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Thread: Accuracy

  1. #1
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    Accuracy

    Gentlemen,....I would like to know some of the factors that determine accuracy of an airgun, not the shooter.....I'm working with 2 Crosman 38t's in .22 cal (1st variant, all metal).....I securely clamped each one,in turn, and shot into a heavy blank cardboard at 30' (I'm not metric!).......Each gave me a pattern the size of a quarter(Cdn).....The object was to adjust the sights to the pattern......I only had Crosman Premier hollow point hunting pellets, which were a loose fit in the cylinder.....Fresh CO2 carts, warm day........Shouldn't the pattern be smaller at 30' with the guns held solid?.....Does the type of pellet make a difference?....Both guns are in excellent condition...........As an added note, I drew bullseyes around the patterns and said it was 50' just so my boys would be intimidated (we're fairly competitive and I always need an 'edge',eh?)....Thumper

  2. #2
    Member Gippeto's Avatar
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    Would try some other pellets...JSB Exact Jumbos (15.9grain) work very well in everything I've tried them in.

    That said, you have to keep in mind that the pellet is jumping from the rotary magazine into the barrel (not sure if the 38T has a forcing cone, but think it would)...any minor variation chamber to chamber will have an effect on this entry...any inconsistent "disturbance" of the pellet head will result in an increase in group size. Greatest accuracy will likely be derived by utilizing only one chamber for all shots.

    Just my .02

    Al

  3. #3
    Senior Member SeanMP's Avatar
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    A quarter sized group at 10yds is actually excellent from that pistol. As Al says you may get slightly better results from a true wadcutter or a round headed pellet.

    There is no forcing cone on that gun but you can adjust the gap between the barrel and the cylinder if it's excessive by loosening the small set screw on the top of the barrel and pushing the inner barrel tube back with your thumb. Essentially the 38 is a smoothbore and that is going to limit the accuracy at distances past 10yds.
    Sean

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    I'm quite familiar with the 38 and all the gaps are as tight as they can be without any binding.....the barrels are rifled, although not as deeply as on a real firearm (.22)....but I suppose if the pellets fit "sloppy" then the rifling would be ineffective...........I do go through CO2 fairly quickly and I'd like to know which pellets have the widest 'skirt'?.......More important than weight at this point..............Thumper

  5. #5
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    OK....I just made a few measurements...........The Crosman 'pointed' have a skirt of .2205, the Daisy precision max 'flat' have a skirt of.223 , The bore of the barrels is .217 and ..212 the only measurement I could come up with for the "cylinders" was .219 from a spare plastic one, the metal ones in the guns were inaccessible.................Now, if I had a computer, I could maybe formulate how it all works, maybe.......I'm suffering from a complete lack of expertise here....anyone have any thoughts? Can a 38t be re-barrelled with something more deeply rifled, and is it worth it?.............Maybe I should look for a Mark 1 or a 1322? Thumper

  6. #6
    Senior Member SeanMP's Avatar
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    That comment about the forcing cone and adjusting the barrel as if it were a forcing cone was directed mainly at Al's question.

    I have a 38 barrel and a regular crosman barrel here is front of me.

    With pin guages the lands measure virtually identical at .217 however the 38 is scantly rifled (I can't even measure it at .0001") and the regular crosman is closer to .002

    The OD of the 38 is 0.370"
    The OD of the 7/16 is .436"

    It would be a simple matter to turn a piece of 7/16 barrel stock to the 38 size and put a long leade on the rifling.

    Is it worth it? That can only be answered by you. I'm not a huge a huge fan of someone sharing their subjective opinion.

    It would be fun to try.

    PM me if you need further info
    Sean

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