Geometric puzzlement

[xbow]

Most of the mounts I've seen are pretty poorly made (extruded rather than CNC'd) but are at least affordable. I did see a guy on the net in the US who makes nice looking CNC mounts for about £60 but you'd still need to lap them. The best affordable solution IMO is to use a one piece mount (if you can on your rifle, I can't on mine ) and spend some time lapping it as suggested. RS components sell Silver Steel (ground bar) 333x30 which is just long enough, for £10.

[Barry]

Thanks XBow. The only one piece I can find are for 1 iinch tubes but Ill keep looking.....

Thanks for your input, much appreciated

[Baldie]

Thanks XBow. The only one piece I can find are for 1 iinch tubes but Ill keep looking.....

Thanks for your input, much appreciated

Unless I'm very much mistaken ( ) Sportsmatch do 30mm adjustables, and these come highly recommended. If you have a problem getting the product number, let me know and I will ring them.

Funny you should mention the HW100.

Do not lap your ring mounts. Great idea, but ... No, thinking about it, useless idea. This procedure will allow you to line up the scope tube through the rings if they are misaligned, but a one piece adustable from Sportsmatch won't need this. IIRC they released a two piece version 3-4 months ago. But a HW100 should have a one piece.

Lapping a 25 or 30mm ring will make it larger. Lapping a mis-aligned ring will make it eccentric (oval). Use Burris Signature rings if you have to, but don't lap your air gun mounts.

Remember:

If the gods wanted you to lap your rings, They would have supplied a 1" or 30mm ground bar with every set of rings, and a side order of grinding paste.


Sportsmatch are the best ring/mount manufacturer (for airgun) bar none. I doubt they would design anything that didn't work. Don't worry about adjustables not working. You've nothing to lose by trying. If they lose zero on your rifle, you get your money back. Simple, eh?

[Gary C]

The problem is airgun related, we pretty much use the rifle as a mortar bomb compared to a C/F. To achieve this excessive elevation it's better to "pack" the rear mounts than over extend the scope

Packing can be simply a couple of pieces of film or an adjustable mount. The latter is better but I do the former as I have a lot of rifles and BSq are exy

[sarf]

Do not lap your ring mounts. Great idea, but ... No, thinking about it, useless idea. This procedure will allow you to line up the scope tube through the rings if they are misaligned, but a one piece adustable from Sportsmatch won't need this.

I know you are having a laugh, Baldie . . but try this:

Put some engineer's blue on your scope. Rotate it in the scope mounts whether Sportsmatch or whoever's, see how much contact there is. In my experience, not a lot. Same with the caps. The finished surface of the mounts is not the result of precision line-boring, for a start there is the paint/anodising.

Lapping gives you a certain reassurance of a good mechanical bond between scope and mounts, possibly slightly improving reliability and definitely minimising the risk of damage to the 'scope tube.

Lapping may be a waste of time, but it's not a bad idea!

[Baldie]

I know you are having a laugh, Baldie . . but try this:

Put some engineer's blue on your scope. Rotate it in the scope mounts whether Sportsmatch or whoever's, see how much contact there is. In my experience, not a lot. Same with the caps. The finished surface of the mounts is not the result of precision line-boring, for a start there is the paint/anodising.

Lapping gives you a certain reassurance of a good mechanical bond between scope and mounts, possibly slightly improving reliability and definitely minimising the risk of damage to the 'scope tube.

Lapping may be a waste of time, but it's not a bad idea!

Well, if you can afford to customise your rings .....


I understand what you're talking about in terms of contact. But for airguns, especially PCP's, Sportmatch remain about the best. I use them on HMR and LR too, and they perform very well.

For full-bore shooting, I use Tactical Precision mounts on a Picatinny rail. Concentricity of the rings is probably better than the tolerance on the scope tube. And I'd never grind the coating off the scope tube to get the tube round to the rings.


Mindful people are using £500-£1000 rifles and £200-£400 scopes, it makes no sense at all to skimp on mounts. Most expensive isn't always best either.

£50 for an adustable mount seems very very reasonable to me.

[sarf]

But for airguns,[] Sportmatch remain about the best. I use them on HMR and LR too, and they perform very well.
[]
£50 for an adustable mount seems very very reasonable to me.

I agree Sportsmatch are the best out there and £50 is very fair for what you get, but they still need a bit of finishing.

Perhaps Sportsmatch could do an "elite" range where the mounts were precision line-bored (like TP), at a guess it would increase the cost by 50 - 100% but some people would buy them . . well I would anyway

[Adam77K]

It strikes me that these days with more and more people using bigger (longer) scopes it's about time that airgun manufacturers started making their scope rails with a built-in incline. I know that you can get inclined rails for Steyrs etc but why is this not more common on mid-range guns?

I'm not including the budget end of the market here of course. With a cheaper springer where the rails are cut into the compression cylinder it would unnecessarily add to the costs.

Scopes do perform so much better when they are near optically centred. What I'd like therefore is a precision engineered one-piece scope riser, which clamps to standard dovetails on most rifles but has another dovetail on the top surface, is machined with an incline.

If someone manufactured something like this I'm sure it would sell well. I envisage one aimed at FT, with an angle optimised for typical 12 fpe trajectory drop at 50m range and high line of scope above bore. It's at 50m (55 yds) you need the scope to be performing at its best. Also there could be one optimised for hunting/HFT with a lower sight line optimised for maybe 30m.

[Goes off to play with Chairgun and scientific calculator]

[Adam77K]

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.

[sarf]

The problem is airgun related, we pretty much use the rifle as a mortar bomb compared to a C/F.

My Chairgun and I reckon pellet drop at 55yds is going to be around 12" with a full power .177"

Like centrefire at 200 yards?

About 1/2 a degree of downslope required on the scope?

[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.

[Adam77K]

My Chairgun and I reckon pellet drop at 55yds is going to be around 12" with a full power .177"

Like centrefire at 200 yards?

About 1/2 a degree of downslope required on the scope?

Yep about that.

Working in metric 'cos numbers are rounder that's 300mm give or take.
High mounted scope 50mm above bore, so vertical displacement sight line to target = 350mm
50m range so horizontal displacement = 50,000 mm
Let angle be x

tan(x)=350/50000
x = atan(0.007) = 0.4 deg (24 MOA)

[Baldie]

Continuing what is becoming an extremely fascinating thread.....

My Chairgun and I reckon pellet drop at 55yds is going to be around 12" with a full power .177"

Like centrefire at 200 yards?

About 1/2 a degree of downslope required on the scope?

What CF is this?

I have this at - 43.6 inches at 200 yards if -12" at 55yds?

Yep about that.

Working in metric 'cos numbers are rounder that's 300mm give or take.
High mounted scope 50mm above bore, so vertical displacement sight line to target = 350mm
50m range so horizontal displacement = 50,000 mm
Let angle be x

tan(x)=350/50000
x = atan(0.007) = 0.4 deg (24 MOA)

That's quite a lot. CF rails are available for -20MOA for long range shooting, in the expectation you can't dial in enough adjustment on your scope.

No wonder we had as many problems as we did with the higher mag scopes.

Well, problems with scopes not being able to do the (seemingly) impossible?