I recently installed an AK Quad Rail onto my MAK 90. There are four allen screws at each corner. It appears that the upper assembly and lower assembly close around the barrel and gas tube to secure itself upon the weapon once the screws are tightened. After I put it all together I noticed that the bolt carrier and piston (that normally slid back and forth without any friction) now stops about a half an inch from the fully closed position. It looks like the end of the piston is hitting the gas block at the end of the barrel. I noticed that the gas tube is loose and moves around. I read on other forums that many AK parts were loose when it came to the gas tube. It was just part of the design. Once I install the spring, it forces the bolt carrier to the closed position. I am concerned that it hitting the gas block before entry. I would think over time it would eventually wear out the part of the piston that is hitting. I am not worried about a gas leak since the gas tube is vented and has holes in it. I am just concerned about the integrity of the piston and gas block with continued impact after each shot. I have also noticed some very small chips at the end of the piston (really, really, really small) after I spent two days taking it apart and putting back together a dozen times to find the resistance.

Looking for comments to the problem and my next step.

Thank you!

http://i1320.photobucket.com/albums/u538/Loaki8/ak_zps005d4d5f.jpg

Is that a UTG piece of crap hand guard? If so, the hand guard is the problem. I put one on a MAK90 and the way it is secured to / wedged between the barrel and gas tube, when tightened it actually bent the gas tube like a mandrel, allowing the gas piston to contact with and deform the upper side of the gas tube when fired or otherwise cycled. As testament to the robustness of the AK, it still functioned.

Get rid of the UTG handguard and replace it with a Midwest Industries handguard and replace the bent gas tube with a new (vented) unit.

It is not a UTG but it is a knock off. I say that because the box had no markings and the hand guard wasn't labeled either.

I will take the advice and get rid of the handgaurd. But no luck finding any parts for it. Especially the gas tube.   Know of any parts house for MAK 90's?

Check-out the equipment exchange of this site for they are sometimes available.
Just click on the red EE box located @ the top and bottom right.
Those aftermarket parts can be junk. If you do a bit of research you will find something appropriate for your mak.

Good grief, a UTG knockoff? Even worse! Get that piece of junk off of there!

This Bulgarian gas tube should work, although kind of pricy and may take a while to get from Kvar: http://www.k-var.com/shop/AK-080BH.html

Also might try one of these to cut out any gas tube wobble / rattle: http://www.k-var.com/shop/AK-081TS.html

Check Brownells, Midway or Numrich for these parts, too.

If you want a railed gas tube...

will work with any standard fore end. some for $10 here.

A Chinese gas tube isn't hard to find.  Just gotta try and match the rest of your WOOD!