First Time OCW resulsts and Question

[sigma2chi]

Just got back from the range with my first OCW test results and as per the insructions........ I have question. Here is the results

Using 168gr SMK in my .308 with H4895 powder. Charges are on the targets. As per the instructions I should choose 42.7 as my Optimal Charge. I understand that this will be my most "resiliant" charge pressure wise, etc,.. yada yada yada... The quesiton eating at me is why in the wide world of sports would I NOT choose the 43.3 charge which was the most accurate??? It's not like I'm shooting in 28 degrees one day and 120 degrees the next. So why does "resiliance" trump accuracy. I have not played with seating depths yet. This was all conducted at 0.020 off the lands seating depth

Oh, distance was all at 100yds and the CB shot was my cold bore shot with Federal 168's

 

[roggom]

Yes, your accuracy node looks to be 42.7 - 43. The 43.3 is tighter but a little lower and than the previous two.

You could work the seating depth of 42.7, and just for grins, roll up 10 rounds of 43.3. Shoot two 5 round groups of 43.3 and see where you are at.

 

[JGorski]

Just got back from the range with my first OCW test results and as per the insructions........ I have question. Here is the results

Using 168gr SMK in my .308 with H4895 powder. Charges are on the targets. As per the instructions I should choose 42.7 as my Optimal Charge. I understand that this will be my most "resiliant" charge pressure wise, etc,.. yada yada yada... The quesiton eating at me is why in the wide world of sports would I NOT choose the 43.3 charge which was the most accurate??? It's not like I'm shooting in 28 degrees one day and 120 degrees the next. So why does "resiliance" trump accuracy. I have not played with seating depths yet. This was all conducted at 0.020 off the lands seating depth

Oh, distance was all at 100yds and the CB shot was my cold bore shot with Federal 168's

Using that powder Id think 41-41.5grs would be optimum since 42grs of RE15 is really accurate in a buddies old 700 Varmint, he had his bullets seated closer to the lands and it shot bad, he then seated them at 2.800" and that produced one ragged hole at 100yds, yeah, thats like .145" off the lands, but damn it shot good, my SPSS is the same way with 168AMAXs.
What rifle do you shoot?

 

[Break Bad]

I've only done a few ocw but here's my take: Because it could be luck at 43.3? Do another ocw in .1 grain increments in between groups that show large vertical spread....unfortunately you could probably use more data above 43.3 unless its getting to warm. In your case I would think about .1 gr ocw from 42.7 to 43.5 give or take.

 

[sigma2chi]

The Rifle is a BAT Machine, with a 26" Kreig. Bl, Surgeon metal, Mannars T5. Gradous Built

Thanks for the replies so far guys

Also, if anyone can still answer why I should disregard the 43.3 as per the OCW instructions.......

 

[roggom]

^^ because the instructions state you are shooting for POI "You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets." and "Remember, don't get "bowled over" by a tiny group which falls outside the OCW zone"

but the 43.3 is not that far off.

Maybe run the 42.7-43.3 again, and make sure to use the "round robin" method to rule out heat shift. Either way, you are very close to wrapping that load up.

 

[1lnbrdg]

The key here is from the O in OCW, Optimal. If you were to be throwing charges (with it's variances) and not weighing them, the 42.7 charge would be optimal for sure. Try a 10 or 20-shot group from both loads and work from there.

 

[jfields]

Try round robin 5 shot groups at 42.7 using 3 or 4 different seating depths. I would be looking for one of those seating depths to be really close to your 43.3 group's size and will theoretically be much less susceptible to variations in brass, weather, differences in powder lots, etc.

 

[X-fan]

The Rifle is a BAT Machine, with a 26" Kreig. Bl, Surgeon metal, Mannars T5. Gradous Built

Thanks for the replies so far guys

Also, if anyone can still answer why I should disregard the 43.3 as per the OCW instructions.......

OCW is good, but if God didn't want you to see it he wouldn't have given you a bughole!
You can answer that question by retesting and adding a 43.6 (yes that is 0.1 over book max).
This would rub Dan the wrong way, but if it was me (sorry Dan ) I would test 43.0, 43.2, 43.2, 43.6 in the quest for a higher accuracy node.

 

[JGorski]

They're all pretty much hitting the same POI, as long as you're not getting pressure signs with 43.3grs load some more up and do some verifying tests. I remember trying some H4895 in my 308 a few years ago, I was about a grain from max and that was a HOT load, pretty sure the bullet was the 150SBT, never tried that powder in my 308s again.