See WARNING note above in first post of this thread.wildcatter wrote:... If you were Not experiencing pressure problems, those double base powders actually like compressing and tend to light up when done so. Now, I Wouldn't try compressing #9 for fear of getting wild pressures, but compressing 1680, in the 450b "Might" show you far different, positive results.
When compressing those powders you can, experience Powder Clumping, so pull some bullet off your compressed loads and look for the clumps. If you are getting some amount of clumping then back off on the compressed charge some. I personally have not had any problems with mild clumping, but excessive clumping can be difficult to ignite or yield excessively high pressures, when they do ignite! As long as you are getting safe pressured loads you have room to do this. A compression of 2%-5% (Might be able to push pass 5% All through this process, let the clumping and pressure signs show the way or you may rue the day) causes, say 1680, to take off and to really light up, so-to-speak. Just keep pressure margins safe, or else (Kaboom)!! ...
Well, I do like to avoid Kabooms. I carry a length of string in my kit so that with a questionable load I can sandbag the rifle and attach the string to the trigger. Then I can put distance and maybe a big tree between the rifle and my tender torso while pulling on the string. "Hey y'all, watch this!" is no longer one of my reloading mantras.
In response to T's suggestion above, I just did a very brief trial with a compressed load of Accurate 1680 powder. I had to learn a couple of techniques that were new to me. The weight of my lot of 1680 that puts the FTX bullet on top of the powder with the recommended COL for the 200-grain FTX is 50.0 grains, +/- a couple of tenths. This 50-grain charge requires using a 12-inch powder drop tube, and judicious tapping of the filled case to settle the powder.
Just for this trial, I used a charge of 53.5 grains of 1680, which is a 7% increase above the 50-grain trial load that produced only 2220 fps. I used four FL-sized multi-fired cases; case lengths were 1.697-1.700".
The 200-grain FTX bullets didn't want to stay put with the usual seating operation using the Hornady seating die. The bullets would be pushed up several hundredths of an inch by powder as it decompressed. So, I backed off the seating stem a bit and seated the bullet with four separate press strokes, screwing in the seating stem after each one. I paused for about 10 seconds at the end of the ram upstroke to allow the powder to compress. This seemed to help. When I was finished, the COL was 2.200. However, before I could apply a side-crimp, the bullet had moved out so COL was 2.210. I had to settle for this. The case was not measurably bulged by the compression.
To hold the bullet in place, I applied a double side crimp, with the crimps about 0.03" apart.
I fired these trial rounds from the bolt gun described above over a chronograph place 12 feet from the muzzle. Average velocity was 2429 fps, which was a gain of about 200 fps greater than with the 50-grain trial. Even with compression 1680 powder was not able to approach the velocities possible with the five other powders used in the 200-grain trials.
It's possible that with compression, either Lil'Gun or Enforcer might equal or exceed the max velocities obtained with No.9. I'll leave that for some some other time or some other person.
I'm planning some trials with the 200-grain Barnes #45115 XPB bullet designed for the 460S&W. I hope to get these started before rifle deer season puts everything on hold, and then the snow shuts down the local range through March (or April or May).
TEASER: I have completed a set of velocity trials with 150- and 140-grain bullets. Even more than the work reported in this thread, the results have little practical application. They may have some intellectual or entertainment value, and I'll try to post them on this site soon.
--Bob
Posted: Fri Oct 18, 2013 9:51 am