Bullet Sorting Question

[shepardsonp]

I just weighed 1,000 Berger 300g VLD's and have them grouped in the following buckets:

299.7
299.8
299.9
300.0
300.1
300.2
300.3
300.4

How many of you guys then go through and measure the bullet bearing surface and then sort each group (300.0, etc.) by bearing surface? I have a Berger Bullet Seating stem in my Redding Competition Seating Die and was curious if there is any reason to go through this extra step. I know it can't hurt but don't know if it it is worth the time and effort for the amount of benefit.

Welcome your thoughts.

ALSO .... If there is something else i should be doing that i am not, very open to that as well.

 

[royinidaho]

I like shootin' and messing with numbers.

First thought is bullet weight is proportional to bullet weight which is "usually" proportional to bearing surface length.

One or the other method should be decent enough.

For shootin' tests I'd have fun with the following:

Sort brass to same weight.
Weight powder as usual.
Load one round with each bullet weight. (8 loads)
Seat each with same base to ogive length.
Arrange 8 targets @ 200 yds to be able to shoot 1 shot at each target.
Keep shade over the rifle and shoot with sufficient between shots to cool barrel.
Chrono each shot.

Carefully assess all information.

My guess that you won't see much of a trend in any given direction.

But hey it was fun and you'll know that you know.

Have fun

 

[shepardsonp]

That does sound like a fun time - after i pack my elk out

I did just purchase a new powder balance that is accurate to .005 of a grain (Sartorious GD503) so now I won't have to wonder if the standard RCBS Charge Master be pay $900 for a scale just to measure powder is beyond me - well, not really.

Here's my buddy AJ's video on his new powder scale.

[ame=http://www.youtube.com/watch?v=gfl9C0-5zYw&feature=related]Reloading with Sartorius GD503 - YouTube[/ame]

 

[royinidaho]

I'm gonna be watching for how this goes for you.

 

[Boss Hoss]

I posted this on another Board a while back and it makes sense here:




Good question-----first I measure the total length of the bullets and sort then in 2 thousandth increments.
2nd I use the John Buhay ogive checker and measure each batch by the thousandth
3rd when Speedy closed the shop I bought his point up die for the 6.5 142 SMK and I point up the bullets

I then load and keep the rounds segregated by the above sort criteria for example I sorted 500 bullets last night and had 7 bags by total length. Tonight I will use the Buhay gauge to sort further and then will point up and load---time consuming yes but it pays off in the end.

 

[Bart B]

I've never seen any need to sort bullets and cases to the Nth degree. With a 190 and 200 grain bullet weight spreads of 4/10ths grain, length and ogive datum spreads of near 10/1000ths inch, 230 grain case weight spreads of 4 grains and even using new, virgin unprepped brass, my 30 caliber magnums had no problems shooting 15-shot test groups at 1000 yards of well under 7 inches.

 

[shepardsonp]

I posted this on another Board a while back and it makes sense here:




Good question-----first I measure the total length of the bullets and sort then in 2 thousandth increments.
2nd I use the John Buhay ogive checker and measure each batch by the thousandth
3rd when Speedy closed the shop I bought his point up die for the 6.5 142 SMK and I point up the bullets

I then load and keep the rounds segregated by the above sort criteria for example I sorted 500 bullets last night and had 7 bags by total length. Tonight I will use the Buhay gauge to sort further and then will point up and load---time consuming yes but it pays off in the end.

Not sure i understand why you would measure bullets by the true over all length since the bullet tip never touches anything. The pointing or trimming of the meplat may have some merit but i don't know if i have the patience to do that. Different strokes for different folks they say.

 

[Bart B]

Regarding all the weight and measurement sorting criteria with bullets and the following:

---time consuming yes but it pays off in the end.

How much does it pay off?

What's the difference you get between doing all that stuff and not?

How do you measure the difference? If it's extreme spread group shooting, you have to shoot at least 15 shots per group for the results to be meaningful. 5 shot groups have only a 55% probability of being meaningful. 10 shot ones raises the probability to 65%. Whereas a 20 shot group's mean radius has about 85%. If you don't get at least 80% confidence in the results, credibility of the results ain't very good.

 

[Boss Hoss]

Regarding all the weight and measurement sorting criteria with bullets and the following:
How much does it pay off?

What's the difference you get between doing all that stuff and not?

How do you measure the difference? If it's extreme spread group shooting, you have to shoot at least 15 shots per group for the results to be meaningful. 5 shot groups have only a 55% probability of being meaningful. 10 shot ones raises the probability to 65%. Whereas a 20 shot group's mean radius has about 85%. If you don't get at least 80% confidence in the results, credibility of the results ain't very good.

The reason that measuring the bearing surface is important is that is what determines the pressure in the chamber when the bullet enters the barrel. The pressure curve also determines the ultimate velocity so at 1K which is the rang I compete this is important. Variations in velocity are significant because it causes vertical dispersion which makes the difference between winning and losing. Additionally, pointing up the bullet will eliminate any yaw that would be imposed by small deformations at the tip of in my case the 142 SMK.

There are many other things that are done such as verifying concentricity but I will say that on a factory rifle depending on the way that it was built may or may not be able to fully take advantage of these actions. To equate any of these actions as a standalone to a specific accuracy gain is problematic however, for example when testing velocities after sorting bullets I had almost a 25% decrease in velocity variations compared to using the bullets that were not sorted. First and foremost the shooters equipment, process and technique must be refined to the point where he or she can properly determine what difference if any these modifications will make.

In the end by reducing variables in any process which shooting is a great example the more consistent the process is performed the more repeatable your results will be.

 

[Boss Hoss]

Not sure i understand why you would measure bullets by the true over all length since the bullet tip never touches anything. The pointing or trimming of the meplat may have some merit but i don't know if i have the patience to do that. Different strokes for different folks they say.

When using a point up die the OAL is critical because if the die is off by .001 the bullet can be deformed or not pointed up correctly.

 

[Bart B]

Additionally, pointing up the bullet will eliminate any yaw that would be imposed by small deformations at the tip of in my case the 142 SMK.

There's more bullet yaw (tip moving in a circle about the trajectory axis) caused by slight unbalance of the bullet than making its point perfect. Over 90% of all bullets are unbalanced by some degree. The yaw caused by unbalance makes small changes in drag, or bullet coefficient. Although it's typically 2% or less with Sierra's best match bullets, the difference in vertical shot displacement caused by this is significant. Do you know how much it is compared to a muzzle velocity spread of 20 fps or a standard deviation of 7 fps?

 

[Boss Hoss]

There's more bullet yaw (tip moving in a circle about the trajectory axis) caused by slight unbalance of the bullet than making its point perfect. Over 90% of all bullets are unbalanced by some degree. The yaw caused by unbalance makes small changes in drag, or bullet coefficient. Although it's typically 2% or less with Sierra's best match bullets, the difference in vertical shot displacement caused by this is significant. Do you know how much it is compared to a muzzle velocity spread of 20 fps or a standard deviation of 7 fps?

In my game the the velocity spread is one of the biggest killers an my 10 shot strings must maintain a minimum of 25fps or less spread (for the 142smk). Sometimes I am lucky and get single digets with a barrel.

I do not know where you are getting your data from nor do I know how to address your question. You might call Sierra.

 

[Bart B]

I do not know where you are getting your data from nor do I know how to address your question. You might call Sierra.

Spread in BC data's been in Sierra's reloading manuals for some time. It's interesting to see how time of flight between two points changes with measured BC's of the bullet. Their software allows one to change a bullet's BC for a given muzzle velocity and see the change in drop due to different times of flight to the target.