by Tom Gaylord, a.k.a. B.B. Pelletier
My rifle is actually a BSA Super Meteor.
Today, you’ll see how I fixed the bad muzzle crown on the BSA Super Meteor, and then we’ll see if that had any effect on the rifle’s accuracy. You might want to read Part 7, again, just to remind yourself of what I faced.
The BSA project has been just that — a project from the start. All I wanted to do was test another vintage spring-piston air rifle for you and report the results, but this particular air rifle has challenged me at every turn. From the time I bought it at the Roanoke airgun show last September, it’s been nothing but a prolonged learning scenario. I won’t bore you by recapping all that’s happened; but if you want to find out, read Parts 1 through 7.
At the end of Part 7, I showed you a nasty muzzle crown, which I surmised was the reason that all the pellets were leaving the barrel with a yaw to their axis. They weren’t tumbling, because every one of them struck the target paper in exactly the same orientation. They were yawing, or traveling forward while pointing off to one side. Because the barrel is rifled, they were spinning on their long axis, but that axis didn’t happen to coincide with their flight path.
The BSA Meteor crown has some serious nicks in it. The dark spot at 10 o’clock is the deepest. Compressed air could escape through this channel before any other part of the pellet leaves the bore, and the jet of air could push the pellet over on its side.
The solution was to crown the bore; but as you can see in the picture, the Meteor’s muzzle is counterbored by more than an inch. In other words, it isn’t where it appears to be from the side. It’s deep inside the barrel, where the theory says it shouldn’t get damaged as easily. Only this one was — perhaps from over-zealous cleaning through the muzzle. Who knows? The point is that it had to be fixed.
My shooting buddy Otho suggested a piloted counterbore to face off the crown true and square to the axis of the bore. And he volunteered to make the pilot, so I slugged the bore for him and found it was a diameter of 0.176 inches. That seemed odd to him because it’s larger than the bore of a .17-caliber rimfire bullet that’s about 0.172-inches. But that’s the difference between .17 caliber and .177 caliber — which is important for airgunners and firearms shooters to know. The pilot he made measures 0.1745 inches and fits the Meteor’s muzzle comfortably.
Otho made the pilot for this counterbore.
The counterbore chucked up perfectly in my portable electric drill. I allowed extra length for the bore to go down into the barrel and touch the muzzle without the drill chuck touching the barrel.
The counterbore is chucked in the drill and set to run true. It sticks out far enough to cut the crown without the drill chuck touching the barrel.
Plugging the barrel
Before starting the work, I pushed 3 fat pellets into the breech and then pushed them with a cleaning rod to within 2 inches of the true muzzle. These will keep the metal chips from dropping down the bore.
I oiled the counterbore and pilot with a good grade of light machine oil before inserting it into the muzzle of the gun. The drill was set on a slow speed, but I can also control the speed by how hard I squeeze the trigger. I wanted a slow steady turn without putting much pressure on the drill. The counterbore is sharp enough to cut the soft barrel metal without a lot of encouragement.
The drill is set to run slow, and I’m also slowing it more with the trigger. You don’t need speed for a cut like this.
After about 10 seconds of cutting, I removed the counterbore and cleaned the new crown with a cotton swab. There was a band of bright metal around the muzzle where the counterbore had cut. Upon close examination, I could still see gouges in the bright band. The gouges were deeper than the first cut.
The new crown is bright after the first cut, but there are still gouges that need to come out.
I cleaned the counterbore with a swab and oiled it again. Then, I made a second cut on the crown. This time, I felt the drill pulse as the cutter removed the uneven metal. It became smooth, and I knew the cut was finished. When I cleaned and inspected the new crown this time, it appeared smooth and even. The job was done.
I apologize for the blurriness of this picture. Focusing on the crown is very difficult when I’m also trying to light it from the same axis as the lens is pointing. The lens is about one inch from the end of the barrel, and this was the best picture I got. There are still some faint marks on the crown. After examination with a loupe, I didn’t think they would be a problem.
At this point, I felt the crown was as clean as I could get it. And there was a simple way to see if this had made a difference. I drove the pellets in the bore out the muzzle and a few steel chips came with them. Next, I shot two RWS Hobby pellets offhand from 12 feet. If the crown was good, they would cut the paper perfectly instead of hitting sideways. And that’s what happened.
So, I backed up to 8 yards and shot 2 more shots from an improvised rest. These 2 pellets landed very close to each other and also showed no signs of tipping. I felt the job was done.
The two lower shots were from 12 feet. They confirmed the pellets were hitting the paper straight-on. The two upper shots were from an improvised rest at about 8 yards. They told me the crown is probably working.
Now for the test!
The test is a rerun of the Part 7 accuracy test. I used every pellet from the last accuracy test and shot at the same 10 meters.
Ten Eley Wasps went into 2.256 inches at 10 meters.
If you compare these targets to those in Part 7, one thing jumps out at you. None of these pellets tipped when they went through the paper. So, crowning seems to have solved that problem!
But the accuracy seems no better. The Hobbys did group better in this test, but the Falcons grouped worse. With groups this large at 10 meters, I’m not willing to say anything has improved. I’ve had cheap Chinese air rifles group better than this.
I have one trick left up my sleeve. I’ve noticed that the Meteor rear sight seems hinky and difficult to adjust, and I suspect it jumps around as I shoot. It’s not loose to the touch, but I don’t trust it to hold zero.
I’ll do one more test of this rifle with either a dot sight or with the See All Open Sight if I can get it mounted to the Meteor. If that doesn’t work, I’ll probably abandon this air rifle as a bad investment.