OCW interpretation help

[marvthehamster]

View attachment 22353So I shot an OCW yesterday for my Savage model 10, 20" barrel chambered in .308. The load I am testing is using IMR 4064, new Lapua brass, 155 grain SMK's, and fed 210 primers, COL is 2.800". The test was shot at 100 yds at an indoor/outdoor range (wind was not an issue) and the temps were about 30 F. I am in the Denver area so call the elevation 5200 ft. I shot off of a rear bag and bipods from a prone position and felt pretty View attachment 22350good about all of my shots, there were no called flyers. I shot 5 shots for each charge weight except for 46.5 grains because I had a bad primer in one of those loads. My sighter/fouler charge weight was 45.5 grains and is the bottom right target. The charge weights I was testing started at 46.3 gr and went to 47.1 gr in .2 grain steps. I shot the test round robin style as recommended and waited about 2 min between shots.

I'm having trouble getting too much out of the groupings here, they all seem to be centered about an inch or so low and 1/2" right of POA. I just don't see anything that I would call an accuracy node, but this is the first time I've done this so perhaps I'm not looking for the right thing. I know that my target dots are hand drawn and not completely uniform. I assumed that this wouldn't make much of a difference for this test but maybe I'm wrong? It has been recommended to me that I shoot the test again at 200 yds and hopefully see a more distinct difference in POI for group centers. Any help here is greatly appreciated. Thanks, fellas.

 

[waveslayer]

I personally don't like the OCW test, just my 2 cents. It's tough to see any real nodes at that distance, especially if you are going to shoot long distance with it. I like a ladder test. I did a OCW and the results were a bit different then my Ladder test. In the ladder test I was getting half inch to an inch groupings at 300 yards. But using the OCW load it wasn't even near that close for groupings!

I'm no expert and people swear by the OCW.... I think going farther out would help you.

 

[Dan Newberry]

You have an issue that is splitting the groups. I think you'll find the node at 46.0 to 46.4 grains (or just load up 46.2 and shoot--it'll run great)...

But you need to check your scope base screws. It almost looks like they've worked a bit loose... check action screw torque as well, put it around 65 inch pounds... and the scope base and rings at 25 inch pounds.

If all of your screws are tight, I would next suspect the scope itself, as having a loose lens.

Dan

 

[blurry6]

I think you're load-range is way too narrow,... you're splitting hairs by ony dissecting approximately 1-gr of powder variation at this point. You can fine-tune it in 0.2gr increments once you've narrowed it down sufficiently. Personally, I'd start at 44.0gr of 4064 and run data-points at 0.5gr increments up 'til I started seeing pressure signs (stiff bolt-lift, flattening primers, etc.). You can go to 200-yards, but it's not necessary. I know velocity is alluring, but it often comes at the cost of accuracy and in my opinion, it ain't even close; accuracy is what matters.

Ry

 

[marvthehamster]

Sorry for my super delayed response on this, thanks to all for their advice. I have loaded some 175 SMK's under 41.7 grains of IMR 4064 since last posting this and that load shoots lights out on sub moa targets out to 500 meters. I haven't pushed it further and my holds may get a little ridiculous at 1k yards, but so far so good. Dan, I may try that recipe for the 155's since I still have quite a few of those bullets laying around.

I also have to say that in my original OCW test, I may have not been as solid in my shooting position as I originally thought. After some more practice my groups tightened up considerably. Even with the flimsy stock I am extremely impressed with this Savage. Hopefully I'll be making some other shooters very jealous at the next long range shoot I attend.