Bullet OAL vs. BOGive - related to pointing & trimming

[roklock]

Hello,

So this winter I figured I am going to see what if any value pointing and trimming the meplat could be. The goal is to improve consistency in vertical. I shoot 600 & 1000 yard matches in bench and F-class.

So I sorted some unprocessed bullets base to ogive then I decided to measure my largest sorted set for OAL. I was shocked to see they varied anywhere from -.002-+.010.

Should I trim them all to the same length, then close up tips by pointing? Thinking that they need to be the same length to be consistent with the pointing.

Thanks for any input.

Steve

 

[Nick Caprinolo]

In most cases total length is irrelevant. The ogive is what most pay attention to. Mostly Ogive is a constant in a batch of bullets. It will vary a bit though.

 

[roklock]

In most cases total length is irrelevant.

Yes, all I did previously was base to Ogive but now that I am going to try pointing I added the step of measuring OAL, not sure how I can create a consistent point if I don't sort by OAL.

That is my question though, do I trim the meplat to the shortest OAL then point or is there a +/- factor that pointing die will work with?

 

[Ned Ludd]

Hello,

So this winter I figured I am going to see what if any value pointing and trimming the meplat could be. The goal is to improve consistency in vertical. I shoot 600 & 1000 yard matches in bench and F-class.

So I sorted some unprocessed bullets base to ogive then I decided to measure my largest sorted set for OAL. I was shocked to see they varied anywhere from -.002-+.010.

Should I trim them all to the same length, then close up tips by pointing? Thinking that they need to be the same length to be consistent with the pointing.

Thanks for any input.

Steve

You may wish to try several different trimming approaches and see which you like the best. I personally sort bullets into OAL groups of .0015", then point directly without trimming. I am very happy with the results. Others like to trim the shortest bullet just barely enough to uniform/flatten the meplat, then trim all longer bullets to the same length. However, trimming a much longer bullet to the same length as the shortest will caused the resulting [trimmed] meplat diameters of the two bullets to be different. IMO - the two bullets will not point up exactly the same, and can never be made to do so. To address this issue, you can first sort into groups by OAL, then trim and point from within a single length group. These are probably the most common approaches. You can play around with your pointing setup and see what works best in your hands.

Edited to add - because I don't trim bullets, I want to keep the bullet OAL within 1.5 to 2 thousandths. Sorted bullets within that length range can all be pointed without having to change the die micrometer setting. Once you have determined the optimal die micrometer setting for a single OAL group, if you need to point bullets from another length group, simply adjust the die by length difference between the two sort groups. In my hands, using bullet length groups much longer than about 2 thousandths will start to generate points that are not uniform in length to the naked eye. I typically get about 6 to 8 total sorted OAL groups from a single Lot# of Berger bullets, with both the longest and shortest OAL groups possibly having a very few "extreme" OAL outliers.

 

[Nick Caprinolo]

While I don't bother with the meplet, the object, as I understand it, is to have a uniform shape to the end of the bullet.

I would trim all to the same shape and seat the bullet according to the ogive. Ogive uniformity is the measurement everyone strives for.

Also you have to be very careful that by trimming, you do not have bullets of different weights. You are striving for the same point of impact by using exact powder measurements. Vary the bullet weight and point of impact may change dramatically.

 

[roklock]

You may wish to try several different trimming approaches and see which you like the best. I personally sort bullets into OAL groups of .0015", ....

Thanks Ned, extremely useful information.

 

[Ned Ludd]

Thanks Ned, extremely useful information.

Whatever approach you decide to use, I would recommend some side-by-side testing at 300+ yards. I can see the effect of pointed versus unpointed bullets at 300 yd. Although the difference is typically small at that distance, pointed bullets normally require 0.125 to 0.25 MOA less elevation than unpointed to "center" a group. The difference should increase with distance. I generally also see tighter groups with pointed bullets. Regardless of the method used, IMO the real key to pointing bullets is moderation. I set the pointing die to close the meplats anywhere from about 50-75%. It is not necessary to completely close the meplat to achieve some benefit from pointing. If you do, you may run the risk of "over-pointing" the bullets, thereby creating a bulge behind the point, which is not desirable.

Good luck with it.

 

[mikecr]

Consistent Ogive radius establishes sound datums, but there is nothing you can do about this other than measure and cull out differences. That's not BTO, OAL, or nose length, but radius.
Never trim all of anything to a worst value (an anomaly).
Ned's approach is pretty good. There can still be ogive radius variance in it, while unmeasured, but he is getting good points, and with lower efforts.

The object with meplat trimming is to get the bullets you're going to use(not all) at the same diameter (normalizing BC).
Pointing from this same diameter, if within a good range, regains lost BC from trimming while again normalizing BC.
There is the Whidden system from bullet bases, and Hoover from ogives. I believe Hoover's is best. Especially if ogives were pre-qualified with a Bob Green Comparator (BGC).

 

[roklock]

Thanks again Ned, appreciate the further detail. I plan to do my testing at distances beyond 600 yards.

