Air Venturi Tech Force M12 combo: Part 5
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report is an important one, but it may be confusing until you hear the whole story. The last time I reported on this Tech Force M12 combo was back on November 19 of last year. A lot has happened with this rifle since then, and I’ve kept daily readers informed of what’s been going on, but it would have been easy to overlook and even easier to forget. So I’ll summarize.
The M12 I’m testing is a drooper, and I first had to solve that problem. Once I did, I noticed it threw fliers. I cleaned the barrel — but it got no better. I tightened all the screws — again, no change. I cleaned the barrel with JB Non-Embedding Bore Cleaning Compound — and still there was no improvement. Then, I shot the gun just to break it in — again, no change.
All of this work took a lot of time, as I was testing and reporting on other guns. I also set the rifle aside for weeks at a time out of sheer frustration. In late January of this year, I decided to have another go at discovering what the problem was. I had to locate a drooper scope because, by this time, I’d used the scope that was on this rifle for other tests. I reread the early reports and discovered that this rifle had shot very well at 10 meters with JSB Exact RS pellets. So, that was the pellet I tested, but at 25 yards.
At 25 yards, I got several groups that had a bunch of shots close together and then some fliers. But one group stood apart as extraordinary. Seven of the 10 shots were in an extremely small group, and 3 others were huge fliers. This was what I had been looking for. When you see something like this, it tells you the rifle wants to shoot, but something is interfering intermittently.
The group at the top left with the one shot that isn’t quite touching is 7 shots from 25 yards. That’s a 0.439-inch group. The other 3 holes are fliers shot at the same time. This is a clear indication of a problem.
I looked down through the muzzlebrake with a powerful flashlight and saw the real barrel muzzle deep inside. It appeared very rough, plus I could see bright bits of lead clinging to the inside rear edge of the muzzlebrake. I showed this to Edith, and she confirmed what I was seeing.
Apparently, the crown of the muzzle of my rifle was uneven and was causing pellets to wobble just a tiny bit when they left the barrel. A few of them were hitting the inside rear edge of the muzzlebrake, causing them to destabilize in a big way. Those were the random fliers I was seeing.
I communicated this to Pyramyd Air. Gene, the tech manager, took apart an M12 to look at the crown. He said it looked rough to him, as well. He crowned it and sent me the barrel to exchange with the barrel in my rifle.
The barrel Gene sent is .22 caliber, while my rifle is .177, but that makes no difference. One barrel works as well as another, as they’re the same size on the outside. I followed Gene’s instructions and switched barrels in 15 minutes. I didn’t have to disassemble the rifle because of how it’s made.
Once I got the original barrel out of the gun, I could see that the muzzle wasn’t as rough as I’d thought. I had seen grease on the end of the muzzle when I looked down inside, and it looked like rough metal to me. The muzzle is finished rather well, but the actual crown, which is a chamfer cut into the bore, is cut on an angle rather than perpendicular with the bore. It allows compressed air to escape the muzzle on one side of the pellet before the other.
The muzzle of the .177-caliber barrel that came in the rifle was crowned lopsided. The chamfer appears narrow at the bottom of the muzzle. That’s not an optical illusion — it really does grow narrow there!
Following the assembly of the barrel to the rifle, I remounted the scope and proceeded to start my sight-in. I decided to test the .22 barrel with JSB Exact RS pellets, as well. One shot at 10 feet was all it took…and I was on target. Two more shots at 10 meters and I was sighted-in. Next, I shot a 10-shot group. The rifle behaved very stable and did not appear to throw any wild shots.
The 10-meter group I shot was consistent, if not terribly small. But the lack of fliers, even at 10 meters, gives me hope that the crowning of the barrel has solved the problem.
Test is not finished.
By no means is this report finished. I still need to shoot several groups at 25 yards to see what the M12 can really do. I have no idea what the best .22-caliber pellet might be. After rereading the first two parts of this report, I see that I very much liked the way the gun handles. That’s still true. It lacks the two-bladed Mendoza trigger — and that’s a shame, but the trigger it has isn’t that bad. Obviously, I’m able to use it.
I now have both a .22-caliber barrel and a .177-caliber barrel that fit on the same powerplant. If I can hold onto them both, I may be able to get a little more milage from this gun. First, I could do a redneck crowning job on the .177 barrel and report how well that works.
Next, I could test the .22 barrel for velocity and then swap barrels and retest the .177 barrel to get a comparison between calibers from the same gun. I’ve always been able to do that with my Whiscombe, of course, but this is more of a real-world air rifle to which many can relate.
I know there are several shooters who wanted the M12 to be a great buy, and my early tests didn’t bear that out. If they’ve continued to follow this blog, they’ll get the chance to see how the story ends!