Bullet Pointing
- Thread starter rwj
- Start date
Dusty Stevens
Shiner
rwj
Gold $$ Contributor
Rats! At least they looked nice!
Ned Ludd
Silver $$ Contributor
I've shot in a 300 yd F-Class match using both unpointed and pointed bullets in otherwise identical loads in sequential relays on a number of occasions. I have observed both improved BC (higher elevation on target) and more consistent grouping on the target with pointed bullets. One caveat - I sort bullets by OAL prior to the pointing process into length groups of .0015". I have never compared bullets that were length-sorted only to those both length-sorted and pointed, so I can't say what the relative contribution of the length sorting process might have been, particularly with respect to better group consistency.
Is there an advantage for the higher BC bullet regarding group size, if there are any inconsistent winds?
Dusty Stevens
Shiner
Theoretically there is but im sure its offset by the damage done to the jacket/core relationship
Bryan Litz co-designed the Whidden bullet pointing die system.
If I were making a bet, I would go more with the theory that there is a net accuracy benefit with a pointed bullet. The advantage will become larger, the greater the distance, obviously - 300 yards may be too short to generate a difference.
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Ned Ludd
Silver $$ Contributor
This is simply pure disinformation. The jacket/core relationship is not damaged if the bullets are pointed correctly. If they're improperly pointed, that's the user's fault, not the pointing process. I'm guessing Dusty does not point bullets and apparently doesn't approve of the process. Other readers might want to keep that in mind for his responses to this thread.
BC, in and of itself, really has little to do with "grouping", if you're using the term in the most common way. The only thing higher BC realistically buys you is greater resistance to wind deflection. If shot dispersion was solely caused by wind deflection, at a sufficient distance and under a sufficient wind condition, the higher BC bullet should always theoretically print smaller "groups" than the lower BC bullet when fired at comparable velocity. That is because the higher BC bullets would be deflected on average to a lesser degree in any given wind condition than the lower BC bullets, so theoretically, the group horizontal dispersion would always be less.
Unfortunately, shot dispersion isn't caused solely by wind deflection. So that is not what we typically mean by "grouping", at least as far as load development/precision is concerned. Because of the [sometimes very] poor uniformity found in the meplats of commercial target bullets, pointing meplats also has the potential to improve the uniformity of the bullet nose, an effect that can easily improve "grouping", an effect noticeable even at short range or under dead calm wind conditions.
If you want to take the time, you can read the forums here over some period of time and form some idea for yourself of which disciplines are, or are not, using bullet pointing as a common practice. In F-Class shooting, the course of fire is typically 20 shots + sighters/foulers over a 22 to 30 minute time period. During that relatively long time period, the wind conditions are often changing constantly and you will typically lose far more points to missed wind calls than any other cause. A load that will print groups at 100 yd in the 0.1s doesn't mean a whole lot when you're shooting long strings of fire at 1000 yd in challenging wind conditions. So reloading and/or shooting strategies that might work well in other disciplines don't necessarily always carry over to F-Class. The reverse is also true. In other words, you should use the approaches that have been proven to work in your specific discipline.
For that reason, many F-Class shooters choose to point bullets, because it buys a small increase in BC, which by definition also means a small benefit in decreased wind deflection. Typically, the BC increase is not large; typically on the order of about 3-5% over unpointed bullets. However, if a shooter has the ability to make reliable wind calls at that distance to within a 3 mph spread, even that small increase in BC is sufficient to make the difference of one or two dropped 9s just barely outside the 10-ring during the course of a match. We're not talking about a quantum leap in performance here. However, in this day and age in F-Class, even that small improvement in BC can mean the difference between winning and not winning. The score margins are often very small, so every little bit can help.
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1shot
Gold $$ Contributor
I don't point my bullets for 600 and in as I feel it is a waste of time. However, all my 1K loads get trimmed and pointed. I have found the new bullets that are long and heavy for caliber seem to have a larger discrepancy in OAL than their lighter counterparts. I have found an ES in OAL of up to .013 in multiple lots of bullets. Through testing at 1K proved to me that the outlying lengths always are out of group of equal length bullets.
