Crosman 1300KT has lost accuracy

Forums Springers, Pumpers, C02, & Vintage Crosman 1300KT has lost accuracy

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    fishinwrench
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    I did a complete reseal job even though I don't think it needed it because I could only get 460ish FPS out of it and I thought it should be 500 or better.   After all was done it shot great (accuracy-wise) but velocity was still under 500 (475ish) with 12 pumps.  

    Then suddenly groups went to hell.   I cleaned the barrel…..no help.  Took 20 shots over a chrony and all were within 8 fps of each other.   Switched pellets…..no help.   Switched scopes…..same deal.   

    What the heck could be wrong NOW?  

    Oh yeah, checked all the screws…still tight.  

    WTF?

    When I look down the barrel the rifling is barely noticeable.  Has the barrel "shot out"?   Is that even a possibility?

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    attaglance
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    Having the same situation today with my Diana 34.  It's 7 or 8 years old, installed a 12 fpe spring last Fall.  Been accurate – one inch groups to 30 yds till today.  Tightened all the screws as you did,, and yea all tight.  Scope and mount the same.  Still patterning all over  a 3" circle.  

    It's been hot here already, 105 today, 112 over the weekend.  There's a race track 5 miles from here and their internet weather readout gave density altitude of over 8100 ft.  I'm at 4300 feet.  So I'm thinkin' there isn't as much air there to be had.  Springers and pumpers, are down on performance.  I didn't set up the chrono for numbers, but will be testing some lighter pellets for accuracy tomorrow. Hope this helps.  

    The track's weather is presented by Kestrel.  I'll take their word on that…

    Buck n Willcox.

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    Vetmx
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    I highly doubt you shot the rifling out of it. I would look at the barrel band pump plug thing. If yours is plastic, maybe from all the pumping it has developed some play. Every time you pump it up, your barrel is either moving around or the pressure that is exerted on it is different.

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    fishinwrench
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    I'm with ya.  So, an engineering/design flaw?

    Gonna be difficult to rectify that, or keep it from happening.  

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    Vetmx
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    Just replace it or at least see if your barrel is snug. I am at work now so I cant look at my 1300kt to give you more guidance.

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    Mike_Lenardon
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    Steel or plastic breach? If plastic the barrel could be moving around. 

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    fishinwrench
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    Mike_Lenardon

    Steel or plastic breach? If plastic the barrel could be moving around. 

    Steel breech and all is snug and aligned properly.  

    About every 5th or 6th pellet curves off crazy.  It has always shot CPHP's and Polymags really well, but now it doesn't seem to shoot ANY pellet well.   Groups are so flakey at 25 yards that I can't even get sighted in.    

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    Vetmx
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    Inspect your crown and the rifling just inside the muzzle. Fliers are usually a last inch of the barrel issue. Crosman has been known to chew up the rifling just in from the muzzle. When your gun was really dirty, it may have masked the issue.

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    fishinwrench
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    Vetmx

    Inspect your crown and the rifling just inside the muzzle. Fliers are usually a last inch of the barrel issue. Crosman has been known to chew up the rifling just in from the muzzle. When your gun was really dirty, it may have masked the issue.

    Was wondering about that.  Is there a possibility that I damaged the crown with weedeater cord while cleaning it?    I was hot, frustrated, and whipping those patches through there with "attitude".  

    😄

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    Vetmx
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    Vetmx
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    No, you were cleaning it properly. Maybe just got it too clean.

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    fishinwrench
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    Vetmx

    No, you were cleaning it properly. Maybe just got it too clean.

    So maybe keep shooting it and see if groups tighten up after awhile?    Or just replace the stupid barrel?     For the cost of a tin of pellets I can probably just get a fresh barrel, hu?

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    Vetmx
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    If you have slop in this area were the pivot pin goes through, or the barrel isn’t pinched tight, that could be an issue.

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    fishinwrench
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    Vetmx

    If you have slop in this area were the pivot pin goes through, or the barrel isn’t pinched tight, that could be an issue.

    No noticable slop.  I have a Alchemy pin in there.

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    Vetmx
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    Inspect the rifling inside the muzzle and look for chatter marks before you do anything.

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    Vetmx
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    Did you switch to a hollow pellet probe looking for more velocity? They are accuracy wreckers in .177

    • This reply was modified 5 months ago by Vetmx.
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    fishinwrench
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    Vetmx

    Inspect the rifling inside the muzzle and look for chatter marks before you do anything.

    I kinda did.  Nothing glaringly obvious, but I'm kinda bugged that the rifling is so shallow and hardly even noticable throughout the length of the 14" barrel. 

    It almost looks like a smooth bore with tiny TINY scratches for rifling.     

    It always shot good though…..until now.

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    Vetmx
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    Take the barrel off and push a pellet through it. Nice and slow and then inspect it. See if it has nice little rifling marks on the skirt. Or maybe it will show signs on the skirt that it is snagging on the transfer port.

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    Skillet
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    I’ve found Crosman barrels to be a crap-shoot. Had a 1322 with ‘ghost rifling’, never grouped tight ‘till I replaced the barrel.

    Wouldn’t break the bank to try

    As Vet suggested, slugging the bore can often reveal problems. Sometimes you’ll feel rough spots or a burr at the crown.

    • This reply was modified 5 months ago by Skillet.
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    fishinwrench
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    Vetmx

    Did you switch to a hollow pellet probe looking for more velocity? They are accuracy wreckers in .177

    No I am using the probe that came with the steel breech.

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