More powder = no velocity gain?

[Wannashootit]

First time for everything, I guess...
New .338 LM (Savage 110 BA Stealth), 24" bbl (1 in 9.3, 5R)
300 SMK's, H1000, new Lapua brass. OAL gauge had length the lands @ 3.560 (seems to be a bit short on the leade?), loaded 20 thou less at 3.540.
Horrendously hot bright sunny day here in West Central FL, my trusty ol Chrony Alpha had a few misfires...

Started OCW at 89.0, worked up in .5 increments to 91.0
89.0 Scattergun, 2618, 2626, chrono error
89.5 not much better, two inch group with a lot of vertical 2631, 2645, error.
90.0 Like turning on the light switch. .75 moa, two holes touching, spread horizontal; 2722, 2778, error. Not happy about the ES of 56...wish the chrono hadn't failed on this one.
90.5 Going downhill, slightly over an inch, two holes touching but spread vertical. 2721, 2714, 2706
91.0 Scattergun again. 2721, 2714, 2706

One more grain, no velocity gained. Hodgdon lists the OAL with this bullet at 3.600, wondering if the load is more compressed than it should be due to a short leade causing this? Full disclosure....got to the range late, only one hot session for OCW after getting on paper and setting up- so little time for barrel to cool. All fifteen shots taken in about 1/2 hour.

Going to pick up some 285 ELD-X's and give them a shot- but wondering if this rifle might benefit from me throating it for a bit more freebore, freeing up some case capacity. Thoughts?

 

[Geno C.]

The odds of your last 2 charges having 3 shots at the exact same speeds are damn near impossible. I’d say chrono problems. I’d say if you’re happy with the speed, then try and see what 90.2 looks like.

You didn’t say if you reached any pressure signs yet. If not, then try to go higher and see what happens.

 

[Boostinmarc4]

I look at that and wonder if you can try another chrono or magnetospeed or labradar and try again...

 

[Wannashootit]

Might be the nudge i need for the Labradar. Didn't make sense to me either, but I did also get a crazy 5,000+ fps on a fouling shot so bad chrono fits...

No pressure signs, figured I'd see them if the load wers overly compressed so going to move up a couple notches carefully next week for round two.

Anyone able to comment on this OAL with the 300 SMK? Fine? Short?

Thanks for the feedback.