Bullet variations:

[Pete Wass]

I loaded 100 rounds of .223 this week and when I was seating bullets I observed a large variation in the OAL's measured near the base of the ogive. I segregated them by OAL and discovered that they generally fell into 4 groups. I ended up re-adjusting the seater stem for each group until I had them all the same length. I had to pull the bullets on some to get back where they belonged. ( great reason to have a good bullet puller in your press turret )

It appears to me that the bullets were either made by 4 seperate machines or they were made in 4 different runs and mixed. These are Sierra 69g Match King bullets. I must say I am not particularly pleased.

If a person were to shoot them without measuring, their accuracy is likely to be lackluster, at best. Some were .009 short, some were .006 long, some, 003 short with some the correct length I had set the seater for. I am surprised the QC isn't better than this.

 

[j mckinnie]

Pete

I know a "custom BR bullet" with the same charicteristics.

 

[f d shuster]

Bullet variations

Pete: I've also found differences with the Sierra #1380, which I use a lot of. Can sort them using a bullet comparator and come up with 2 or 3 different "groups", all coming out of the same box of 500. We had a discussion on another site several months ago about this problem, and I suggested they were being made on different machines, then all dumped into the same lot number. I was roundly criticized for my thoughts, and several big name people said that no reputable bullet maker would do that, but, the differences continue, and no one has come up with an explanation of why.

 

[Andy B]

Hey Pete,

I ran into this with some 6mm factory bullets / sierra and tnt last year. Up to .010" was not uncommon. I found as long as the points were not distorted to impact seating depth, and base of cartridge to ogive measurements were the same they shot very good.
223 // are we shooting factory match this weekend ?
Andy B

 

[Lynn]

Pete
I recently posted about this in a couple of threads loosely named Ogive variation.
In my fathers 6 Dasher using a 6mm comparator I was getting up to 0.013 variation in my seating depths after using a seater that made contact closer to the meplat.His gun would shoot lights out at 2.509 inches including the comparatoras length.It shot good at 2.510 and 2.508 but would really start to open up at 2.508 or 2.511 in length.
I would let him fire groups with 4 shots at 2.509 and one shot at 2.512 and it consistantly ruined the group in our experience.
If you look at those threads you will see posters saying they will all be the same but I personaly have not seen that.
My custom bullets show some variation but it is generally 0.003 or less.
In my humble opinion I think there are alot of shooters out there who are getting several shots into a ragged hole then a flier and there seating depth being inconsistant is the cause.This of course is my opinion but I think they are blaming the wind and not realising it is there ammo.
Waterboy aka Lynn

 

[Boyd Allen]

Lynn:
If you are right, it is good news, since it is easier to check and correct seating depth than the wind.

 

[Lynn]

Boyd
I ended up buying a arbor press with the seating pressure indicator on it and while the neck tension variation was responsible for some error I elieve ogive variation was A major factor.
As for the wind I probaly should have explained that better.While testing with 3 shot groups at 100 yards it was vary easy to get a nice triangle cluster.If you kept going deeper you would get 2 shots into a single hole with the 3rd shot touching but making the group look like the number 8.My father wanted to stop the testing at this point and call it all good saying the one shot was wind related as it was blowing.Me being stubborn I had him keep going and instant one hole groups at 2.509 inches.As the day progressed I noticed he was shooting several one hole groups and several that looked like the number 8 in various different positions.
I was using qualified bullets but was still seeing some seating variation so I lumped them into like groups of 0.001 extreme spread.
The window for best grouping appeared to be 0.003 wide with everything else giving fliers.
As a side note it is important to rotate the loaded rounds when measuring.
Lynn aka Waterboy

 

[1000mstudent]

I run into a variation in OAL using a comparator in loaded rounds. I am thinking that one way to deal with part of this problem would be to have the seater in the die to make contact .005" into the ogive from outside diameter of the bullet. This should be enough material to ensure that the seater can work properly. The effects of ogive variations would then be minimized in the seating process, thus helping to ensure consistancy in seating depth.

I believe that this has been thought of before. Has anyone any experience or knowledge about dealing with seating depth consistancy this way? Are there seater/stem replacements for this purpose?

 

[GerryM]

Bullet variations

One thing you can do to help get uniform seating .
You can lap the seater stem with the bullet your using.
now the seater stem is set for that particular shape and ogive.
If you use the wilson type seater stem i think you can buy extras and lap them for different ogives. I know it's been done before with some pretty good results , with benchrest grade bullets.