Testing the .177 Pelletgage: Part 3
by Tom Gaylord
Writing as B.B. Pelletier
The Pelletgage comes in .177 caliber at the present. The holes are in a steel plate. A plastic plate above the gage plate helps guide the pellet head to the gage hole.
This report covers:
- The test
- Blind test
- I called it
- What to make of these results
- Observations so far
Before I get into the test, I received a message from the Pelletgage maker, Jerry Cupples, telling me that he has measured a large sample of the gages he has made — they’re all measuring 0.01mm smaller than what’s marked on the gage. In other words, a gage hole that’s marked 4.52mm actually measures 4.51mm, and so on. This holds true for all the gage holes in a gage plate.
So, in the last report, all the pellet sizes I gave you were off by the same amount. This is not a problem. All I need to do is change my pellet sizes by reducing all on them by 0.01mm after gaging.
Jerry measured the holes with gage pins traceable to NIST standards. Before that, he was using an optical comparator that might be uniformly off for various reasons — with the edge of the kerf being a prime suspect.
I’ll continue to use my gage, as it’s the uniformity that I’m looking for. I can simply adjust the numbers now that Jerry has informed me. This changes nothing, except how I record sizes.
Today’s test is as different from the last test as I can make it. Today, I shot 7.9-grain Crosman Premier lite pellets from my TX200 Mark III at targets 25 yards away. I know this rifle likes the Premier lite, and I thought this would be a good test for the gage.
Since I have no idea how uniform Premier lite pellets are, the first task was to sort them and see what I got. As it turns out, Premier lites in the cardboard box are very uniform. Most of them had a head size of 4.54mm (yes, that is after I corrected for the gage). But every once in a while, I got one that was smaller or larger. They only differed by 0.01mm each way. At the end of my task, there were 111 pellets with 4.54mm heads, 11 with 4.53mm heads and 10 with 4.55mm heads.
I decided to shoot 4 10-shot groups at 25 yards off a bag rest. We know the TX200 Mark III does well when rested that way. Two groups would be with the most common 4.54mm heads, and the other 2 groups would be with an equal mix of 4.53mm and 4.55mm heads. There are several ways to ldo this, and today I just wanted to see how uniform pellets did compared to pellets I knew were not uniform.
To keep my bias out of the test, I gave the pellets to my wife, Edith, who marked them in bags that I gave her. She knew which bag was which; I did not. As it turned out the results were dramatic and obvious — just not what I was expecting. I have a theory about that which I can test next — thanks to the Pelletgage. But for now, let’s look at the results I got.
I will now show all 4 targets in the order in which they were shot. Then, I’ll discuss what I think may have happened.
Looking at the groups, I don’t see what I expected — which was 2 very small and round groups and 2 groups that were larger. But I do see differences that allow me to place these 4 groups into 2 categories. There are 2 larger groups and 2 other groups that both have small main clusters of shots with one or 2 outlying pellet holes. The second group and the last group have these small clusters.
I know for a fact that, in the second group, the 2 pellets that are not in the main group were fired number one and two in the string. On the last group, I think the one low pellet was one of the first 3 pellets shot, but I’m not sure.
The smaller group in the second target contains 8 pellets and measures 0.253 inches between centers. The small group in the last target contains 9 pellets in the main group that measures 0.286 inches between centers. In the last group, it looks like one shot may have gone between the outlying pellet hole and the main group. That would make the main group 8 shots rather than 9.
I called it
I told Edith that I suspected the second and last targets were shot with pellets having 4.54mm heads and targets 1 and 3 were shot with the pellets that were a mixture of 4.53mm and 4.55mm. She told me I was exactly wrong. Targets 2 and 4 — the targets that contain the tightest groups within the main group — were shot with the mixed head sizes! And groups 1 and 3 were shot with the uniform 4.54mm pellet heads.
What to make of these results
It looks like Premier lites with 4.54mm heads are not the optimal size pellets for my TX200 Mark III. It further looks like either 4.53mm or 4.55mm heads may be the ideal size. This test did not test for that.
If you can think of anything I’ve overlooked, I’m open to your thoughts. My plan is to rerun this test and shoot 3 more 10-shot groups — this time with 10 pellets of each head size — 4.53mm, 4.54mm and 4.55mm. I hope I have a better idea of what is happening after that.
Observations so far
I’ve now run 2 tests using the Pelletgage, and both times I got demonstrable results. In today’s report, the results were not what I was expecting, but that’s why we test. And the Pelletgage makes testing possible, where before it existed it wasn’t possible to measure pellet heads this precisely. It’s an instrument like a chronograph. No, you don’t need one to shoot airguns and have a good time; but if you want to know more about how your gun works, it’s starting to look like a Pelletgage is essential.