Help interpreting OCW results

[tcoz]

I shot an OCW test on Sunday and would appreciate the opinion of some people more experienced than I am in interpreting them. I posted this on another forum that I frequent and never got an answer but instead started a discussion on the merits of the OCW method which isn't what I wanted.

Three shot groups at 100 yards fired "round-robin" style with the order of shooting reversed after each string. Barrel was allowed to cool 1-2 minutes between shots. There is a black dot indicating the center of each group. I should have used red dots since it's hard to tell the dot from the shots in some cases unless you look closely.

The second picture is the center of each group plotted on a single target with the charge weights indicated. The one plotted lower left is 41.5gr as part of the charge weight was cut off.

41.8, 42.1 & 42.4 are the three consecutively charged groups closest together which would lead me to choose 42.1 as my OCW but I'm not sure whether I'm looking at it correctly. I don't have a range longer than 100 yards to verify results so I'll have to go with what I have here but I'm not very experienced in assessing the results. Any input will be appreciated.

https://www.thehighroad.org/index.php?attachments/img_1297-jpg.230341/https://www.thehighroad.org/index.php?attachments/img_1318-jpg.230342/

[squirrel_slayer]

42.1 looks like the one to pick. how is the es/sd on that load?

[tcoz]

I'm doing thus as I've always done, without the benefit of a chrony. I know this makes it more of a guessing game but the range where I shoot doesn't allow them or anything else forward of the firing line. A MagnetoSpeed is in my future but it just isn't in the budget right now.

[bigedp51]

Below a good read with Erik Cortina giving advice on the groups.

Long range load development at 100 yards.
Erik Cortina
Team Lapua-Brux Captain
http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/

[m12lrs]

Well with an OCW series of targets i ignore the horizontal and focus on the vertical. Can't see the targets on my phone but i believe i would work with the charges on the center two targets. Looks like the widest node. I would run several groups with smaller powder charge increases in that range. Find the load and move on to seating depth test.

Seating depth test will tighten them up

[Zero333]

I vote for the top left group in pic #1

[s3silver]

Another vote for top left group.

[tcoz]

41.8, 42.1 and 42.4 are the three consecutive charges with the least vertical spread so I'm going to shoot a group of 20 with each charge. From that I'll use the charge with the best overall group.

I matched the ogive to base OAL in all of the test rounds to Hornady 168gr HPBT Match ammo which gave a 0.077" jump to the lands in my rifle. I'll work the final load down in 0.010" increments and see whether the groups tighten.

Unfortunately I only get to the range once every 2-3 weeks so this turns into a two month project.

[squirrel_slayer]

Unfortunately I only get to the range once every 2-3 weeks so this turns into a two month project.

I know the feeling. same problem here.

[Chamdaddy]

41.8, 42.1 and 42.4 are the three consecutive charges with the least vertical spread so I'm going to shoot a group of 20 with each charge. From that I'll use the charge with the best overall group.

I matched the ogive to base OAL in all of the test rounds to Hornady 168gr HPBT Match ammo which gave a 0.077" jump to the lands in my rifle. I'll work the final load down in 0.010" increments and see whether the groups tighten.

Unfortunately I only get to the range once every 2-3 weeks so this turns into a two month project.

I agree with your assessment, 42.1 looks to be in the middle of the group with least vertical dispersion. M12lrs was thinking the same thing, but since he was looking at it on a phone he probably could not tell your image is turned 90 degrees so what looks like horizontal dispersion was actually vertical. That is assuming your handwriting is not at 90 degrees. Took me a minute on a full screen to notice it. Let us know how it turns out.

[tcoz]

I agree with your assessment, 42.1 looks to be in the middle of the group with least vertical dispersion. M12lrs was thinking the same thing, but since he was looking at it on a phone he probably could not tell your image is turned 90 degrees so what looks like horizontal dispersion was actually vertical. That is assuming your handwriting is not at 90 degrees. Took me a minute on a full screen to notice it. Let us know how it turns out.

I finally made it out to a range yesterday and it was probably a mistake. Rainy, cold and extremely windy so it wasn't exactly conducive to good shooting. Unfortunately I don't have targets to show you because the rain and wind basically destroyed them but I was able to draw a conclusion from them. I was able to get 12-15 good shots out of 20 total of each load but I looked at all 20 in assessing them.

With 41.8gr, all 20 were grouped within 4.17". At 42.1, all 20 were within 2.17" and at 42.4, eighteen were within 2.57" And I had two called flyers that were in a different galaxy. Except for the two flyers all of the other shots felt similar as far as marksmanship fundamentals went. I plan to use 42.2gr as my load for now.

I hope to make it out one more time before the range closes for the month of April (turkey season). All of my rounds for load testing were loaded to the same depth as Hornady Match ammo with the same bullet which is 2.175" ogive to base. My rifle is 2.250" to the lands giving a jump of 0.075". I'm going to load ten rounds each with a 0.060, 0.050, 0.040, 0.030 and 0.020 jump and shoot two 5-round groups of each. I'm interested to see whether seating depth makes much of a difference with this bullet (Hornady 168gr HPBT Match) in my rifle (Savage 10 FCP-SR 20"). If I find a couple depths that stand out I may try a few loads in between seated at 0.005" increments but that remains to be seen.

