Your thought on my OCW test?

[SWThomas]

I took my 308WIN GAP-10 out yesterday to conduct an OCW test. I'll list all the specifics and if you could give me your thoughts on what you think that would be great.

Conditions:
Temperature: 54
Humidity: 37%
Pressure: 29.89 in
Visibility: 10 Miles
Elevation: 335 ft

Load:
Bullet: 175g SMK BTHP
Brass: Lapua
Powder: IMR 4064
Primer: CCI #34

Velocities:
43.5: 2604, 2619, 2604
43.8: 2640, 2650, 2619
44.1: 2635, 2619, 2640
44.4: 2682, 2661, 2645
44.7: 2677, 2677, 2645
45.0: 2682, 2699, 2666
45.3: 2699, 2715, 2704
45.6: 2721, 2726, 2726

It started to cool off a few degrees for the third round robin, so the velocities seem to have taken a small hit.

I'm thinking somewhere between 45.3 and 45.6. They seem to be pretty similar in relation to the center, they're tight, and the ES SD and AV velocities look pretty good too.

What do you think?

 

[AZ.noob]

hey Tom, try editing your image hyperlink... it didn't go

 

[SWThomas]

Fixed it.

 

[pell1203]

I'd have to agree with your observations regarding the 45.3 - 45.6 range. Maybe try 45.8 to see if it still holds. If not, I think I would pick 45.5 and vary the seating depth if you want to be OCD about it. There is nothing wrong with tightness of 45.3 - 45.6 range at whatever seating depth you loaded at though. Good luck!

 

[SWThomas]

I think I'm gonna reshoot it just to make sure. Measure twice and cut once.

 

[Thumper580]

SW - those seem like rather warm loads with a 175. How did the gun feel and the brass look like?

 

[shoot4fun]

45.6 is Hodgdon's max recommendation. Usually, gas guns like to run at a little lower pressure but it appears yours really likes that top node.
If you are good with how it functioned and felt in the gun then I would go to step 18, as it looks like you have the proper seating depth.
I would like to see what Dan has to say about it though.

 

[SWThomas]

SW - those seem like rather warm loads with a 175. How did the gun feel and the brass look like?

The gun felt fine and the brass looked good. No signs of over pressure. I've fired the same combo with 46.0g of 4064 and there weren't any signs of over pressure.

 

[limige]

Imo shoot it at 300 and you might be able to get something out of it.

 

[TwentyFiveTwenty]

As pell said - I'd play around in the top end (46.4 has an *extremely* good ES) and then twiddle OAL next, but I'm OCD like that. I shoot 4 rounds instead of three on my round robins now - I think it helps in particular with ES to have the extra shot.

Are you weighing your cases and bullets? I do both on testing so all 4 rds have the same weight bullets and cases. Just to eliminate that too...