sass_kevin 2 Posted March 8, 2012 Report Share Posted March 8, 2012 So i have owned my s12 for about six months now and i have done a few things to it. I have the MD arms V-plug (love it) and a tapco stock and Carolina shooters supply heat shield (badass) UTG quad rail (left the top rail off since I havent decided what sight to put on it). My S12 hasn't been cycling low brass so i took off my gas block and realized mine only had three holes in the top of the barrel so i drilled them out two sizes larger (because it was easier than drilling a new hole at an angle). Low brass shoots amazingly well now. The only problem I am having now is it seems that my ProMAg 10 round mags shoot perfect, five round factory mag shoots perfect, but the MD20 mag has cycling problems. I dont know what it could be. It loads great and I love it. Is there any filing or modifications I can do to make it work better? The mag seats fine it just has problems cycling. Any help guys? Thanks! -Kevin Quote Link to post Share on other sites
lbsrdi 1,078 Posted March 8, 2012 Report Share Posted March 8, 2012 The MD drum has a higher spring tension, your gun may be borderline. You could check your hammer profile to make sure you are not losing energy in the cycle. You could adjust the spring tension of the drum.... 1 Quote Link to post Share on other sites
sass_kevin 2 Posted March 8, 2012 Author Report Share Posted March 8, 2012 Ok so what is the best way to check my hammer profile? I will look into adjusting the spring tension as well. Thanks for the help any other advice?! Quote Link to post Share on other sites
gunfun 3,931 Posted March 8, 2012 Report Share Posted March 8, 2012 Yep. the manual says to try seting the spring with only 2.5 turns of tension. Quote Link to post Share on other sites
evlblkwpnz 3,418 Posted March 8, 2012 Report Share Posted March 8, 2012 The MD-20 does not have cycling problems.... 1 Quote Link to post Share on other sites
sass_kevin 2 Posted March 9, 2012 Author Report Share Posted March 9, 2012 I will try that gunfun thanks. I haven't taken the drum apart yet but is seems easy enough...? evlb I have used the same ammo (1-1/8 oz target loads) in my ten round mags, and my five round factory mag and they both cycle fine. When I put the MD20 on it has problems. I am going to try and go out shooting this weekend and see if i cant figure out a solution. Thanks all for your input! -kevin Quote Link to post Share on other sites
The_Caged_Bird 474 Posted March 9, 2012 Report Share Posted March 9, 2012 He meant that your gun is having the problem. The drum mags have stronger springs, this provides greater resistance to the bolt travel. On guns that are borderline, this will cause cycling issues. I decreased my spring tension to 2 1/2 turns and all is well... Quote Link to post Share on other sites
sass_kevin 2 Posted March 10, 2012 Author Report Share Posted March 10, 2012 ok i understand. Is decreasing the spring tension easy to do? I haven't looked into it. So 2-1/2 turns is the magic number huh? That sounds like its hopefully the solution to the problem. Thanks guys for all your help. I will post back after a test run! Quote Link to post Share on other sites
The_Caged_Bird 474 Posted March 10, 2012 Report Share Posted March 10, 2012 No, you SHOULD tune the weapon to run with the MD-20 at three turns. I've made my choice on my own and accepted any possible malfunctions this may cause as my fault. I have yet to experience one but that doesn't mean that it won't happen. If you put it at 2 1/2 turns, you probably won't experience anything bad but you'll need to state that if you DO have any problems with it in the future and need help. 1 Quote Link to post Share on other sites
sass_kevin 2 Posted March 13, 2012 Author Report Share Posted March 13, 2012 I agree with stating that if I do need some help later. I turned it down a little bit and if its nice out here in Western Wa i will be headed to Elbe this weekend to check it out. Thanks again for all the help! I will post later with some more feedback. Quote Link to post Share on other sites
evlblkwpnz 3,418 Posted March 13, 2012 Report Share Posted March 13, 2012 No, you SHOULD tune the weapon to run with the MD-20 at three turns. I've made my choice on my own and accepted any possible malfunctions this may cause as my fault. I have yet to experience one but that doesn't mean that it won't happen. If you put it at 2 1/2 turns, you probably won't experience anything bad but you'll need to state that if you DO have any problems with it in the future and need help. +1 If the OP likes to rapid fire like some of the other ammo wasters here , reducing spring tension is a bad idea. It can cause the drum to not feed the weapon fast enough. Axe me how I know. Do as you will.... Less friction + more gas = "low brass" reliability with the MD-20 drum at 3 turns.... if you do it right. Quote Link to post Share on other sites
xICEMANx 13 Posted March 13, 2012 Report Share Posted March 13, 2012 I'm getting about 2 FTE's out of 20 on my drum. It's set to the default tension. So your not recommending adjusting if you rapid fire? Heck isn't that why we all bough a 20 round drum? None of my other mags ever have FTE's including my 12 round drum. Quote Link to post Share on other sites
The_Caged_Bird 474 Posted March 13, 2012 Report Share Posted March 13, 2012 We can agree to disagree, I've done many drum dumps at this setting and not had a single problem BUT I would immediately return it to the proper setting if I ever experienced a hiccup. Quote Link to post Share on other sites
xICEMANx 13 Posted March 14, 2012 Report Share Posted March 14, 2012 We can agree to disagree, I've done many drum dumps at this setting and not had a single problem BUT I would immediately return it to the proper setting if I ever experienced a hiccup. The 3 or the 2.5 setting? Quote Link to post Share on other sites
lbsrdi 1,078 Posted March 14, 2012 Report Share Posted March 14, 2012 Ok so what is the best way to check my hammer profile? Thanks for the help any other advice?! This is where I would start. The hammer causes a lot of friction. I would suggest you take an hour and study how the action works. Get an idea of how the parts interact while the gun is cycling. When you remove material from the hammer it is important to make sure to leave enough to ensure the dissconector grabs your hammer while you hold the trigger back, as the action cycles. Don't alter your FCG based on anything I say, I am not an expert! For all I know this is bad advice. Here is a tip based on what I did: Remove the dust cover, hold the trigger back and push the hammer down until the dissconector grabs it. While continuing to hold the trigger, hand cycle the action, as the carrier comes back across the hammer face the hammer is pushed down. If while being held by the dissconnector the hammer is still pushed down quite a bit then you can remove more material. In my gun, if the hammer is captured by the dissconector, when the carrier comes over the hammer my hammer is only pushed down a little bit. It is my opinion that a properly profiled hammer makes a huge difference. If you are not confident in your abilities, seek professional help. Hammer profile is only one of many things one should do or check when tuning or modifying for low brass reliability. Good luck Don't alter your FCG based on anything I say! 1 Quote Link to post Share on other sites
sass_kevin 2 Posted March 30, 2012 Author Report Share Posted March 30, 2012 ***********************UPDATE********************** I took the MD20 drum apart and brought it to 2 complete cycles when empty. I took it out last weekend and..... WHAM -O She fires perfect!!! Thats all i had to do. I guess there was just too much tension from the lower round on the bolt and it wasnt letting the bolt move smoothly enough. So there you go. Maybe not the perfect solution for everyone but it definitely worked for me. Thank you everyone so much for all of your help! 1 Quote Link to post Share on other sites
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