Picked up a used but excellent condition Galil ACE .308 last year (thanks, Marv). Runs excellent on everything I've fed it, but, like many AK-pattern rifles, it is very enthusiastic about brass ejection. I've been wanting to add a can (suppressor) but adding a gun muffler to an already fairly over-gassed baseline...well, lets just say it 'enhances' both things 
To give you an idea of how far the Galil ACE likes to throw my brass, here is a pic:
The Dam police are getting a bit irritated at the random rainstorms of 308 brass and are getting less cooperative about my brass hounding on their turf (its my brass and I want it back ).
Since I absolutely must be able to run a can, and do not want to deal with the terror tales (see I used an alternate phrase there) from other Galil ACE .308 owners, I decided to see if KNS had one of their adjustable gas pistons for this rifle. Lo and behold they do: part number AGP-A-8.
The part arrived a few weeks back and instructions in hand (okay, 'in iPad') I went about installing the new piston. In case anyone else with an ACE decided to go about doing this, I took some pics of the process (it is the same for all models except the 'pistol') as I went along.
The Retail Package:
The package includes the assembled piston, piston head, and 'star guide', as well as a second star guide (more on that later), a couple of roll pins, a sticker, some basic instructions, and staples that will bite you. Damn things.
Sorry about the glare, a photographer I am not.
The Piston:
The piston assembly is composed of three parts: The piston rod, the piston head, and the star guide. The piston head includes the ratcheting gas adjustment collar, which (at least on this model) has 60 very-positive 'clicks' of adjustment from fully closed, to fully open.
Stock piston and KNS piston for comparison
The 'star guide' is not included on all models of the adjustable piston, however, since the Galil has one in it stock form, KNS include it in the design for their piston. What is it? I'll quote the KNS manual:
KNS includes two different sizes of star guide in the package. The 'large' one is installed from the factory, with a slightly smaller unit also included. They recommend using the large diameter one unless it has clearance issues when installing it back in the rifle. The smaller of the two can be swapped in by driving out the roll pin (see above pic), unscrewing the piston head, pulling off the large star guide, replacing it with the smaller version, screwing the piston back in, then driving the roll pin back in place.
I measured mine to see what the differences were:
As you can see, the version that comes installed on the KNS piston is a bit larger, however, I did check fitment on the piston head in the gas tube and gas block and it seemed to have good clearance (more on that later). Note: I did measure the small star guide and it was slightly undersized from the stock version (and the pic turned out very blurry, sorry).
Disassembly:
Now it was time to remove the stock piston from the Galil.
The first thing to do is get a measurement from the end of the piston head to the end of the piston carrier 'nose'. You'll need that for a reference when installing the new piston. Once you have the measurement the stock piston can be removed.
Here it is actually easier on the Galil than on some other AK-pattern rifles as the Galil uses a spring pin to secure the piston rod in place, rather than a rivet like some others. That makes removing the stock piston as simple as tapping out the stock spring pin with a roll pin punch and unscrewing the piston.
Items of note:
Once you have the stock piston removed, you'll notice two differences on the threaded portion between the stock and KNS pistons:
To give you an idea of how far the Galil ACE likes to throw my brass, here is a pic:
The Dam police are getting a bit irritated at the random rainstorms of 308 brass and are getting less cooperative about my brass hounding on their turf (its my brass and I want it back
).Since I absolutely must be able to run a can, and do not want to deal with the terror tales (see I used an alternate phrase there) from other Galil ACE .308 owners, I decided to see if KNS had one of their adjustable gas pistons for this rifle. Lo and behold they do: part number AGP-A-8.
The part arrived a few weeks back and instructions in hand (okay, 'in iPad') I went about installing the new piston. In case anyone else with an ACE decided to go about doing this, I took some pics of the process (it is the same for all models except the 'pistol') as I went along.
The Retail Package:
The package includes the assembled piston, piston head, and 'star guide', as well as a second star guide (more on that later), a couple of roll pins, a sticker, some basic instructions, and staples that will bite you. Damn things.
Sorry about the glare, a photographer I am not.
The Piston:
The piston assembly is composed of three parts: The piston rod, the piston head, and the star guide. The piston head includes the ratcheting gas adjustment collar, which (at least on this model) has 60 very-positive 'clicks' of adjustment from fully closed, to fully open.
Stock piston and KNS piston for comparison
The 'star guide' is not included on all models of the adjustable piston, however, since the Galil has one in it stock form, KNS include it in the design for their piston. What is it? I'll quote the KNS manual:
KNS includes two different sizes of star guide in the package. The 'large' one is installed from the factory, with a slightly smaller unit also included. They recommend using the large diameter one unless it has clearance issues when installing it back in the rifle. The smaller of the two can be swapped in by driving out the roll pin (see above pic), unscrewing the piston head, pulling off the large star guide, replacing it with the smaller version, screwing the piston back in, then driving the roll pin back in place.
I measured mine to see what the differences were:
As you can see, the version that comes installed on the KNS piston is a bit larger, however, I did check fitment on the piston head in the gas tube and gas block and it seemed to have good clearance (more on that later). Note: I did measure the small star guide and it was slightly undersized from the stock version (and the pic turned out very blurry, sorry).
Disassembly:
Now it was time to remove the stock piston from the Galil.
The first thing to do is get a measurement from the end of the piston head to the end of the piston carrier 'nose'. You'll need that for a reference when installing the new piston. Once you have the measurement the stock piston can be removed.
Here it is actually easier on the Galil than on some other AK-pattern rifles as the Galil uses a spring pin to secure the piston rod in place, rather than a rivet like some others. That makes removing the stock piston as simple as tapping out the stock spring pin with a roll pin punch and unscrewing the piston.
Items of note:
Once you have the stock piston removed, you'll notice two differences on the threaded portion between the stock and KNS pistons:
- The hole on the stock piston is quite a bit larger in diameter than the hole on the KNS piston. Per the instructions KNS did this intentionally and notes that "the threads carry all the piston force, and the pin simply prevents the piston from turning".
- The stock piston has a single hole through the threaded portion of the piston, while the KNS has two holes perpendicular to each other. This was done to allow for a more 'precise' adjustment for the overall length, with a hole every 90degrees.
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