There is the Whidden system from bullet bases, and Hoover from ogives. I believe Hoover's is best. Especially if ogives were pre-qualified with a Bob Green Comparator (BGC).

Thanks Mike, I have purchased the Hoover trimmer and pointer. I have been using the Holland gold to measure the BTO. How are you measuring the radius and at the same time making sure you are measuring all bullets at the same exact spot?

 

[mikecr]

I don't care about BTO, but I care about ogive radius, which qualifies all nose datums (incl. your BTO measure and Hoover results).
For ogive radius comparison you can use a Bob Green Comparator (BGC).

 

[dcali]

Sort by OAL into tight groups if you're going to point. I don't get why people trim at all. The whole point is to change the shape of the bullet nose to a more optimal drag configuration. You can do that by sorting by OAL. Trimming just shortens the bullet which is bad for BC. And it isn't necessarily going to give you a consistent point unless you've already sorted them by length prior to trimming. What Ned Ludd is doing is the right way, in my opinion.

 

[roklock]

Sort by OAL into tight groups if you're going to point. I don't get why people trim at all. The whole point is to change the shape of the bullet nose to a more optimal drag configuration. You can do that by sorting by OAL. Trimming just shortens the bullet which is bad for BC. And it isn't necessarily going to give you a consistent point unless you've already sorted them by length prior to trimming. What Ned Ludd is doing is the right way, in my opinion.

Thanks for the response, again still trying to understand all of this and I don't understand why you say trimming doesn't make sense.

So, bullets have a ragged meplat. I have measured OAL and have from -0.002 to +0.010, why not trim that spread into 2 or 3 groups and then point? I thought pointing reshaped the nose and "closed" the nose to a uniform point. I was figuring the pointing won't be consistent if I don't trim due to the ragged meplat my bullets have. I am going to do some "testing" this winter of trimmed and pointed, pointed only, and stock from box to see what results I get.

 

[Bc'z]

@rokloc, from what I've observed @damoncali makes a bullet that visually dosen't have a ragged meplat, it's more of a radius and quite uniform in appearance.
All of this is a mute point unless your shooting 200gr .30's

 

[roklock]

@rokloc, ...
All of this is a .ute point unless your shooting 200gr .30's

Thanks, I didn't realize he manufactured custom bullets. I am shooting a straight 284 win, 180 grain bullets, in F-Class and long range benchrest, why do you think anything below a heavy 30 caliber bullet is a mute point?

 

[Bc'z]

Thanks, I didn't realize he manufactured custom bullets. I am shooting a straight 284 win, 180 grain bullets, in F-Class and long range benchrest, why do you think anything below a heavy 30 caliber bullet is a mute point?

At the moment it's all he makes.
Here's a look at his work on these dummy rounds, you can see the meplat uniformity.
Bbto and weight are pretty uniform also.

 

[dcali]

Thanks for the response, again still trying to understand all of this and I don't understand why you say trimming doesn't make sense.

So, bullets have a ragged meplat. I have measured OAL and have from -0.002 to +0.010, why not trim that spread into 2 or 3 groups and then point? I thought pointing reshaped the nose and "closed" the nose to a uniform point. I was figuring the pointing won't be consistent if I don't trim due to the ragged meplat my bullets have. I am going to do some "testing" this winter of trimmed and pointed, pointed only, and stock from box to see what results I get.

The reason I like it is that you get the benefits of sorting by OAL and pointing without having to shorten any bullets. And it’s easier to sort than trim. I suppose if the meplat is ragged enough that it makes pointing a problem, you’d have not choice but to trim. Whatever works is what you should do.

I’m not an expert on pointing, though, as I’ve seen too many guys jack up bullets by getting overzealous about it. The ones I see doing it successfully are generally length sorting. Some are also trimming, but that’s a bit much if you ask me.

My bullets are weird in this regard and shouldn’t be pointed. The rounded nose is already “pointed”, and it’s done in one operation as the ogive is formed. In fact, this issue is partly what drove the design. I was thinking about things that could be done to better optimize the tip without a pointing operation and George Ulrich, who made the dies, mentioned that he had made short range benchrest bullets with a rounded meplat that shot well and had very consistent OALs. That sounded great to me, because old military (BRL, if I recall correctly) experiments found that a hemispherical tip has roughly 10% less nose drag than a flat tip. So we gave it a whirl, and it works really well.

 

[Texas10]

I would like to see a close examination of how meplat shape affects supersonic shock wave formation while using Schlieren photography. This may shed valuable light on how meplat design affects ballistic performance. If nothing else, it would be very entertaining.

 

[mikecr]

Meplat diameter can have a huge affect on drag. Reducing drag as the meplat gets smaller, to a point where drag goes back up some(I think <15thou).
The object in all of this is not to get the same OAL, but the same drag.

So whatever your method, trim/point, point/trim, it should be taken from an ogive qualified datum (not OAL).
And which applies everywhere -don't take it all to the worst in batch.