top velocity at under max loads. Is this normal?

[Wilderness Blacktail]

Hi folks, Ive been reloading for several years and have several rifles Im loading for however Ive only had a chronograph for two months.
A few times Ive seen my top velocity with any given combo come at a grain or two under max loads (per book or via pressure signs) with velocity going down after that, often with very small deviation.
Is this fairly common? The norm?
I may go back and rework every load Ive ever come up with just to see if I do have top velocity with best accuracy with each. Not that I need to, just for my own knowledge ya know.

 

[Mikecr]

Can you provide cartridge & barrel length for a case?

 

[Wilderness Blacktail]

Most notable example is 30-06 in 22", H4350 with two different bullets so far but it happened in another rifle or two as well. Im away from my notes but may have been same powder.

 

[Mikecr]

Your answer is 22" barrel + 30-06.
A 30-06 is incredibly inefficient.
The high body taper low shoulder angle case funnels powder into an extension of the bullet(a slug). This reducing amount of actual powder burned.
Now combine it with a short barrel, and even less of the powder 'slug' is burned(not enough time).

So adding more powder here doesn't mean more velocity, it means heavier effective mass pushed down the bore, and while pressure and recoil goes up, velocity goes down.

 

[brentc]

It's very normal. It is actually quite a good indicator of your max load especially when pressure signs aren't present. I'm betting your Extreme Spread at your highest charge is fairly large as well. I've seen this several times with several cartridges. Load it up where you get the best performance and run it.

 

[Wilderness Blacktail]

Thanx guys. That makes sense!
Just looking my notes it happened in the same gun with H Superformance, 165 H SP as well. Top velocity at 61 grs and declining after that up to 62.5 grs where I started to see a lil bit too flat primer and it sounded hot so i stopped.
My 250 sav showed something similar, with velocity declining for a notch or two and then picking back up again at book max. Is this normal as well? Im assuming that it is and now I want to rework every combo I have and chrony em all just for the heck of it! lol. What the heck, why not right.