155 Scenar Velocity Question?

[midmoguy]

Ok i started to develop a load for my Kimber AT using Lapua brass, WLR primers and varget. I shot the first three at 44.5gr and it was in the .2" range so i decided to just stop there. Yesterday i decided to break out the chronograph and see what kind of speeds i am getting. I averaged 2670 with 44.5 gr. I already had 45gr and 45.5gr loaded to test for accuracy so i decided while the chrono was out i would just check them too. This is the weird part, the 45 gr jumped over 100fps to 2777 average but the 45.5 averaged just 2802. Why would the first .5 incrament give me an extra 107 fps and the second only 25 fps?
Thanks

 

[Dan Newberry]

That's just the way the powder continuum works... you see a good velocity jump with a small amount of powder, and for the span of a full grain or so, things stabilize. That's what you're really looking for in a good load, one that has pretty steady velocity over a 2 percent or larger spread (1 percent in either direction from the optimal charge weight).

 

[RADcustom]

What length and brand of barrel are you using?

 

[turbo54]

Why is the sky blue?

How is a rainbow made?

How does the posi on a Plymouth work?

It just DOES!

all kidding aside, I've seen the same phenomenon in various cartridges, with many different powders. Velocity will climb with increasing charge, stay put a while, then climb again.

If these velocity "dead zones" correspond with an accuracy node, you'll have a helluva load worked up.

 

[midmoguy]

Lets hope so, im going to run the 45gr on paper and see how it does. If its as good as the 44.5 that would be great. Otherwise i will probably run the lower charge, i figure it would be super easy on brass. Im just using the factory barrel at 24". It didnt shoot factory ammo worth a damn when i got it, then i bedded it and started handloading and couldnt be happier with it.

 

[xdeano]

You can run varget a lot hotter. I think I was in the 46.4 range with my old rifle with a 22" barrel. I've got a buddy that went all the way up to 48grn. I wouldn't recommend that.
Xdeano

 

[DamnYuppie]

I am running them at 46.6 of Varget. In the old barrel they were going 2900ish, in the new they are going 3000.

 

[RADcustom]

You can run varget a lot hotter. I think I was in the 46.4 range with my old rifle with a 22" barrel. I've got a buddy that went all the way up to 48grn. I wouldn't recommend that.
Xdeano

Were you using Lapua brass?

 

[xdeano]

Roger! Fed210m
Xdeano

 

[midmoguy]

I don't know how you would even get 48 gr in a lapua case without seriously crunching it. I'm not really one to push the envelope with powders, I figure since i'm not matching shooting yet there no reason to push it too hard. And thanks for the replies, glad to hear that its a normal thing.

 

[jephthai]

Why is the sky blue?
How is a rainbow made?
How does the posi on a Plymouth work?
.

The problem with your joke is that those three questions have easier and more satisfying answers ;-).

Sent from my ASUS Transformer Pad TF300T using Tapatalk 2

 

[xdeano]

I don't like it that hot either. I've been up to 47 and that was enough for my gun. Groups went to crap too. Even at 46.4 grn it was crushing powder. I was getting 2875 fps.
Xdeano

I don't know how you would even get 48 gr in a lapua case without seriously crunching it. I'm not really one to push the envelope with powders, I figure since i'm not matching shooting yet there no reason to push it too hard. And thanks for the replies, glad to hear that its a normal thing.

 

[redneckbmxer24]

I've worked all the way up to 47.5gr in various rifles with the 155 scenar and Lapua brass. One load that I've found that worked in a variety of my rifles (AI AE MKI, 5r mil spec, 700P, LTR, and a couple rock barreled rifles) was 46gr Varget, Winchester primer, and FL sized Lapua brass at 2.85OAL (2.215 ogive if I remember correctly). Before trying it be sure to make sure it's not jamming into the lands, and of course work your load up to there. It's definitely worth a try though and is very easy on brass too.