The process has been a lot of fun but I just wish I didn't have to stretch it out over 3-4 months. Within the next couple of days I'll probably be buying a SA M1A Loaded but since it doesn't gave the accuracy potential of the Savage, I won't be doing any long drawn out load development with it.

[Chamdaddy]

I did not see what cartridge you were shooting, I assume 308. I have never loaded for 308, but if you don't see acceptable results with you closing the gap don't ignore the possibility of a longer jump. In my 6.5 Creedmoor my initial load had a jump of .132 with a Berger VLD resulting in 0.2" and 0.3" groups. According to conventional wisdom this should not be possible. I am planning on working on the seating depth and expanding my samples but at least I know I have a fall back plan. However this works for me because I have magazine COAL issues and can't get any closer than a .055 jump with my current magazine.

[Zero333]

I'm wouldn't mind knowing more about the components used...

Brass make
Primers
Base to tip COAL

I have a feeling 43.5 gr will be the next and better node. Next time you go out to shoot this rifle, load some at 43.5 gr and don't be surprised if it shoots like a laser.

[tcoz]

I'll give it a try. I'm always open to suggestions.

Hornady Match brass
Hornady 168gr HPBT Match
CCI LRP (#200)
2.797" base to tip
2.175" base to ogive

[m12lrs]

I did not see what cartridge you were shooting, I assume 308. I have never loaded for 308, but if you don't see acceptable results with you closing the gap don't ignore the possibility of a longer jump. In my 6.5 Creedmoor my initial load had a jump of .132 with a Berger VLD resulting in 0.2" and 0.3" groups. According to conventional wisdom this should not be possible. I am planning on working on the seating depth and expanding my samples but at least I know I have a fall back plan. However this works for me because I have magazine COAL issues and can't get any closer than a .055 jump with my current magazine.


Interesting

Working with my .308 hunting rifle trying to find that less than mag length seating depth for the berger 168 hunting VLD was frustrating. Finally tried the berger jump test. Found my seating depth 0.127 off the lands. I was suprised to say the least.

Lapua brass CCI Br2 44gr varget 168 gr berger hunting VLD

Below is a pic of my final seating depth test. Each one of these is only 0.010 apart. You can plainly see the 0.030 wide accuracy node.

http://i1056.photobucket.com/albums/t379/rcoody1/Berger%20168gr%20hunting%20VLD_zpsr7bylmqu.jpg (http://s1056.photobucket.com/user/rcoody1/media/Berger%20168gr%20hunting%20VLD_zpsr7bylmqu.jpg.htm l)

[tcoz]

m12lrs, that's a very good and surprisingly obvious illustration of the difference that seating depth changes of 0.010" makes. I can only hope that my test gives such definitive results.

I dont load a VLD type bullet so mag length may not be a problem anyway, but I load single round (just because I enjoy it) so it becomes totally moot.

[m12lrs]

m12lrs, that's a very good and surprisingly obvious illustration of the difference that seating depth changes of 0.010" makes. I can only hope that my test gives such definitive results.

I dont load a VLD type bullet so mag length may not be a problem anyway, but I load single round (just because I enjoy it) so it becomes totally moot.

In my range guns i shoot the VLDs jammed about.0.010. Great accuracy.

With the creedmoor bench gun i am putting putting together i am going to try John Whidden's idea. He loads them with light neck tension with a 0.040 jam and lets the bolt do the final seating. I ordered his sizing die and expander ball kit. Try about .001 neck tension to start.

I like to experiment

[tcoz]

I don't really have the confidence to experiment very much. Even though I've been handloading for about ten years, this is my first bolt gun and my first attempt at loading for accuracy.
I have a Garand, M1 carbine, 9mm carbine and a couple ARs so for obvious reasons I've been concentrating mostly on function with mid-range loads.

Also, since my range is only 100 yards I'm probably wasting a lot of time and effort but I enjoy it so much that I'll continue trying to wring out every bit of accuracy that I can.

[m12lrs]

For your .308 try this

Lapua brass, BR2 primer, 44 gr Varget, 168gr Sierra Match King

Try it at different seating depths. Match kings are not real sensitive to seating depth but there is one out there that is magic. Use the berger seating depth test starting just.off the lands to at least 0.120 off the lands in 0.030 increments

After you find the best seating depth then you can fine tune your charge weight.

If you decide to stretch your legs a bit when you go over 600 yrds use the 175 match king

[tcoz]

Those of you who have responded to this thread, would you mind looking at another thread I just started and offering your input there as well?

http://www.savageshooters.com/showthread.php?56243-RCBS-Competition-vs-Lee-sizing-dies

Thank you.