Duk Il Arms 22cal AR-5

[Racing]

Guys. Came into this rifle on a sorts of barter. Donīt really know what to make of it yet.

Sheīs the long flavor, sporting a 650mm barrel in 22cal. The little iīve got her to actually fire.. loud Mrs too. Hence the moderator. Therein lies the main issue iīve got though.
Performance was erratic to say the least, tore her down and found an entire o-ring crammed into "under the seat" ahead of the exhaust port. No IDEA how that ended up in there but.. there it was.
Removed that and bolted the thing back together. As i fill her up to 200 bar there simply ainīt oumph enough to open the valve.



Took the entire trigger assy apart, nothing inherently wrong there. As i did i opted to thread and tap the stock rivets using M3 screws, which works just as well if not better even.
I thus came to replace the hammer spring and guide with a way heftier spring and in turn a shorter guide (got a machine shop so not an issue) but that done still no dice.
Then came to challenge the actual valve, and it seems opening pressure is out of this world at them 200 bar? What gives?
Yes.
She DOES fire when around 100 bar or so and then hands me decent power seeing the limited pressure. Still not correct however...?



Itīs gotten to the point where i will rip that valve out of there again and look at the dimensions involved. Things have after all happend since this piece was new.. Am NO stranger to making an entirely new valve need be.

But.
Iīm dead certain thereīs those of you out there that can fill in the blanks for me on this piece. What gives?

[dcorvino]

Hi
Hope this will help out
https://www.pyramydair.com/airgun-resources/manuals/hunting-master-air-rifle-manual.pdf

[rkr]

I did some tuning to my AR6 pistol and never had problems opening the valve, rather I had to use softer spring and tune down a bit as it only gave me 5 shots with long valve opening. Others have added weight to the hammer to get more power. I made a 2mm valve stem to keep it open for longer with less spring force. Could it be valve sticking or something like that as it is an old gun?

[Racing]

Where weīre at, dunno.
Like stated, tore the thing down didnīt really notice anything out of the ordinary.
So.. will have to come apart again.
That simple.

Will report back.

[Racing]

Results are in, and you Sir were correct.

The actual poppet sticking AND letting loose at the same time  .
Material used is some white plastic goo whos best before seems to have passed a while ago.

Thing is on a massive 11.5mm outer on a just shy of 7mm seat. The whole thing slightly countersunk. Will snap a few pics as i tear it down to go 2mm and PEEK once again cause this is just stupid.

Anyways. At first it stuck right. So tossed The poppet on the lathe and dressed outer to 8mm flat and back together again.
Issue tho is that the spindle seems to have hogged itself a cavity within the plastic so it can move around at will.

None the less. Now the valve didn't stick but the spindle eats up force from the hamner no matter
In short..time for a redesign.

Shoved a few pills down the barrel and this barrel seems within reason at least.

As such let it rip which netted a whopping 26J 

Seeing the 650mm barrel...i've got a tad different performance level in mind here so..
Time to get to work.

As stated. Will snap pictures as I go. Certain they'll be to use to someone down the line.

[rkr]

There are AR6 tuning threads by me and Hobbyman in this forum, check those for some ideas. Hobbyman got good power out of his gun.

[Racing]

Given this some thought and what strikes me the most is the rather massive, for a 22cal, 7mm under the seat.

So.
As per previous through RKR iīll bush that "head" to take a 2mm spindle instead and fab me a new poppet on that stem diameter. Thing is that these are known, or at least the later ones are, to hand decent power and..
Well.
The diameter under the seat is 7mm right, and no doubt unotuched, while the transfers are on 4,5mm. As much as i can understand the reasoning we do it a tad different these days.

Whatīs more... End shake for the cylinder, and thus air gap, is set by the barrel thatīs screwed in place on the main block. Of course things wear with time and this needs to be reset. No argument there, but it still leaves that there IS an air gap and i of course wonder by what margin this will affect performance.
Ditto.
As the valve is placed as it is and the revolving cylinder is in turn them two 90 deg bends ainīt really optimal either, so will put on a kettle of coffee and take a good stare at it..
In turn, i already threaded the barrel 1/2"-20 UNF up front and installed a LDC. Them air gaps sure donīt help on that count...

The trigger group in turn, as iīve explained previous i drilled the rivets out and then turned to drill and tap them M3. A good move as it hands total freedom as far as replacing hammer spring, spring guide/divot and what not. Trigger per se isnīt really adjustable at all, which is of less concern as the trigger is actually rather nice as is.
However.
The two plates that mandates the major structure of the trigger group does rub on the hammer, which of course is a bad thing. Iīve already setup for a way stiffer mainspring should the need arise, but most likely seeing the implement of a 2mm stem it will not. The option is there tho..

Ditto. As this unit to a large degree will be about power and making the best out of its 650mm long barrel iīm going to up the transfers slightly. Running 200 bar i know more or less what to expect so...

