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PostPosted: Fri Nov 05, 2010 2:34 am 
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Posts: 2523
Location: Vancouver
Many moons ago I posted some nonsense about modifying a Beeman P17 (hence my noob nicname) to be a sort of laser-sighted steampunk piece... which was supposed to still shoot pellets. Turned out I had a serious of seal and mechanical difficulties, so that one's shelved for now, though the intention is to get back to it when patience is available. That'll mean some significant machining challenges... so maybe not.

Anyway, my intentions for my newly acquired, near-mint Gamo Center springer pistol are not nearly so bizarre. Almost everything I want to do with this pistol will be reversible to factory spec, with the exception of making and installing a safety switch of some sort. More on that later. I picked this gun up from a fellow forum member yesterday, and was immediately impressed with the condition; only minimal rust spotting, most of the finish intact, and the plastic grip is in as-new condition. The worst damage is a non-fatal crack running right through the windage adjusting wheel, which I've knitted together using Hot Stuff CA from Lee Valley. Looks fine now. Running some pellets through it today showed astonishing power for what must be at least a 20 year old pistol which obviously hasn't been shot much. I'll be taking it down for tuning of course, but before getting into that want to figure out what else needs to be done for this one to be truly 'mine.' Here's the list:

- new muzzle break, or sight base/underlever lock, or whatever it's called (now complete)
- crown barrel end as it was rather rough/sharp (finished to high polish)
- design, build and install some sort of safety switch
- replace plastic one-piece grip with custom hardwood grip (done this before on a Crosman using Koa with a French polished finish and it still looks sweet after 20 years)
- adjust, add spacers/washers, bushings, whatever is needed to make the underlever less sloppy side-to-side (currently about 1/4" total lateral movement just below bearing seat)

After those I'll inspect the guts and consider whether anything needs fussing, like a new seal maybe, though from the potency of my test shots this seems unlikely to be necessary. I'm seeing penetration through 7 layers of corrugated cardboard in a loose stack at 2metres, with hollow-points and with wadcutters, the pellets bursting but not coming out the 8th layer. Seems impressive enough for a novice-level air pistol!

So here's my new muzzle thingy. It's carved from 6061 T6 aluminum, 3/4" x 1-1/2" bar. I decided not to try and emulate the original nylon piece's side flanges, so it takes a bit more dexterity at this point to guide the sprung bearing on the lever arm into its nesting hollow. That hollow is bored into a stainless machine screw with a domed head, so the bearing spring compresses as it hits the edge, then drops into the hollow nicely. Nesting it into the aluminum would have worked, but worn out in a few thousand shots I should think. The press-fit isn't too hard, as I wanted to secure it with set screws anyway. There are two along the top, one longer and with the last 3mm turned down just below the threads for a smooth finish. That's the fore-sight for now, though it's about 1mm lower than the original 14mm above barrel centre where original was 15mm) as I might add a coloured blob of plastic or something else bright for contrast against targets.

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Now I have a couple of questions, hope there are folks around here with one of these things who've done some modding and might lend an idea or two. The most obvious has to do with safety, mine and that of whatever might be in the vicinity when I'm shooting. See, today while making this muzzle thingy I managed to do something stupid. Since the underlever only pulls away from the barrel about 1.5" at the front end when un-cocked, I wanted the underlever out of the way while driving the friction-fit muzzle cover home with a mallet. So I cocked it. Brilliant. I mean, I knew there was no safety catch, had made a mental note earlier not to do anything STUPID because there was no safety catch, but there I went, banging with a wooden mallet on a block of aluminum at the end of the barrel... my left hand firmly wrapped around the barrel and the stock against my belly. What do you think happened?

The second whack with the mallet released the sear. Whap, right across my index finger, middle bone, which was closest to the fulcrum at about halfway down the barrel. Thought I broke it at first. The swelling was immediate and very painful, but I gingerly flexed the finger to test for a break and found it intact. Ran to kitchen freezer and grabbed a gel pack and wrapped it up, within 10 seconds of impact. Thank goodness for gel packs (or bags of peas, whatever works). Swelling went down after an hour and I was able to finish the mod without further stupidity.

