TerryYu Posted October 18, 2012 Share Posted October 18, 2012 Can anyone give me their opinion as to why this jam is occuring? This is a brand new SIG Scorpion and I am shooting home cast 230gr round nosers from a Lee tumble lube mold. I broke it out for its first ever timed shoot and I was getting jam after jam from the OEM mags. They are of the hybrid feed lip design (tapers out) which I though was supposed to be good at feeding round noses. I switched to other mags which have the straight wadcutter lip design and the jams went away. The factory mags also feed factory ammo with no problem. When I got home I started hand feeding rounds to reproduce the jam and here is the photo evidence. It will jam out of the wadcutter lip mag if I slowly cycle the slide. Jams good out of the hybrid feed lip design. Jammed cases. Note how the brass is nicked in the 6 o'clock posistion so down on the feed ramp. The mag that works Photo of the chamber/feed ramp. Perhaps the edge is a bit sharp? The bullets are loaded to 1.250 and the crimp is set to .470 inches. Thanks Enosverse! Link to comment Share on other sites More sharing options...
TheBoss Posted October 18, 2012 Share Posted October 18, 2012 Do you load the mags by hand or do you use an Up Lula? I had something similar happen when loading with an Up Lula. The Lula feed ramp peeled or crimped the lip of the casing as you are showing in the photos. My were bad enough not to go fully into battery and cause a severe jam. I now load by hand. Link to comment Share on other sites More sharing options...
TerryYu Posted October 18, 2012 Author Share Posted October 18, 2012 Loaded them by hand. The barrel/feed ramp is causing the brass nicks Link to comment Share on other sites More sharing options...
TheBoss Posted October 18, 2012 Share Posted October 18, 2012 Take a sharpie and color up some areas on the feed ramp you think maybe cauding the casing is binding. Load the mag and chamber the round. Then make safe and look at the area you colored if it binds there will be a rubbed out area where you colored the feed ramp with the sharpie. Link to comment Share on other sites More sharing options...
pskys2 Posted October 18, 2012 Share Posted October 18, 2012 Hard to tell but the bottom lip of the barrel feed ramp should actually be forward of the frame. They should never be flush to each other. Other than that try some other mags? With the bullet pushed back looks like classic nose diving. Are you sure the "nicks" aren't happening when you hand eject the round? Link to comment Share on other sites More sharing options...
Pat Miles Posted October 18, 2012 Share Posted October 18, 2012 There should be at least .060" of the frame visible when the barrel is ramped all the way down as shown in your third picture. If the barrel overhangs the frame you have a life long serious problem. New gun or pre-owned? Pat Link to comment Share on other sites More sharing options...
TerryYu Posted October 18, 2012 Author Share Posted October 18, 2012 I've taken more photos. Wadcutter Jam Round nose Jam Barrel to frame fit. There's enough frame exposed. Went back and tried some more combinations of mags/bullet lengths. It really seems like the reason the gun is jamming is the cartridge is too short and fat and has to make a very large angle change and can't quite do it. With that in mind, I made some dummy rounds that were backed out to max spec, 1.275 to where the driving band of the bullet just barely stuck out of the brass. Feeds like butter. I guess my search is at an end. For this specific bullet's ogive it will not feed 100% reliabily at 1.250 with wadcutter lip magazines (I could induce a jam by slowing down the slide stroke) and not reliable at all with hybrid lip mags. Eats bullets as fast as I can rack the slide from 1.27 to 1.28 and at any speed. At 1.280 the lube grooves hit the rifling and the gun will not go into battery. So I suppose my gun/ammo combination only works within 1/100th of an inch of COAL. I wonder if this is normal or if the chamber is a bit tight on the gun? Link to comment Share on other sites More sharing options...
Mikethor Posted October 18, 2012 Share Posted October 18, 2012 Sorry to hear about the issues. I use 230 grn LRN by Best Bullets at 1.265 and they have always fed perfectly in all magazines.Too short looks like the issue to my very inexperienced eye and based on your test results. You will enjoy that Sig once you start shooting it. Link to comment Share on other sites More sharing options...
jaggy13 Posted October 18, 2012 Share Posted October 18, 2012 You may need to tune your extractor. I had similar issues with a new build. As we tuned it the jams became less frequent until finally gone. Undercut, tension and in my case a little polishing of the chamber. If the rim can't slide under the extractor while picking the round it can cause this type of malfunction. Good luck! Link to comment Share on other sites More sharing options...
TerryYu Posted October 18, 2012 Author Share Posted October 18, 2012 It's an external extractor design. One of the reasons I bought it was I was tired of the ejector always needing tuning on my old gun so I went to the external. I will be polishing the chamber and perhaps breaking the edge on the barrel a bit. Link to comment Share on other sites More sharing options...
sti38super Posted November 2, 2012 Share Posted November 2, 2012 You hit the nail on the head with the semi wad cutter length. They must be loaded as long as possible to feed correctly.The semi wad cutter bullet must be long enough to hit the top of the camber and true up the round before the slide comes in to far and locks the round in to the feed ramp. Round nose are not quite so lenght sesitive as semi wad cutters are. Link to comment Share on other sites More sharing options...
Steve RA Posted November 2, 2012 Share Posted November 2, 2012 The "plunk" test is your friend !! Link to comment Share on other sites More sharing options...
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