
If you can improve both bc and consistency without compromising one or the other the same prep will serve both arenas.
Greg
G
gonehunting378
Guest
ogive+1
most of us are sorting by bearing surface length, or at least base to ogive length. so either way you end up with the same oal for a particular "group" of bullets anyway. i am not sure what the b.c. difference is between 2 bullets if bullet a is 1.237 and bullet b is 1.232. i really have no friggin clue, but i do know this, if there are tools to make them both the same, i use that tool. i use, and like the hoover tool, im sure the one dave mentions is very good also.
tom
most of us are sorting by bearing surface length, or at least base to ogive length. so either way you end up with the same oal for a particular "group" of bullets anyway. i am not sure what the b.c. difference is between 2 bullets if bullet a is 1.237 and bullet b is 1.232. i really have no friggin clue, but i do know this, if there are tools to make them both the same, i use that tool. i use, and like the hoover tool, im sure the one dave mentions is very good also.
tom
Dave Tooley
Active member
Tom
I've tested 6MM bullets out of the same box that had .030" difference in the length. There was no measurable difference in the BC between the two groups of bullets. I think with that wide a gap there were two lots of bullets there. All other things being equal I don't think we can see minor variations in ogive to base length on the target.
Dave
I've tested 6MM bullets out of the same box that had .030" difference in the length. There was no measurable difference in the BC between the two groups of bullets. I think with that wide a gap there were two lots of bullets there. All other things being equal I don't think we can see minor variations in ogive to base length on the target.
Dave
I agree with about Ogv-to-Base variance being low on the totem pole for BC variance. I don't see it as worth checking anymore than weight.
I don't know of any meplat trimmer taken to base. All I'm aware of are taken to a point on the ogive.
What I wonder though, and Dave you might have checked it, are trimmed meplats ending up the same size(same diameter)?
What if the nose length variance is due(partially) to ogive radius variance?
As an example, let's say most of my bullets have meplats running around .050, but a higher radius leaves one bullet with a meplat that is .070..
If the trimmed meplats have been opening from .050 to .080, then what is the .070 meplat going to end up at?
I ask, because nose length(like BL) is a relatively small contributor to BC -compared to meplat diameter. So I wouldn't want to trim or point unless it resulted in the same size meplats.
I don't know of any meplat trimmer taken to base. All I'm aware of are taken to a point on the ogive.
What I wonder though, and Dave you might have checked it, are trimmed meplats ending up the same size(same diameter)?
What if the nose length variance is due(partially) to ogive radius variance?
As an example, let's say most of my bullets have meplats running around .050, but a higher radius leaves one bullet with a meplat that is .070..
If the trimmed meplats have been opening from .050 to .080, then what is the .070 meplat going to end up at?
I ask, because nose length(like BL) is a relatively small contributor to BC -compared to meplat diameter. So I wouldn't want to trim or point unless it resulted in the same size meplats.
See my original post.
Thanks for the responses everybody. Definitely gives me something to chew on, and perhaps tinker with just a bit come spring.
Originally I picked up one of the older meplat uniformers sold by Tubb for .22 cal, but I never really used it. Later, when Doug Giraud came out with a meplat uniformer for his motorized case trimmer I figured I was in heaven. It made the task incredibly quick and given the snaggle-toothed meplats I was seeing on some SMKs at the time, a lot easier. Some time ago I happened to measure a handful of 6mm S107MKs and as per usual, they varied about 20-30 thou in overall length. Just for giggles, I buzzed them all in the meplat uniformer, and measured again... they still varied maybe 15-20 thou in OAL. That was kind of disappointing - I didn't expect them to be perfect, but that was a bit more than I expected.
