3/8" vs 11mm Scope Mount

[Scrambler82]

Hello to all,

I am wondering if there is enough difference between the 3/8" Dovetail Mounting and the 11mm Dovetail Mounting  to cause a poor fit on the rifle ?

3/8" = .375 = 9.52mm. Vs  11mm = .433

My thinking is the dovetail will not seat properly when a mount is designed for an 3/8 dovetail and it it mounted on an air rifle with an 11mm dovetail.

Also, will the position of the scope to barrel centerline be a problem ?

Thanks for reading and I hope there is a definitive answer.

[Roadworthy]

Some mounts are made to work with either 3/8" or 11mm dovetails.  These scopes will have a reversible side.  Besides a difference in distance between the slots the angles of the slots themselves are different.  You do bring up some valid points.

You are correct - theoretically the centerline of the scope may not coincide precisely with the centerline of the barrel.  I hadn't even thought about that.  The closer the target is to the gun, the more noticeable it will be.

 The combination mounts may not be perfect but they seem adequate to me. 

[monophonic]

According to Tom at PA's blog 11mm is very much a nominal width, especially as older air rifles are concerned. They may range from 9.5mm (3/8") to 14mm (0.55") and the angle of the groove also varies. I'm still building up the reputation to be allowed post links, but if you google "pyramyd air blog 11mm width" the two first hits at least have this information.

If the scope is off to one side from the barrel line, the point of aim will coincide with the point of impact at most at one range. When shooting closer or further up, they will be separated in the horizontal direction. In practice the difference in centerlines would rarely be big enough to become noticeable.

[condor22]

  The manufacturer/OEM should know the dovetail rail size, call to find out.   3/8in rail was typically American and 11mm rail European. You can get compatible rings or 3/8 in only, 11mm only.  If you ever actually mount a 3/8 in ring on a 11mm rail,  you'll see the difference, and it looks wrong to me.  The consensus here is theres no difference, then why the two different rails and I can buy rings made for each. 

[Scrambler82]

I have read the postings on many sites and will probably but the mount suggested but I am not happy.

As stated, if the mount is made for 3/8 mount the center line will be off in width, yes only about 10or 15 thousandths but off none the less.

As stated, why do they make both if they are the same thing, which in my opinion they are not ?

Thanks for the comments.

[condor22]

 IMHO all dovetail rails are 11mm as is all air rifles are BB guns! 

[TooJung2Die]

There is a solution. It is not uncommon for the scope centerline to be slightly off from the barrel centerline. Tilt the gun until the centerlines of the scope and barrel align vertically. Rotate the scope crosshairs until the horizontal is parallel to the horizon. When you shoot keep this alignment. Unless the centerlines are off by a lot the tilt of the gun will only be slight. If you have to tilt the gun a lot then you probably have the wrong mount for your grooves.

[Scrambler82]

Thanks for the replies.
I am thinking a different route, 11mm Dovetail to Weaver Mount Adapter, then Weaver/Hawke Rings.

I get too involved, OCD, in the choices, Quality Engineer for too long.

Thanks for all of the ideas and thoughts.

[condor22]

 Just a couple of weaver base rings I use and highly recommend:

 Leupold PRW-QRW Permanent/quick release weaver base. http://swfa.com/Leupold-Permanent-Weaver-Style-30mm-Rings-C695.aspx http://swfa.com/Leupold-Quick-Release-Weaver-Style-30mm-Rings-C705.aspx These rings are worth 3x price! 

 Weaver Detachable Top Mount : http://swfa.com/Weaver-Detachable-Top-Mount-30mm-Rings-P10408.aspx These are cheap and wont break the bank.

 Not to knock Hawke 11mm to weaver rails, I returned a set of 2pc Hawke 11mm to weaver rail adapter to Optics planet (Model HM17013) http://www.hawkeoptics.com/38-or-11mm-to-weaver-2-piece-adaptor.html Where the screw went through the clamp with very little effort.  First time use


 Sam 

[Railbuggy]

I go with the 3/8 or 11mm to Weaver adapter by UTG and then use high rise or see thru rings. I lost my right eye and still shoot right handed using my left eye. My scopes sit about 1.5 to 2.0" above the barrels.

[Scrambler82]

I guess I should post up what I did.

I ended up purchasing the 11mm Dovetail to Weaver Adapter with the Weaver 1" Rings mount, along with a 3x9-40mm Hawke Sport Scope.
The Weaver Adapter is also a droop unit so in the long run, if it stays put, it will work out for the best.

There is so much information out there on which scope is best, which does this and which does that, I was totally confused and I need to start somewhere, so enter the Hawke Sport Scope.

Thanks for all the information and suggestions.
I will report on it once the Rifle is ready and I have had sometime to shoot.

Ltr,

[45Bravo]

If this is going on the Bone collector you have listed in your signature,
Then the scope being 0.001 - 0.0015 of an inch off of centerline of the bore is the least of your worries...

If you are worrying about that minuscule amount of misalignment,
Then the .375-.5 of an inch you raised the the scope above the nominal height must be driving you bonkers.

Yes it will be on zero, 2 times in the flight path, (near and far zero)

But I don't think there is a sub $240 gas ram gun on the market that can shoot well enough to actually show the optics being 0.001 out of alignment, especially at the distances we shoot.

Springers and gas ram guns are very hard on scopes and mounts as we all know.

With the rings mounted to the dovetail, you have 2 places for scope movement to possibly occur in the shot cycle(the rings on the dovetail, and the scope in the rings.)


With the addition of the adapter, you have introduced a extra possible source of misalignment/movement..

Now, if this was a $5000+ Olympic  rifle, and you are shooting for record, or you are building this for the world record attempt to beat the current score, then yes I can see where 0.001 might make a difference.

[Scrambler82]

Thanks for the comments.
Reviewing the height of the piece, problem is I can find the measurements I want for the parts, will have  to wait until I get back to MA.   From what I can get it appears to be close to the one pice mount is height.
Yes off the center line of height but not the side to side center line of the barrel.

I have come away from this idea with a new outlook on the Air Rifle, nothing is perfect and I need to accept that... 

[Ol'DeadEye]

I didn't see any mention of BKL mounts.
They are touted as being self-centering on both size dovetails.
If price is the only reason to not consider them, is there any good reason to worry about such small misalignments and not do anything about it.
Airguns are short range, relatively cheap amusements. Are they not?
At least they are to me.  And I use BKL mounts on my 3 PCPs.
And no one is shooting back at you if you do miss slightly.
My only breakbarrel is my Trail-NP, which has Weaver mounts and isn't a problem.

[Scrambler82]

You are correct, I am looking at AGs from a new view now.

No worries !

Thank for the input.

I didn't see any mention of BKL mounts.
They are touted as being self-centering on both size dovetails.
If price is the only reason to not consider them, is there any good reason to worry about such small misalignments and not do anything about it.
Airguns are short range, relatively cheap amusements. Are they not?
At least they are to me.  And I use BKL mounts on my 3 PCPs.
And no one is shooting back at you if you do miss slightly.
My only breakbarrel is my Trail-NP, which has Weaver mounts and isn't a problem.