MARK2112 Posted April 22, 2015 Report Share Posted April 22, 2015 (edited) so I finally got around to it and made a functioning 28a1 from a philly display receiver. Yes it is my shops post sample, so nobody can say im not nfa compliant. I did all my own 28a1 markings and parked the entire kit. I learned a lot about the Thompson machining the receiver out, but the fun was loading up a 50 rd drum and letting her go...not a hiccup....I did good.im wondering if this receiver needs to be heat treated now or if bob had it heat treated before he sent it. Edited April 22, 2015 by MARK2112 Link to comment Share on other sites More sharing options...
Kocapuff1 Posted April 22, 2015 Report Share Posted April 22, 2015 How about some pictures of the work? Link to comment Share on other sites More sharing options...
reconbob Posted April 22, 2015 Report Share Posted April 22, 2015 The receiver is stress relieved so it does not/will not bend or warp when it is machined into the thinsections - especially the cross section thru the mag cutout and ejection port. The receiver is 4140 steel. This is a high tensile strength steel - much stronger than any originalgun. The receiver is, relatively speaking, soft at about 190 Bhn. I believe that these are good mechanicalproperties for this gun that basically has a hardened steel block sliding back and forth in the receiver.The steel is strong enough to absorb impact of the bolt, yet soft enough to resist failure due to fatigue cracking. I have been making receivers/guns for over 30 years now. Most of the guns are at rental ranges wherethey receive constant use - far beyond what was ever intended for any gun - hundreds of thousands ofrounds. If I am to believe the customer I know of one gun with over 1 million rounds thru it. Original M1928A1 receivers were "heat treated" from the middle of the receiver to the front, but whenhardness tested they are only slightly harder than the rear section. This light hardening was done forwear resistance, not strength. It would not be appropriate to hardened the receiver because then it would not be able to absorb thehammering of the bolt. However, during normal use when the bolt slams shut the cartridge acts as a shockabsorber and you do not get steel-on-steel impact. You only get that when you pull the trigger on an emptygun. Of course, in the back the impact is conveyed to the receiver thru the buffer. Bottom line - it is not necessary or desirable to "heat treat" the receiver. Bob Link to comment Share on other sites More sharing options...
MARK2112 Posted April 22, 2015 Author Report Share Posted April 22, 2015 Great news,understanding why that .250 keyway cutter was used in the front perplexed me at first.why is it there? I think its for bolt clearance,and do we really need an oiler?She ran 50 rds without fault after some minor filing with that pesky blish lock channel.all in all what a great learning experience. Thanks for a great product bob....ill be back for another soon. Link to comment Share on other sites More sharing options...
MARK2112 Posted April 22, 2015 Author Report Share Posted April 22, 2015 How about some pictures of the work?pictures soon. Link to comment Share on other sites More sharing options...
MARK2112 Posted April 22, 2015 Author Report Share Posted April 22, 2015 (edited) this is not nearly as nice as my display.....but she shoots.we are going to do a savage commercial with this one in a carbonia bluing.i was told just to make a blaster and when the man seen it he got all excited and said " lets make this one pretty".the engraving isnt to my liking,id pay to have somebody else do it because finding the right engraving tool and font is a bitch. Edited April 22, 2015 by MARK2112 Link to comment Share on other sites More sharing options...
Paladin601 Posted April 22, 2015 Report Share Posted April 22, 2015 that is nice Mark! You doing the engraving on the CNC mill? Link to comment Share on other sites More sharing options...
reconbob Posted April 22, 2015 Report Share Posted April 22, 2015 Gee Mark, I could have engraved your receiver - it was on the worksheet... http://i51.photobucket.com/albums/f392/reconbob/IMG_1479.jpg http://i51.photobucket.com/albums/f392/reconbob/IMG_1475.jpg http://i51.photobucket.com/albums/f392/reconbob/IMG_1476.jpg http://i51.photobucket.com/albums/f392/reconbob/IMG_1477.jpg Bob Link to comment Share on other sites More sharing options...
laurencen Posted April 22, 2015 Report Share Posted April 22, 2015 that darn font, I have resorted to digitising each letter of the alphabet and numbers so I can engrave a dummy, anyone have the history on engraving font? was it a widely used font years ago and vanished or custom designed for AO only? just curious Link to comment Share on other sites More sharing options...
LSU Tiger Posted April 22, 2015 Report Share Posted April 22, 2015 That's fantastic work! Link to comment Share on other sites More sharing options...
MARK2112 Posted April 22, 2015 Author Report Share Posted April 22, 2015 You should have engraved it,but he didnt want to spend the extra money on it...ughi used mastercam to cnc engrave it with a dead sharp carbide engraving bit........DRs engraving on his 21s is absolutely perfect,he said he pantographs it at another shop. ..... $350.00 though. Link to comment Share on other sites More sharing options...
06AngusSG Posted April 23, 2015 Report Share Posted April 23, 2015 20150422_125347_HDR.jpgthis is not nearly as nice as my display.....but she shoots.I think being a working shooting TSMG makes it gorgeous!Great work Link to comment Share on other sites More sharing options...
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