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Thread: When did BSA change to 5.5mm barrels

  1. #1
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    When did BSA change to 5.5mm barrels

    A short while ago somebody asked this and nobody knows.
    I checked my small Meteor collection plus my Mercury S and got this very limited result. Just by loading superdomes into the breech.
    All Meteor Mk 1-4 allow the pellet to drop in 3-4 mm without resistance, ditto the Merc.S.
    My Mk6 needs the pellet to be pushed firmly into the breech just as my Hw99 does suggesting it is meant that way and I suspect it to be a genuine 5.5.
    Sadly my Mk5 is .177 so can any one else do the same test then assuming we can date the various Mks, we might be able to infer a rough date.
    The Mk6 barrel also differs in that it has only one hole for the front sight, matching the modern front sights.
    The more I think I know, the more I realise the less I know.

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    It is a very good question and one that I think I asked before too. I don't recall that there was a definitive answer. Perhaps someone will know and respond.

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    Andrew.

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    I have Meteors, Airsporters etc in my collection….up to Mk4 Meteors (in my lot) Superdomes “drop” in a few mm into the barrel…in my Mk5 they don’t but “seat” normally. So as far as my guns are concerned, 5.5mm barrels start from Mk5 onwards !

  4. #4
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    look no hands is offline Even better looking than a HW35
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    I shall check on Sunday (if I remember) as I have several .22 beezas now, I have mk1 and 2 Mercury S and an early Supersport and Lightning, I shall try a Superdome in each and see what happens.
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    We generally say around 1986 was the change, when they went to European sizes (something to do with EU)

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    Quote Originally Posted by gunshop View Post
    We generally say around 1986 was the change, when they went to European sizes (something to do with EU)
    1986 was when GAMO bought BSA....
    Too many airguns!

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    Quote Originally Posted by evert View Post
    1986 was when GAMO bought BSA....
    Well then with this mix of slight evidence and Everts/Gunshop's knowledge we can assume 1986.
    When did the Mk6 Meteor come out any body?
    Last edited by Dornfelderliebe; 30-05-2023 at 11:12 AM.
    The more I think I know, the more I realise the less I know.

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    Thumbs up

    This RB2k (WR01916) is 5.5mm, It also doesn't have the screw in trigger block but rather a crossbolt (Or two screws, Never had it apart!), Don't know the exact age either but Knibbs puts them between 1992 and 2001..






    John
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  9. #9
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    Quote Originally Posted by gunshop View Post
    We generally say around 1986 was the change, when they went to European sizes (something to do with EU)
    Quote Originally Posted by evert View Post
    1986 was when GAMO bought BSA....
    Quote Originally Posted by Dornfelderliebe View Post
    Well then with this mix of slight evidence and Everts/Gunshop's knowledge we can assume 1986.
    When did the Mk6 Meteor come out any body?
    Yep, that would seem to make sense, wouldn't it? My early Supersport most certainly has the tighter barrel (the Hobby needs a very firm thumbing in). I think the Supersport was launched 1986/7?
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    All as previously detailed here but again this will probably be ignored or just plain not believed.
    In the early to mid 1990's Bowkett was working on was was to become the first BSA pcp, the SuperTen. This came about as a result of his work with El Gamo on a pcp suitable for the UK market as CO2 was subject to FAC in the UK killing sales.
    JB worked closely with the rifling man who was also factory floor manager and had been responsible for the production of barrels since the year dot when he emerged from the Military Police. He ruled with a rod of iron and most of the rifling procedures were only known to a few. It was regarded as a black art. Brian was the daddy behind all of the pre-Gamo buyout (1986) rifling machines which were of the cut rifling type cutting one groove at a time. Imagine that with the sheer volumes of Meteors that went out of the gates. One of the hammer forged rifling machines that were just starting to be used on some centrefire rifles pre-Gamo was included in the buyout and then used for spring air rifles.
    With the hammer forged set up using mandrels these had to be changed from time to time due to breakages and wear. JB wanted a different type of rifling for pcps to that used on the springers and worked closely with Mr Barrel Maker to develop it. He had large mandrels made to give a loose bore and once the blank emerged had a small amount trimmed from the end which had a choke formed by the rifling process and the breech end cut to suit the overall length required.
    This was a different direction from previous and initially against Mr Barrel Makers first thoughts. The rifling for the spring air rifle production carried out by the hammer forging method had been changed to use a tight bore, easy by making a small mandrel, chop off the choke and pick the end that looked the most concentric as the breech.
    The reason for the change to a smaller bore on the springers was nothing to do with going metric but simply a way of consistently controlling the power output of their products. Many alternatives had been tried but most were either uneconomical or not suitable for production. Situations occurred when the gods of muzzle energy were shining on the springers and BSA would get a batch that went over 12 ft/lbs. For production changing springs was not on as was altering piston weight even drilling tiny holes through the piston seals was tried. By reducing bore size the "base" power output could be consistently lowered and if the gods shone again there was more of a safety margin.

    All this and more info on the Facebook John Bowkett Fanpage.

  11. #11
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    Sorry for being obtuse but are we to understand that reducing bore size presumably caused more friction thus slowing the pellets and reducing power?
    This is a very interesting post.
    The more I think I know, the more I realise the less I know.

  12. #12
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    Quote Originally Posted by Dornfelderliebe View Post
    Sorry for being obtuse but are we to understand that reducing bore size presumably caused more friction thus slowing the pellets and reducing power?
    This is a very interesting post.
    That was the general idea. Dont forget that at the time BSA Pylarm pellets were identical to Eley Wasp made in Witton Birmingham and supplied to BSA to rebrand. They were a large stiff pellet although power levels were checked with BSA Huntsman which were not available to the public. It was made exclusively for BSA as a pointed pellet and unusually was quite accurate. JB told the fanpage that during development he used several one gallon paint tins full of them. It worked well and gave good power in the springers too even the magazine fed ones despite weighing 16.3 grains.

  13. #13
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    Absolutely fascinating; thank you.
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    Quote Originally Posted by TonyL View Post
    Absolutely fascinating; thank you.
    You are welcome. JB also told me that the sloping back block of the Gamo equivalent couldnt use the same component as the old Airsporters and Mercuries because BSA's subcontractor wouldnt release the tooling for that forging. Thats all I was told.
    Personally the sloping back feature gave one of the best "lines" of almost any air rifle yet produced.

  15. #15
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    Quote Originally Posted by greenwayjames View Post
    You are welcome. JB also told me that the sloping back block of the Gamo equivalent couldnt use the same component as the old Airsporters and Mercuries because BSA's subcontractor wouldnt release the tooling for that forging. Thats all I was told.
    Personally the sloping back feature gave one of the best "lines" of almost any air rifle yet produced.
    Hear hear, a design classic, for me culminating in the Stutzen tap loader.
    The more I think I know, the more I realise the less I know.

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