GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => China/Asian AirGun Gate => Topic started by: Missed-Em on April 28, 2018, 07:02:53 PM
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I want to try polishing the trigger on my SPA PR900 but have no idea how to start. Is there a thread or video with layman discussion on what and how? Yep I've been to the Library and tried the search but not getting much help. How about someone walking me thru this?
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I haven't seen any video on this topic but I would guess they are out there. I've been doing it since high school years and I'm near 60 now. The basic concept is to polish the existing angles, not to change the angles. If you change the angles on the trigger or sear you CAN render it unsafe (it is rarely necessary to change any engaging surface angle). Your goal is to debur and polish the engaging surfaces (those areas of the triggers/sears that move against each other when the trigger is pulled) until completely smooth. Stones are often recommended for this purpose but I use needle files along with cratex wheels/points/discs and Flex-I-File sets for trigger work. Go slowly and carefully and you can improve most triggers noticeably. Also, checking the SIDES of many triggers and sears will reveal sharp edges and burs that can hang and drag. These non engaging surfaces are much less critical in working them than the actual engaging surfaces but it can improve feel. I usually go completely around all edges of sears and triggers looking and feeling for sharp corners that aren't needed. I like to attain a mirror finish on engaging surfaces of trigger and sear but it does take some time.
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That's some solid advice and great information on general trigger polishing.
Moving to the Chinese gate where someone might have polished the trigger on their SPA and can provide some specific information on parts of the trigger than need polishing, and not others, since triggers are designed differently by most manufacturers.
Harry
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Another plug for Foredom from me. I use a variety of things in it, for polishing something there are tiny flap discs with very fine grit. Then polishing compounds and cloth wheels. I got this kit a few years ago and never looked back after using a dremel for a couple decades. It's like comparing a 87 Toyota pickup to a semi.
https://www.foredom.net/k2230-3.aspx (https://www.foredom.net/k2230-3.aspx)
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FYI for the SPA trigger group, polishing the contact surfaces helps but the trigger blade has a ton of travel before it fires, and I got a comparatively bigger improvement by adding a bushing to the bottom pin of the trigger group. That took up most of the travel and made it much more predictable. People have used a variety of things for the bushing and you can probably improvise but I used a 5/32" aluminum rivet. Knocked out the mandrel with a punch (or suitably sized finish nail), kept the aluminum body, enlarged the hole with a #39 drill bit (so the 2.5mm pin will go through it), then cut off the flange with a Dremel wheel.
To reduce the pull weight, I took a spring from under the flint of a disposable cigarette lighter and cut it to the same length as the original (much heavier) spring.
Those two things made an absolute night and day difference.