Sierra 183 SMK Length Change?

[Cole440]

Anybody know if Sierra has changed the length of the 7mm 183 SMK since they introduced it?

Long story short I recently picked up a 284 F-Class rifle that came with some loaded ammo from the P.O. I started measuring some of the loaded ammo just to see where he was running the OAL. Noticed variation, that led me here.

I'm seeing about a 0.025" difference in the bullets I have. Both from base to ogive and from base to tip (though this measurement is predictably less consistent). There are two distinct lengths, one group measures 0.625" and the others measure 0.599" base to ogive. The two groups have ever-so-slightly different boat tails also. Bearing surface and everything else looks identical. All weigh in right at 182.5-183 gn.

All of his notes indicate that they are 183 SMK and the weight agrees. I'm thinking it has to be an OAL change or a significant lot-to-lot variation. I have no further info about when he purchased the bullets.

The 183 SMKs I just purchased are within 5 thou of the shorter group . Leading me to believe that the longer group is older.

I'll shoot them all just the same, just curious!
Merry Christmas all,
Cole

 

[John Glidewell]

This is what I found with Google search:

Yes, Sierra Bullets has updated their 183 grain bullet design, specifically within their MatchKing line, featuring a new, more elongated ogive and a refined meplat for increased ballistic coefficient and accuracy; this change is considered a recent modification to their classic 183 grain bullet design.

Key points about the Sierra 183 bullet change:

• Bullet type:
  The updated design primarily affects Sierra's MatchKing line of bullets, designed for competition shooting.
• Design change:
  The new 183 grain bullet has a longer ogive and a more pointed meplat, which helps it fly more efficiently and provides better accuracy.
• Benefit:
  This modification leads to a higher ballistic coefficient, allowing the bullet to better resist wind drift and maintain velocity over longer distances.

 

[Schw15]

Anybody know if Sierra has changed the length of the 7mm 183 SMK since they introduced it?

Long story short I recently picked up a 284 F-Class rifle that came with some loaded ammo from the P.O. I started measuring some of the loaded ammo just to see where he was running the OAL. Noticed variation, that led me here.

I'm seeing about a 0.025" difference in the bullets I have. Both from base to ogive and from base to tip (though this measurement is predictably less consistent). There are two distinct lengths, one group measures 0.625" and the others measure 0.599" base to ogive. The two groups have ever-so-slightly different boat tails also. Bearing surface and everything else looks identical. All weigh in right at 182.5-183 gn.

All of his notes indicate that they are 183 SMK and the weight agrees. I'm thinking it has to be an OAL change or a significant lot-to-lot variation. I have no further info about when he purchased the bullets.

The 183 SMKs I just purchased are within 5 thou of the shorter group . Leading me to believe that the longer group is older.

I'll shoot them all just the same, just curious!
Merry Christmas all,
Cole

I use to shoot a lot of the 183 and the 197 smk. I found the 183 have more length differences lot to lot than the 197s. But weird thing was I just left my seater the same and they always shot the same....... not sure if it was a fluke but I since moved to 30 cals for my shooting. I would just separate lots with there measurements.

But I've seen this in other brands and calibers as well.

 

[Cole440]

I use to shoot a lot of the 183 and the 197 smk. I found the 183 have more length differences lot to lot than the 197s. But weird thing was I just left my seater the same and they always shot the same....... not sure if it was a fluke but I since moved to 30 cals for my shooting. I would just separate lots with there measurements.

But I've seen this in other brands and calibers as well.

That was my plan! I ended up just kind of copying the old loads with my seater and then used the comparator for a baseline with the new bullets.