Yet another OCW help thread

[Blackjack988]

I know I should probably just contract Dan Newberry to help me out but I just wanted to ask everyone's opinion of which load I should go with:

Rifle:
Tac Coord FN SPR in .308 Win
Bushnell XRS 4.5-30

Ammo:
Sierra 175gr SMK
Lake City LR 11 Brass
IMR4064
Winchester #9 1/2 Primers
Loaded to 2.8 OAL

Target was at 100 yards.

My initial thought was that I had nodes at 43.5 and 44.0 because of how similar the groups looked. Looking at the specs again though I think my nodes are actually at 42.8 and 43.5, meaning my OCW would be in between those at 43.1. How far off is my thinking?

Unless of course i'm misunderstanding how to analyze the targets.....

 

[Twoboxer]

. . . My initial thought was that I had nodes at 43.5 and 44.0 because of how similar the groups looked. Not the basis for finding an OCW. Looking at the specs again though I think my nodes are actually at 42.8 and 43.5, meaning my OCW would be in between those at 43.1. Again, not the basis for finding an OCW. How far off is my thinking?

Unless of course i'm misunderstanding how to analyze the targets.....

Yes, you are. You are looking for a couple of consecutive charge levels that produce good groups with a similar group POI. Using that as guidance, choosing a charge level properly in that area allows you to reload with the knowledge that even with variations in powder charge you will get good groups.

The problem (for me) looking at your groups is they seem to alternate to different sides of the bullseye . . . as if your POA was actually a bit different (angled) as you shifted to the next target. My *guess* is your node is around 43.0/43.1 . . . which would predict a scattered group possible at 43.7 or so, and your next node somewhere around 44.4.

 

[Blackjack988]

Yes, you are. You are looking for a couple of consecutive charge levels that produce good groups with a similar group POI. Using that as guidance, choosing a charge level properly in that area allows you to reload with the knowledge that even with variations in powder charge you will get good groups.

The problem (for me) looking at your groups is they seem to alternate to different sides of the bullseye . . . as if your POA was actually a bit different (angled) as you shifted to the next target. My *guess* is your node is around 43.0/43.1 . . . which would predict a scattered group possible at 43.7 or so, and your next node somewhere around 44.4.

Thanks for the quick response. I may have misspoken. When I was talking about the groups looking similar I was referring to their position in relation to the point of aim which, in this case, was the center of the diamond. For example, targets 4 and 2 have 2 rounds that are in pretty much the same location.

I was having some trouble getting my target level so that may be part of the issue. I'll likely end up loading up this same series of charges and shoot it again sometime soon.

 

[Rprecision]

I would want to see what's above 44.5, provided you don't have any pressure indications

If 44.8 prints like 44.5 its on!

 

[Darkside-Six]

whatever you used for your sighter grouped nice and in the POI. Looking at this, your accuracy node is 43.1 based off these targets here.

 

[bax]

Concur. 44.3 and 44.5 printed at nearly the same POI. The 44.3 group size could be a weather report. If the POI for 44.7 is similar then you nailed it -- load 44.5 and be happy. If you do not have pressure at 44.5, you might reshoot 44.1, 2, 3, 4, 5, 6, and 7. If you do have pressure at 44.5, you might reshoot 44.1, 2, 3 and 42.9, 43.1 and 43.3.

I also shoot LR brass with 175 SMK in LR cases using IMR 4064 with a COL of 2.795. I use Federal 210M primers. I have had very good luck with two thing: sort cases by weight and debur the flash hole.

Here is my suggestion: decap and size a bunch of cases, clean the primer pockets, debur the flash hole, and trim them all to the same length - mine are 2.007 but I don't think that the the exact number is critical. Sort your cases by weight. You should have a small group that weight 175 grains, a big group of 176, another group nearly that big of 177, and a smaller group of 178. Those are my results, your mileage may vary. By the way, if you happen to prime them first, a 210M primer weights about 4.3 grains. Pick one of the sets -- say the 176 grain cases - and load and shoot those. I will be pretty surprised if you do not see a difference using weight-sorted brass.

In my rifle my good groups are 41.2 grains in the 175 and 176 grain cases and 41.0 is the 177 and 178 grain cases. Those shoot to exactly the same POI out to about 800 yards. If I change the charge in my 176 cases from 41.2 to 41.0, the POI drops by about 0.15 MOA at 400 yards but the groups are the same -- that is, if I load all case weights with 41.0 or all with 41.2, the POI moves up and down but the group size stays at about 0.5 MOA. FWIW, if I load those cases with 42.2 grains, the group sizes go all to hell -- 8s and 9s.

I am a fan of lower velocities because it is easier on my brass (I only have a couple thousand pieces of that LR brass) and my barrels. My load has a muzzle velocity of about 2620. I expect my barrel to shoot well for another 3,000 to 5,000 rounds. Barrels cost real money.

 

[Blackjack988]

More Data!

