Bullet measurements-Anyone notice this too?

[amlevin]

I just recently sorted a box (500 count) of Sierra 175 gr Match Kings.

Was measuring from Base to Ogive and found one group to measure .671" +/- >001" and the other group exactly .006" less +/- .001".

Almost like two different dies were used to form the bullets in the same box.

When I trimmed the meplats in the first group (.670") the finished meplat's looked exactly the same as far as diameter is concerned leading me to believe that the Ogive to Meplat measurement was the same for this group.

I find this a little strange that a "Match Bullet" manufacturer would "mix production" like this. Nosler claims to fill boxes with bullets made on the same equipment and my experience has been that the 175 Nosler Custom Competition bullets are more uniform in measurements (their jackets have gone south recently but at least they measure the same).

Just curious if anyone has noticed this distinct variance with Sierra Match Kings they've purchased. Where they've ended up with two separate groups of bullets, rather than a scattered bunch with varying base to ogive measurements.

 

[jlow]

You must have missed this recent thread:

http://forum.accurateshooter.com/index.php?topic=3832451.0

 

[amlevin]

You must have missed this recent thread:

http://forum.accurateshooter.com/index.php?topic=3832451.0

Yes I did miss it. But I didn't miss the comment (when I went over and read the thread)

sierras current policy is only one lot/run in a box, it was not always so.

Apparently this isn't true as the box I measured was brand new.

 

[jlow]

It's always been that way with the two lots, and the Nosler also appears to also have a more consistent lot.

 

[gotcha]

With the SMK's I usually see two distinct +/- .001" lengths in a box. Have seen as much as .012" variance when opening a 2nd box. ...... No significant difference in group size at 100 yds. But, at 300 or more yds. noticeable changes in group POI based on the bullet lengths I've sorted to. With all of the demand placed on Mfr's lately, probably a good idea to Q.C. and sort your own. Even the stuff that is normally very tight tolerance. Just my .02

 

[anyrange]

Yes, I see similar results measuring 175 & 107 SMK's. sometimes I have seen three groups.

 

[amlevin]

.. No significant difference in group size at 100 yds. But, at 300 or more yds. noticeable changes in group POI based on the bullet lengths I've sorted to.

As I get older I get a lot slower. It took me a while to pick up on the fact that this may be why I see "two groups" on a regular basis when shooting at 300 yards. 2-3 holes nice and tight in one group and the rest of the 5 shots in a tight group about 1/2 " away.

Sure would be nice if Sierra would just "box" from a single machine and not mix.

 

[tomon]

Back in the late 80s and early 90s, Winchester was selling bulk 147gr fmjbt in boxes of 1000, and you could SEE three different bullet shapes. One shorter and fatter with a blunt nose, one "normal", and one with a longer very pointed nose. It was fun getting a Garand clip with same size cartridges! These were all used at 200 yds. Want to buy any?????

 

[Raythemanroe]

I found my 190 SMK to be very good on weight and ogive.

 

[SWThomas]

I sorted two boxes about a month ago and got 3 groups with each box.

 

[308 f/tr]

Just because a box of bullets has multiple ogive to base measurements does not mean they came of multiple machines. I can tell you that Sierra does not change lots every time they change a die in a machine or make an adjustment to the machine. This is one major flaw that they have(not sure about other companies), and the reason you are seeing variations in the same lot. Also over time dies wear out and it may happen very rapidly, so the difference from the beginning of a run to the end of a run on the same die could be very different also. Still doesn't mean it came out of two different machines, just that there were changes made or tooling wearing out.

 

[jlow]

Would have to disagree. If it was simple wear and tear, you will see a Gaussian distribution in size. This is not the case - you normally see two distinct population in their box....

 

[308 f/tr]

Wear and tear can be pretty severe with a bullet press. On top of that something like a die change or a adjustment on the machine 1/2 way though a "lot" does not merit a "lot" change as long as it meets the accuracy and QC specs promised. No where does Sierra promise ogive to base within x amount of variation. It would be nice if they changed lots after every tooling change or every time a machine is down but it doesn't happen.

 

[Raythemanroe]

I just did a box of SMK and the majority was within .003 and weight was much better then the Horandy box.

 

[jlow]

Wear and tear can be pretty severe with a bullet press. On top of that something like a die change or a adjustment on the machine 1/2 way though a "lot" does not merit a "lot" change as long as it meets the accuracy and QC specs promised. No where does Sierra promise ogive to base within x amount of variation. It would be nice if they changed lots after every tooling change or every time a machine is down but it doesn't happen.

You are right, there are no guarantees, but it’s all relative. Considering how great people say SMKs are compared to the lowly Noslers, I am normally hard press to find a box of Nosler CC 223 vary more than a thousand.

 

[Ringostar]

I've run into these variations with .284 smk's. Would it be practical to get a swage die, to fit a reloading press, that would lightly resize them to be consistent?

 

[amlevin]

I've run into these variations with .284 smk's. Would it be practical to get a swage die, to fit a reloading press, that would lightly resize them to be consistent?

The problem with re-swaging a jacketed bullet is that the copper jacket could spring back from the lead and leave a void. Not so much a problem with Pointing Dies as they're merely pressing the copper jacket in against itself and are working in the area of the "Hollow Point", not bullet body.