WW748 in the 30-06

User avatar
mtngun
Site Admin
Posts: 1638
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

WW748 in the 30-06

Postby mtngun » Sun Feb 10, 2008 6:47 pm

WW748: a spike-friendly powder?

'Since WW748 powder seemed to alleviate the secondary spikes in a 7-30 carbine, it seemed worth trying in the 30-06, too. Since the last range session, my 20 year old can of 748 was used up and replaced by a new jug, so there may be some small differences in burning rate.

47.5 gr. WW748, 180 gr. cast loverin, 0.314" x 0.308", heat treated wheelweight, Rooster HVR lube, 2.965" COL, seated to engrave lightly.

10 rounds were loaded with WLRM primers, 5 with CCI #250.

5 shot groups at 100 yards
#1 (WLRM) = 2"
#2 (WLRM) = 4 shots in 2.5", 5th was flyer making 7.4" group
#3 (CCI250) = 2.25"

You guys who only shoot jacketed or low velocity cast may not be impressed with 2" groups, but this is as good as this rifle has ever done with full throttle cast loads. I'm delighted.
Image

Velocities & pressures
#1 (WLRM) = 2572 fps, 94 ES
#2 (WLRM) = 2575 fps, 70 ES, 59.2 ksi
#3 (CCI250) = 2610 fps, 20 ES, 61.2 ksi

Here's the trace for WLRMs. Lots of shot-to-shot variation, but only moderate secondary spikes.
Image

Here's the trace for CCI 250s. Very consistent traces and velocities -- so go figure why the group had vertical stringing. :? Maybe due to the differences in muzzle pressure ??????? I should add that there were large differences in seating effort. Some cartridges chambered effortlessly while I had to use my fist to hammer the bolt closed on others. That's a common problem with cast bullets that are seated to engrave, due to variations in diameter or due to lube build-up in the seating die.
Image

I've never had good luck using 748 for jacketed bullets in any cartridge. 748 has been prone to vertical stringing and mediocre accuracy. But it seems to be the trick for getting rid of secondary spikes, and these low-spike loads were more accurate in this rifle than any other high velocity cast bullet load that I have tried. Coincidence? :?

Next time I'll drop the powder charge a bit, because today\'s pressures were too high. I'd like to try still more primers, and I need to work on getting a consistent degree of engraving.

User avatar
mtngun
Site Admin
Posts: 1638
Joined: Fri Feb 01, 2008 5:45 pm
Location: Where the Salmon joins the Snake

Re: WW748 in the 30-06

Postby mtngun » Wed Feb 13, 2008 8:31 pm

Since low-spike WW748 shot some decent 2" groups last time, I tried it again with a few small changes.

The powder charge was dropped 0.3 grains to bring the pressure down to safe levels.

The bullet was seated about 0.005" deeper so I didn't have to hammer the bolt closed with my fist. Also, I seated the bullet in two steps. First, I seated all the cartridges part way, then I cleaned the seating die and wiped excess lube off the bullet noses, and then I seated the bullets the rest of the way. This eliminated variations due to lube building up in the seating die.

Three 5-shot groups averaged 1.95" at 100 yards. :D Yippeeeee. :D After struggling with 3" - 4" groups for two years, it feels good to break the 2" barrier.

Image
The bad news is that the ES averaged 89 fps, and the traces also showed a lot of shot-to-shot variation.

Image


Return to “pressure measurement”

Who is online

Users browsing this forum: No registered users and 2 guests

cron