IHMSA80x80
New member
Rimfire Benchrest Folks...
I have one of those nifty XP-100 pistols converted to .22LR. It is an amazing little gun that is killer accurate and so much fun to shoot. I didn't get it new, but it came set up this way, with a Leupold 40x Competition scope on a standard Weaver base.
Bill offered to make me one of his single-base, double-ring mounts, so I got a new Weaver base and sent it off. Then he asked me to run an experiment for him. In his own words:
The first spearment to do is this:
Foul the bore, then shoot a couple of groups..........then, remove the cross bolt from the rear ring, then remove the top strap of the rear ring.
Then you can carefully slide the rear ring off of the base.......you might lift up slightly on the scope as you slide the rear ring off...
Now, with only the front ring holding the scope, foul a shot, then, taking the same aiming hold as you did for the first two groups, fire another group.
Now, see where this group strikes the target as compared to the first two groups shot with the scope held by both rings....
Here's the point of this spearment:
If the group you fired with just one ring holding the scope strikes the exact same location as the two groups using both rings, you have a perfect scope mounting system..........
If the one ring group strikes a different location, this shows that the scope was in a bind with the two ring set-up.
And, depending on how far apart the group locations are, determines how "bound up" the scope was in the two ring set-up. ( the single ring will hold the scope just fine...I've tested a lot of guns using just one ring)
I was able to get the first part of the spearment done this week. My target was set at 50 meters as that was the only distance I could utilize that day. I fouled the bore, then shot some sighters on the left, then a couple of groups, the center two The wind was at first light and steady, but I wasn't able to set out any wind flags due to the range event that day. Here's the two groups.
Then I removed the rear cross bolt and ring half and carefully removed the lower ring. Then, without changing my aim point, I fouled the barrel and shot a couple more groups, with the following results.
Of course, by now and with the range breaks I had to endure, the wind had picked up and become a bit switchy. Disregarding my poor wind guessing holdoffs, you can see these groups are definitely higher than the first two, and also not as small. Just to confirm, I shot a third group next to the original two, and it was also in the same location, higher than the original ones.
Obviously, I didn't have a perfect scope mounting system...the scope was in a bind.
I hope to complete the second part of this test next week, with the new single-base and two-ring system, but besides seeing the light on the singe-base system (which I had read about and agreed to it's merits before this test), it raised some interesting questions for me.
One: The single-base mount is supposed to remove the binding in the scope mounting system, but this one had the Burris Signature rings with inserts already in place. Theoretically, that type of mounting should remove any binding in the scope, so my groups should have been in the same location as the original ones. Why did the point of impact move when only one ring was used?
Two: Is it possible that with only one ring in place, the scope could have moved when the rear ring was removed because of the plastic insert not being a solid metal to metal contact? It seems just a very slight bump when removing the ring, despite how careful I was, might be enough to cause that change in impact.
Three: I understand the Burris Signature ring system, and, like Wally and the others, I was always convinced it was a better way to go, In fact, I also use it on most of my guns. I can see how the plastic inserts can self-center when you first start tightening the ring halves, but as the screws are tightened further and the insert halves join together, can the tightening process cause those plastic pieces to become solid enough to end up binding the scope?
Since I haven't removed the scope yet and it is still mounted with just the front ring, I could go back to the range and try putting upward or downward pressure on the scope, shoot a couple of groups and see if the impact point changed. That would confirm whether I had bumped the scope to cause the vertical change on the targets or whether the scope was actually in a bind.
Maybe I will need to replace the Burris Signature rings and inserts and go with a solid Weaver ring setup. More to come later, when I can get to the range again.
I have one of those nifty XP-100 pistols converted to .22LR. It is an amazing little gun that is killer accurate and so much fun to shoot. I didn't get it new, but it came set up this way, with a Leupold 40x Competition scope on a standard Weaver base.
Bill offered to make me one of his single-base, double-ring mounts, so I got a new Weaver base and sent it off. Then he asked me to run an experiment for him. In his own words:
The first spearment to do is this:
Foul the bore, then shoot a couple of groups..........then, remove the cross bolt from the rear ring, then remove the top strap of the rear ring.
Then you can carefully slide the rear ring off of the base.......you might lift up slightly on the scope as you slide the rear ring off...
Now, with only the front ring holding the scope, foul a shot, then, taking the same aiming hold as you did for the first two groups, fire another group.
Now, see where this group strikes the target as compared to the first two groups shot with the scope held by both rings....
Here's the point of this spearment:
If the group you fired with just one ring holding the scope strikes the exact same location as the two groups using both rings, you have a perfect scope mounting system..........
If the one ring group strikes a different location, this shows that the scope was in a bind with the two ring set-up.
And, depending on how far apart the group locations are, determines how "bound up" the scope was in the two ring set-up. ( the single ring will hold the scope just fine...I've tested a lot of guns using just one ring)
I was able to get the first part of the spearment done this week. My target was set at 50 meters as that was the only distance I could utilize that day. I fouled the bore, then shot some sighters on the left, then a couple of groups, the center two The wind was at first light and steady, but I wasn't able to set out any wind flags due to the range event that day. Here's the two groups.
Then I removed the rear cross bolt and ring half and carefully removed the lower ring. Then, without changing my aim point, I fouled the barrel and shot a couple more groups, with the following results.
Of course, by now and with the range breaks I had to endure, the wind had picked up and become a bit switchy. Disregarding my poor wind guessing holdoffs, you can see these groups are definitely higher than the first two, and also not as small. Just to confirm, I shot a third group next to the original two, and it was also in the same location, higher than the original ones.
Obviously, I didn't have a perfect scope mounting system...the scope was in a bind.
I hope to complete the second part of this test next week, with the new single-base and two-ring system, but besides seeing the light on the singe-base system (which I had read about and agreed to it's merits before this test), it raised some interesting questions for me.
One: The single-base mount is supposed to remove the binding in the scope mounting system, but this one had the Burris Signature rings with inserts already in place. Theoretically, that type of mounting should remove any binding in the scope, so my groups should have been in the same location as the original ones. Why did the point of impact move when only one ring was used?
Two: Is it possible that with only one ring in place, the scope could have moved when the rear ring was removed because of the plastic insert not being a solid metal to metal contact? It seems just a very slight bump when removing the ring, despite how careful I was, might be enough to cause that change in impact.
Three: I understand the Burris Signature ring system, and, like Wally and the others, I was always convinced it was a better way to go, In fact, I also use it on most of my guns. I can see how the plastic inserts can self-center when you first start tightening the ring halves, but as the screws are tightened further and the insert halves join together, can the tightening process cause those plastic pieces to become solid enough to end up binding the scope?
Since I haven't removed the scope yet and it is still mounted with just the front ring, I could go back to the range and try putting upward or downward pressure on the scope, shoot a couple of groups and see if the impact point changed. That would confirm whether I had bumped the scope to cause the vertical change on the targets or whether the scope was actually in a bind.
Maybe I will need to replace the Burris Signature rings and inserts and go with a solid Weaver ring setup. More to come later, when I can get to the range again.
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