Another Drop tube question

[C.Smith]

I started using a drop tube (approximately 24 inches long) to drop 62.8 grains of RL 22 into my 30-06 case. I had chronographed up to 63 grains with out dropping it in the tube (just used the funnel) and got an average velocity of 3000 fps with 165 grain AccuBond. But when I run it through the drop tube I get an average velocity of 2915 fps.

In that same test I worked up in .2 of a grain increments starting at 62.4 and going up to 63 grains. With the 62.4 grains I got 2943FPS. I'm have a couple of questions of the lack of velocity with 62.8 and even the 63.0 which was 2941fps. What is causing the loss of velocity? Is it the drop tube. With out the drop tube the powder is almost right up to the lip of the case. Or could it be something else.

Now the last test I did was with a different batch of RL22. Could that cause that much of a drop in velocity?

Now the 62.8 grains shoots around .5" at 100 yards, so no complaints about it. I just am curious about the differences and what may be causing it.

Corey

 

[Savage99]

Things vary such as test temperatures which may affect velocity and certainly powder lots. I buy RL 22 10 lbs at a time and make sure the two 5 lb bottles are the same lot.

I see the Nosler manual shows RL 22 with that 63 gr load at 3000 fps.

Good luck with it. Don't sweat the details.

 

[C.Smith]

The temperatures where only 10 to 15 degrees. As for sweating it I'm not just the curious side of me wanting to know what is causing that. Thanks for the reply.

Corey

 

[tjen]

I have found that loads that seemed compress when loading them were not. This after traveling 200 miles in the cab of my truck in the 50rd. plastic ammo boxes. The vibrations settle the powder. I have not seen any real differance it them. One load I can remember is a 35rem with 40.0grs of H4895 and 200gr CLRN bullets. I use a 6" drop tub and the powder was hafe way up the neck, and after settleing you could just hear the powder when the cartridge was shook.