Please help me analyze this OCW test

[ReaperDriver]

OK, it was my 1st try at OCW after doing some lengthy ladder testing hoping there's a better way.

I read and re-read Dan Newberry's site and I think I followed his method to the letter. I wanted to try out and compare some 155's (155SMK 2155 Palma vs Lapua 155 Scenar)in my .308 so I chose to work the exact same load keeping all things equal with the bullet the only variable.

Here's my set up:
Rem 700 20" SPS-Tac
50F, 15% humidity, winds 0-3 mph, clear and sunny
CED M2 Chrono

155 SMK 2155 Palma and 155 Scenar
Lapua Brass
Fed 210 primer
RE-15 powder

I started at 46.7 grains of RE-15 and worked up in .3 grain increments to 47.6 for both bullets. I shot round robin just like I'm supposed to and waited two min between each shot.

Here are the results. Overview 1st and then each load. Grid is 1/2" squares.

Now the 155 Scenars:

And just to prove that I CAN actually shoot a decent group and that the barrel was not too fouled - the last group of the day was NOT a round robin but just 5-shots of a 168 AMAX load that has worked well for me.

I'm a bit confused by the results of the OCW and not sure how to interpret the results. None of the flyers, felt like flyers - I was really concentrating and I got up and walked around between each shot so I felt relaxed and not rushed.

Is anyone seeing a true OCW node or do I need to keep going?

 

[Witch_Doctor]

Re: Please help me analyze this OCW test

I just did my first OCW test also, I did a wider variance starting at 41gr of Varget working up to 44gr using .3gr increments. Based on what I have read and the one I did, my target that was similar to your #3 with 155 SMK was were I started to see the follow up targets on POI. Meaning I had a wide spread like #3 and then the 3 successive charges were fairly close with each other at POI. I would think that if you tried two more charges at 47.9gr and 48.2gr you see successively similar POI.

Because I did a wider variance I could see the succession across the target and the OCW was easier for me to discern.

 

[Unsichtbar]

Re: Please help me analyze this OCW test

First of all how did you come up with a starting load of 46.7 RL 15 in a Lapua case!! That is alot powder, I shoot alot of RL 15 155 L. any pressure sigh

 

[kombayotch]

Re: Please help me analyze this OCW test

Here is a tutorial I did a while back:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1436621#Post1087602

Four groups isn't really enough IMO... I do six minimum. Ideally, you want to bracket the OCW. That being said, I don't think it will help your results. Your results mimic what I get when the powder is too slow for the weight of bullet and/or barrel length. Got similar results with the 87 VMAX and Retumbo in 6mm Crusader last weekend. Pressure Trace was also showing secondary pressure spikes, which is common with this. With that much RL-15, 155s and a 20" barrel, my guess is you are getting the same. Go with a faster burning powder.

 

[LoneWolfUSMC]

Re: Please help me analyze this OCW test

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unsichtbar</div><div class="ubbcode-body">First of all how did you come up with a starting load of 46.7 RL 15 in a Lapua case!! That is alot powder, I shoot alot of RL 15 155 L. any pressure sigh </div></div>

I run 47gr of RE15 in a Winchester case with no pressure signs on 90+ days. It just kisses the high end of 2900 fps (26" barrel). I have been thinking of pushing it a little faster and seeing what I get.

 

[Unsichtbar]

Re: Please help me analyze this OCW test

In one of my rifles tight 95 Palma chamber 24.5” barrel mag. length jump .10, Lapua case 155 Lapua Bullet Bare 46.1 2940 Fps at 82F single digit SD & ES. In this rifle I have shot up to a node at 46.8 but pressure sign. I my AWAI with 7.62 chamber Molly 47.4 2960 82F., In cases fire in the tight chamber 46. gr is up to the neck.

LW In a Winchester case with a Tac. chamber room to investigate, there is a higher node but OP running above 47. gr in a Lapua case with a naked bullet sure seems high. His OCW is not what I have come to expect with this load, something is not right as Komb. suggested.

 

[ReaperDriver]

Re: Please help me analyze this OCW test

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unsichtbar</div><div class="ubbcode-body">First of all how did you come up with a starting load of 46.7 RL 15 in a Lapua case!! That is alot powder, I shoot alot of RL 15 155 L. <span style="font-weight: bold">any pressure signs? </span></div></div>
No. I <span style="font-style: italic">just </span>started to get some pressure signs (Primers just beginning to flatten, barely sticky bolt) with the top two loads (47.3 and 47.6). The Lapua's more so than the SMKs based on the seating depth. The Scenars were definitely a compressed load and the velocities showed compared to the 155 Palmas.

And why I started with 46.7 is because I did a preliminary workup on the 155smks but using FC brass. I topped out there at 47.0 but knowing that FC brass is close a bit heavier than Lapua, I thought I could start in the same region. Based on some other loads in my FC brass, I was about 1-1.5 grains heavier in FC than I was in the Lapua to get the same velocites with the same powder and bullet. AS it was the 155 Scenars topped out at 2796 with 47.6 of RL-15 whereas the 155 SMK in FC brass with only 47.0 ran at 2810.

 

[Wil]

Re: Please help me analyze this OCW test

remember that the 155 scenar is longer than the smk... and will sit back in the case further when seated at like depths compared to the smk.

this will cause more compression....creating a bit more pressure...driving velocities higher...etc..etc..etc.