MBX Extension help!

[Southpaw]

I just got an MBX Mega extension last week. I assembled it according to the video on the MBX site and tried it at a match this past weekend. Well it turned my PCC into a single shot where each round nosedived and I had to rack the charging handle to chamber it. After about 8 of those in a row I ditched the mag for rest of match.

 

I've been playing with it at home and see just manually stripping rounds about the first 10 from starting fully loaded want to nosedive into front of mag while round moves forward to feed from the mag. Once the mag is downloaded to about 45-46 the problem stops and rounds seem to point up like normal. 

 

Anyone have this happen with their MBX extension and know how to fix it?

 

I tried 2 different OEM mag tubes and an ETS tube, also tried factory FMJ, all same results. Below pics show how top round points down when nearly fully loaded, but then next pic is after downloaded to 45 rounds.

 

[Dannybot]

did  you use extrapower springs?

[Southpaw]

Yes, it came with an extra long spring. 

[L9X25]

I would pull off the cleaning plate at the bottom, remove the spring and follower, and look at the transition from the base pad to the mag ... maybe run a pencil up the insides to see if there is any interference on any of the sides or back.  The transitions should be as smooth as possible.

[Patrick Scott]

Had the same issue with mine(nose dive even with a Taccom feed ramp in the gun), I was using an old tube so I swapped that out first, better but not perfect. Cut four-five coils off the spring and its been perfect so far. I remembered another PCC shooter having a similar problem that he tracked down to excessive spring pressure so I gave it a try. 

[Southpaw]

Thanks for replies. One thing I'm wondering about is just how much everyone chamfers the bottom edges of the mag. Do y'all go all the way to the edges of the mag with the beveling or just break the corners some to round them off?

 

That would make sense that it could be too much spring pressure as that would explain why the problem stops once it's downloaded about 10 rounds. I'll leave it fully loaded and see if spring takes a set first and then maybe try cutting spring.

[L9X25]

Remove as little material as possible, at least initially, just round off the sharp edges. 

You do not want to create a recess in the transition, you want that to be as smooth as possible.  

[Patrick Scott]

I just broke all the corners and made them smooth. I also give a little love to the follower. MBX has a video somewhere about the tuning part. 

 

Made sense to me as my mag ran fine out of the box after the first 6-10 were gone.

[TRUBL]

could have something to do with the angle of the dangle and the OAL of your rounds.....try factory ammo 

ALso.....have you proven that the factory magazines actually work with out an extension?

[TRUBL]

All I am saying is......it's not the extension, it's something else

[MikieM]

 

Yes, it happened to me at a match. I began a stage with a 47 round MBX in the gun, chambered the first round, the gun went bang, and that was all she wrote. It was single shot for me for the next several rounds. I had another 47 rounder ready for the next stage and damned if it didn't do the same thing. Up until the time of the match they were both working fine. As it turned out I only loaded what was necessary for the next 5 stages and things were fine.

When I got home I took the mags apart and saw that rounds was sticking at the junction of the magazine and the extension as the follower brought them up. It appeared that there wasn't enough room in the extension (at that point) for the ammo to pass through without scraping the inside of the mag bottom. Each time the follower would come up it would scrape of a bit of polymer and drag it up with it, until, (it always happens at a match) it would bind and the magazine wouldn't feed properly.

I don't think there is a solution to this problem because I'm of the opinion that the interior dimension of the extensions are too tight.

My fix was to go with Taylor Freelance. Which I did.

 

 

Edited December 13, 2017 by MikieM

[MikieM]

41 minutes ago, Patrick Scott said:

I just broke all the corners and made them smooth. I also give a little love to the follower. MBX has a video somewhere about the tuning part. 

 

Made sense to me as my mag ran fine out of the box after the first 6-10 were gone.

 

Mine too. Like you, I had done all the tuning when they were new. Deburred and sharpened the ramp on the back of the follower, and removed the sharp edges from the extension, and the mag bottoms. If all that helped, it didn't help much.

[MikieM]

9 minutes ago, TRUBL said:

All I am saying is......it's not the extension, it's something else

 

It most certainly was the extensions. I took those same two magazines and put TF carbine extensions on them and they work fine.

