Sunday, July 23, 2006

Final shot prep and initial testing

The last installment of the shotmaking saga left our hero counting pellets and weighing shot charges. Today I actually managed to put some pellets on paper with the new loads, although not as many times as I would have liked. Don't take that wrong.....the patterns were good, I just didn't get to shoot enough of them. I had to work as an RSO at the range today, so I was only able to fire 3 shots at the paper. I suppose I could have stayed after everyone else left, but with the temperature hovering around 115 degrees and having been at the range since before dawn I was finished for the day when we closed up at noon.

Before we cover the patterning, I want to step back a bit to the final finishing step in the shotmaking process. The shells I loaded last time were done with untreated shot. The bare metal oxidized to a pretty greyish blue color as it dried and had a somewhat grainy texture. My original intention was to split my first loaded batch into groups of finished and unfinished so that I could pattern the shot both ways and try to quantify the effects of surface finish on the pattern. It wasn't until I had half of my original supply loaded that I realized it needed to be split into thirds, not halves.......I had missed an important step in the finishing process that needed to be tested.

I was sitting in the garage, staring at the bucket of shot, lubricating my synapses with a bottle of RedHook ESB and a pastrami sandwich, trying to decide what the best way would be to apply a thin coating of graphite to the unfinished shot. We're eventually going to use a cement mixer to do large batches, but at the moment I didn't have a cement mixer handy. The most common method of small scale graphite application that I have seen mentioned on the web is to simply put the shot into a bucket, add a few poofs of graphite, and swirl the mix around until the shot is coated. That was way to simple for me.....there had to be a more complicated, time consuming, cumbersome, and expensive method available. My gaze wandered over the assorted equipment in my loading area and settled on my brass tumbler. Aha! A way to spend lots of time coating the shot and make a boatload of noise at the same time!

That was when I realized that there was an intermediate finishing step that I needed to test. By running the shot in the vibratory tumbler I would not only be coating it with graphite, I would be peening the shot as well........much like the old rock polishers that we had as kids. What would be the result of simply peening the shot in the tumbler without any graphite? Would it soften the edges and drip marks? What would happen to the coating of oxidation? Inquiring minds want to know..........

I divided my remaining shot into two groups and placed one batch into the tumbler without any additives. One hour later I had this:



The unfinished shot is on the left. The peening process actually did a fine job of polishing the shot. In fact, it did such a good job that I was tempted to skip the graphite process altogether. The oxidation had disappeared and was replaced with a black, shiny finish that looked exactly like factory produced shot. The next batch of shot was tumbled for an hour with two poofs of graphite. The shot from that batch had the same smooth, hard finish but wasn't nearly as shiny and left behind a slight graphite residue when handled. Both types flowed and rolled quite a bit more smoothly than the untreated shot. At this point I'm upset that I loaded as much of the unfinished shot as I did.

In my last post I mentioned that the pellet count and total weight thrown by my one ounce charge bar was lower with our homecast #7 3/4 shot than with factory #8. The same held true for 1 1/8 ounce loads. The average pellet count was 420, and the average weight was 470 grains - roughly 1 1/16 ounce. If we do go into mass production with this setup I will customize a bar just for this shot so that we get a full 1 1/8 ounce charge. For now, this is close enough.

Today at the range I fired 3 test patterns, two through my BT-99 and one with the modified barrel of Kathy's Citori. Nathan's gun is still at Carlson's, so it will have to wait until next time. My first shot with the BT was pulled to the right, so that pattern was set aside. It looked good, but was obviously off center and part of the pattern was missing off the side of the paper. The second shot was well centered, as was the shot with Kathy's Citori. Before everybody starts griping let me say that I know that one pattern does not constitute a thorough test. It's what I had time for and it at least will let me know if I should proceed or not.

Here is the pattern data for Kathy's gun, with the pattern results from Winchester factory loaded AA target shells as a comparison:

12 gauge Browning Citori, 28 inch "modified" choke, actual restriction .025

Winchester AA light target 2 3/4 dram, 1 1/8 ounce, #8 shot
total pellets: 460
total pellets impacting in a 30" circle at 40 yards: 303
pattern percentage: 66%

Reload, Winchester AA hull, Winchester 209 primer, 17.5 gr 700X, Winchester WAA12 wad
1 1/16 ounce # 7 3/4 homecast shot, peened and graphited
total pellets: 420
total pellets impacting in a 30" circle at 40 yards: 302
pattern percentage: 72%


With the BT-99 the results were even more interesting:

12 gauge Browning BT-99, 32 inch "improved modified" choke, actual restriction .030

Winchester AA light target 2 3/4 dram, 1 1/8 ounce, #8 shot
total pellets: 460
total pellets impacting in a 30" circle at 40 yards: 349
pattern percentage: 76%

Reload, Winchester AA hull, Winchester 209 primer, 17.5 gr 700X, Winchester WAA12 wad
1 1/16 ounce # 7 3/4 homecast shot, peened only
total pellets: 420 total
pellets impacting in a 30" circle at 40 yards: 376
pattern percentage: 89%

Yes, that really does say 89%. This is where that off-center pattern that I fired earlier comes back into play. I couldn't believe that I really had just produced an 89% pattern, so I went back and counted the pellet strikes in the off center pattern. Even with part of the pattern obviously off the paper it still came out with 360 pellet strikes or 86%.

I don't know why the pellet count in these patterns is so high. Perhaps the ungraphited shot is clumping in the barrel and not spreading out until farther downrange. Next weekend I'll do more testing with the graphited and un-graphited shot and try to duplicate these results. For now they are so far off the scale that I have a hard time believing that it is credible data..........except that I have the pattern paper sitting in front of me.


note - the big black dot is not a clump of pellet strikes....it's just a big black dot that was on the paper. There are 3 pellet strikes in the black dot.

Stay tuned folks, this is getting interesting!

_

Comments:
Excellent write up... Keep it coming... As you say it is getting interesting...
 
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