I modified my AR-9 by adding a left side charging handle.  Pretty easy to do if you have a mill.  I cut a .270" wide by 4" long slot in the left side of the upper receiver.  I made a new "gas key" out of 12L14 steel.  I used a 1/4 x 1" shoulder screw for an operating handle.  I purchased a plug for the normal operating handle opening in the back of the upper.

Jim Skeel

Looks good! I've been tempted lately to do it to one of mine, but after I finish modding it for lrbho

I'll bet you could modify one of the aftermarket bolt handles they sell for hi-point carbines to work with that. Just a thought

Looks like a great place for dirt to find its way in the receiver.  My.02

Do you close your receiver's dust cover between each shot ??  
You do realize that receivers that don't have a dust cover are being manufactured and sold ??
 






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That's really cool

Dirt can get in that big hole the empty brass comes out of too

Nice mod, OP. 

You could maybe install a strip brush dust cover if you are concerned about dust entry. (Think parking brake dust brushes.) 

I wouldn't worry about it.

I have run several hundred rounds through the left side charger modification now.  I have done two others for my shooting buddies.  The carrier key needs red permanent Loctite on the screw threads.  Staking is not adequate.  The operating handle (shoulder bolt) needs blue Loctite to keep it tight.  The Gas Blocker Plug for the rear opening which I obtained from Accurate & Reliable Rifle works well.

All in all I am very happy with the left side active charger modification.  It is easy to operate and you can tell the bolt is fully closed just by looking at the handle position in the slot.

I just installed a Tubb AR-10 Flat Wire recoil spring.  It made a noticeable reduction in felt recoil over a standard carbine spring.  The AR-10 spring reduces the bump when the buffer hits the bottom of the buffer tube.  I am using the PSA 9mm buffer (5.8 ounces).  I cannot decide if limiting the bolt stroke to just past the LRBHO latch is a good idea or not.