[Southpaw]

49 minutes ago, Patrick Scott said:

I just broke all the corners and made them smooth. I also give a little love to the follower. MBX has a video somewhere about the tuning part. 

 

Made sense to me as my mag ran fine out of the box after the first 6-10 were gone.

 

Thanks, that's what I did with the bottom of mag and I did also touch up edges of follower as well with sandpaper. I watched the video and think I did everything it says to. 

 

And follower doesn't seem to hang up in transition from extension to mag body; it nosedives when fully loaded but seems to stop at around 46 rounds and the follower is still inside the extension at that point.

 

13 minutes ago, TRUBL said:

All I am saying is......it's not the extension, it's something else

 

So the same gun, mag, and ammo work 100%, I add the extension and it won't feed, but it's not the extension?  yes I tried factory ammo too.

[Patrick Scott]

1 hour ago, TRUBL said:

All I am saying is......it's not the extension, it's something else

 
Im my case the MBX was installed on a mag tube that previously had a TF 41 kit on it and has been flawless with that setup and with any ammo. I don't believe it was the extension itself, but the amount of spring.  And yes, I did let the spring take a "set" or "break in" before I hacked it.  

[L9X25]

I built, modified and worked on many mags (all metal) and never had a problem with too much spring pressure.  Not enough spring was a common problem, but never too much.

 

Maybe it is possible the spring pressure is expanding the mag body on these plastic mags, but I have never seen the metal reinforced mags flex enough to cause that kind of problem. 

 

 

[Darqusoull13]

I must be the only person that has not done a single thing to the MBX, TF or TTI extensions/mag bodies/followers and had 100% reliable function. 

[Neomet]

5 minutes ago, Darqusoull13 said:

I must be the only person that has not done a single thing to the MBX, TF or TTI extensions/mag bodies/followers and had 100% reliable function. 

Nope. ;-)

 

[Patrick Scott]

24 minutes ago, L9X25 said:

I built, modified and worked on many mags (all metal) and never had a problem with too much spring pressure.  Not enough spring was a common problem, but never too much.

 

Maybe it is possible the spring pressure is expanding the mag body on these plastic mags, but I have never seen the metal reinforced mags flex enough to cause that kind of problem. 

 

 

Not trying argue, but was all that work done in guns that lack a feed ramp and the cartridge has to make an almost 1/4" jump in some guns? I think that changes things quite a bit and taking some coils off the spring was the only thing I did to get a higher bullet presentation and so far(few hundred rounds) 100% reliability. Maybe it was luck? As I said earlier, Im not the only person who has done this with the same results  Also, the gun had a very hard time charging off of a full mag even with a 308 win buffer spring 

Edited December 13, 2017 by Patrick Scott

[L9X25]

I am not saying it is impossible, just counter intuitive.  

[Southpaw]

If it's not the spring then I have no idea what else the issue could be or what else to try to get this thing to work. As much as I'd like to have it working, I'm inclined to just see if I can return it as I hate dealing with all this trial and error testing trying to get it working. And if I cut down the spring then I'm sure I couldn't return it after that...

 

I'll try leaving the mag fully loaded for a few days and see if that helps. If anyone has any other ideas of what I can try I'm all ears as I'm out of ideas 

[Patrick Scott]

4 minutes ago, L9X25 said:

I am not saying it is impossible, just counter intuitive.  

I when I was dealing with this I did also run across more than a few threads here where handguns were having nosedive issues as a result of too much spring pressure. 

[L9X25]

I would call them ASAP, it is their part and you are not the first person to have that problem.  

 

If they can't tell you how to fix it, send it back and get something else.  I will have the Taccom version in a few days and report on that.  

 

I have a 62 rd splice that works, but I rarely use it.  It is really big and I rarely need that many rounds.  I have a TF extension that gives me 40 100% reliable rounds

and that covers 95% of the stages I see.  

[L9X25]

1 minute ago, Patrick Scott said:

I when I was dealing with this I did also run across more than a few threads here where handguns were having nosedive issues as a result of too much spring pressure. 

 

Other plastic mags?  Maybe that is the combination, strong springs with plastic mags?

[Patrick Scott]

Just now, L9X25 said:

 

Other plastic mags?  Maybe that is the combination, strong springs with plastic mags?

No metal mags, but remember Glock mags are metal lined so different yes, but not completely