Meplat trimming only

[AJC]

Is it worth trying to meplat trim only to have more consistency in bc than not trimming at all. If consistancy is king I had considered trying trimming my 175 SMKs because the tips are so wildly different. Pointing seems to have the possibility of again cause variation unless done with great skill.....

 

[RegionRat]

You have answered your own question pretty well.

Meplat trimming is for reducing variation and bullet pointing is for BC.

They can be independent or combined.

 

[rwj]

Doubtful that either will have much impact on POI unless you’re shooting at distances over 300 yards...

 

[JohnKielly]

My experience is if you trim with a trimmer that indexes off the base, your trim diameter will be scattered, not uniform.

If you trim with a trimmer that indexes off the ogive, you'll likely come up with at least two batches of meplat diameter. That's when I separate them & point each batch separately. Pointing also serves to move any "swarf" from the cutting procedure away from the edge of the point.

 

[Ned Ludd]

Is it worth trying to meplat trim only to have more consistency in bc than not trimming at all. If consistancy is king I had considered trying trimming my 175 SMKs because the tips are so wildly different. Pointing seems to have the possibility of again cause variation unless done with great skill.....

I regularly estimate at JBM Ballistics BCs using LabRadar velocity drop data. Even straight out of the box, the BCs of most bullets for which I've made estimates are consistent enough you would not be able to discern the difference in point of impact solely due to BC variance, even at distances of 600 yd or more. You can run the numbers yourself for estimated individual bullet BCs, but you will likely find that the difference in the predicted point of impact due to BC variance is much less than the general precision of the rifle/load. In other words, it's not usually going to be the limiting factor in terms of precision.

With that in mind, I view the primary function of trimming and pointing bullets to be the increase in BC. Even though it's typically relatively small, on the order of 3-5% or so, it's still an increase and might mean the difference in a point or two in an F-Class match, which could be the difference between winning and not winning. I personally find trimming bullets to be a large PITA. For that reason, years ago I tested the difference between bullets that had been trimmed and pointed, versus pointed only. In my hands, there was not a significant difference between the two approaches in terms of the average BC.

Since that time, I point bullets without trimming first. I sort bullets straight out of the box into overall length groups of .0015". I can do this while watching TV, as opposed to trimming, which by necessity forces me to be at the reloading bench where the trimmer is mounted. For example, one length group would be 1.2500"-1.2515", the next longest group would be 1.2520"-1.2535". Out of a typical Lot# of Berger bullets, I will usually get about 8 different lengths groups that are sufficient to cover the entire Lot, with the caveat that there will always be a few extreme outliers in the very shortest and longest length groups, that fall outside the range of those length groups. It is easily possible to length sort several hundred of bullets in an hour or less. Most of the time when using this sorting approach, you will find a reasonable Gaussian distribution (i.e. a "bell curve"). That is, the groups in the center of the overall range have the highest number of sorted bullets, and the numbers in groups toward the low or high end have fewer bullets. I typically use the bullets from the longest/shortest length groups solely as foulers/sighters, or for practice, so I'm less concerned with the outliers. Nonetheless, you can always re-measure bullets in either of those two groups to cull the extreme outliers if desired.

Once the bullets are length-sorted, I carefully adjust the pointing die, starting with the micrometer dialed out past the point where it will ultimately be set for a given length group. I dial it down in small increments until the point is visually where I want it to be. That is, the meplat will be closed up from about 50-75%, and the size/length of the point is not too large. If you're using the correct pointing insert for the specific bullet you're using, this is really not too difficult to achieve. Your eyeball is more than sensitive enough to do it properly. Don't waste your time trying to close the meplat up any more than this. It won't generate much further increase in BC, and you run the risk of generating a "bulge" in the bullet ogive below/behind the point. Once I have a bullet from a single length group pointed satisfactorily, I record the micrometer setting. From that point on, it is only necessary to add/subtract the difference between any length group you have to determine the correct pointing die micrometer setting for a different length group (i.e. add/subtract .002" per length group). Although the length-sorted bullets should only differ by .0015" within a given group, the overall difference between groups will be .002", if you subtract the length of longest or shortest bullet in any group from the respective longest or shortest bullet from an adjacent length group. In my hands, the length variance of .0015" within a single length-sorted group is not sufficient to create a need to sort them into finer length increments, or to change the die micrometer setting when pointing bullets from the same length group. So I just use bullets all from the same length group, then set the die micrometer and start pointing.