So anyway, I want a safety switch on this gun. I don't want to deface the finish any more than minimally necessary, just a neat little hole with a button sticking out somewhere, or a discrete lever behind the trigger. For reference, here's a couple of pages displaying a part diagram and side views of the pistol:
http://www.aceros-de-hispania.com/airgu ... airgun.htm
http://www.muzzle.de/N3/Druckluft/Gamo_ ... enter.html

I'm tempted to put a switch under the trigger guard, a stop of some sort which could catch the hollow trigger end until released. But it could be that something added higher up around the release mechanism would prove more reliable and more easily accessed. Any thoughts? I have a TAIG lathe and basic metal working fittings for that, including the mill head. And I'm a violinmaker and long ago put in a year as a machinist and welder, so fabrication can be somewhat complex if needed.

I may add to this list, such as doing a better job finishing the aluminum and having it anodized black... but that seems a lot of fuss, when it looks sort of cool in raw aluminum and will of course grey with age and handling. Scopes aren't something I've ever tried, but that nicely machined pair of grooves makes it tempting to put something up top. Maybe a laser? But really I just want this already nice pistol to be that much nicer. Replacinging the plastic tip felt like a satisfying start, and making everything solid and safe to shoot should set me up for years of fun plinking. Any help would be appreciated. Falcon users may have insights as well, as they're virtually the same gun.


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PostPosted: Sat Nov 06, 2010 3:30 am 
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Posts: 2523
Location: Vancouver
Tonight I took some time to fully dismantle the Gamo except for the trigger mechanism. My bench vise with a couple of padded dogs allowed for easing out the mainspring retainer without difficulty - probably manageable in this pistol with just a good bar clamp really, as there's only a couple of inches of pre-compression on it.

Found a bit of rust on the piston head under the leather, but not significant and easily polished off. The leather is in great shape as is the delrin insert which keeps the leather in a cupped shape. The mainspring ends were sharp and rather roughly ground level, so those are now polished. The cutouts in piston and cylinder had razor-sharp edges, so those are all rounded over... and I found a diamond file was the only file that'd touch the cylinder, as it's extremely hard. So hard it's like a knife after quenching but before tempering. A wonder it's not shattered.

The main pin mounting the underlever to the cylinder's front end was about 5mm too short and its centre-peened ends had some bits of sharp steel coming off. Same on one side of the punch-cut (not drilled) hole in for this pin, with nasty-sharp and flaking off bits of steel all the way around it. Cleaned all that out and replaced with a longer section of 5/32" drill shank, which with a light pass of a chainsaw file was a perfect fit with zero play.

Slightly re-peened the next underlever pin as that was were most of the lever flop was coming from. Once re-assembled the lever showed only about 1mm of play at the bearing; more than acceptable and feels really solid. No need for shims nor anything else with this kind of fit.

While in there I had a look around for safety location options. Nothing obvious so far. It'd be great to have something along the lines of a Crosman 1377 safety, as that's really easy to release yet firm enough to stay put while cocking and loading, but not sure if that sort of thing would fit.


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PostPosted: Tue Nov 09, 2010 12:23 am 
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Location: Vancouver
Nothin' huh? Oh well, self-bump just because I decided to do a baked enamel finish on the muzzle tip thing:

Image

Still thinking about the safety. Don't want to commit to a grip design for carving until I've settled on a safety mechanism and position.


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PostPosted: Tue Nov 09, 2010 8:40 am 
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Location: Vancouver Island BC
It's a tap loader leave it open till your ready to shoot kind of a safety and nice work on the gamo ............

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PostPosted: Tue Nov 09, 2010 3:23 pm 
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Location: Vancouver
Thanks. Yes, I realise that no pellet will fire until I turn the pellet carrier into the breach. But I'd still like a safety as a 'just in case I forget to do that' sort of thing. And I'd REALLY not like to have that underlever smack into my hand again. My finger's getting better, but the joint still hurts a bit. That spring packs a lot of power, and a safety would prevent any more such stupid accidents. Of course if the safety isn't automatic (seems unlikely I'll be able to come up with an auto-safety switch, but will try) there's still the possibility of forgetting to engage it. Will have to rehearse that good habit.


