Backstory here is simple really. The local vendor that i do jobs for had a few of these laying around in 25cal.. and theyīre to be phased out. So a deal was struck and i ended up with yet another 25cal PCP.
That simple.
For those not in the know the M-16A is a kind of budget to mid range PCP that sports a regulator as kind of a key feature. The Artemis line of chinese made PCP guns range from ultra budget (Stormrider) to the auto loaders like the M40, and the P15 to P35 as in between bullpups and what have you not. Iīve been waiting for their new M-60 "FX Impact look alike" to surface.. to no avail yet.
Anyways.
M-16A
IMO to call it a pretty gun would be stretching it. I believe the intent here was a basic regulated PCP rifle, one that sports a barrel length just as the Stormrider. Sports a shroud stock, and weīll get into that.. adjustable trigger and what have you. Regulator is to be adjusted from the outside btw while the stock "buddy bottle" has no provisions in form or shape of check valve or similar.
Like the Kral and Reximex guns the Artemis offerings are often rather accurate in comparsion to much out there IMO. Thatīs to be said as i see it. So i expected this M-16 to shine in that dept..
Shroud. Right. As the thing comes out of the box the shroud simply does not work. Point being that itīs a tube that rides atop the barrel and thatīs about it. Whatīs more the diffusor that rides at the muzzle of the barrel carries some sort of funky thread that iīm sure was a good idea to someone at Artemis/Snowpeak but.. whatever.
As that threadīs larger than the industry standard 1/2"UNF though.. i just recut that and threaded it.
Then. To make the shroud functioning i cut back slightly on the flange and then cut an o-ring groove into it. In this manner the shroud is sealed vs the diffusor, which hands that all gas thatīs expelled behind the bullet is free to move down the shroud and the shroud to pull itīs fair share of work muffling the piece.
All good then?
No. The other end of the shroud tube thereīs a series of holes for "venting" the shroud. Completely uncalled for as the air will just bounce back need be.. and them holes make the shroud omit.. noise.
I just did a McGyver on that one and wrapped the tube with some elastic black electricians tape, adding one layer on the inside of the shroud tube as well to keep rattling to a minimum where it comes to a stop on the guns separate breech piece.
So.
At that point all content and ready to accept a moderator of choice. More on that further down...
The M-16 is a regulated gun. That brings lower running pressures than if not, why i from the onset decided on opening the transfer passages up. In this case for starters to 6mm flat. At that rate the one of the two stock allen grub screws in M5 is out.. cause i drill that passage on one of the bench drills.. with the valve seat body set into the main block while at it, handing me absolute fit between the various opening when done.
That also brought that i in turn had to drill what you see there in the picture to 6,5mm to accept an M8 tap.
The poppet on most Artemis guns is rather small and light. Works off of a 3mm spindle. Opted to cut the center of said spindle, which works within the main valve exhaust port, back to 2,5mm on the lathe.
Future mod, if needed, will be to open the valve seat through hole incl the space beneath it to 7mm flat. Need be.
Hm. Yet another point where this gun sure isnīt "done". Why is that? Anyways. It sports a barrel that threads into a breech piece. For whatever reason that part of the barrel that sticks into the breech bottomed out where itīs absolutely at its thinnest, within the breech, instead of at the flange so intended (in picture).
Whatīs more..
Thereīs two o-rings for the transfer passage between the block and barrel. All good. Thereīs an o-ring to seal vs the probe. Again all good. But thereīs nothing to keep it air tight between the barrel and the breech piece?
So.. barrel on the lathe to cut an o-ring groove and then countersink the opening for the barrel on the breech piece.
NOW it seals 100.
To make that there happen i had to cut back 0,8mm on the piece that sticks into the breech, which in turn handed that i needed to cut back 0.6mm on the shroud tube - to make it all come together.
So. There i was.
Rifle now shoving "34 grain" (i use that phrase loosely) pill downrange at a reasonable 950-960fps (even saw 97o).
But.
That IS stonewall if weīre to use some sort of reason here. Mind you, at this stage i had ALSO weighed the stock hammer of a mere 19 grams down to approx 34 grams by "leading" it (melting lead into the cavity of it) and in turn replace the stock hammer spring with one for an FX Impact.
So whatīs the issue then? Welp.. regulated guns in essence NEED whatīs known as plenum volume. Ie; an entity AFTER the regulator that only sees regulated pressure. This plenum is what the guns to draw from as the valve opens, and if not there.. the reg sure becomes a bottle neck to keep up with the pace weīre talking here.
Issue is that the M-16 plenum is of a mere 11ccīs... We normally say that 10ccīs per 10fpe is a good rule of thumb..
So what iīve done is look into this, in more ways than one.
Where weīll end up is anybodys guess as of current, but that it WILL happen and it WILL show the results to go with it.. you can take that to the bank.
Anyways. Shooting.
The M-16 sports what iīve come to call a "semi weighed" trigger group. As thereīs plenty of direct contact in there, while other parts of it is spring loaded. Like the sear for instance (hidden by the frame work in the pic).
No matter itīs kind of neat that it sports an entirely stand alone trigger group as i regard it.
Anyways. Shooting.
So the trigger can be adjusted for 1st to 2nd stage slack and then sear engagement too. This via two separate adjusting points holding M3 allen grub screws.
I adjusted the trigger... and it wouldnīt hold after a few shots. Adjusted again.. repeat n rinse.. sorta.
Tracked that down to that the adjusting screw for sear engagement was way to loose in its threads...
Indeed. Took the trigger assembly apart and handed that pesky little screw some blue Loctite and done deal. Since that was let to cure.. trigger is downright wonderful.
In turn. Me i like VERY light 1st stages and as can be seen in the picture of the entire trigger group thereīs a small spring to act on the trigger for the first stage. Replaced that.. very happy.
Sear adjustment in turn is such that thereīs no creep what so ever and iīd say that after cutting the angles of the sear as i see fit iīve got a trigger pull somewhere around 1-1,5lbs approx. Real happy with that.
Actual trigger blade holds the safety too btw. Completely useless..
Then today.
No pics, coming up.. But anyways, i sanded that god dreadful stock down. For some reason Artemis/Snowpeak friggin DIP their stocks in pore filler which hands a rather "plastic" feel to them, albeit wooden stocks. So fact is ALL my Artemis guns has undergone this. Have treated it with some dye and in turn linseed. Will revisit the dye come tomorrow.
While at it.. that "forend" is simply to much. So i took the saw to it, getting rid of approx 1" of the absolute bottom of it.
WAY WAY WAY better... now it looks like a "normal" rifle at least.. But iīll get back to you on that.