In summary, I would suggest you give length sorting and pointing (without trimming) a shot, and see if it works out for you. I know quite a few others that regularly use this approach for F-Class shooting, because it works. When you point a bullet without trimming first, you are moving the somewhat jagged edge of the meplat in closer to the bullet longitudinal axis of rotation, which minimizes any negative effect it might have on BC and trajectory. In theory, if you pushed the jagged meplat edge all the way down to touching the longitudinal axis of rotation, its effect would disappear entirely. Nonetheless, it's not necessary to close the meplat all the way. As I mentioned, closing it 50-75% will buy you the desired increase in BC, without worry of creating a bulge behind the tip. In my estimation, a little goes a long way when pointing bullets, so a conservative approach is warranted.

I think if you try this approach, you will find that it gives you what you're after (i.e. an increase in BC and consistency), without the trouble of trimming first. Trimming bullets alone is not likely to do what you're wanting it to do. I'm not sure how much you can increase the BC consistency, because due to typical bullet nose length/ogive variance within a Lot# of bullets, you'll end up with trimmed, flat meplats of different diameter, unless you length sort the bullets first. If anything, the difference in the diameter of bullet meplats that are trimmed only (i.e. not length-sorted first) will increase the BC variance. This effect is largely abrogated when the bullets are trimmed first, then pointed, which is why most people that trim also point their bullets after trimming. Further, if you have to length-sort bullets prior to trimming alone, you're already halfway to being finished using the length-sorting then pointing approach. All you really need to try this approach is a decent set of calipers and a pointing die with the correct insert for your bullet of choice. If you know someone with a pointing die that would let you try it out as a test, you'd only need the calipers, which every reloader usually already has.

 

[DocBII]

AJC,

Trimming alone works fine for me out to 1k as long as I'm not worried about that last little bit of BC or velocity. I don't worry too much about meplat diameter, but I do try to keep the bullet overall length and the ogive length to plus or minus 0.002". My trimmer measures off the ogive, and I sort by ogive length before trimming.

If you are going to point, do it after trimming and don't over point. Better too little than too much.

HTH,
DocBII

 

[AJC]

I regularly estimate at JBM Ballistics BCs using LabRadar velocity drop data. Even straight out of the box, the BCs of most bullets for which I've made estimates are consistent enough you would not be able to discern the difference in point of impact solely due to BC variance, even at distances of 600 yd or more. You can run the numbers yourself for estimated individual bullet BCs, but you will likely find that the difference in the predicted point of impact due to BC variance is much less than general precision of the rifle/load. In other words, it's not usually going to be the limiting factor in terms of precision.

With that in mind, I view the primary function of trimming and pointing bullets to be the increase in BC. Even though it's typically relatively small, on the order of 3-5% or so, it's still an increase and might mean the difference in a point or two in an F-Class match, which could be the difference between winning and not winning. I personally find trimming bullets to be a large PITA. For that reason, years ago I tested the difference between bullets that had been trimmed and pointed, versus pointed only. In my hands, there was not a significant difference between the two approaches in terms of the average BC.