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PostPosted: Tue Nov 09, 2010 3:41 pm 
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Location: Okanagan,BC
p17 wrote:
Thanks. Yes, I realise that no pellet will fire until I turn the pellet carrier into the breach. But I'd still like a safety as a 'just in case I forget to do that' sort of thing. And I'd REALLY not like to have that underlever smack into my hand again. My finger's getting better, but the joint still hurts a bit. That spring packs a lot of power, and a safety would prevent any more such stupid accidents. Of course if the safety isn't automatic (seems unlikely I'll be able to come up with an auto-safety switch, but will try) there's still the possibility of forgetting to engage it. Will have to rehearse that good habit.


I always thought the "good habit" with ANY type of gun was to never, EVER put your finger on the trigger until you are pointed at your target and ready to shoot... :?


8)


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PostPosted: Tue Nov 09, 2010 4:15 pm 
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Location: Vancouver
True enough. Learned that one when I was about 7-1/2, with my first airgun - a Daisy BB rifle with underlever cocking and about a 300 BB reservoir in a large tube around the barrel. Thing was a bit random in power, but it nailed me my first quail from about 25 feet. Right through the head behind the eye. But yeah, I made a few dumb accidental holes in walls and stuff, and shot my cousin in the hindquarters semi-accidentally, and shot the webbing between my left thumb and forefinger while trying to hold the gun in odd ways at the age of 11.

But I smacked my finger last week while working on the gun with the underlever cocked. Never touched the trigger. Momentum triggered the release, as I tapped the aluminum part into place. I have the trigger set about 1/3 up from minimum pressure, so it's not hair-trigger, just about a comfortable 2 pounds or so. Admittedly smacking the gun with a wooden mallet isn't something I plan to do a lot. But it put a bright, painful light on the fact that no safety equals the potential for sudden spring release when the lever is down, whether it's from a slipped finger or whatever. I've used a P17 (obviously) and my brother's Crosman pump pistol, both with safety catches, and I liked that layer of protection against silly accidents. Even the old Daisy had one, I think... My later boyhood Daisy .22 break-barrel and a slightly more accurate and powerful .177 from Czechoslovakia each had safeties. Just seems like something a gun should have.

---------------

My shooting's a lot rusty, but for what it's worth, here's a 5 shot test this morning at 5metres in my house. The flier on the upper left shows what happens when I forget the slightly firmer grip needed to accomodate recoil. Haven't used a springer in over 30 years. But it'll come back. Too bad about BC's pistol hunting ban, and Vancouver's ban on shooting anything, anywhere outside. Black squirrels make a total mess of my fig tree and my neighbour's fig and grapes, every year before they get anywhere close to ripe. Walnuts too. Those cute little rats take off every single walnut, 2 months before they get ripe. From the holes this Gamo puts into 50-year-old hard fir, I suspect a squirrel would be toast from under 10metres, at least once I tighten up my groups. But alas, it's not to be. Have to stick with 'Have-a-hart' trap and taking them to Stanley Park for release. Wouldn't want to set any nastier trap, for fear of messing up a cat or a child. Of course what I'd really like would be to travel back in time and slap the silly Englishman who thought it'd be clever to bring black squirrels over...

Image


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PostPosted: Thu Nov 18, 2010 1:17 am 
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Seems I was able to resolve my own question. Just took avoiding work for the evening and really thinking about it with the pistol apart. So here's my solution in pictures. Basically found the one place where an unobtrusive element could be added which very solidly locks the sear, preventing release until it's moved into a 'home' position.

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There is no return spring. Couldn't figure out how to integrate that without getting in the way of something else, nor how to make a spring total reliable. So it's a friction fit, the thicker step on the file-steel (de-tempered an old thin file and worked it - you can see the pattern of the old teeth a little in the third picture) just wedges into the space between the cocked sear and the back wall of the aluminum chamber. There is enough surface area in contact above and below the slot to prevent wear becoming a problem. With a drop of oil, this safety functions pretty much perfectly, preventing accidental discharge, and if I so choose, preventing cocking, as it won't let the sear engage.