When I got my Whidden pointing die set up, it came with a holder for use with a Wilson case trimmer, and at first I trimmed, pointed, and then took just a whisker off the tip (this was with Berger 6mm 105 VLDs), and those bullets were pretty much perfect every way I could measure - and shot accordingly. Later someone suggested that it probably wasn't necessary to trim at all if I was pointing (I think the Whidden die instructions mention something like this), so I tried just pointing. As it turned out, about that point I was moving from the tail end of one 100ct box of B105VLDs, to one of the new 'bulk' 500ct boxes. The meplats on those were(are) all raggedity looking - kind of like a SMK sometimes does. They didn't point up worth a darn. I'd had to adjust the pointing die considerably to begin with (the bullets were as much as 20 thou longer on average), and the ragged meplats tended to 'fold' up during pointing. When I attempted to trim afterwards, the cutter on the Wilson trimmer would catch on the folds and rip them open - not what I was looking for. I tried trimming, then pointing, then trimming again to get those bullets looking half-ways decent but it was a lot more work than I think it was worth.
Sometime there after I got a pretty good deal on a used SSS/Tubb bullet comparator stand with a couple caliber sleeves (.22 & 6mm). I haven't done much with sorting vs. pointing vs. trimming yet... but given that I had two different ways available to trim meplats - by length with the Whidden holder on a Wilson trimmer, or by ogive on my Giraud trimmer... I was curious what others were using. Doesn't sound like a whole lot of folks have tried the Wilson style trimming.
Monte
Originally I picked up one of the older meplat uniformers sold by Tubb for .22 cal, but I never really used it. Later, when Doug Giraud came out with a meplat uniformer for his motorized case trimmer I figured I was in heaven. It made the task incredibly quick and given the snaggle-toothed meplats I was seeing on some SMKs at the time, a lot easier. Some time ago I happened to measure a handful of 6mm S107MKs and as per usual, they varied about 20-30 thou in overall length. Just for giggles, I buzzed them all in the meplat uniformer, and measured again... they still varied maybe 15-20 thou in OAL. That was kind of disappointing - I didn't expect them to be perfect, but that was a bit more than I expected.
When I got my Whidden pointing die set up, it came with a holder for use with a Wilson case trimmer, and at first I trimmed, pointed, and then took just a whisker off the tip (this was with Berger 6mm 105 VLDs), and those bullets were pretty much perfect every way I could measure - and shot accordingly. Later someone suggested that it probably wasn't necessary to trim at all if I was pointing (I think the Whidden die instructions mention something like this), so I tried just pointing. As it turned out, about that point I was moving from the tail end of one 100ct box of B105VLDs, to one of the new 'bulk' 500ct boxes. The meplats on those were(are) all raggedity looking - kind of like a SMK sometimes does. They didn't point up worth a darn. I'd had to adjust the pointing die considerably to begin with (the bullets were as much as 20 thou longer on average), and the ragged meplats tended to 'fold' up during pointing. When I attempted to trim afterwards, the cutter on the Wilson trimmer would catch on the folds and rip them open - not what I was looking for. I tried trimming, then pointing, then trimming again to get those bullets looking half-ways decent but it was a lot more work than I think it was worth.
Sometime there after I got a pretty good deal on a used SSS/Tubb bullet comparator stand with a couple caliber sleeves (.22 & 6mm). I haven't done much with sorting vs. pointing vs. trimming yet... but given that I had two different ways available to trim meplats - by length with the Whidden holder on a Wilson trimmer, or by ogive on my Giraud trimmer... I was curious what others were using. Doesn't sound like a whole lot of folks have tried the Wilson style trimming.
