Author Topic: Minimum Allowable Scope Clearance (Read 926 times)

gharnden · « **on:** December 16, 2005, 03:12:13 PM »

I am buying a Webley Patriot. I was planning to use a Leapers 4-16x56 scope (30mm tube), with a BKL 360 mount, but then I found a super good deal on a Leapers 3-9x50 scope (25mm tube). This forces me to use a BKL 260 mount, which positions the scope .3" LOWER than the 360. Now I need to know what the ABSOLUTE MINIMUM clearance must be between the bottom of the scope objective and the top of the gun. (Note: The Webley and Beeman mounts I found, that were made specifically for the Patriot, state that they will NOT take a scope with a 50mm objective, and I decided long ago to stay away from B-Square. Any other suggestions for mounts that can handle a scope with a 50mm objective and a 25mm tube, and also that have an ESTABLISHED reputation for staying put on a Patriot, would be greatly appreciated.)

Here are the gruesom details:

I called Leapers and asked them to measure the objective O.D. on this scope (because they didn't know what it was) - ABOUT 60mm they said. So the distance from the centerline of the scope to the outside bottom of the objective end is ABOUT 60mm/25.4/2=1.18".

A dimensioned sketch of the 260 mount on the BKL website tells me the distance from the centerline of the scope to a point somewhere BETWEEN the true bottom surface of the mount and the true top of the curved surface on which the mount clamps, i.e., the receiver or barrel or whatever you want to call it, is 1.27". (I emailed BKL for clarification but they just regurgitated what it said on their website (except they incorrectly copied the dimension) so that was no help.) It looks like the top of the gun is ABOUT 1/16" closer to the centerline of the scope than 1.27" (or ABOUT 1.21").

So the distance between the bottom of the scope objective and the top of the gun is ABOUT 1.21"-1.18"=0.03" (subject to the amount of error in each of the "ABOUTs".)

I seem to recall reading in a forum (

) that the BKL 260 was good for scopes with objectives up to 50mm, but in light of the above, I decided it best to seek guidance from someone who hopefully doesn't have any "ABOUTs" in their experience. (Have any of you ever used a scope with a 50mm objective with a 260 mount?)

dave · « **Reply #1 on:** December 17, 2005, 11:35:27 AM »

Theres no "minimum" distance. As long as the scope doesn't touch the top of the receiver you are fine. In fact, 1.2 inches is a bit much. You want the centerline of the scope as close as possible to the boreline to minimize accuracy error due to gun cant and any slight misalignment between the bore and the scope dovetails.
What you do need to measure is scope length, especially in a longer multipower unit. Some longer scopes can interfere with the breech when mounted on break-barrel spring guns.
The Beeman 5038H mount is what you are looking for.Its made for the Webley, has the hardened stop pins to keep it in place and accepts up to 56mm objectives.

Lawdog · « **Reply #2 on:** December 17, 2005, 01:53:50 PM »

Quote from: dave

Theres no "minimum" distance. As long as the scope doesn't touch the top of the receiver you are fine. In fact, 1.2 inches is a bit much. You want the centerline of the scope as close as possible to the boreline to minimize accuracy error due to gun cant and any slight misalignment between the bore and the scope dovetails.
What you do need to measure is scope length, especially in a longer multipower unit. Some longer scopes can interfere with the breech when mounted on break-barrel spring guns.
The Beeman 5038H mount is what you are looking for.Its made for the Webley, has the hardened stop pins to keep it in place and accepts up to 56mm objectives.

'dave' has it right. Lawdog

gharnden · « **Reply #3 on:** December 19, 2005, 09:02:57 AM »

Thanks Dave & Lawdog for taking time to respond to my post.

With the Beeman mount number from Dave, I was able to do a search that got me to some adds that specified which Beeman mounts were made specifically for the unique cross-notch scope stop machining on the Kodiak & Patriot, and that was exactly what I was looking for. So thanks a million! (Previously, I couldn't find that info for any mount except the B-Square.) Since I prefer a 1-piece mount, I will be ordering a Beeman 5038H, and life is about as sweet as it can be without a BKL 260 in my future. (I am still frustrated by not being able to get meaningful info from BKL, because that 260 is definitely my mount of choice.)

(Now all I need to do is figure out why both of you think I have 1.2" of clearance from the bottom of the objective to the top of gun. I have 0.03", which was calculated from what I believe to be INACCURATE measurements from Leapers and BKL, and that's why I was concerned.)

Hope you guys both have a GREAT Christmas, and thanks again for the help.

gharnden · « **Reply #4 on:** December 22, 2005, 05:06:39 PM »

This post is for the benefit of anyone else out there with a similar problem.

I finally got the information I needed from BKL. (Unfortunately, it came the day AFTER I ordered my #2 choice, the Beemen 5038H mount.) The 260 mount holds the centerline of the scope 29.5mm above the top of the gun. They didn't think that was sufficient for a scope with a 50mm A/O objective. (Leapers told me their 50mm A/O scope is about 60mm in dia, so that agrees with BKL - the 260 mount will not accomodate a 50mm A/O scope.) Why in the world they don't publish this info in their specs is beyond me, because the dimension they publish doesn't really do any good unless you are trying to mount a scope with an objective of about 40mm or smaller - then it's a no brainer.

Here's the part that may help someone else. They have a new mount that raises the scope 0.2". They have them in stock right now, but they won't get it added to their website until next week or so. If you are interested, you can get one now by contacting customer service.

gharnden · « **Reply #5 on:** December 22, 2005, 05:08:47 PM »

This post is for the benefit of anyone else out there with a similar problem.

I finally got the information I needed from BKL. (Unfortunately, it came the day AFTER I ordered my #2 choice, the Beemen 5038H mount.) The 260 mount holds the centerline of the scope 29.5mm above the top of the gun. They didn't think that was sufficient for a scope with a 50mm A/O objective. (Leapers told me their 50mm A/O scope is about 60mm in dia, so that agrees with BKL - the 260 mount will not accomodate a 50mm A/O scope.) Why in the world they don't publish this info in their specs is beyond me, because the dimension they publish doesn't really do any good unless you are trying to mount a scope with an objective of about 40mm or smaller - then it's a no brainer.

Here's the part that may help someone else. They have a new mount that raises the scope 0.2". They have them in stock right now, but they won't get it added to their website until next week or so. If you are interested, you can get one now by contacting customer service.