BC Variation bullet to bullet is real, and its a problem.

[DocUSMCRetired]

BC Variation from bullet to bullet in the same box is something that is hard to detect with short range work but the further you try to shoot the more that problem compounds. We have been providing shooters who get PDMs a print out which shows this variation. We will have more on this topic in the future but picking a high quality and consistent bullet will help minimize this problem.

 

[cohunt]

so basically you are saying it doesn't make much difference until you hit transonic speeds

 

[DocUSMCRetired]

so basically you are saying it doesn't make much difference until you hit transonic speeds

That depends on how much variance. We generally look at the variation in 3 zones. Some bullets do have enough variance to make a difference at mid range.

 

[elkaholic]

That depends on how much variance. We generally look at the variation in 3 zones. Some bullets do have enough variance to make a difference at mid range.

Hi Doc. Good stuff! Do you have a feel for where most of the variation comes from?

 

[DocUSMCRetired]

Hi Doc. Good stuff! Do you have a feel for where most of the variation comes from?

Quality and manufacturing tolerances. Some of it is also the actual design of the bullet.

 

[elkaholic]

Quality and manufacturing tolerances. Some of it is also the actual design of the bullet.

I would GUESS more of it being in design? I know weight variations dont amount to much but maybe tip (meplat) etc.

 

[cohunt]

so lathe turned/machined bullets may be more consistent?

 

[DocUSMCRetired]

I would GUESS more of it being in design? I know weight variations dont amount to much but maybe tip (meplat) etc.

so lathe turned/machined bullets may be more consistent?

The opposite is actually true for Solids. "BC Variation is a bigger problem with solid bullets than it is traditional bullets. Just because they are longer and it is a stability challenge. A lot of solid bullets that are out there have really high average BCs, and you can get your gun to shoot really good groups at 100 yards at short range. But it is very common to kick that out to long range and see the group just really spread out and it is because that shot to shot variation you can't see at short range" - Bryan Litz

 

[cohunt]

so you are saying the manufacturing tolerances are better on jacketed/swedged bullets than on cnc turned/machined bullets? --I cant hear the audio very well on your posts here on my work computer.

 

[elkaholic]

so you are saying the manufacturing tolerances are better on jacketed/swedged bullets than on cnc turned/machined bullets? --I cant hear the audio very well on your posts here on my work computer.

I think its more shape (length) etc necessary to overcome density than it is maching.

 

[DocUSMCRetired]

so you are saying the manufacturing tolerances are better on jacketed/swedged bullets than on cnc turned/machined bullets? --I cant hear the audio very well on your posts here on my work computer.

I think its more shape (length) etc necessary to overcome density than it is maching.

It is more complicated than simply turning a bullet to spec. Especially when it comes to the transition to subsonic. The longer the bullet (the more you separate the CG from the CP) the less inherently stable it is in that transition. Lead jacketed bullets have more opportunity for better consistency since they are shorter. We have made some progress with this however, with the Berger Solids and found a solution to some of the issues.

 

[cohunt]

so shorter bullets are more consistent? so high BC bullets are less consistent than lower bc bullets? I guess that would make sense if it is on a % basis

 

[DocUSMCRetired]

so shorter bullets are more consistent? so high BC bullets are less consistent than lower bc bullets? I guess that would make sense if it is on a % basis

Can be, but it is more complicated than that due to different designs, different manufacturing tolerances, varying levels of build quality in rifles etc.

 

[jebel]

Doc, how do you distinguish the source of variance you see in recorded BCs between that attributable to the bullet and that attributable to the tolerances of your recording instruments?