GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: PGunner on August 20, 2013, 11:18:52 PM
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And what is the best metal to make a breech for a 1377?
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This, from the GTA Library, covers cutting and recrowning but you can skip the cutting part and just recrown: http://www.network54.com/Realm/CFTech/BioCrown.htm (http://www.network54.com/Realm/CFTech/BioCrown.htm)
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And what is the best metal to make a breech for a 1377?
I like an aluminum breech for the weight reduction.
Barrel crowning link above is good. I have had good luck using a countersink drill bit of the appropriate size for the caliber. I follow up Dremel felt points and two or three polishing compounds.
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No matter what method you use, a good follow up is to take a Q-tip and run the cotton swab over the point where the crown meets the bore, if you did a good job there will be nothing to snag any cotton fibers from the swab.
I have been told by some in the know folks that some barrels seem to be made by sintering and pay present some special challanges when machinng them (the metal may try to flake or crumble rather than cut).
But on other barrels for sure made of chrome moly and 416 stainless I use a tool just like this.
http://www.cylinderheadsupply.com/sc-5.html (http://www.cylinderheadsupply.com/sc-5.html)
IMHO the barrel should be running so the bore is perfectly true, and the end is running perfectly square, but that type of tool applied to a rotating barrel (slow rotation, say 100 rpm) does a really nice job that will pass the "Q-tip" test.
Another thing to look at once you have fired the gun some is the buildup of deposits (lead dust)...it should be perfectly even...if it is not you can suspect your crowning job may need to be redone.
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You tube videos on recrowning barrels.
http://www.youtube.com/watch?v=oVcKOPUE25w&list=PL6SE3g1Tc5eM6K7qp_nVZewzlB8eUssGY# (http://www.youtube.com/watch?v=oVcKOPUE25w&list=PL6SE3g1Tc5eM6K7qp_nVZewzlB8eUssGY#)
http://www.youtube.com/watch?v=OorpZlG28fI&list=PL6SE3g1Tc5eM6K7qp_nVZewzlB8eUssGY&index=8#ws (http://www.youtube.com/watch?v=OorpZlG28fI&list=PL6SE3g1Tc5eM6K7qp_nVZewzlB8eUssGY&index=8#ws)