[rkr]

The holes at the back of the drum are the limiting thing for flow. They need to be slightly smaller than bore as the ball bearing that locks the drum after rotation is too small and making it larger was too much work IIRC. That limits you to about 5mm ports which is actually not too bad.

[Racing]

5 mills for a 22 running 200 bar.. i can live with that.
Especially if we opt to throw a few other trix at this thing, net power out the snout of it should be the least of our problems.

What does strike me tho is the absolute lack of adjustment points, at all. Itīs sort of "4 doors, no waiting and you WILL like it".
Me... i beg to differ. So i believe iīll take my time and figure this thing out. Adjusting it "tight" as far as cram down on the barrel in its own rights.. might be, itīs STILL just a half *ss solution in my book.
What DOES attract me tho is the concept in itself. I just feel they could have gone at least another few yards before putting the thing into production.
Then again.. itīs an old piece and i guess iīll leave it at that.

Thing is tho.
Seeing that 650mm barrel, that tells that given enough air this thingīll hand us the numbers no doubt. Since this thing was spawned things has happened to say the least and iīm dead certain this thing will make good use of the new H&N 40 grainers and what not.
..which of course hands us an entirely different starting point vs when this thing was new.

However.
Power without control is pointless and if i want an "elephant gun" iīll reach for one of my powder burners. Hence why i install LDCīs to anything PCP in sight, i see NO reason what so ever for a PCP being loud.
..enter a "revolver cylinder setup"... Yeah well.

Anyways.
Weīll have to start somewhere and i guess a fresh poppet on a 2mm spindle is as good a starting point as any, and if nothing else will tell where this thing will reach..

Ya know.
Since you adviced me to go 2mm.. That was an eye opener. If you recall first up was that Kral PB in 25 cal and since... i honestly have an "issue" keeping that thing UNDER 100J. 
So yeah. You sure made a believer out of me, iīll tell you that much.

Which.. kind of hands us the current situation. As the poppet on this thing is shot anyways i see no reason what so ever holding back.

[SILENT SQUIRREL]

Very interesting

Please document your work Jesper
and take pictures too.
Pretty Please!
Edward

[Racing]

Does anyone out there know what wood the stock is made out of?
As i absolutely HATE clearcoated stocks i will have that there plastic goo removed and then take it from there. Oil finish all the way baby...

[Habanero69er]

Possibly, Indonesian Walnut. My Rainstorm, Sumatra & Recluse are that wood.

[Racing]

Thank you. 

[Racing]

Yeah well. As i absolutely LOATHE clearcoated gun stocks this could really just end up one way... and the pic tells the story i believe.
Wood strikes me as beechwood, but i could of course be wrong. Those more in the know than me, voice up.. hollar. I sure donīt mind either way, and a carpenter iīm certainly not either.
Either way, rather tough wood.. bright (as can be seen).
What Duk Il did here is the same stunt the Stormrider and many other PCPīs are setup today, an absolutely MASSIVE amount of pore filler, then some color and finally a layer of clearcoat.
In this case semi flat. Sanding that stuff down it sure proved how much "plastic" was involved, which was.. a lot. Pity me thinks as the wood in case actually carries a bit of graining and sure looks like a TON better when let to show what it is.



Here far from done. I just added a bit of dye to see how the material would take to it, not all aged woods do, and iīd say weīre golden from the looks of it.

So that done i pushed forward, going down in grit size until i reached 240.



No. No the gun will NOT be this dark. Not by a longshot. What i did was start out with some mahogony red, to be followed by "dark oak". Know from previous experience that as i oil sand that finish down, ending in 1200 grit actually, the wood starts to show what it was made of..
So yeah.
The hue will become WAY lighter as i go. But.. itīs a starting point at least and whatīs more one SANS all that plastic goo.. thank god.

Might be useful information to other owners of these guns. Now or down the line.

Only real "modification" i have in mind for the stock is first up the inletting needed to make the small screws i installed to the trigger assy clear the wood.. and in turn the install of a Picatinny rail up front, in essence to make the piece enter the 21st century. Sorts of.

Final product? Well, letīs see where she ends up performance wise first. As noted above thereīs a number of points i want to look into but if it all pans out i wouldnīt mind yet another of them Accufire active IRīs ontop.
Like the one i just installed to the BSA R-10.

[Racing]

Further.
Now just me thinking out loud.

I get it that the gun hands us two power levels, kind of. One when cocked single action and then yet one using it double action. All good, but i also feel that itīs way to basic why iīm giving thought how to make the entire setup more adjustable.
Adjustable and PCP kind of goes hand in hand to me...

Sear and thus trigger engagement i find rather on the money to be honest but then again.. a "competition grade trigger" this is anything but.
in turn the rather short and stubby hammer spring.. Fact is the entire trigger group is about as simple and common as it gets. In essence two pieces of stamped sheet metal with the working innards sandwiched between.

