OCW Test results... Which would you pick????

[Rem7targetactical]

I have a new Shilen 308 win. barrel and am past break in. I did a ladder test and didn't really come to any real good conclusions. I've been reading a lot lately about the OCW tests and see that most of them increase in .3 grain increments, but myself being OCD have to use .2 so I land on 42., 43., 44. etc.. Lol! Anyway I have two areas that look pretty good And would like some input from anyone who has performed one of these tests. I like the 42.2-42.6 area with 42.4 in the middle and all close to the same POI. But I really like the 43.6-44.2 area with the 44 in the middle of the group and also the smallest. (I know your not supposed to be looking at the size) But this group is SMALL and what looks to be in the middle of a node. (if you look close part of the group is torn paper from it not laying flat against the cardboard backer) These were all shot today under slightly windy conditions from a 23.5" barrel with Lapua brass, Sierra MK 175's, CCI BR2's and Varget at 100 yards. 2.81 COAL

 

[Dan Newberry]

As you noted, 44.0 grains is centered very well. An OCW load ought to shoot tight, but as you mention group size is not always the indicator of an OCW node. In this case, you got the best of both worlds.

See if 44.0 grains give you repeatable accuracy at the seating depth you used in this test, and if so, you're done. 44.0 grains it is.

Dan

 

[Rem7targetactical]

As you noted, 44.0 grains is centered very well. An OCW load ought to shoot tight, but as you mention group size is not always the indicator of an OCW node. In this case, you got the best of both worlds.

See if 44.0 grains give you repeatable accuracy at the seating depth you used in this test, and if so, you're done. 44.0 grains it is.

Dan

Thank you Sir for your answer, especially since you are the creator and master of this type of testing! I shall make some more 44.0 and see what happens. I was pleased with the results but was unclear if my increases of .2 were throwing off the test. Thanks again.

 

[trailrider121]

Wow, you have a strong ocw around 44grs. Very nice work!
Dan's post pretty much nailed it. Corroborate the 44grs. and go shoot.

 

[Rhyno]

Yea 44 looks great. 42.6 looks like the low node.

 

[Rem7targetactical]

This might be a silly question but will removing my muzzle brake change any of this?

 

[JByrd]

only one way to answer for certain. the bullet knows the answer

 

[Rem7targetactical]

Lol.

 

[Aflac]

This might be a silly question but will removing my muzzle brake change any of this?

I asked this same question once. The answer I got is that removing the break, or suppressor, would move the impact point slightly but should not affect group size. Evidently the weight of the brake changes the barrel whip, which affects impact point, but the shockwaves traveling through the barrel itself is the main thing in group size. That's what ocw checks for. Finding the node where the shockwave is at the breach end and not the muzzel end when the bullet leaves the barrel. And since the brake is a different piece of metal the shockwave does not propagate into it so thus it does not affect the shockwave bounce.

 

[Rem7targetactical]

I asked this same question once. The answer I got is that removing the break, or suppressor, would move the impact point slightly but should not affect group size. Evidently the weight of the brake changes the barrel whip, which affects impact point, but the shockwaves traveling through the barrel itself is the main thing in group size. That's what ocw checks for. Finding the node where the shockwave is at the breach end and not the muzzel end when the bullet leaves the barrel. And since the brake is a different piece of metal the shockwave does not propagate into it so thus it does not affect the shockwave bounce.

Awesome! Thanks for the reply.

 

[Krazyjohnny]

I find it odd that I have experienced the same nodes except with a different powder. Used same bullets and OAL out of my sons Rem 700 AAC-SD with 1:10 twist 20 inch barrel and JP brake. We have been using BLC-2.

 

[Aflac]

Awesome! Thanks for the reply.

If you want a better expansion of the whole thing read this paper. He took ocw and went a step farther with it.
Optimal Barrel Time Paper

 

[Rhyno]

If you want a better expansion of the whole thing read this paper. He took ocw and went a step farther with it.
Optimal Barrel Time Paper

I just wish I didn't need a program like quick load to try and determine OBT.

 

[Aflac]

I just wish I didn't need a program like quick load to try and determine OBT.

Yeah if you do not have quick load you can't use OBT to predict your nodes, however the paper is still really interesting for learning the concepts behind whats happening and why some loads work and some do not.

 

[Hondo64d]

Looks like 44gr is it. That charge weight is one I see VERY OFTEN listed as most accurate by folks shooting 175s. More than a coincidence, I think...

John