Sanity check - MV of 300WSM 175SMK 65gr RL19 24" barrel

[PrepareSmarter]

I'm working on my first load for a 300WSM. Groups showed that 63.75 and 65.00gr charges of RL19 worked best with the harmonics of the barrel.

I loaded 40rd: Hornady 300WSM brass (full length sized, shoulder set back 0.007, no neck turning), Federal Champion primers (not sorted by weight), 65gr±0.02gr RL19, and 175SMK projectiles (not sorted by weight) set at 2.905 (magazine length.)

Ambient temptature was 56f-57f, same as the cartridge temperatures. I opened the chamber and gave time for cooling after each shot.
Here are my MV readings from a Shooting Chrony F1 @ 10ft (+6MV correction applied): 2567, 2570, 2538, 2587, 2597, 2597, 2610, 2587, 2609, 2580.

The variation in MV is 71fps, standard deviation of 21.8fps, with average MV of 2584.2fps. That seems slow, and the variation seems high.

Do you think my Chrony is giving bad readings? It also would fail to give a reading on a large number of shots.

 

[cornhusker86]

That's actually a mild load. All of my manuals list win. brass. Not sure how the capacity compares to Hornady. Sierra lists a max charge of 70.5 grs. w/ win brass and win mag primer.

 

[PrepareSmarter]

That's actually a mild load. All of my manuals list win. brass. Not sure how the capacity compares to Hornady. Sierra lists a max charge of 70.5 grs. w/ win brass and win mag primer.

Thanks for the input. I see my Nosler Reloading Manual (2012) lists 67 as MAX load @102% load density. They estimate 80fps gain with the extra 2gn load, so I'll have to experiment with a heavier charge.

As far as the MV variation, I suppose that having a compressed charge would help with that somewhat. I'm still questioning my Chrony.

 

[918v]

R U shooting these though a .323 WSM ?

 

[Supersubes]

Op, why are you pushing the shoulders back so much?

 

[PrepareSmarter]

R U shooting these though a .323 WSM ?

No, 24" Tikka T3 in 300WSM. That's why I'm questioning my Chrony.

Op, why are you pushing the shoulders back so much?

That is how much shoulder bump I get with a slight cam over of my lee dies. Do you think backing it off would help with my SD/ES?

 

[Supersubes]

No, 24" Tikka T3 in 300WSM. That's why I'm questioning my Chrony.



That is how much shoulder bump I get with a slight cam over of my lee dies. Do you think backing it off would help with my SD/ES?

No, probably won’t help your velocities, but most definitely will help with brass life. You’re looking for about one third of what you’re doing now.

 

[Lynn Jr]

When you push the shoulders way back you lose velocity forming the case back to its full size.
If this is a bolt gun use 0.002 and you will be fine.

 

[PrepareSmarter]

UPDATE

I sold my Shooting Chrony and switched to a Magnetospeed. I did some groups with different powder loads and saw the following:

71.5f, 24" #2 barrel, 175gr SMK 2.900", 0.005" bump, RL19 powder, Fed Champion primer, Hornady brass
65.00gr - AVG 2836.3 SD 14.01 ES 27
65.33gr - AVG 2788.3 SD 6.11 ES 12
65.66gr - AVG 2812.0 SD 17.09 ES 34
66.00gr - AVG 2901.3 SD 12.7 ES 22
66.33gr - AVG 2919.0 SD 8.7 ES 16
66.66gr - AVG 2953.7 SD 12.9 ES 25
70.00gr - AVG 2947.7 SD 15.4 ES 27

Besides the strange readings at 65.33.. it makes a lot more sense than the data I collected with the Chrony.

 

[918v]

.005” jump or .005” bump? Why u bump so much?

 

[PrepareSmarter]

.005” jump or .005” bump? Why u bump so much?

0.005" bump because this is what my dies can consistently produce. I might need a new base holder to get it to 0.003"

Jump is 0.010" due to magazine COAL limitations.

 

[918v]

Get some Redding competition shell holders