Making the hammer spring cutout both longer and in turn adjustable is doable, hopefully "semi" within the stock setup. My point being that a longer spring will make for a way more linear setup and in turn making that adjustable is just common good practice while at it.

Trigger. Much of it can be handled the same way would we a regular revolver, i guess, in its most basic form. That being said i feel like for instance an overtravel adjustment would be of worth.
It being what it is..

That said, any other ideas out there from the rest of you guys?
As you know the barrel wasnīt threaded which i handled kind of right off the bat. Barrel is on a full 650mm which should suffice getting this thing hitting like a ton of bricks at will.
As youīre also aware the placement of the barrel vs the tube in essence rules out the app of any and all shrouds, and TBH a well designed LDC will handle whatever power level this thing ends up at anyways so..
Maybe at the cost of a slightly "snappier" exhaust note, but all said and done thatīs about it..

This all in all of course also brings that the Hunting Master is anything but a short rifle by any measure but.. i donīt really mind that either. One of my favorite other PCPīs used for ratting is a full size Reximex Daystar in 25cal sporting a prototype LDC of mine that works VERY very well... None the less it makes for a rather long package all in all but being accustomed to some rather tall powder burners as well..
What iīm saying is that i really donīt think about that bit all that much.

On the topic of sealing in turn, or lack thereof. Any ideas as far as that? Donīt mind it being service items one yota, the imperative here is to bring leakage down to a bare min.
Have played around with the idea of the stocker, just placed different. In that a small spring loaded ball would push the entire thing either slightly rearward or forwards (whatever is the most reasonable) to have it come to rest "off" said steel ball and at that point meet up with some kind of seal.
OR.. the other way around.
Have the seal protrude whatīs needed as the thing goes into battery.
Might even be a more viable option no?

[rkr]

You could insert small ptfe o- rings in front of magazine chambers, that would seal the front as magazine is pushed against the barrel by air blast while still being relatively easy to rotate. For the rear of the mag you could open up the port going to magazine and insert a ptfe sleeve that would be pushed forward by the air blast thus sealing against the drum rear. Haven't tried it but that's as far as I got when I was thinking it. At 30fpe the blowby from drum system is not too loud so I never got around making those seals.

[Racing]

Yeah.
On that note, power that is, i believe the 650mm stock barrel kind of tells the story.
Put another way, this one sure wasnīt designed to handle any 12fpe from the onset. Iīve read up that many set them up around the 60fpe mark but have to say that i question that to a degree.
Partly due the limited transfers but also due the inherent leaks in the system. As weīre aware ANY leak is bad news for a PCP, let alone deliberate such. 40-45fpe on that 650 barrel would be more like it i think.

What we canīt do away with is that the cylinder needs a tad of clearance to be able to work/rotate. But we can first up keep that to an absolute minimum and if possible in turn hand the thing seals worth their name too.

Compare for instance the early Nagant revolvers, where the entire setup moved rearward upon battery and met up with a cone.. System worked rather well and thus the Nagant is one of the few revolvers there is that can make good use of a suppressor.
To keep in mind here is that the stock solution TO A DEGREE does exactly that as the steel ball in there needs to overcome the springforce to let the cylinder rotate, thereby "eating up" any and all clearance there is when setup correctly.
Would it be an idea to have a sealing ring at the exit point where the air goes from the block into each respective chamber? Might be.. All a matter of how much it protrudes i guess.
Could that seal just as well be set on the cylinder? I guess...

For a regular revolver we normally aim for an end shake of like 7-9/100mm (some even 12-15/100). Even if we get close to that number there will STILL be rather elaborate amounts of blow by out the sides and i fare to say this Evanix is no different - albeit flame being absent of course.

In short, due just common sense if nothing else, it stands to reason that ANYTHING we can do to enhance the sealing properties of this is a giant plus.

[Racing]

Yeah, look. So this thing happend today right...

[Racing]

Weīve been over this with sealing as well as power management.
That a 2mm valve stem will help increase power potential i guess is clear, but iīm still at it trying to figure out what to do as far as the trigger group, essentially making it adjustable for hammer spring as well as creep and what not.

The stock trigger group certainly is rather archaic while at the same time rather compact as far as measurement.
Thus..

[Racing]

I've got no issues to admit when i've been wrong.
...and I sure was.
Got the thing together on a 200 bar fill, filled the cylinder with 25.4 knockouts.
As I had tried the action there was about 180bar left or so.
First hit across the FX brick = 80 Joules 

Second hit i added 30 grams of generic brass i had laying around to the hammer and filled her up with JSB 33.9 diabolos = 100 Joules 

Well. She sure hands power seeing what it after all is. Time for a restrictor me thinks...

Going to make hammer spring adjustable asap. Got a simple solution on that in mind.

In turn, with a moderator added and end shake set via barrel she's WAY more silent in operation than I thought she'd be.
Still..
Wouldn't a countersunk X-ring be an idea both sides of the cylinder? Or am i off on that one?

Pics coming up as I get home and can upload them