Bullet meplat trimming and tipping

[SteveOak]

I don’t know a whole lot about either, mostly just what I have read on this site.

It seems as though some, but not all, bullets show an improvement in BC as the result of meplat trimming and some, but not all, bullets show an improvement in BC as the result of meplat trimming and pointing.

Three questions;

1. Do some bullets also demonstrate an improvement in accuracy as the result of either meplat trimming or meplat trimming and pointing?

2. Do some bullets also demonstrate a degradation of accuracy as the result of either meplat trimming or meplat trimming and pointing?

3. Is there a way to reliably predict if a bullet will show improvement in BC or accuracy or both as as the result of either meplat trimming or meplat trimming and pointing?

I am mostly interested in the affects on BC but the potential affects on accuracy are also of interest.

 

[Ballisticboy]

For a constant bullet nose length, having a meplat of around 10% of the bullet diameter, with the meplat being hemispherical in shape not flat, will give the lowest drag. Shortening a pointed bullet nose to produce a meplat will not give you any improvement. If you take a bullet with a meplat and produce a point, while keeping the bullet nose length the same, there will be an increase in drag.
The size of the drag change will obviously depend on the nose shape being used. Having a small hemispherical meplat tends to reduce drag as, crudely, it fools the air into thinking the bullet nose is longer than it is in reality.
A meplat on a bullet nose will tend to make the bullet slightly less stable for a fixed nose length.
Hope the above makes sense.

 

[johara1]

For a constant bullet nose length, having a meplat of around 10% of the bullet diameter, with the meplat being hemispherical in shape not flat, will give the lowest drag. Shortening a pointed bullet nose to produce a meplat will not give you any improvement. If you take a bullet with a meplat and produce a point, while keeping the bullet nose length the same, there will be an increase in drag.
The size of the drag change will obviously depend on the nose shape being used. Having a small hemispherical meplat tends to reduce drag as, crudely, it fools the air into thinking the bullet nose is longer than it is in reality.
A meplat on a bullet nose will tend to make the bullet slightly less stable for a fixed nose length.
Hope the above makes sense.[/QUOTE

If you trim and point the bullet grows in length to where it as long as it was before you trimmed it.... jim

 

[Ballisticboy]

If you trim and point the bullet grows in length to where it as long as it was before you trimmed it.... jim

Sorry I obviously wasn't clear. I am talking about noses with constant length so they are all the same length with a meplat or a point.

 

[DaveTooley]

Here are the known basics that I learned years ago when I first explored this in 2003 using an Oehler 43.
1. Uneven meplats cause yaw or don't allow the bullet to settle down.
2. yaw means variations in BC
3. trimming meplats lowers the BC by an average of 2% but it also reduces the BC spread
4. I did a test for Sierra where I installed their green tips. BC increased 2-3% over a standard bullet with a reduced BC spread.
I have never pointed a bullet but many do.

Any improvement in accuracy doesn't show up until beyond 600 yds.

 

[Titan]

If the goal is to uniform bc of a box of bullets you can sort by length, base to tip in lots by the one or two thousands, the idea being the longer ones were jammed further up into the die during production and probably are a bit more pointy with a smaller meplat diameter so length is a proxy for BC variance. It is not exact but it is easy to measure and the results seem to be good at 1000.

Why would you want a uniform BC? Well it can reduce your vertical at long range.

 

[SteveOak]

Good info! Thanks!

Part of this may be materially useful, part of this is I enjoy learning about all things shooting related and external ballistics is particularly interesting. It is an intellectual exercise that may have a benefit for shooting. Win - Win!

The shooting I do is up to 500 meters. We shoot standing so once you bring the rifle up there is no chance to read the wind. I can't really see changes in the mirage in the scope nor the wind flags. The wind flags are just pennants at the ends of each range and not a lot of use to begin with. We have a spotter but that is not as good as seeing the mirage myself and there is a delay in getting the info.

Given this situation, improving the BC, even at the cost of a slight degradation in accuracy, is beneficial.

If trimming or pointing might help I might have a go at it. Since it is only 500 meters, maybe not worth the effort.

 

[Down South]

Good info! Thanks!

Part of this may be materially useful, part of this is I enjoy learning about all things shooting related and external ballistics is particularly interesting. It is an intellectual exercise that may have a benefit for shooting. Win - Win!

The shooting I do is up to 500 meters. We shoot standing so once you bring the rifle up there is no chance to read the wind. I can't really see changes in the mirage in the scope nor the wind flags. The wind flags are just pennants at the ends of each range and not a lot of use to begin with. We have a spotter but that is not as good as seeing the mirage myself and there is a delay in getting the info.

Given this situation, improving the BC, even at the cost of a slight degradation in accuracy, is beneficial.

If trimming or pointing might help I might have a go at it. Since it is only 500 meters, maybe not worth the effort.

I trim and point but i'm shooting 600 & 1000 yards on F-class targets from a prone stable position on a bipod. In your situation, standing and only shooting 500 meters i doubt it'll make much difference and probably isn't worth the effort. Just my thoughts.

 

[SteveOak]

I trim and point but i'm shooting 600 & 1000 yards on F-class targets from a prone stable position on a bipod. In your situation, standing and only shooting 500 meters i doubt it'll make much difference and probably isn't worth the effort. Just my thoughts.

Are you speaking to accuracy or wind drift or both?

 

[DaveTooley]

Are you speaking to accuracy or wind drift or both?

Trimming and or pointing will not change a poorly performing bullet into an accurate bullet.
Premise #1 you have an accurate bullet out of the box.

Trimming and or pointing the meplat does not change or improve the accuracy between 0-600 yds.
600+ yds variation in BC means something. The further the distance the more important it becomes. Trimming and or pointing helps accuracy at distance by having uniform BC's.


A high BC number isn't the end all. I shot flat base bullets for years and did well. I wanted an accurate bullet and then I would learn how to read the wind. They were well made bullets. I didn't have to trim the meplats.

 

[dcali]

I absolutely agree that the BC race has gotten a tad out of hand. A well balanced design is what we ought to seek. For some applications, that’s going to be heavy on BC, but we want to seek a balance between BC and other factors, because the things that make BCs high also create some undesirable effects.

 

[skiutah02]

1) yes
2) yes
3) not that I am aware of.

Jade's comments are worth a second read.

That said, the gain in accuracy that you get is from uniforming the bullets. For me, it's very often the case that I do not see an increase in BC, but often see the pointed bullets shooting inside the untouched bullets with a (sometimes) dramatic reduction in vertical (90vld, 185jugg, 105hy). I have a picture somewhere here that shows one test that I did with the 185.

 

[johara1]

Here are the known basics that I learned years ago when I first explored this in 2003 using an Oehler 43.
1. Uneven meplats cause yaw or don't allow the bullet to settle down.
2. yaw means variations in BC
3. trimming meplats lowers the BC by an average of 2% but it also reduces the BC spread
4. I did a test for Sierra where I installed their green tips. BC increased 2-3% over a standard bullet with a reduced BC spread.
I have never pointed a bullet but many do.

Any improvement in accuracy doesn't show up until beyond 600 yds.

That is true to a point, I have seen it at 300 yds, if you and your equipment is at a sub.1 level..... jim