The two depths filed and polished onto the stepped plate were achieved by trial and error. Once those worked to allow cocking then to prevent release, I used some soft silver solder plate and boric acid flux to solder the end of a bolt onto it. Polished it up. Then after drilling and filing the opening in back of the frame for the two positions, I filed a full-width groove for the brass slider to travel within. Then made the brass slider, over-thick to start, drilling under-size then filing out to a flat-sided oval to press lightly onto the bolt, on which I had filed flats to prevent rotation. I drilled a small steel acorn nut out to one size larger, then tapped a matching 10-32 thread into that. Some Loctite and then a small hole drilled part-way through, a matching aluminum pin swaged into place to prevent it coming loose (while allowing drilling out in case of necessity later), and the thing was finished. Bit of oil here and there, re-assembly, and all worked according to plan.

The rocker (or whatever the largest trigger component is called, the thing first encountered when removing the grip frame from the cylinder) is pinned rather firmly, with three stamped cuts into the left end to make removal to the left side advisable. These cuts distort that end of the pin, making it a very tight fit in this case. The sear pin was a lot easier to remove, with no such markings. The spring wasn't overly difficult to figure out on re-assembly; mainly just important to avoid pressing against the right-side coil when pushing the pin back through, lest it be damaged by tapping the pin home.

Unrelated to the safety there is considerable wear along the trigger pin and rocker pin from the cylinder push-rod, or third element in the cocking lever chain. I've lubricated this since getting the pistol, and of course polished the lever (which was VERY rough, accounting for the wear as it's rather harder steel than the pins) to a smooth finish. I'll probably replace the pins someday, just for peace of mind. Doubt they'd ever wear through now that the lever arm is polished and I keep it oiled, but still...

Image

Thanks for reading and following along to all who have. Next on the agenda will be fitting and carving a wooden grip. But work calls, so not for a while, and that's probably a subject for another thread.


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PostPosted: Thu Nov 18, 2010 9:55 am 
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p17 wrote:



---------------

Too bad about BC's pistol hunting ban, and Vancouver's ban on shooting anything, anywhere outside. Black squirrels make a total mess of my fig tree and my neighbour's fig and grapes, every year before they get anywhere close to ripe. Walnuts too. Those cute little rats take off every single walnut, 2 months before they get ripe. From the holes this Gamo puts into 50-year-old hard fir, I suspect a squirrel would be toast from under 10metres, at least once I tighten up my groups. But alas, it's not to be. Have to stick with 'Have-a-hart' trap and taking them to Stanley Park for release. Wouldn't want to set any nastier trap, for fear of messing up a cat or a child. Of course what I'd really like would be to travel back in time and slap the silly Englishman who thought it'd be clever to bring black squirrels over...


Nice work on the nose of your pistol. 8) And like others, not too certain that all that work needed to be put into the safety. You did come up with a nice solution though. 8)
Those Eastern interlopers are classed as "Schedule C" in the Hunting regs which means they can be captured or killed anywhere and at anytime and you do not need a licence to do such. Considered pests here in BC, Six were introduced by some bright boys, from eastern Canada, to Stanley park in 1909. Good article from UBC

http://www.geog.ubc.ca/richmond/city/squirrels.htm

If you do trap them don't get caught trying to release them as that would be Illegal and hefty fine would result. One behind the ear with your Favorite would be my suggestion. :wink:
Alien Species from Eastern Canada. :P

http://www.kania.net/GreySquirrelPoster11X17.pdf

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PostPosted: Thu Nov 18, 2010 5:02 pm 
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Location: Vancouver
Thanks for your generosity Scruffie. Considering all the pristine examples in your fine collection, I'd not be overly surprised had you come down a bit hard on me for modifying an out-of-production pistol. When I add wooden grips I'll probably fit a slightly better looking slide on the safety, more in line with the appearance of the gun generally, and try to integrate a bearing catch into the grip to hold it more firmly into the safe position. A shaped aluminum slide with a socket for a sunken slotted nut should work well, with a baked enamel finish to blend better.

And thank you for the schooling on my rodent problem. That's somewhat reassuring. Although the report from this springer is kind of loud, so a bit dicey as to time of day and neighbours getting offended should I happen to go squirrelling in the back yard. And mutes of any sort don't really work with springers (besides the legality issue), as most of the sound seems to emanate from the cylinder, not the muzzle, at least in this case. The old P17 damped down rather dramatically when I tested it with a steel wool filled silencer. If it had kept working, that would have made a much superior city squirrelling tool.


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