OCW input .308

[axarob44]

I haven't done one of these in a while. This is a .308 with 175 SMK at .020" off with Varget. 28" barrel This is my first .308

This OCW was shot round robin and the velocities are below

I'm thinking 42.6 gr to 42.9 gr but not sure because I could go a little higher and lower maybe

I'm just not sure. Any input is welcome

 

[nn8734]

I haven't done one of these in a while. This is a .308 with 175 SMK at .020" off with Varget. 28" barrel This is my first .308

This OCW was shot round robin and the velocities are below

I'm thinking 42.6 gr to 42.9 gr but not sure because I could go a little higher and lower maybe

I'm just not sure. Any input is welcome


View attachment 7423970

I’d load 10 rounds at 42.6 and another 10 at an adjacent charge weight (perhaps 42.8) keeping everything else constant and shoot 5 shots of each at 100. If everything looks good (low SD, ES) id fire the second group and then review the data for all 10. If things still look real promising, I would load 20 more at the best performing charge weight and engage 300 and 500 yard ipsc-sized targets, five - seven rounds each. The extra rounds are to help you get on initially at those distances.

My m40A5 loves 42.2g Varget in a lake city case and prints similar numbers to yours at 42.6. I’m also .020 off the lands.

 

[FLIGHT762]

43.0 Grs. and call it Macaroni. Been a standard load for years W/ Varget and 175 Sierra MK. The Rifle shoots. Load it up and go shooting.

 

[axarob44]

I'm liking 43.0 gr now that you point it out as being a known load. Ill see what the numbers look like there. If they don't look good Ill go down to what nn88734 said. Go the easy route first

 

[nn8734]

I'm liking 43.0 gr now that you point it out as being a known load. Ill see what the numbers look like there. If they don't look good Ill go down to what nn88734 said. Go the easy route first

43g is a relatively common node in 308 with Varget but you also should listen to what your particular rifle is telling you. Consider making 10 rounds at 42.6 and 43...shoot all 10 of each test group and assess the results (share them too). You should have some good direction to go on from there.

 

[axarob44]

Yes your right. Its easy to short cut sometimes when you're sweating barrel like I do on my 7 SAUM and .300 win mag (sometimes takes the fun out of it). I got this rifle to have some fun. You are right though, got to look at what its telling me. I will post the results

 

[Dthomas3523]

43.0 Summer and 43.1 winter if there are big temp swings where you are.

Mess with seating depth if you want an be done.

No need to worry with it at distance if you’re using good bullets. If it shoots at 100, it will shoot at 1,000 unless the BC is different enough from bullet to bullet to cause too much vertical stringing. All this “shooting at distance to confirm” is wasting ammo.

There are only three factors that matter at distance.

Shooter
Velocity
BC

The shooter is self explanatory. You are the weakest link.

Velocity, you already know if your velocity is stable or not due to your chrono.

BC......if a group “falls apart at distance” and you have ruled out shooter error and velocity (chrono), then the only thing left is the bullet. Variations from bullet to bullet are causing the vertical spread. Either switch to a more consistent bullet or sort/trim/tip bullets to make them more consistent.

 

[axarob44]

Yep, big temp swings here in Ohio. Thank you for all the input!

 

[Deleted member 113831]

43.5 grains

 

[axarob44]

Velocity spread looks good on 43.5 also. I'll load series of those too. Thank you Skookum

 

[308pirate]

Consistency in group center location is what you're looking for in an OCW.

Your node is 42.6 - 43.2

Fill up your cases with 43 grains and stop wasting components and time on experiments.

Go to Thunder Valley

 

[Dthomas3523]

Velocity spread looks good on 43.5 also. I'll load series of those too. Thank you Skookum

Don’t fall into the trap of the smallest numbers or best group.

 

[b2lee]

I have ammo can after ammo can filled with mixed head stamp brass... 43.0 grains of Varget....and some military pulled 175gr SMK's. After over 4500+ rounds through the barrel....it still shoots great...for a 308 at 1000 yards. Recently I've switched to 168gr Everglades Match bullets...but for 600yd paper targets..and they shoot great. And a literal crap ton of 175gr SMK Military pulls with BL-C(2)....for an AR-10...and they shoot great.

I'll be out at TVP this Saturday shooting some ELR with the 300PRC if you happen to be in the neighborhood....might stay the night and shoot the .308 all day on Sunday on Open Range Day. I'll second what @Dthomas3523 said....generally... 1. Shooter is the problem. If you load the 308 with 43.0 grains and slap a 175SMK on top...it should shoot all day long.

