6.5 Creedmoor OCW Testing

[CaptNemo]

I had a range session this AM with my 6.5 Creedmoor to do some OCW Testing.
I had just restated handloading again from a long lay off and was shooting Hornady 140g AMAX Match ammo to build up a brass horde.
I changed out the 0 MOA picatinny mount for a 20 MOA mount and mounted an Athlon Ares BTR- 4.5-27 X50 that Doug and Neil at Camera Land hooked my up with last Christmas.
I used some of my Hornady stash to zero the scope and get some chrono data with the Labradar.
The conditions were quite nice low 70°, relative humidity was 80% cloudy in the early AM clearing to broken clouds, baro pressure was at 30.22 inHg.
DA varied from 767' to 899' as it warmed up and it got a little breezy once the sun came out.

On to the handloads:
Once Fired Hornady Case - Flash holes deburred and dry tumbled
CCI BR2 primers
Sierra 142 Matchking bullets Seated to give 0.022" jump to the lands
H-4350 Powder
Charge weights were 40.5g, 40.8g, 41.0g, 41.3g & 41.5g

The horizontal line was the baseline for the OCW test and the 5 shot groups were shot round-robin with three of each load ( 15 rounds ) let the barrel cool a bit and shoot the final 2 of each load ( 10 rounds ) this gave more chono data. There were a few rounds that the chrono didn't register so the additional rounds helped with data acquisition.

ETA: the squares on the targets are 0.1 mil / 0.360” so that one line space = 1 click on the turrets.



Here are the detail photos:
40.5g


40.8g


41.0g


41.3g


41.5g - listed as a max load


So... Where is the OCW ?

 

[rduckwor]

I see a low node on the first two charge weights. Velocity is pretty good on the 41.5 Gr load. Are you seeing any pressure signs? If not, you might work up a little farther and see if you have a high node developing just above the 41.5 group. Might be something decent around the 41.3 charge weight. That one vertical flyer makes it tricky to call. With a SMK 142, I could live with that velocity at 41.3.

Good Luck,

RMD

 

[CaptNemo]

The 41.5 load was staring to see some minor cratering on the primer, but no worse than what I see in the factory Hornady 140 AMAX and the 129 SST loads. I may pull some of the bullets on some of the cartridges I loaded during the same session to tweak in the 41.3 to 42.0 range. I loaded another 25 rounds that I didn’t shoot today, I have these bullets seated .002” off the lands

 

[Marksman10x]

Between 41 and 41.3. This is seen two ways. First, the group's, while not pretty, do have the same relative poi. Second, they have nesrly identical velocities.

A tweak in seating depth will close those groups right up. I would pick a direction to move the bullet; preferably towards the lands, but away if your COAL is maxed out due to magazine restrictions.

Then load up five groups in .003" increments. I'd use 41.1 grains, but you could do a powder test in 0.1 grain increments from around 40.8 to 41.4 to see exactly where the node begins and ends. But, 41.1 should be pretty close to the middle. The velocities will all be within about 10 ft/s of each other inside the node. They will then jump 20-30 ft/sec outside.

Pick the group that shoots the best or look for a spot in the depth test where two or three groups (probably two) also have the same relative poi. This will be your load and should shoot fucking awesome!

 

[Marksman10x]

Here's a couple groups at 500m with load developed exactly as described above.