I hope this helps,
Lloyd
I hope this helps,
Lloyd
I Meplat trim & point the bullets I use in the British commonwealth match rifle event over 1000-1200 yards for 2 reasons:
- Meplatting & sorting on resultant meplat diameter allows me to make the same sort that I would achieve by measuring base to ogive at the same time as I clean up the front end. Two for one is always good, particularly when I've found most devices to to compare ogives are not particularly repeatable
- I have come to expect that at the maximum distance my third maybe second standard deviations are tighter.
Pointing makes a small improvement in BC, but should also make the effective BCs of the bullets used in a match more consistent. That is for the straightforward reason that if meplat sizes / shapes vary enough, the drag each bullet suffers in flight varies too as a result. More consistent drag / average BC should reduce elevation spreads on the targets and the longer the range, the greater any benefit obtained. I'd not expect to see a noticeable improvement at 300 yards though.
I've found it to be rather bullet specific on a purely subjective / empirical approach, so I'd never claim any scientific validity for my views. I won't point 90gn 224s as it seemed to detract from L-R performance for me. (Many avid 223 L-R F-TR competitors say the opposite and to them pointing is a key ingredient in the 1,000 yard precision 'mouse gun'.) I saw neither improvement nor deterioration with the 155.5gn Berger in 308 Win, so gave up on that one. Against those experiences, a combination of BTO batching, trimming and pointing transformed the 1,000 yard elevation consistency of the early pre-factory pointing Sierra 7mm 180gn MKs that I use in my 284.
Group patterns / size aside which are affected by no end of factors, with the widespread introduction of microphone technology electronic targets that measure velocities at the target, it should now be straightforward to identify any improvement (or maybe the word that should be used here is change) in BC consistency and value. That is, if BCs really are more consistent, the velocity spreads at the target should be less than for unpointed examples all other factors being unchanged. If BCs are improved, the average retained velocity should be slightly higher than for the same bullets without pointing. That assumes of course that this feature of electronic targets measures speeds accurately enough to draw valid conclusions from the results. This should be a more valid way of checking pointing's effect than whether more or less sight elevation is needed and what sort of group is being produced - although, the experienced competitor who shoots enough groups or takes place in enough L-R matches is going to have a vedry good idea as to what works or not in practice.
I've found it to be rather bullet specific on a purely subjective / empirical approach, so I'd never claim any scientific validity for my views. I won't point 90gn 224s as it seemed to detract from L-R performance for me. (Many avid 223 L-R F-TR competitors say the opposite and to them pointing is a key ingredient in the 1,000 yard precision 'mouse gun'.) I saw neither improvement nor deterioration with the 155.5gn Berger in 308 Win, so gave up on that one. Against those experiences, a combination of BTO batching, trimming and pointing transformed the 1,000 yard elevation consistency of the early pre-factory pointing Sierra 7mm 180gn MKs that I use in my 284.
Group patterns / size aside which are affected by no end of factors, with the widespread introduction of microphone technology electronic targets that measure velocities at the target, it should now be straightforward to identify any improvement (or maybe the word that should be used here is change) in BC consistency and value. That is, if BCs really are more consistent, the velocity spreads at the target should be less than for unpointed examples all other factors being unchanged. If BCs are improved, the average retained velocity should be slightly higher than for the same bullets without pointing. That assumes of course that this feature of electronic targets measures speeds accurately enough to draw valid conclusions from the results. This should be a more valid way of checking pointing's effect than whether more or less sight elevation is needed and what sort of group is being produced - although, the experienced competitor who shoots enough groups or takes place in enough L-R matches is going to have a vedry good idea as to what works or not in practice.
Dusty, if you sort them by base to ogive and bearing surface. OAL length varies the most have seen .060 in some custom bullets and it doesn't matter? Factory stuff is even worse. I sort +-.0005 in base to ogive and bearing surface. Then trim and point being very careful not to disturb any prior measurement, they must grow I'm length to know you are doing it correctly and never try to close the meplate. I can see gains at 300 but if you don't, you may have done something wrong or your equipment isn't up to the level you need..... jim
dcali
Bullet Maker
A few random comments on pointing:
1) Small variations in bullet length will impact BC slightly, pointed or not. Longer bullets will have a _slightly_ higher BC.
