Accurate 1680 in 221 FB with 35 gr bullets ?

[17cal Fan]

I've used it with 40's with great results at 20.2 grains and max shows to be 20.5.
Yet with a 35gr bullet 18.7 is max.
Seems strange to me.

Tested some 35 grain Hornady and 36 grain Barnes bullets this week with 18.3 and 18.5 and they shot very well.
Why not 20 plus grains?

 

[alf]

WAG would be the 35, being a flat base, has a longer bearing surface than the 40 with it's boat tail. You'd think the 5 grains less would overcome that though?

 

[Frankm]

19 grs with 40 gr flat base Varmageddon gives me 3400 fps out of 24” Rem 700. Worked up from 18 and .3 gr increments kept getting better and better ES and accuracy. Settled at 19 as 3400 fps is “plenty”. I d think you could work up in similar fashion with your 35 gr bullet. Watch your velocities and ES/accuracy if you have a chronograph.