So I finally managed to get a re-shoot of the previous loads. All the specs are the same as above. Also, this time I used my brand new Magnetospeed (thanks [MENTION=69879]herofish[/MENTION]) to get average velocities for each group. Finally I took note of some of the suggestions above and added another charge at the high end. I'm not sure how much higher I can go charge wise. The combination of brass, bullet, and powder seems to be resulting in compressed loads at ~44.6

Velocities:
40.1 - 2496
40.4 - 2482
41.7 - 2600
42.5 - 2641.3
42.8 - 2646
43.1 - 2674.7
43.4 - 2676
43.7 - 2698.6
44.0 - 2722
44.3 - 2691.3
44.6 - 2767
45.0 - 2755.6

I have no idea what happened at 43.1, not my best work.....

Also, I should note that the point of aim was the top tip of the diamond and that the charge that reads 44.5 on the first image (target 2) is actually 45.0

 

[rduckwor]

43.7-44.0 Look pretty good to me.

I think I would not be loading much higher in LC brass as it is milspec and has a lower case capacity than commercial.

Nothing wrong with that, but something to be aware of. Any pressure sign anywhere above 44 Gr?

 

[Blackjack988]

43.7-44.0 Look pretty good to me.

I think I would not be loading much higher in LC brass as it is milspec and has a lower case capacity than commercial.

Nothing wrong with that, but something to be aware of. Any pressure sign anywhere above 44 Gr?

I didn't notice any obvious pressure signs anywhere along the range. No hard bolt lift, no ejector swipes that i could see. Although I am getting crated primers pretty low down the range. Seems to be my FN with any ammo, even factory. I've included an awful image of the cases just in case someone sees something I don't.

Also, I was bored and made a scatter plot of horizontal/vertical offset from POA using On Target. The diamonds are my first OCW workup at the beginning of the thread. No real discernible clustering or pattern. The squares are my second. There's a nice clear cluster right near 43.4. I may give that a shot and use that as my final load.

 

[sib1948]

I use IMR 4064 42.8 gr. with both my 168 & 175 SMK and 43.9 gr. with Berger 185 gr. VLDs. Win brass with Fed 210 & 215 primers (see no difference between the two). OAL 2.86" Consistently 1/2 MOA at 100 yards and 300 yards. 2675 fps out of 22" Bartlien barrel with SD 7 fps. Best group out of 100s was 0.16 MOA at 100 yards. First group I had that day after cold bore shot. I should have packed up and left. Everything else downhill!!!

 

[rduckwor]

I didn't notice any obvious pressure signs anywhere along the range. No hard bolt lift, no ejector swipes that i could see. Although I am getting crated primers pretty low down the range. Seems to be my FN with any ammo, even factory. I've included an awful image of the cases just in case someone sees something I don't.

Also, I was bored and made a scatter plot of horizontal/vertical offset from POA using On Target. The diamonds are my first OCW workup at the beginning of the thread. No real discernible clustering or pattern. The squares are my second. There's a nice clear cluster right near 43.4. I may give that a shot and use that as my final load.

O.K. What variable did you plot in the scatter chart? Vertical dispersion or group size?

Also, looking at the case heads, it is a bit hard to tell, but I "think" I see a trace of ejector swipe on the 44.6 cases. Maybe a little on the 44.3 loads too. The primers are flattened and cratered, but that may or may not mean anything.

Go carefully up there.

Good Luck,

 

[Jaxdialation]

OCW generates many "what should I do" questions. Enough that I see Mr Newberry offers
for fee consulting to help with load development. I think I'd just spend the $$
and get his personal help. Its a buy once cry once deal.

I don't use the OCW technique. But it has a LOT of fans.

 

[Blackjack988]

I use IMR 4064 42.8 gr. with both my 168 & 175 SMK and 43.9 gr. with Berger 185 gr. VLDs. Win brass with Fed 210 & 215 primers (see no difference between the two). OAL 2.86" Consistently 1/2 MOA at 100 yards and 300 yards. 2675 fps out of 22" Bartlien barrel with SD 7 fps. Best group out of 100s was 0.16 MOA at 100 yards. First group I had that day after cold bore shot. I should have packed up and left. Everything else downhill!!!

Thanks for the insight!

O.K. What variable did you plot in the scatter chart? Vertical dispersion or group size?

Also, looking at the case heads, it is a bit hard to tell, but I "think" I see a trace of ejector swipe on the 44.6 cases. Maybe a little on the 44.3 loads too. The primers are flattened and cratered, but that may or may not mean anything.

Go carefully up there.

Good Luck,

The X axis is horizontal deviation and the Y axis is vertical deviation. Both of these are relative to the points of aim.

I'll take a closer look at the ones you're referring to.

OCW generates many "what should I do" questions. Enough that I see Mr Newberry offers
for fee consulting to help with load development. I think I'd just spend the $$
and get his personal help. Its a buy once cry once deal.

I don't use the OCW technique. But it has a LOT of fans.

Thanks for the input. I actually considered contracting him to take a look at them, especially since i'm on a time crunch. I may reach out.

I'm using OCW only because I don't have access to a long range to run a proper ladder test.

 

[rduckwor]

The scatter plot is a good idea.

I typically try to find consecutive charge groups that have similar or close vertical dispersions from teh POA and work those charges.

On those run where there isn't a clear winner, group size comes into play for me.

Good work you are doing here.