GTA
All Springer/NP/PCP Air Gun Discussion General => BB Guns and Such => Topic started by: bantam5s on March 27, 2025, 02:11:00 AM
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I quite like them but accuracy could be better.
Originally I had hoped to find a cheap donor pistol or spare shot tube, but I got tired of waiting/looking and I've got guns 2 so I bit the bullet on sacrificing one of my shot tubes.
I thought about it and couldn't come up with a way to retain the repeating gravity feed, so I took the simplest route and opted for a muzzle loading single shot like the 499.
This whole thing was actually pretty simple.
1-measure the overall length of your shot tube and the position of the BB detent wire
2- drill both ends of the barrel out of the muzzle and base pieces with a 17/64 drill bit.
3- cut the BB feedway off of the base leaving just the threaded end.
4- cut and crown a properly sized length of 499b barrel
5- turn down both ends of your barrel to fit into the muzzle and threaded base.
6- file in a notch for your BB retention magnet.
The sidewall is 1.5mm thick, no amount of neodymium magnets I could fit had the strength retain a BB , so I filed in about 1.mm and got good retention with a pair of 1/4 magnets
7 - press & glue everything together.
(https://i.postimg.cc/RF2GMWBf/20250326-165901-2.jpg) (https://postimg.cc/JDcjx4t4)
(https://i.postimg.cc/hvxshKDY/20250326-165913.jpg) (https://postimg.cc/2LkhKRBd)
(https://i.postimg.cc/pV91gHHz/20250326-165924.jpg) (https://postimg.cc/14QHqb43)
I temporarily super glued everything together so I could test it before proceeding, and here were my initial accuracy results.
( it does not like the match grade BB's used in the 499 )
A couple 6 shot groups before with the original barrel from about 7 feet away, standard daisy bb's.
(https://i.postimg.cc/tCKD0Z5H/20250326-174841-2.jpg) (https://postimg.cc/Wh70g4C9)
(https://i.postimg.cc/d1VjR8qG/20250326-174836-2.jpg) (https://postimg.cc/jWBftnnj)
And a 6 shot group from the same distance with the 499 barrel, same bb's
(https://i.postimg.cc/ZqcLyfhT/20250326-174825-2.jpg) (https://postimg.cc/v14nJtBj)
The trigger on these could be worse, but it's a bit heavy and quite thin, so it's hard to really tell just what this is gaining me.
The overall group size isn't that much less, but there was enough of a noticeable improvement for me to proceed.
For the final glue up I used JB weld, and to hopefully keep everything straight and square I have rod ( actually a Crosman 38T clearing rod ) pressed into a squarely drilled hole in a hardwood block.
(https://i.postimg.cc/W4WXH9Y5/20250326-200303.jpg) (https://postimg.cc/KKTPK52T)
Now the most surprising thing about all of this is that I gained at least 50% more velocity.
After noticing a difference I took it out back for some testing.
It is very noticeably more powerful, it has more pop and Carrie's much further.
I shot a can full of water with both of my guns and it was night and day.
This was originally the weaker of my 2 guns, and it will now cleanly penetrate one side of a pop can full of water while the stock pistol needs 2 shots in the same spot to just barely compromise the can.