GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Ribbonstone on November 18, 2012, 06:18:44 PM
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Guess I have too many toys.
Get all involved with the new toys and tend to neglect the old ones. Taking the old ones for granted and not getting them out for a little range time as much as they deserve.
If they were people, would be like the Maytag Repairman in the old TV ads.
(Cheap) .22 BAM 51
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/IMG_0072-1.jpg)
Odd shot string. Got it running at low pressure, but only for a short pressure range (about 45BAR), Not real sure why, but over that range, it shoots very well for 20 shots.
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/IMG_0068-1.jpg)
40ayrds
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/IMG_0066-1-1.jpg)
While the shot string is kind of short and the pressure range is kind of small, do believe the efficiency is pretty good.
Something like 1.33 FPE/cu in (or about 12.3 bar cc/fpe).
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Take no credit for that stock...nice...but bought the gun used. Original owner did a very nice job of reworking the issue stock.
Only keep 3 higher powered PCPs (quite a few under 30 foot pounds, but just 3 over) but shoot them less often that I should. Just don't often have the distance.
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Very nice. Care to enlighten us with how you was able to get that good shot string .
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Nothing too drastic.
Just adjusted the stroke, adjusted the spring tension, and used a lightened striker.
Actually, the striker it self is stock (although polished). Striker has a guide that rides along inside the striker, so is part of the striker’s weight, and that part is easier to replace with a lighter unit than changing the striker itself. That lighter striker probably accounts for the more narrow pressure range (only 45BAR of working pressure as it is currently set).
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/DSCF0262-1.jpg)
Yes, I even made some light weight ones out of screwdriver handles.
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/DSCF0261-1.jpg)
(http://i157.photobucket.com/albums/t50/ribbonstone/BAM51/DSCF0347-1.jpg)
Made several of them, and settled on the last picture (the “spool” shape) for that internal guide. By changing the thickness of the “head”, the spring pre-tension changes, so it’s a two way balancing act of weight and pre-tension.
If I had it to do over again, may just leave the striker full weight to allow for a higher fill pressure, then go for a velocity reduction (and air use reduction) by way of strangled off transfer ports.
Early on, found a burr at the transfer port that was an accuracy problem. Easy to test for. Chamber a pellet and then push it back out from the muzzle with a rod. If there is a burr, the pellet will show it as a cut or slice. Polished that burr the simple way rod with a bit of fine abrasive paper run by hand (want the burr gone, but not an enlarged breech).
Only other “trick” was to reshape the trigger a bit to a more pleasing profile (it comes a bit too curved to feel quite right). Taking the trigger unit apart, cleaning up any stray burrs, lubing, and adjusting didn’t hurt.
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Thanks for the information. Mr. Ribbonstone I assume that's with the stock transfor port. I've been tinkering with the b50 for over a year and finally I'm going in the right direction with 20 shots from 783 to 806 with 14.3 CP's. I had to add more spring tension by placing two small washer inside the end cap and replacing the transfor port with a smaller one that Mr. Scotchmo sent me.
I also find out the bur inside the barrel, I still need to smooth it out some more. What grit sand paper did you use? Will 400 grit work?
I liked the trigger right out the box, so I have not messed with it but it could be better. After reading " the book " and several hundred post about the 50 I believe that the sear engagement would benefit from it. Could you tell any difference from your trigger tune with sear?
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Removed the barrel/breech and took out the bolt.
Worked from the rear end.
Used a thin wooden dowel (probably a whittled on chop-stick) with a small pad of abrasive paper (think it was 600grit) rubber cemented to the dowel.
Didn't spin it, just ran it by hand ontop of the burr until it was gone (rubber cement makes changing abrasive easy).
Then a quick spin (also by hand) with the same dowel and 0000 steel wool.
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Thanks for the infor again. Will try it out tomorrow.