 

[axarob44]

Kind of hard to ignore all the testimony on the 175SMK with 43grs. So much to learn. I guess I was assuming that consistent MV (or ES and SD) was an indicator of being in the node. Not the main consideration with OCW but a contributing factor or clue.

I knew it was location of the center of the group was the main indicator, but mostly confused on this one because to me they all ALMOST are in the same location for the most part.

That's why I asked. Thank you guys for showing me what to look for. I still have a lot to learn

b2lee, I wish I could get down there to TVP, I'll be able to soon, maybe I'll drop you a PM when I can go to see if you're going to be there ?

 

[b2lee]

TVP is a 3.5hr drive for me.....and I'm there twice a month....you can always drop me a PM and if I'm off work that weekend...I'll be there.

 

[axarob44]

Ok, cool I'm about 2 hours away.

 

[Dthomas3523]

Kind of hard to ignore all the testimony on the 175SMK with 43grs. So much to learn. I guess I was assuming that consistent MV (or ES and SD) was an indicator of being in the node. Not the main consideration with OCW but a contributing factor or clue.

I knew it was location of the center of the group was the main indicator, but mostly confused on this one because to me they all ALMOST are in the same location for the most part.

That's why I asked. Thank you guys for showing me what to look for. I still have a lot to learn

b2lee, I wish I could get down there to TVP, I'll be able to soon, maybe I'll drop you a PM when I can go to see if you're going to be there ?

This is a reason many are moving away from OCW.

I can show 10 people OCW groups and will get 7 different answers. The ones who really know it will pick the same or similar. Everyone else is all over the place.

But, I can take 10 people, show them how to find powder nodes via a chrono and they will almost all see the same thing as it’s not really left you to subjective interpretation.

 

[axarob44]

Dthomas, what I usually do is pick a velocity range I want. Then I load groups of 4 rounds at powder charges .3 grains apart within that range and shoot groups with a Labradar and look for similar impact points with the lowest ES and SD and then play with seating,

I wanted to do this one with textbook OCW because my last rifle I did my method didn't pan out and wasted a bunch of barrel life and components to get a load.

I know it's probably not the best method but I've be fairly successful up until the 7 SAUM that got me chasing my tail.

 

[Gustav7]

TVP is a 3.5hr drive for me.....and I'm there twice a month....you can always drop me a PM and if I'm off work that weekend...I'll be there.

Ok, cool I'm about 2 hours away.

I'm just northwest of Columbus, about 90ish minutes away from TVP. I'll have to throw out a PM when I go...which ironically I've never been. Heard its pretty legit though.

 

[Dthomas3523]

Dthomas, what I usually do is pick a velocity range I want. Then I load groups of 4 rounds at powder charges .3 grains apart within that range and shoot groups with a Labradar and look for similar impact points with the lowest ES and SD and then play with seating,

I wanted to do this one with textbook OCW because my last rifle I did my method didn't pan out and wasted a bunch of barrel life and components to get a load.

I know it's probably not the best method but I've be fairly successful up until the 7 SAUM that got me chasing my tail.

Look for a range of charge weights that have consistent ES and load in the middle. Or low side in summer and high side winter.

Tune to best group via seating depth. No need to shoot groups for powder charge anymore if you don’t want to. It’s fast and pretty objective.

 

[phlegethon]

Bryan Litz said in one of the recent podcasts he didn't think there were really velocity nodes in modern heavy barrels. If that were true, you'd expect to see OCW results just like those posted here. He said he just loads half a grain below pressure and moves on to other things. Seems like it could work.

 

[Gustav7]

Look for a range of charge weights that have consistent ES and load in the middle. Or low side in summer and high side winter.

Tune to best group via seating depth. No need to shoot groups for powder charge anymore if you don’t want to. It’s fast and pretty objective.

Would you say this is only valid with a Magneto Speed or a Labradar?

I have the ole Pro Chrono special and I was a little hesitant about only using that for my last load development

 

[b2lee]

I don't know about others....but I wouldn't trust an optical chronograph...or atleast one that you can actually afford. I prefer my MagnetoSpeedV3 over the Labradar....but then again...all my barrel profiles are the same...so going rifle to rifle is rather painless.

 

[Dthomas3523]

Ya. Magneto, labradar or oehlar are the only ones I would trust.

Also, if your brass prep and powder throw isn’t g2g, nothing will matter

 

[axarob44]

Quote

Bryan Litz said in one of the recent podcasts he didn't think there were really velocity nodes in modern heavy barrels. If that were true, you'd expect to see OCW results just like those posted here. He said he just loads half a grain below pressure and moves on to other things. Seems like it could work.

Yes, I listened to that podcast