Monte
G
gonehunting378
Guest
dave,
i was refering to o.a.l. differences, and weather or not they matter as it applies to the final b.c.? but on the subject of how much it really matters as it applies to our demands is a huge ? we can't really test, unless someone has a 1000yard tunnel?
was it the base to ogive, bearing surface length, or o.a.l. that varried .030"?
i have a lot i will use this season that sorting by bearing surface length, have 95% that run from.240 to .244 but there are the other 5% that are .025-.028 shorter. i don't think the 5% are "bad bullets", i just don't want to shoot them in a relay mixed in with the others. and since there are so few of them, i will just fireform with them to be sure.
tom
i was refering to o.a.l. differences, and weather or not they matter as it applies to the final b.c.? but on the subject of how much it really matters as it applies to our demands is a huge ? we can't really test, unless someone has a 1000yard tunnel?
was it the base to ogive, bearing surface length, or o.a.l. that varried .030"?
i have a lot i will use this season that sorting by bearing surface length, have 95% that run from.240 to .244 but there are the other 5% that are .025-.028 shorter. i don't think the 5% are "bad bullets", i just don't want to shoot them in a relay mixed in with the others. and since there are so few of them, i will just fireform with them to be sure.
tom
Dave Tooley
Active member
Mike
Whether it's my trimmer or others on the market all are going to cut a meplat very close to the same diameter. Trimming the meplats reduces the BC by about 2% If after trimming the meplats you have a variation in diameter of say .005" on a meplat that measures .065" that's only a 7.7% variation over 2% of the BC. 2% of .600 BC is .0012 then figure in a 7.7% variation in that and .005" doesn't mean much. Within reason it's all about shape which effects in flight yaw.
Now if you go to different bullet with a different ogive you've gone to a different point up die and may well have a different diameter ejection pin in it resulting in a different meplat diameter. Even with the same die bullets made in a different setup may have a slightly different meplat diameter. The reason the press operator sets the dies up slightly different each time depending on the jackets, lube etc. New bullet means reset the trimmer.
I advise my customers to trim only what is needed to get a clean cut. Depending on the bullets that may not even clean up the entire meplat. If it cuts cleanly and only cleans up 75% then that's great. It's the 80-20 rule. Take care of 80% of problem and the other 20% will dissappear. Hope this helps.
Dave
Whether it's my trimmer or others on the market all are going to cut a meplat very close to the same diameter. Trimming the meplats reduces the BC by about 2% If after trimming the meplats you have a variation in diameter of say .005" on a meplat that measures .065" that's only a 7.7% variation over 2% of the BC. 2% of .600 BC is .0012 then figure in a 7.7% variation in that and .005" doesn't mean much. Within reason it's all about shape which effects in flight yaw.
Now if you go to different bullet with a different ogive you've gone to a different point up die and may well have a different diameter ejection pin in it resulting in a different meplat diameter. Even with the same die bullets made in a different setup may have a slightly different meplat diameter. The reason the press operator sets the dies up slightly different each time depending on the jackets, lube etc. New bullet means reset the trimmer.
I advise my customers to trim only what is needed to get a clean cut. Depending on the bullets that may not even clean up the entire meplat. If it cuts cleanly and only cleans up 75% then that's great. It's the 80-20 rule. Take care of 80% of problem and the other 20% will dissappear. Hope this helps.
Dave
Dave Tooley
Active member
Tom
It was ogive to base.
It was ogive to base.
G
Greg Culpepper
Guest
Dave,
Am I inferring correctly that bc variation is principally the product of varying in flight yaw as induced by ragged meplats and not so much directly the result of meplat variations that affect the pointedness of bullets but don't induce variations in the magnitude of in flight yaw?
Greg
Am I inferring correctly that bc variation is principally the product of varying in flight yaw as induced by ragged meplats and not so much directly the result of meplat variations that affect the pointedness of bullets but don't induce variations in the magnitude of in flight yaw?
Greg
Dave Tooley
Active member
Greg
I can't say with certainty that what's happening but it makes sense that the two are linked. This all stared with the results of a test shot at 1000 yds with 30 different bullets. The tipped bullets had the lowest BC spread. They all had exactly the same tip profile. Ok lets trim the standard HP bullets and see what happens. The BC spread went down. Then I installed tips in HP's, spread stayed low and BC increased. Then one day at Hawks Ridge I observed that the bullets were cutting cleaner holes, meplat in the center, at 1K. I already knew there was something to this from my short range days. A barrel that would cut very clean holes at 200 yds. was going to perform better in the wind. Sort of backed into this idea but it makes sense to me.
