Man, did we have a LOT of interest and speculation about the R7 accuracy results. I guess you guys just like a little test now and then. I thought the clues I gave were huge, but some of you didn’t seem to grasp them, so today we’ll look more deeply into this rifle’s performance.
Well, how many of you guessed correctly what is wrong with out test Beeman R7? I thought you might see some similarity between what is happening with the R7 and what happened to me during the FWB 124 25-yard test. In fact, our new reader Steve picked up on that. The only difference between the two tests is that because the 124 has open sights, I was able to test it at 10 meters before relying on the scope sight, and so I knew for certain that the 124 should not give me vertical groups. The scope had to be the cause.
But Beeman doesn’t sell the R7 with open sights any more, so you can’t use that as a means of checking the rifle. However, when you see groups that are predominantly vertical, you know that the scope is probably to blame. And Mac did say he noticed this R7 has a very large droop when he first examined it. I missed his comment until this happened, but we carried the test a bit farther, so everybody will be able to see exactly what’s happening.
Because the rifle came sighted in from Pyramyd Air, Mac never checked to see where the scope was adjusted. He was shooting it just as it came from the box. He used RWS Superdomes, even though they’d given the largest groups in the previous test.
Several of you thought that Pyramyd Air simply shipped out a returned gun from another customer. That wasn’t the case. And they don’t do that the way those who implied that they do might think. When a gun comes back it gets tested before going out again. Pyramyd Air cannot afford to pay shipping on guns that have a problem, so it would be foolish to just turn around a gun that way.
I was hot off the 124 test, so after examining that large vertical RWS Superdome group in yesterday’s test I suggested that Mac crank in 40 clicks of down elevation and shoot another group. He did that, continuing to shoot RWS Superdomes, and the point of impact didn’t change! That’s clear proof that the scope is at fault. He cranked in another 40 clicks of down and shot a third group that was lower but also strung out vertically. We’re now down by 80 clicks.
After that, Mac dialed in a third set of 40 clicks down and this time he shot a well-rounded group. Finally! So, after 120 clicks of downward adjustment, the gun starts shooting circular groups with one called flier. Then, he dialed in a fourth set of 40 clicks of down and shot another elongated group!
What? That’s not supposed to happen. Once the groups start shooting in a round pattern, they’re not supposed to go back to vertical stringing. In fact, when the vertical adjustment is coil-bound, the group should be as tight as it will ever get, though not in the right location. However, looking at the whole picture at once — the 50 shots fired over 160 clicks of vertical adjustment — you’re struck by one obvious fact. There’s no sideways dispersion! It’s all up and down and very little side to side. In fact, in over 12 inches of up and down adjustment, there’s only about one inch of side-to-side. That says something, and the something that it says is that the scope’s the problem.
All shots were with RWS Superdomes. Looking at all 50 shots made during the vertical scope adjustments reveals this interesting image. There is very little sideways dispersion. The shots simply string up and down. Notice that the first 20 shots are intermingled despite 40 clicks of adjustment after the first 10 shots. Clearly, the erector tube was floating big time when this target was shot until the fourth group was fired.
After 120 clicks of down were applied, the group rounded into this pattern. It’s still not great, but at least it isn’t as vertical as the others.
After Mac shared these groups with me, I asked him to crank the scope all the way down until the adjustment knob quit turning. That would be where the erector spring becomes coil-bound. And even there, which was 200 more clicks down from what you see here, the group was still vertical.
I also asked him to try the JSB Exact 8.4-grain pellets that were the most accurate in the previous test. He did, and they strung out vertically, just like the Superdomes. They were a larger group than in the previous test. Crosman Premier 7.9-grain pellets delivered similar results, except the group was even larger.
So, what we have here is a scope that’s unresponsive. No amount of shimming or droop compensation will fix what cannot be fixed. At least we now know that, so we can try a different scope and see how the rifle shoots.
We also know that this particular R7 has a lot of droop. Regardless of what other scope we try, we’ll have to compensate for it.
How much better it is to know this, than to curse the darkness and send everything back to Pyramyd Air. Anyone who plans to use a telescopic sight should know how to analyze these sorts of results. You need to learn how this works, so you can diagnose problems like these when they arise.
I am pleased to be doing this report because it’ll answer so many questions I get about scope mounting and “scope shift.” I often have to drag the facts out of the person with the question, when all they want is “the answer.” One guy wanted to sight in his scope at 10 yards. Okay, I told him, but it’s going to be way off at every other range. He got angry about that and wanted to know what was the matter with scope makers that they couldn’t simply make a scope that worked the way the customer wants it to work.
Physics is the answer to that question, and not many of the people who ask it want to hear that. They don’t want to hear that since the scope and bore are in two different planes that there must be a planned intersection of the two. Because the pellet starts falling the moment it leaves the muzzle, the trajectory must be taken into account, as well.
I’m getting off the subject, which is this R7 and what we’re going to do about it. Well, Mac is going to mount a different scope on the gun after the Roanoke airgun show, and he’ll use a mount with some built-in droop compensation. We’re also talking about stripping the gun to see what’s happening in the powerplant. One of our readers also mentioned that his new R7 is dieseling just like Mac’s test gun (you can smell the diesel but not hear it), so perhaps we’ll discover something there, as well. At any rate, we are going to get to the bottom of this together.
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