Bullet Length Variation

[nicky]

Bought some MBC 9mm SWC's to try. Measuring 10, the diameters were all very consistent. Measuring the lengths I am getting a .01 difference from the longest to the shortest.

I think that's a big variance.

Your thoughts would be appreciated.

[Wobbly]

How do the weights looks ?

 

[ReloaderFred]

A Magma Bullet Master, which is what almost every commercial caster uses, (I have one) uses a carousel with 8 molds for each bullet.  Each mold is a two cavity design, so this means the bullets are being dropped from 16 different cavities in the molds.  While Magma makes every attempt to keep the cavities consistent by using the same cherry to cut each cavity, there are going to be some very minor differences, due to manufacturing processes. 

The difference you're measuring could also be from the where the sprue is cut off when the sprue plate opens on the mold.  Sometimes there is a little bump there, but it really makes no difference in the performance of the bullet at handgun ranges out to 50 yards.

Measure from the solid base of the bullet and see what that measurement is, and it may be different than measuring from the center of the bullet.

I'll be gone all day today, but I'll check back when I get home tonight to see if you've measured anything different.

Hope this helps.

Fred

[nicky]

The original that I had measured I threw back in the box when I was finished so I took another 10.

The weight of these were 126.6-127.9. A 1.3gn difference.

Measuring these from the center of the bullet I got .6185-.6230. A .0045 difference.

Measuring these a bit off center as Fred suggested  I got .6180-.6210. A.003 difference.

Originally my measurements were .6170-.6265 which was actually a .0095 difference.

I wish that I didn't throw the first bullets measured back in the box. Now it seems that I either can't:
                                                                                                                                                             A- see,
                                                                                                                                                             B-read
                                                                                                                                                             C-do math
                                                                                                                                                             D- all of the above

[1SOW]

I received a batch of PD 124 JHPs (a well thought of bullet) and had trouble seating them with my normal OAL variations.  I measured them,  and found twice+ the length variation you are seeing in your bullets.  The length variations were all negative,  "shorter bullets".  This length variation affected the way my press seats these bullets.

This was found with about 5-8% of the bullets in this order.  This IS too much variation,  BUT they still chrono & shoot normally for action shooting uses.

Just irritates me to show double+ the OAL variations I get with all my other bullets.

[IDescribe]

MBC's are often not as pretty as some of the other manufacturers, and I would bet that it's, as ReloaderFred suggested, where the sprue was cut, OR possibly sloppy Hi-Tek coating applications if these are coated.