Dave
I can't say with certainty that what's happening but it makes sense that the two are linked. This all stared with the results of a test shot at 1000 yds with 30 different bullets. The tipped bullets had the lowest BC spread. They all had exactly the same tip profile. Ok lets trim the standard HP bullets and see what happens. The BC spread went down. Then I installed tips in HP's, spread stayed low and BC increased. Then one day at Hawks Ridge I observed that the bullets were cutting cleaner holes, meplat in the center, at 1K. I already knew there was something to this from my short range days. A barrel that would cut very clean holes at 200 yds. was going to perform better in the wind. Sort of backed into this idea but it makes sense to me.
Dave
G
Greg Culpepper
Guest
Dave,
It makes sense to me to. Food for thought for sure. You know it has been popular for decades to claim (in the popular press at least) that bullet bases and jacket/core concentricity must be close to perfect to minimize yaw but points don't affect accuracy (much). Maybe this is an example of once you attend to the bigger issues, the smaller ones emerge from the noise.
Greg
It makes sense to me to. Food for thought for sure. You know it has been popular for decades to claim (in the popular press at least) that bullet bases and jacket/core concentricity must be close to perfect to minimize yaw but points don't affect accuracy (much). Maybe this is an example of once you attend to the bigger issues, the smaller ones emerge from the noise.
Greg
G
gonehunting378
Guest
what was the combo that made the meplat hole in the center of the black? none of my stuff has ever been centered up like this, now i will lose sleep over that toooooo, thanks alot dave.
tom
tom
Dave Tooley
Active member
Tom
Assuming you have good bullets to start with all that's needed is to trim the meplats. As Greg pointed out for 1K benchrest BC isn't that important but in F-Class and HP shooting it is because of slow shot strings. So trimming and pointing is the way to go, said with reservations. I've been shooting BIB 187 gr. FB bullets for years with some success. That bullet holds both the NBRSA and IBS Heavy Gun small group record. Good bullet made better by meplat trimming. I think it's all about a uniform shape. Remember as a kid or as an adult sticking your hand out the window of a car into the wind and how small an angle into the wind it took to exert a force on your hand. There are counter balancing forces that keep the bullet flying point on but they never completey cancel out the inflight yaw with a hook nose bullet.
Dave
Assuming you have good bullets to start with all that's needed is to trim the meplats. As Greg pointed out for 1K benchrest BC isn't that important but in F-Class and HP shooting it is because of slow shot strings. So trimming and pointing is the way to go, said with reservations. I've been shooting BIB 187 gr. FB bullets for years with some success. That bullet holds both the NBRSA and IBS Heavy Gun small group record. Good bullet made better by meplat trimming. I think it's all about a uniform shape. Remember as a kid or as an adult sticking your hand out the window of a car into the wind and how small an angle into the wind it took to exert a force on your hand. There are counter balancing forces that keep the bullet flying point on but they never completey cancel out the inflight yaw with a hook nose bullet.
Dave
I'm not saying Dave is wrong in that meplat trimming reduces yaw. What we know for sure from both Dave and Larry Bartholomew's testing is that bullets with a consistent nose profile have less variation in BC. Maybe in-fligh yaw is reduced. But if you ever play with the variables on bullet shape, you'll note that the meplat and ogive have the greatest impact on drag (BC). (http://www.jbmballistics.com/cgi-bin/jbmdrag-5.0.cgi)
Whether it is just the consistent shape or whether it is a reduction in yaw -- or both -- the point remains that meplat trimming results in a lower SD/ES for drag (B.C.), and that shows on the target.
Whether it is just the consistent shape or whether it is a reduction in yaw -- or both -- the point remains that meplat trimming results in a lower SD/ES for drag (B.C.), and that shows on the target.