Help re Dovetail to Weaver rail + BSA Dovetail etc re FT

Discussion in 'Hunter (HFT) & Field Target (FT)' started by skires, Oct 13, 2015.

  1. skires

    skires Well-Known Member

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    Edited for the sake of sanity ...

    Anywhere in the UK that you can get long ( 6 inches or more ) 11mm to 11mm rails?

    Will a standard 11mm dovetail fitting be ok on a BSA 13mm dovetail?

    If an Ft shooter is just zeroing at a set distance and then leaving the elevation turret ( say 35y ) and using holdover/under, do they need to worry about shimming or MOA adjustment?
     
    Last edited: Oct 13, 2015
  2. Conor

    Conor Never been banned from sales Staff Member

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    I actually can't believe I read the whole way through that!
    My head hurts.
    Go with the cheap option, shim and suffer a headache like I had reading through this.

    Get a rail made and you'll always have it without the worry of POI shift associated by cheap materials and a scope not optically centred!
     
  3. Tench

    Tench WHFTA World Champion 2016.

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    Hi Colin, I am not an FT shooter but I imagine the moa slant built into an FT riser rail is more to do with the close targets than the long ones, a very high scope will give massive hold over aimpoints on close targets, I see having some slope a bigger benefit here?

    I have a 16mm tall 11mm to 11mm dovetail riser rail that is not being used if you need one.
     
  4. skires

    skires Well-Known Member

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    Conor

    Sorry for the long post and the headache.

    Your migraine had probably kicked in at this point ... but I'd mentioned the reason I don't want to spend 75 quid or so on a proper rail at this point, is this is just a temporary option whilst I sort the springer out. I'm sure any rail that I had made for the BSA then won't fit the springers so I'd have to have another rail made for the springer ( BSA is 13mm Dove Vs 11mm Dove ).

    I'm not sure I need shims or slanted rails if I'm zeroing at 35y and holding over/under?

    Thanks for the reply.

    Get well soon.
     
    Last edited: Oct 13, 2015
  5. skires

    skires Well-Known Member

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    Simon

    Yeah the worst of the holdover is at very close range. My 55 yard aim point tied in with about my 12 yard aim point on the 77s if I remember correctly. At 8 yards I was aiming about 5 feet over the poi. You really don't have to worry about it ... you don't get much close stuff ... it's usually telescope territory. I flick stones at the ones closer than 12 yards.

    I've read the BFTA instructions on setting up a scope and Optically Centering etc. They suggest you set up at 10 yards as it is about the same as 55 yards.

    As I've said above a couple of times I'm not sure I need worry about the shims or sloping rail if I'm just zeroing at 35 yards and using the dots to aim. I'm not sure ... so that's why I'm asking.

    I can't find 11mm to 11mm rails? Where did you get that? How long is the one you have please ... and thankyou for the very kind offer.
     
    Last edited: Oct 13, 2015
  6. Tench

    Tench WHFTA World Champion 2016.

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  7. RobF

    RobF Administrator Staff Member

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    Shimming or sloping the rail is about either getting the scope in it's adjustment range, or even better optical centred and in it's adjustment range.

    Slope doesn't change your trajectory, it just offsets it. So more or less makes no difference.

    Scope height does make a difference, higher will push the top of your trajectory out, and give you less clicks (although it's usually in the region of 1) at 55, but many more at 10. In fact you are more likely to run out of clicks at 10yds than at 55.
     
  8. tillygti6

    tillygti6 Tilly's gun stocks

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    Tench if the chap above doesn't have the rail **** my name on it please mate.
    ;)
     
  9. tillygti6

    tillygti6 Tilly's gun stocks

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    Obviously you can't say b,u,n,g on here hahaha.
     
  10. Tench

    Tench WHFTA World Champion 2016.

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    No worries Tommy, If Colin doesn't have it I will bung your name on it!
     
  11. skires

    skires Well-Known Member

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    Cheers Rob

    I got stuck in a bit of a woods n trees corner yesterday. My brain's working a bit better today.

    Simon

    The only reason I didn't rip your arm off yesterday was I was trying to get an answer on the 11mm rail on a BSA 13mm rail question. I was hoping someone on here may have been able to comment.

    I know the S10 rail is 13mm and not normal air rifle 11mm. I know they sell special 13mm mounts for the BSA rails so the rings line up with the barrel properly.

    All I can think of if I put 11mm on a 13mm rail is the rings won't be perfectly in line with the barrel by a fraction, and that may lead to some cross over issues at extreme ranges either side of my zero. I've never been a massive believer in cross over being a major issue on air rifles. Just get the cant sorted and don't worry about it but I'm not sure whether it may leave my poi's either side of vertical at certain ranges ( 8 - 55y ).

    Anyway ... If Tommy wants it and will have a definite use for it then I'd sooner him be using it rather than it end up another item sitting in my box of bits. So let him have it please but thank you for trying to help me out.

    Col
     
    Last edited: Oct 14, 2015
  12. hmangphilly

    hmangphilly Not quite a full phil

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    would that crossover be avoided if you aimed (zero'd ) (adjusted windage ) 1mm off at all ranges ?
    or am i having a moment ?
     
  13. Tench

    Tench WHFTA World Champion 2016.

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    I know where you are coming from Colin, being a BSA man myself I have seen all sorts of scope off sets with various rings on BSA breaches. The mounts BSA used to supply with the Ultra were some of the worst! I have a pair of Sports match 25mm medium mounts that align near to perfect though and I have used some Richter optic mounts before that were spot on! these day I tend to use BKL as they are always central.

    I have some BKL risers sitting doing nothing too but these wont solve your problem of getting your forward mount in front of the breach rail, they do however manufacture 4" long riser rails which would do the job. you would also need another riser block for the rear mount though.
     