Since that time, I point bullets without trimming first. I sort bullets straight out of the box into overall length groups of .0015". I can do this while watching TV, as opposed to trimming, which by necessity forces me to be at the reloading bench where the trimmer is mounted. For example, one length group would be 1.2500"-1.2515", the next longest group would be 1.2520"-1.2535". Out of a typical Lot# of Berger bullets, I will usually get about 8 different lengths groups that are sufficient to cover the entire Lot, with the caveat that there will always be a few extreme outliers in the very shortest and longest length groups, that fall outside the range of those length groups. It is easily possible to length sort several hundred of bullets in an hour or less. Most of the time when using this sorting approach, you will find a reasonable Gaussian distribution (i.e. a "bell curve"). That is, the groups in the center of the overall range have the highest number of sorted bullets, and the numbers in groups toward the low or high end have fewer bullets. I typically use the bullets from the longest/shortest length groups solely as foulers/sighters, or for practice, so I'm less concerned with the outliers. Nonetheless, you can always re-measure bullets in either of those two groups to cull the extreme outliers if desired.

Once the bullets are length-sorted, I carefully adjust the pointing die, starting with the micrometer dialed out past the point where it will ultimately be set for a given length group. I dial it down in small increments until the point is visually where I want it to be. That is, the meplat will be closed up from about 50-75%, and the size/length of the point is not too large. If you're using the correct pointing insert for the specific bullet you're using, this is really not too difficult to achieve. Your eyeball is more than sensitive enough to do it properly. Don't waste your time trying to close the meplat up any more than this. It won't generate much further increase in BC, and you run the risk of generating a "bulge" in the bullet ogive below/behind the point. Once I have a bullet from a single length group pointed satisfactorily, I record the micrometer setting. From that point on, it is only necessary to add/subtract the difference between any length group you have to determine the correct pointing die micrometer setting for a different length group (i.e. add/subtract .002" per length group). Although the length-sorted bullets should only differ by .0015" within a given group, the overall difference between groups will be .002", if you subtract the length of longest or shortest bullet in any group from the respective longest or shortest bullet from an adjacent length group. In my hands, the length variance of .0015" within a single length-sorted group is not sufficient to create a need to sort them into finer length increments, or to change the die micrometer setting when pointing bullets from the same length group. So I just use bullets all from the same length group, then set the die micrometer and start pointing.

In summary, I would suggest you give length sorting and pointing (without trimming) a shot, and see if it works out for you. I know quite a few others that regularly use this approach for F-Class shooting, because it works. When you point a bullet without trimming first, you are moving the somewhat jagged edge of the meplat in closer to the bullet longitudinal axis of rotation, which minimizes any negative effect it might have on BC and trajectory. In theory, if you pushed the jagged meplat edge all the way down to touching the longitudinal axis of rotation, its effect would disappear entirely. Nonetheless, it's not necessary to close the meplat all the way. As I mentioned, closing it 50-75% will buy you the desired increase in BC, without worry of creating a bulge behind the tip. In my estimation, a little goes a long way when pointing bullets, so a conservative approach is warranted.

I think if you try this approach, you will find that it gives you what you're after (i.e. an increase in BC and consistency), without the trouble of trimming first. Trimming bullets alone is not likely to do what you're wanting it to do. I'm not sure how much you can increase the BC consistency, because due to typical bullet nose length/ogive variance within a Lot# of bullets, you'll end up with trimmed, flat meplats of different diameter, unless you length sort the bullets first. If anything, the difference in the diameter of bullet meplats that are trimmed only (i.e. not length-sorted first) will increase the BC variance. This largely effect is abrogated when the bullets are trimmed first, then pointed, which is why most people that trim also point their bullets after trimming. Further, if you have to length-sort bullets prior to trimming alone, you're already halfway to being finished using the length-sorting then pointing approach. All you really need to try this approach is a decent set of calipers and a pointing die with the correct insert for your bullet of choice. If you know someone with a pointing die that would let you try it out as a test, you'd only need the calipers, which every reloader usually already has.

That's not what I expected to hear at all, thank the lord I asked before buying anything. I really appreciate the depth and explanation in your response. Have a wonderful night.

