hey everyone. A little back story. My rifle was set up originally like a MK18 clone. I am running a 10.5in barrel and a H buffer. I decided to add a can and took a leap into the piston world. I found a good deal on a brand new AA kit with the old style gas key. I purchased said key and put it on the rifle. After a few hiccups and short stroking the buffer was changed out to a regular carbine buffer. The rifle now eats any ammo i put through it including wolf military classic.

Here is the problem. No matter what ammo i run from federal xm193 down to wolf it will not lock to the rear on the last round. It will recock the hammer and then go forward. There is no problem with the bolt catch as i can lock it to the rear using the button.

The only thing i have changed since adding this kit is I put the magpul bad lever on it. Could this be causing all the trouble?

My local class 3 gunsmith said he would take half a coil out of the buffer spring until it locked back.....does this sound plausible?

thanks for the help

mike
UPDATE:  I took the BAD lever off and took it back out to the range.  I ran 5 rounds one at a time and the bolt locked back on every one...i followed that with 3 sets of 3 rounds as fast as i could pull the trigger and it locked back on all three attempts.  Finally i ran the remaining 6 rounds through it as fast as i could and it locked back when  i was finished.

Im happy to see the problem is gone for now...

thanks for the help

I am sure you already tried it but faulty/old magazines are often the cause of this problem.  Try different mags and see if it continues.

wonder if the gas port needs opened a little.  Just thinking out loud.

take the bad lever off and try it then if it locks back then you know what the problem is. try Mags that are proven to work. just want to minimize where the problem exists.

mags used were magpul Pmags and a cproducts mag....the rifle worked perfectly fine before the AA kit and bad lever. I went to the range and shot it in the original DI MK18 setup with no problems....came home and cleaned the rifle..installed AA kit and Bad lever...took it back to the range and now it doesnt lock back.  Does the AA kit require more gas to work properly compared to a regular DI system?

ok lets try this....

is cutting a half coil off the buffer spring a horrible idea?

Just my 2 cents, take it for what it's worth but I'd really try removing the BAD lever first. I had the same problem with my M4gery

Installing an AA kits do need to be "tuned" with different buffer weights and BAD lever is known to give SOME AR problems, It did effect my 2 Bushies.

I'll take a shot at specifically answering your question and not make assumptions on your lever or other pieces, seriously look there first, too easy no to try. I cannot directly answer your question with respect to your application but in theory I would say no problem. This is the procedure that is recommended on a number of the flat coil spring applications. When using the Tubbs buffer spring (decent flat spring), they sell only one length spring for both the rifle and the carbine. If issues are detected with the carbine they suggest cutting 3 coils to begin with and 1 coil there after until the firearm cycles properly. Springs are cheap and I can see no harm in doing this.
I have one DI carbine that sports a Young's National Match M16 BCG, a Spikes ST-T2 Buffer and a Tubbs spring. Think both stiffer spring and more mass when cycling. This rifle was fine with a regular spring but just for giggles I wanted to see just how little recoil I could make this gun have. Once the spring was installed I ran into the failure to lock back situation. I half way expected this outcome and of course I knew what the problem was but wanted to see if shortening the spring was acceptable. I called Superior Shooting and spoke with one of their technical people to obtain this information. I haven't seen it in print. For what it's worth this gun is an incredibly smooth carbine (no FTF or FTE and locks back every time regardless of ammo). You no doubt have heard this claim before but when it comes to recoil in all seriousness it isn't much different than a .22 LR. Much less perceived recoil than an off the rack AR. Take my words for exactly what they are worth, just another opinion.
 

yeah seriously take the bad lever off before you do anything else. that will let you know where your problem is. because if the gun works with out a bad lever whats the point of cutting coils.

nope not mine i through the aa kit on with a st-t2 buffer and went to town. started off on the lowest setting and then ran it on the highest both ran perfect so i left it on the lowest setting.

I had to adjust the size of the gas port as I SBR mine, using a standard buffer from my Vltor kit and works fine too.

I am definatly taking to BAD lever off and giving it a try today.  The last thing i want to do is take the whole thing apart and send it off to open the gas hole.  I had down time and not having my go to rifle with me.  

Thanks for everyones help and I will report back with an update later on this afternoon.

mike