  14. skires

    skires Well-Known Member

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    Er ... I think you are having a slight moment?

    As I understand it if the scope isn't in perfect line with the breech/barrel then you will be bang on zero at your chosen zero range. You have zeroed that range for elevation and windage. However, at distances a good way away from your zero you will firstly ( close range ) impact on one side of the vertical, and then at the other extreme range from your zero ( furthest range ) you will impact on the other side of the vertical.

    Hence the term "Crossover". You poi's will actually cross over your vertical and will only be bang on horizontal zero at the range that you zeroed the windage on the scope.

    I've read a bit on this re airguns and a formula I once saw ( I think ) was actually showing that the scope can be quite a bit out of line with the barrel and the crossover error was still very very minimal at airgun ranges. There was a far far greater chance of any off horizontal error at various ranges being due to light cant of the rifle or the cross hair being slightly off perfect vertical ( or, of course, PA error due to eye misalignment with a set distance focus ).

    So I'm not sure it's a problem to begin with.

    So, theoretically, although the scope is only 1mm off centre to the bore ( horizontally ) it will hold zero at your zero range ( say 35 yards ... because you've set it at that ) but at 55 yards it may be several mm's off. Similarly ... but on the other side ... it may be several mm's off at very close range. So if you try and adjust the windage turret to compensate for the very close ones ... you will now be off at your 35 yard zero ... and even further off at your max distance.

    Is that what you meant? Sorry if that's a Granny and her eggs post.
     
    Last edited: Oct 14, 2015
  15. skires

    skires Well-Known Member

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    Simon

    Yeah ... I know you are a BSA man so I wondered if you'd had any probs with the oversize rail on the newer BSA rifles ( apparently the really old rifles had smaller rails [dovetails] ).

    I edited the first post as it was a bit of a life story. In the original first post I'd said that I could get an 11mm to Weaver ( 20mm ) low riser rail that extended at the front and would suit my purpose. It would then mean me getting Weaver style high 30mm mounts for the Custom Shop scope. I was stuck with the same problem there because those risers were 11m and not 13mm.

    Most mounts will state 3/8 through 11mm to 13mm. They will all phsyically go on.

    I've shot this S10 on occasion ( early days ) in HFT. Those were the early days where you just had 25mm and 40mm kills. I'd still miss the odd stander or mis judge range or wind. So I wasn't clearing courses but I had a number of 58's with it. I just found it a little tedious shooting a PCP prone on the floor at 25mm ( it was max 35 yards then ) and 40mm at 45 yards. That's why I then turned to the dark side and shot springers. Courses, as you know, are much tougher now.

    I mention that because in those days I just used normal 11mm airgun mounts and zeroed at 35 yards. I never had a problem with crossover. Or, if I did, I never noticed it as it didn't make enough difference to be missing 40mm at 45 yards etc. I also used 10.6gr pellets that really did need some wind to shift them up to those distances.

    Let the other lad have the 11mm to 11mm riser please. I'm only messing with the S10 for a short while whilst I sort the springers, so it's nowt too serious. It will only be at a few local club day courses. I'll put an 18x 1 inch scope on using 11mm mounts and have a play on the range ( I could go to Atherton indoors ) and see if the 11mm on 13mm rail gives any crossover over various ranges. I could then get a set of 13mm BSA specific mounts and see if that cures it.

    Cheers mate.
     
    Last edited: Oct 14, 2015
  16. RobF

    RobF Administrator Staff Member

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    I had a chat with the man from Kahles in Lithuania, because I'm fairly convinced (until i get off my backside and go down the tunnel and actually prove it) that there's some crossover issue on my TX. Zero'd indoors at 25 it's going against a very feint breeze to about 5mm at 10yds, and taking around 10-15mm more than i'd say feels right at 55 with the wind). Close left, long right.
    Anyway, suffiice to say it was only a quick conversation and I asked if this is possible. A couple of us had had a chat about if when you dial a scope, does it alter the LOS parrallel to the bore, or does it angle it... eitherway unless you've got it aligned you will see an error. If it offsets parrallel, then it can't ever match the angle the scope and bore deviate by... if the LOS changes angle then it can match the angle, but if there's any offset as well, that can't be dialled out.
    The chap from kahles agreed it was quite possible what I was seeing was due to misalignment, but although his english is superb, it was a quick chat and I didn't quite get to the bottom of what the solution was.
    There was an interesting post on the BBS about cant as well, which I also need to check... because the TX lacks any really good alignment surface to plumb against... so that could also be it. Or it could be in my head.. or me. I never felt confident with her over there and found myself aiming for something I couldn't see... but then that could actually have been the conditions.
     
  17. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    I'd take up golf lads :)
     
  18. skires

    skires Well-Known Member

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    Edited ... that just seemed too easy.

    Hi Martin

    How's life in B grade going?
     
    Last edited: Oct 14, 2015
  19. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    Not the best of starts but that's FT innit, just when you think you have it sussed you get reminded how much work there is to do.

    Feels good to work my way out of C tho and even if I dip this W/L I'm not going back down to C ever. Going to be a lot of work to get out of B but I'm up for it.
     
  20. Tench

    Tench WHFTA World Champion 2016.

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    The maths behind crossover says it is not an issue, with a 1mm off set scope and a 35y zero you should only be about half a mm off at 15 and 55y, I would challenge anyone who says they could show that on a target!
    I think the problem of an off set scope is more to do with the shooters eye view. Your scope will have a small exit pupil requiring an eye alignment tolerance of less than +/- .5mm, so when you are behind the scope positioning your eye for a shot the action and scope can be plainly seen as not being in line which messes with your head and eye scope alignment, well it does with me anyway. The crossover is not an issue but the perceived misalignment is.
     
    Last edited: Oct 14, 2015

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