More powder, less velocity

[sniperaviator]

Loaded up some Berger 140's 2,88" oal in my 260 Remington cases, 24" barrel Rem 700.
41.8gr gives 2805fps (10 shot average)
42.1gr gives 2780fps
42.4gr gives 2770fps
42.8gr gives 2771fps
No blown primers or flowing brass.

Have I entered an upsidedown parallel universe or something? Usually more powder means MORE velocity, NOT less!

 

[winxp_man]

Re: More powder, less velocity

I shot some RL-15 in my .308 and seemed to be doing the same weird. I really don't have a explanation for it.

So I will load a little more with this powder and make sure its not me.

 

[mscott]

Re: More powder, less velocity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sniperaviator</div><div class="ubbcode-body">Loaded up some Berger 140's 2,88" oal in my 260 Remington cases, 24" barrel Rem 700.
41.8gr gives 2805fps (10 shot average)
42.1gr gives 2780fps
42.4gr gives 2770fps
42.8gr gives 2771fps
No blown primers or flowing brass.

Have I entered an upsidedown parallel universe or something? Usually more powder means MORE velocity, NOT less!
</div></div>

What powder??? I'd say you've reached it's peak performance.

I've run into that in pistols a couple of times, but only once in a rifle. Some powders seem to need room to get going and don't like to be compressed.

 

[Asm1]

Re: More powder, less velocity

If useing a crony I would say there is your problem..

 

[sniperaviator]

Re: More powder, less velocity

Powder was h4350 and the chrony was working. I chronied some other rifles and rounds as well and got expected, reliable results.

 

[clmayfield]

Re: More powder, less velocity

Part of it could be the bore warming up... just a theory.

Also, are you running a compressed load? Sometimes when you start compressing, velocity stops increasing or moves backwards, but usually not over an entire grain! That is weird.

Are you sure you labelled your cases correctly?

 

[wyobill]

Re: More powder, less velocity

I observed a simular result with h1000 and 285 hornadys in my 338 90 grs 2721 fps and 91 grs 2698 fps.I am planing to reverify my results and go a bit hotter as i didnt have pressure signs either.

 

[ChadTRG42]

Re: More powder, less velocity

There's 2 things that could cause this- 1- chrono issue, or 2- max pressure.
If you're certain the chrono is not at fault, then you have reached your max pressure. When you reach the max pressure for the rifle, your velocity will level off, and then start to decrease the more powder you add. If you have a new barrel, give it 100 or more rounds to get good and broken in, and you may see the speed pick up more.

 

[Jerkface11]

Re: More powder, less velocity

You're spread between fast and slow loads is 30fps. A change in the sunlight hitting the eyes on the crony would make that much difference.

 

[tomcatfan]

Re: More powder, less velocity

I would question the resolution/accuracy of your chronograph. When you work it out there is about 1.2% variance between all your shots. That is a really small window for error. For something to read within a 1% error is really good.