Geometric puzzlement

[Baldie]

According to my calculations an incline of between 20 and 25moa would be ideal.
This is based on chairgun's drop predictions for .177 Exacts launched at 11.5fpe at a range of 55 yds and sight line 2" above bore line.

Looking more and more like airgunners should have Picatinny rail used for 1000 yard target work. Will wonder off for a mo and take piccy of my CF.

[Baldie]

I use 30mm scopes, with Sportmatch R/F mounts.

Rimfire/airgun with 4-16x56 SWF.

With this exception.

Centrefire with 4-16x56 Custom jobbie.





Didn't take long .....

[xbow]

I checked with "The font of all (engineering) knowledge", (Tim!) at work and he offered the following: "you won't get far trying to lap aluminium with a steel bar, the grinding paste sticks to the softer material and laps the harder one"! I assume then that the benchrest guys are using steel mounts?!

The other thing I don't like about many types of rings are the "this will fit X+X+X size dovetails" Really, and how far off the boreline is you scope going to be then? These: http://www.deltainc-usa.com/jdkstuff...ext15apr02.htm or these: http://www.bkltech.com/ are a better idea I reckon.

[sarf]

"you won't get far trying to lap aluminium with a steel bar, the grinding paste sticks to the softer material and laps the harder one"!

He's got a point. I've only used abrasive paper so far. I'd like steel mounts but haven't been able to find any for airgun 'scope rails.

These: http://www.deltainc-usa.com/jdkstuff...ext15apr02.htm or these: http://www.bkltech.com/ are a better idea I reckon.

Agreed. Does anyone import BKL? I see they offer drop-compensated mounts:

Available Bullet Drop Compensation::
.004" per inch-typical for Rimfire applications
.007" per inch-typical for Airguns applications - and 7/1000 is about what we've discussed as a suitable slope!

[Baldie]

Agreed. Does anyone import BKL?

They do, but you wouldn't buy them if you had a choice. BKL won't export direct though. The UK distributor has to make a profit, but the price difference between US and UK prices, must mean they are hand couriered.

Can't respond to the .308 at 600 yards vs airgun at 55 yards.

















But I may know a man who can.

Will PM "The Cavalry".

[Adam77K]

Nice find - that is exactly what I want - 0.007" per inch is spot on with my calcs too.

Only 50 bucks too, but it's probably nearer 100 quid by the time it reaches these shores

[I'd prefer another inch in length, but wouldn't we all ]

[RobF]

to avoid packing i've used b-squares, and now have them on all my rigs...

if your careful to make sure the windage is the same on each and have a wind free range to check and eliminate any cross over, they only take 20 mins or so to get close to zero just using the mounts. When I mean close I mean less than 10 clicks on a 1/4 moa scope.

getting the windage sorted seems to be the trick with them, so taking time to make sure they are central before mounting them is a good start...the walther and hw rails they sit on are pretty damn straight so i've found they've needed little or no adjustment in the windage dept.

they sit on a gimble, so although it does leave the head worrying that it might come loose, once you've realised that even with a little tightness they cant shift, locking them up and leaving them, with a bit of shooting brings back the confidence. I've had them on for almost a year on one rig without any problems.

The 2 piece ones are easier to setup than the one piece ones...because you can simply undo the rear dovetail section and spin it to adjust elevation (with the other screws loose to allow both gimbles to move).

The only downside i've found with them is that they are built to very tight tolerances...the clamps arent 180 degree split, which means they need carefull effort not to scratch the scope when placed on...and the threads need to line up precisely because the threads wont allow any give on the angle before tightening...they need to be bang on or there is a danger of cross threading...a little bit of countersinking on the threads would go a long way to help.

This tolerance problem revealed itself on the one piece mount which needed to have the rail clamp exactly parallel to the block in order to be tightened...and on a dipped scope which after dipping meant the tube was a little over 30mm, which meant that the scope clamp bolts needed careful alignment. It also happend on a big nikko...which wasnt dipped, but 5 mins with a swiss file on the clamp holes saw that solved.

So, to sum up...can be a bit of work, but they completely solve the need and problems of shimming...and in my book are rock solid in performance.

I'd like to see a set of the sportsmatch mounts to see how they work as well though.

[sarf]

I checked with "The font of all (engineering) knowledge", (Tim!) at work and he offered the following: "you won't get far trying to lap aluminium with a steel bar, the grinding paste sticks to the softer material and laps the harder one"!

Slightly off-topic . . I'm familiar with the effect that Tim is describing. However, I've always presumed that the cause is the fact that all aluminium will have a very thin surface coat (once exposed to air) of aluminium oxide, which is of course extremely hard and often used as abrasive. Unless this surface layer is broken through, the aluminium oxide will resist the grinding paste better than the steel. Well that's my theory anyway.