Bionic BAM XS B3 .177

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Yes stock spring.
Peeked inside this one years ago within weeks of rebuilding my HW55T. Seem to recall the BAM's spring and piston being nearly identical to the HW, all the way down to the leather seal. Never chrono'd the BAM but get the distinct impression it is sprung well... seemed "quick" the few times I shot it. HATED the trigger. Ordered 2 Rekord triggers from Blackpool Air Rifles (BAR) and finally getting around to the retrofit. The barrel bore is stunning, and even with the horrendous trigger it showed remarkable potential. Hoping to get lucky and wind up with a sleeper :)
They sold for $50 when they were still available, and my late uncle only kept what he thought shot well... mine now and going for broke !!
 
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Last night's progress;
  • Machined the side slot for the cocking arm and the its retention screw.
  • Cocking arm is having billet pivot fashioned and tig welded on since its stamped steel end lost real-estate to the trigger housing and would be too weak if simply ground to fit.
  • Rear trunion was removed and having center machined away to make room for Rekord
  • Trunion's old rivet holes are being converted to house action retention screws, which will double as trunion/folding stock mounts since the top assembly screw is not an option with the Rekord in its way
 
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Not sure I grasp all the design changes from your description, but the installation of a Rekord trigger is fascinating and it looks like you have the necessary machinery at your disposal. Do you have a rough draft of the end product you could post?
I was given a Chinese QB97 side-lever awhile back that sort of ended up in the closet, maybe it is worth taking a second look at.
 
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"Wadcutter"Not sure I grasp all the design changes from your description, but the installation of a Rekord trigger is fascinating and it looks like you have the necessary machinery at your disposal. Do you have a rough draft of the end product you could post?
I was given a Chinese QB97 side-lever awhile back that sort of ended up in the closet, maybe it is worth taking a second look at.
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Careful !!!.... those QB 79's can beg for bionics too !! (consider yourself warned)

Will take some pictures of the BAM progress. It's far enough along that the concept might be visible from where the machining has progressed to.

As for the QB 79. I bought one several years ago and tinkered with it. I'll post a few pictures and a brief description right now....

Link provided below...

QB 79 thread title will be; "QB 79 Makeover"
 
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Made some progress.
A little backstory after some research. It appears this may be a predecessor to the BAM version. It bears the "mountain-peak" logo stamp and no scope rail, with different manufacturing processes throughout, but otherwise nearly identical platform to the typical BAM XS3-1 which followed.

Moving ahead;
  • The trigger is now 100% functional
  • Retained the anti-beartrap , with its trigger interrupt feature.
  • Retained the working lever safety with its 2 "SAFE" positions and one "FIRE" position.
  • Made the trigger return "fixed, and eliminated the sear adjustment screw favoring adjustable fulcrums for the 1st and 2nd stages
  • Moved the 1st and 2nd stage fulcrums further away from the trigger pivot to offset the longer trigger, to avoid lengthening the trigger throw... with no loss in mechanical advantage since the longer trigger compliments the relocated fulcrums.
  • Shortened the piston rod to match trigger release, which required longer spring guide.
As usual, it was more complicated than first thought it would be... grrrrrr

Pictures to follow
 
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"JohnL57".....At the rate you're going it's not inconceivable that you might make an entire action. I'm going to take a wild guess here and speculate that you're enjoying this project.
John

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John,

I appreciate the compliment, now be a friend and remind me how dumb it is to put a 454 ci motor into a Vega... something I never did mainly because I never owned either.

Just removed the barrel, to install a Lothar Walther in its place. If that doesn't help it group better... well, like you said... might start digging into the action. Piston sleeve is a little rough... the only cure for this sickness is starting off with a better side cocker to begin with... but Joe Wayne Rhea ain't selling his 300S and still waiting on breech seals for my Diana 75 so I keep trying to pull a rabbit out of a Chinese hat...

 
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It did cross my mind to mention you've put hundreds of dollars of shop time into a $100 gun, but I don't have the shop or skill to do what you're doing, so I held off out of respect till now. I once put a 390 into a '56 Ford panel truck-the project failed to turn me into a motor head. I make my living as a studio potter so I have to be careful not to go down the rabbit hole with this obsession. Back in 2010 all I wanted was to clear out the ground squirrels. I have bought 9 rifles since then, sold 5 and kept 4. Have become addicted to cruising the airgun classifieds and the 'pop' of a headshot. For some reason there are almost no ground squirrels around any more, perhaps due to drought?
Keep up the project, can't wait to see what happens next!
John
 
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Still shot very poorly after the LW barrel install, which seems to indicate abandoning the stock barrel was a mistake.
Got a surprise when I tried to blue the new barrel... it is stainless. Did not order stainless. Usually get them direct from LW, but this one came from MAC1 Airguns back in July. The two-tone look may grow on me.

Summary of latest revisions;
  • Installed stainless LW barrel... NEW length 11" (4" shorter than stock 15" barrel)
  • Took the piston sleeve to a local shop that let me hone out the internal rough spots on their Sunnen hone.
  • Converted the leather piston to synthetic Maccari seal (originally designed for HW 30 etc.) with homemade adapter.
  • Reduced the HUUUUUGE .161" transfer port down to .110" (possibly why it shot so bad in the first place)
  • Installed Lyman 17A front sight
  • Installed Lyman 53D rear sight on the new rear block (permanently removed "AK" style rear sight from main tube)
  • Installed adjustable parallel gib in rear sight elevation slot to eliminate slop
  • Installed Vortek 35 coil / .113" wire /.730" O.D. mainspring
  • Made HDPE top-hat for spring with brass anti-friction washer at both ends of spring
  • Sunnen Honed piston sleeve up from .991" to .995 I.D. which married perfectly with the standard (not oversize) Maccari seal
The gun shoots very very well at last !!!
With shorter barrel OAL is a scant 22-1/2" when stock is folded.
Seems to prefer heavier pellets, and guessing it is a lot faster after the cylinder hone, new seal, spring, and transfer port revision.

Will post pictures and updated chrono results soon.
 
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Finished it.

Drawing of custom transplant trigger for Rekord


Sunnen honed piston sleeve


Trunion remodeled for new trigger



Assembly orientation
https://imgur.com/qKtqOqi



Discarded/upgraded parts (old barrel not shown)


Lyman 40SS rear sight with rapid elevation lever.




Pre BAM version that had actual AK folding stock parts and bakelite panels


Front sight


Collapsed length 22-1/2"




 
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