 

[AJC]

AJC,

Trimming alone works fine for me out to 1k as long as I'm not worried about that last little bit of BC or velocity. I don't worry too much about meplat diameter, but I do try to keep the bullet overall length and the ogive length to plus or minus 0.002". My trimmer measures off the ogive, and I sort by ogive length before trimming.

If you are going to point, do it after trimming and don't over point. Better too little than too much.

HTH,
DocBII

This plan matches my initial thoughts, what bullets are you doing this to and I'm curious if that makes a big or little impact on if it works well.

 

[JEFFPPC]

I shot custom 106 bullets for years.Did well with them. The tipped 107 SMKs came out so I tried them. They shoot just as well as the customs, maybe mreasure even a tad more uniform, plus they took a minute and a half off my 1000 yd elevation. That means they get there quicker, so less wind deflection.

 

[mikecr]

As far as what affects BC from the nose, Meplats are by far the largest drag influence.
The last thing you need to do is vary meplat diameters(MD) just to get nose lengths the same..
I agree with the pointer folks, as it's easier to normalize MD with pointing.
Sure wish there was viable way to measure MDs..

 

[DocBII]

This plan matches my initial thoughts, what bullets are you doing this to and I'm curious if that makes a big or little impact on if it works well.

AJC,

I've been doing this since the early aughts and mostly just trim at this time. If velocity is marginal (below 1300 f/s at target), use a bigger cartridge or better bullet.

I've done Bergers, Hornadys, Sierras, JLKs, Normas and Lapuas. Calibers done are .223, 243, 6.5, 30 and .338. VLD, hybrid and standard ogives. Sorting and trimming as previously mentioned improved vertical on them. Works well enough for me to keep trimming, pointing is optional.

HTH,
DocBII

 

[tom]

It's no problem to buy some good tools, just don't do all your bullets at whatever settings because they look perfect. Go test, consider it part of tuning. Like Ned wrote, I too have had pretty good luck with measuring and then pointing as a definite gain in vertical/precision. Not in every instance however. I've had poor luck at times when introducing a trimmer, whether it be "only", or in conjunction with pointing after. But again, not in every instance. I just consider it part of tuning a barrel/bullet, and advise to do the load development with sorted unmolested bullets. It is possible to make them shoot poorer precision without doing actual damage to them.

My 2 cents, although I've spent a great deal of dollars "trying stuff" lol

Tom

 

[DocBII]

mikecr,

Get a drill diameter measuring gauge. It's close enough.

Three points determine a curve. If you sort by ogive length then trim the point with a device that measures from any other point on the ogive, you'll get a fairly consistent length and diameter as long as the jacket thickness is consistent.

Edited to add: And the if the ogive is consistent as well.

HTH,
DocBII

 

[JohnKielly]

My experience is if you trim with a trimmer that indexes off the base, your trim diameter will be scattered, not uniform.

If you trim with a trimmer that indexes off the ogive, you'll likely come up with at least two batches of meplat diameter. That's when I separate them & point each batch separately. Pointing also serves to move any "swarf" from the cutting procedure away from the edge of the point.

One thing I didn't mention was that I have concluded that meplatting off the ogive avoids the need to measuring the base to ogive length, as they appear to be directly related.

 

[Ned Ludd]

AJC - as Tom, John, and others have noted, the best thing is really to do some testing yourself, and determine empirically what works best in your hands. As I mentioned, if you know someone that has a meplat trimmer and/or pointing die, they will probably let you borrow/use them to set up your tests with a few bullets. You really won't need all that many to reach some kind of conclusion. I'd suggest starting with [unmodified] bullets straight out of the box, length-sorted (OAL) only, length-sorted and trimmed (but NOT pointed), length-sorted and pointed (but NOT trimmed), and length-sorted, trimmed, and pointed. That's only five different test groups, but they ought to be sufficient to point you in a direction. Then you can decide whether you wish to buy additional equipment of your own, based directly on your own test results.