.308 COL variation - why?

[EBR Works]

I'm putting together some .308 precision loads and for some reason I am seeing COL variation of up to .009 and cannot figure out why. All brass is trimmed to 2.005. I'm seating SMK 168g bullets with a RCBS competition seating die to a target 2.800 but am seeing variation between 2.796 and 2.805. Any ideas why this is happening? Thanks.

[Army GI]

maybe there is a little play in between the shell holder and the ram.

[EBR Works]

I'm using the extended shell holder that came with the seating die and a 1 year old Rock Chucker press. There is a little bit of wiggle in the shell holder but when the ram is topped out with the bullet fully seated, would that make a difference?

Let me also add that I'm using Hornady LNL bushings on the press. I wonder if the little bit of looseness in these is to blame?

[bohoki]

uh that is pretty darn precise if you ask me

there are slight variation in the ogive of the bullets maybe

cause it cant be the brass's fault

[22popnsplat]

Are you measuring from the the tip of the bullet or using a Comparator ? the Comparator is a better method measuring from the ogive but is still not perfect , measuring from the bullet tip it would not suprise me to see the variations you mention but with the Comparator it should only be a few thousanths when using a quality bullet.

[Whitesmoke]

Are you measuring from the the tip of the bullet or using a Comparator ? the Comparator is a better method measuring from the ogive but is still not perfect , measuring from the bullet tip it would not suprise me to see the variations you mention but with the Comparator it should only be a few thousanths when using a quality bullet.

I agree...if you are measuring from the tip...you will not be able to measure the OAL consistantly.

[Jonathan Doe]

The tip of the bullets are not even. I always use comparator for measurement on ogive. I have very good results with the measurement. When I change the lot on the bullets, I remeasure the ogive for it can change from lot to lot.

[EBR Works]

Just using a caliper for OAL measurement. I understand that my variation is because I'm measuring to the tip. Thanks for the lesson guys.

[ar15barrels]

Just using a caliper for OAL measurement. I understand that my variation is because I'm measuring to the tip. Thanks for the lesson guys.

Measure the OAL of just the bullets and you will probably find that same 0.009".

[JTROKS]

Different caliber, but when I measure the first round loaded for my 223 loads I try to get 2.265 to utilize maximum space in my AR mags. Never works, too much variation specially with spitzers.

[EBR Works]

Measure the OAL of just the bullets and you will probably find that same 0.009".

Did that and your are correct. I'm surprised that Sierra doesn't maintain a tighter tolerance for the SMKs.

[Jonathan Doe]

Most important parts of the bullet in my opinion is the diameter, uniform jacket thickness, and ogive design. Sierra does excellent job controlling that. The meplat is non issue. The Sierra bullets are excellent bullets.

[ocabj]

Actually, Long Range shooters have discovered that meplat trimming (uniforming) and meplat pointing are resulting in tighter elevation variations. The National Long Range Champion John Whidden makes and sells a 'bullet pointing' die system and it's gaining quite a bit of acceptance (in conjunction with meplat trimming) due to the positive results.

Sierra's new Palma bullet design is supposed to have 'pointed'/shaped meplats as part of the production process.

[Jonathan Doe]

G. David Tubb sells the meplat uniformer. I never used one. My 600 yard load with either Sierra 175 MK or Berger 175 VLD shoots good out of my M-1A as is anyways.

[Ahhnother8]

Sierra's new Palma bullet design is supposed to have 'pointed'/shaped meplats as part of the production process.

I have been shooting these the last five days. The points are so tight that they almost look like FMJ's at the tip. They shoot quite well. I have not measured the OAL, but suspect that it also varies. It just does not matter.

Lane