308 SD or Velocity

[NiMiK]

My question to everyone is, do you load for MV next or lowest SD and why one before the other?
I'm working up a new load for 308 using 175gr SMK, Varget, 1x fired Lapua brass and CCI LRP (not BR or match). I found a good starting load and CBTO for my rifle. Just finished up chronographing 5 rounds each of 10 different charge weights (.5gr increments from 38-42.5)and found some single digit SDs. It's a lot of rounds but the range was empty and I decided to take a longer lunch break today.

[Divernhunter]

I load for hunting so I want speed(especially with non-lead bullets) and accuracy. I shoot 5 rounds over my chrono and save the target. Then move on to the next powder or powder charge. I load at or near max for my testing. I end up with excellent results for speed and accuracy. I also find that usually the lower SD tends to give better accuracy...………..but not always.

[kcstott]

I shoot F class. More LR than MR for sure but I still shoot the MR stuff.
I don't have differing loads for the differing ranges, so my long range load is also my med range load,

I load based on pressure curve or velocity plateau. (I have yet to see it proven that they are one and the same it's just a guess)

So I load rounds to find a flat spot in velocity while increasing powder charges in .2-.3 increments. I then pick a velocity close to max but about two steps off of where the velocity starts to rise again. I load those and shoot for a group, I adjust seating length to suit the bullet used and then go and shoot them at 1K or farther.

[NiMiK]

Thanks for the replies. I don't think I'll be doing any hunting with this rifle though. I pushed the 175gr SMK to about 2682fps but my SD really just shot up. No pressure signs like ejection marks or flattened primers. Should I increase the charge by increments of .3gr? I'm shooting these bullets through a 24" barrel Savage 10.

[highpower790]

As a service rifle shooter I load for velocity.I know that ,for example I will need 2600fps with a 22" barrel and a 175gr bullet to get to a thousand.I don't care about SD when I factor in what Im shooting and my skill level.

[kcstott]

Thanks for the replies. I don't think I'll be doing any hunting with this rifle though. I pushed the 175gr SMK to about 2682fps but my SD really just shot up. No pressure signs like ejection marks or flattened primers. Should I increase the charge by increments of .3gr? I'm shooting these bullets through a 24" barrel Savage 10.

Way to large of a step in powder charge. .3g minimum charge step then you'll find a better node, then push .1 up and .1 down from the node to further refine.

[NiMiK]

As a service rifle shooter I load for velocity.I know that ,for example I will need 2600fps with a 22" barrel and a 175gr bullet to get to a thousand.I don't care about SD when I factor in what Im shooting and my skill level.

Thanks! I think I'll go with a faster velocity at this point.

Way to large of a step in powder charge. .3g minimum charge step then you'll find a better node, then push .1 up and .1 down from the node to further refine.

Right. I started with a low charge but I'll do a few more with .2 increments up to a max of 43.5. Should I be looking for a slight drop of velocity as I move up in charge weight?

[J-cat]

I would go with 44grs of Varget in the Lapua case.

[NiMiK]

I would go with 44grs of Varget in the Lapua case.

[J-cat]

What’s your oal and how much is it off the lands?

[NiMiK]

I'm .020 off the lands with a CBTO of 2.210 for my rifle's chamber.

[J-cat]

What is your coal? Bto on smk varies too much from lot to lot to be of any value.

[NiMiK]

Not sure what my OAL is but they fit in my AI mags. I've been measuring by CBTO for a while since it gives me more consistency when seating. OAL doesnt sit well for me since meplats vary from bullet to bullet no matter the batch or brand.

[NorCalFocus]

Thanks for the replies. I don't think I'll be doing any hunting with this rifle though. I pushed the 175gr SMK to about 2682fps but my SD really just shot up. No pressure signs like ejection marks or flattened primers. Should I increase the charge by increments of .3gr? I'm shooting these bullets through a 24" barrel Savage 10.

Your charts are off. Build a cart with charge weight on the horizontal axis, then speed on the vertical. Then your chart plots your average speeds showing climbs and drops. Thusly looking for a flat spot.

Here's a copy of my latest chart. I ended up loading 42.5 grains.


Load for accuracy, not speed. One, faster rounds just mean you'll miss faster. Two, its more wear and tear on your compoments and barrel. There is no need to push up near max loads for a rifle your just using to shoot paper and steel. Hunting, sure I want the fastest heaviest bullet I can have. If your playing games like PRS or F-Class and want a faster bullet to help you cheat the game, then go to a 6.5 or 6 mm class cartridge.

If your loading in a flat spot and have good reloading practices your SD's will be good. My last outing with my new load I shot 10 rounds over the chrono and got an SD of 14. Good enough for me. I also gained about 30fps because the temps were higher then when I had done the original testing.

[OpenSightsOnly]

Not sure what my OAL is but they fit in my AI mags. I've been measuring by CBTO for a while since it gives me more consistency when seating. OAL doesnt sit well for me since meplats vary from bullet to bullet no matter the batch or brand.

For mag length ammo, OAL is fine.

CBTO is good if your ammo is longer than magazine length.

FWIW, Berger and Lapua are very good but the meplat still gets dinged around during shipping