2) Plenty of people point successfully without damaging bullets. You don't have to look too far to find people who have screwed them up, however.
3) Some unpointed bullets have larger meplats than others. This matters, because there is an optimum diameter for a given a bullet length. It's not zero, but somewhere in the neighborhood of 0.1-0.2 calibers. .031-.062 for a .308 bullet, for example - you'll find a lot of modern match bullets are already in that range or very close to it - maybe 0.050-.070.
4) Mileage may vary - the data that the conventional wisdom in #3 can be traced back to BRL/NACA experiments from long ago. To the best of my knowledge, there's nothing out there that definitively quantifies the impact of meplat geometry that exactly matches the way our pointing dies do it. I would expect it to be very close to those numbers but the data I'm aware of is based on flat (truncated) noses and hemispherical noses, not the sort-of-concial points that we tend to see from pointing dies.
Edit: To make #3 more clear I should say that there is an optimal meplat diameter as a percentage of caliber (10-20%). A longer, sharp bullet will be better than the same bullet after its nose is truncated. But that longer pointed bullet is sub-optimal *for its length*.
And to further muddy the waters, we're talking about drag only - Cd, not BC. When pointing, you're not changing weight, so the distinction is meaningless. But if you're playing around with bullet design and you change the meplat diameter, you've also changed the weight (assuming constant bullet length). And since BC is proportional to weight, it can have a meaningful impact on BC that has nothing to do with drag.
1) Small variations in bullet length will impact BC slightly, pointed or not. Longer bullets will have a _slightly_ higher BC.
2) Plenty of people point successfully without damaging bullets. You don't have to look too far to find people who have screwed them up, however.
3) Some unpointed bullets have larger meplats than others. This matters, because there is an optimum diameter for a given a bullet length. It's not zero, but somewhere in the neighborhood of 0.1-0.2 calibers. .031-.062 for a .308 bullet, for example - you'll find a lot of modern match bullets are already in that range or very close to it - maybe 0.050-.070.
4) Mileage may vary - the data that the conventional wisdom in #3 can be traced back to BRL/NACA experiments from long ago. To the best of my knowledge, there's nothing out there that definitively quantifies the impact of meplat geometry that exactly matches the way our pointing dies do it. I would expect it to be very close to those numbers but the data I'm aware of is based on flat (truncated) noses and hemispherical noses, not the sort-of-concial points that we tend to see from pointing dies.
Edit: To make #3 more clear I should say that there is an optimal meplat diameter as a percentage of caliber (10-20%). A longer, sharp bullet will be better than the same bullet after its nose is truncated. But that longer pointed bullet is sub-optimal *for its length*.
And to further muddy the waters, we're talking about drag only - Cd, not BC. When pointing, you're not changing weight, so the distinction is meaningless. But if you're playing around with bullet design and you change the meplat diameter, you've also changed the weight (assuming constant bullet length). And since BC is proportional to weight, it can have a meaningful impact on BC that has nothing to do with drag.
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Interesting!
A UK 'Match Rifle' competitor I trust a lot on external ballistics issues advised me to use bullet OAL growth as a pointing guide some years back. ie since the bullet becomes longer during pointing, measure its original OAL then increase the amount of pointing effort in small steps remeasuring OAL after each. Drop the die setting back a step when a reading is obtained that shows no OAL increase in the previous run through the die.
dcali
Bullet Maker
See my edit for more...
Litz did an entire chapter on pointing and trimming in Modern Advancements in LR shooting Vol II. His conclusion after a lot of testing is that if you are a elite shooter shooting at 1000 yards the BC improvement is worth the effort. Since 1000 yard ranges are scarce down my way and I am a novice I am not going to waste time and energy.
Wow, are you trying to justify it in your own mind for not trying it ? It is easy to see at 600 also, ES will drop, wind drift will be less and vertical will be way less all things are positive and it not worth your energy? ...... jim
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