.308 load development results--opinions needed

[ncpilot]

I worked up some loads for my .308, with the results in posted images.

Big question, does it make sense? Can it really be only one single load out of 12 that is good?

New Winchester brass, full length resized, trimmed to 2.005". Twelve loads, 6 each with 168/175 gr. SMK, four rounds for each powder weight (Varget), loaded on Hornady progressive, single cartridge at a time. Powder weights on the target images. COAL ~2.8" (some variation around 2.795)

Savage 10, barrel cut to 20", AAC Cyclone, Bell&Carlson stock.

Shot all 4 of each load without much lag time. Waited until I could touch my suppressor (and not get burned) before next set (played with the Savage FV-SR while waiting ) Started with the 168 loads, then to the 175. No cleaning at all--so the best group appeared on the 33rd-36th shots.

Should I just be happy with 175gr SMK and 43gr Varget and call it a day? I plan on verifying the results with another set of loads, but don't want to do all 12 variations again. Hope I anticipated most of the questions. Oops...forgot-100 yards...

Thanks!

 

[JMGlasgow]

I would be happy with that. How does it do further out?

 

[ncpilot]

Don't know yet... I'd like to recreate those results at 100 yds first, then move out further... I suppose I should reload another set and see what happens at 200 and 300 yds.

 

[390fe]

What is your twist rate? What are you wanting your rifle to accomplish - 100 yard groups, 600 yard groups, 1000 yard steel?

Your 43 grains of Varget with that bullet is a pretty standard accuracy load.

 

[Victor N TN]

A lot depends on the rifle, a lot depends on the load components. I have a couple of loads for an "off the shelf" standard rifle that have to be EXACTLY there, to make it shoot.

Good luck.
Victor

 

[dauntedfuture]

The best way to assess a load would be to shoot it at distance. This causes some problems as you introduce environmental factors. While it not should all that different, a 5 round group has 20% more bullets then a 4 round group, as such when you go from a 3 to a 5 to a 10 round group the POTENTIAL to show the real loads potential increases exponentially. If you want to verify that the 43g varget load is good, and its a fairly common one, load and shoot 10 rounds on paper and chronograph the results. If I can get a real 10 round group that shoots MOA with 25 fps or less ES I call it good for my 1000 yd guns. Its even better if I can get 10 round 1.5-2" groups at 200 yds, as my range is 200 yds, that is usually where I test LR ammo and those are the kind of groups I can get. It's not uncommon when you shoot a 10 rd group to see 3-5 shots that are almost on top of each other, and 5-7 other that open the group from .25 to 1".

 

[rduckwor]

43 looks good bearing further proof and reproduction at distance. 20" barrel - you might be a bit light in the velocity department for >6-800 yards.

Good Luck,

 

[djarecke]

I'd say you're on the right track with the notion of a load around 43 grains. I'd load up a few more and re-shoot 43-44 grains behind the chrono and see if you've got a velocity you can live with at your planned engagement distances.


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[Pinecone]

0.5 grain changes with a 40ish grain load is over 1% charge weight increment. You could be skipping over nodes. A 0.3 grain increment would be better.

Also fire the rounds round robin. Shot 1 is Round 1 of Load 1 at Target 1. Shot 2 is Round 1 of Load 2 at Target 2, Shot 3 is Round 1 of Load 3 at Target 3.

Also, space out the shots. I use 2 minutes between shots to reduce heating affects.

 

[ncpilot]

What is your twist rate? What are you wanting your rifle to accomplish - 100 yard groups, 600 yard groups, 1000 yard steel?

Your 43 grains of Varget with that bullet is a pretty standard accuracy load.

As I've gotten older, my twist rate sadly has decreased--and, I want my rifle to accomplish magic!

Ok, back to reality... 1/10 twist, and my max distance at my club is 400 yards, where we have a choice of steel or hanging paper targets. I kinda like the challenge of precision shooting at distance, so I'll probably use targets.

Yeah, I've got a star next to the 43 Varget and 175SMK in my loading notes... saw that one a lot in my research.

 

[ncpilot]

Thanks everyone... I'll try to address everything without copying each post in my reply...

I believe there was a reference to the OCW method of testing, which I've read a few times--something to consider as a methodology change.

Re: % powder change between loads--I would have expected something better with the 168 SMK, and thought about missing a node, although I did want to limit the number of rounds fired, and figured I'd find something close enough at the .5gr spacing so I could go back and tweak around it. I may try to pick the best couple of groups and bracket with .3gr changes.

Re: # rounds per load--I agree, just trying to get close enough to figure out where to tweak without firing a bazillion rounds...

Summary: I need to reproduce results, increase round count per load, check performance at 200/300 yds, chrono the loads for consistency, and try some smaller increments, at least with the 168SMK.

Gonna go back this Sunday and play some more!

 

[dauntedfuture]

If your not shooting past 600 yds then you have plenty of velocity. More realistically I am confident that 43g will 175g sierra supersonic at 800. Possibly a 168g to 800 but that will be pushing it. Past 800 is when the wheels start to come off.

 

[Twoboxer]

0.5 grain changes with a 40ish grain load is over 1% charge weight increment. You could be skipping over nodes. A 0.3 grain increment would be better.

Also fire the rounds round robin. Shot 1 is Round 1 of Load 1 at Target 1. Shot 2 is Round 1 of Load 2 at Target 2, Shot 3 is Round 1 of Load 3 at Target 3.

Also, space out the shots. I use 2 minutes between shots to reduce heating affects.

^ This

While each node has some width to it, the theory would predict nodes 3% or ~1.3gr apart. So *IF* 43.0 is a node, then 41.7 and 44.3 may be as well. You would have missed confirming both of them by using the specific 0.5gr increments you used.

 

[TacticalBoltKnob]

I would take your best two loads and re-test, this time getting some velocity numbers, too. One will come out on top for what you want.

 

[kalindark]

I'm seeing a lot of vertical stringing in your groups. I just started load work with my suppressor and noticed heavy mirage after a few shots. The first time I shot through mine I noticed more vertical than I normally get. I think you should shoot your strings slower and if you see mirage from the can, let it cool some more.
But yes, 43gr looks good.

 

[Pinecone]

Thanks everyone... I'll try to address everything without copying each post in my reply...

I believe there was a reference to the OCW method of testing, which I've read a few times--something to consider as a methodology change.

Re: % powder change between loads--I would have expected something better with the 168 SMK, and thought about missing a node, although I did want to limit the number of rounds fired, and figured I'd find something close enough at the .5gr spacing so I could go back and tweak around it. I may try to pick the best couple of groups and bracket with .3gr changes.

Re: # rounds per load--I agree, just trying to get close enough to figure out where to tweak without firing a bazillion rounds...

Summary: I need to reproduce results, increase round count per load, check performance at 200/300 yds, chrono the loads for consistency, and try some smaller increments, at least with the 168SMK.

Gonna go back this Sunday and play some more!

OCW only needs 3 rounds per charge increment. More does not make it work better. Same thing with distance, 100 yards for load work up, then try the load you choose at a longer range. But history shows, if you do the method right, the load WILL work at longer ranges.

 

[ncpilot]

I'm seeing a lot of vertical stringing in your groups. I just started load work with my suppressor and noticed heavy mirage after a few shots. The first time I shot through mine I noticed more vertical than I normally get. I think you should shoot your strings slower and if you see mirage from the can, let it cool some more.
But yes, 43gr looks good.

Don't remember much if any mirage, but good thought-thanks.