142 SMK and jump

[lennyo3034]

I am trying to switch from the 139 lapua to something a little better BC. I have tried bergers and ELDs and none of them held the accuracy that I get out of the Lapua bullets.

I got a pack of 142 SMKs and am wondering how far I should jump them? I load the Lapuas to 2.815 COAL which gives me a .025" jump. However the ogive one the SMK is much further back and I'm looking at a huge jump. I can load to 2.880" but then I start to see issues with the bullet not fully seated in the neck.

Any suggestions from those that use it?

 

[Kyskeet]

I Jump them .020 on 42.3gr H4350 in Hornady brass

 

[pell1203]

I've been jumping them 0.040" on a 6.5 CM RPR behind 41.2 gr. of H4350 with decent results. 42.6 gr. with same powder and jump has also worked well at the next higher node.

 

[lennyo3034]

What is your COAL with those jumps? Thanks for the info.

 

[pell1203]

What is your COAL with those jumps? Thanks for the info.

lennyo, COAL is 2.816" with a 0.040" jump on my RPR. BTOG is 2.207" as measured with a Hornady 5-26 insert.

 

[jarhead1077]

When I checked with Sierra on 142 SMKs they stated the following: 0.391 bearing surface, 0.215 boat tail, 1.363 total length standard. I have measured on average 0.704 bullet base to ogive. I have also measured total length as much as +0.010 more than standard. Given those dimensions, total COAL of 2.888 is still 70%+ in bearing surface. (Using 1.363 total length.) Remaining issue with jump is dependent on your chamber length and lands.