Artemis's P15 Bullpup ... the good .. the bad & the ugly ( .177 caliber )

[Motorhead]

Did not make a photo essay of the journey, so this will be short & sweet written explanation of what found and what required in correcting.

Wonky regulator that had velocity very unstable, major creep and just fubar.   -1
Initial inspection was WOW nice looking regulator, excellent machine work, anodized body, brass spool, lots of bevel springs, side intake to a center seat bleed hole ... excellent design & execution +1
So why does it work so wonky ? ... taking a 20x eye loupe and inspecting the seat shape and sealing surface on the set point adjuster reviled 100's of micro dents and scratches, which is from in my experience BULK handling / tumbling / deburing of the parts after dropping off the machine making them.
CURE ... chucked up the adjuster in the lathe and did a very light pass over the rim of seal surface and then made a cut that narrowed the diameter of the "Volcano rim shape" to get a narrower sealing band.
Seat on the spool was pulled out ( Looked like white plastic or acetal ? ) replacing it with PEEK.    In testing ROCK SOLID with no drift what so ever ... Nice ! 

Hammer is a very simple one that is a dual diameter little HAT looking piece, it just took some O.D. polishing of both diameters to smooth up it's motion ... +1

Trigger ... well linkage anyway is sorta sloppy having Cotter pins threw clevis's. Not much one can do here without some fabrication to tighten up the connection points at Trigger blade & Sear block.
The actual trigger/sear parts are housed in there own sub assembly held down to receiver block via 3 screws, and 3 cross pins hold the sear parts in place.  Solid assembly, well done & adjusts to a crisp break. +1

That done, we get the gun onto our pressure gauge / tuning fixture and see where the ideal hammer strike / regulator pressure should be   ( Reg opened up into a bypass setting )  Whoa way too much hammer energy -1 
Started running tests in 100+ psi steps from @ 800 psi to @ 1800 psi to see where a natural bell curve was and never found it ... higher the PSI higher went the velocity 
So we start clipping the hammer spring, until when @ 3/8" shorter than we started the speed started to flatten out, peak and slowly fall away +/- @ 1600 psi.   set as such the hammer spring had only a small amount of preload. Gun was firing MUCH quieter too due to much decreased dwell.   Pulled reg, put into the setting fixture and set it at 1600 psi.  Assembled and re-shot ... Perfect right back at 880 fps with a 7.9 crosman.
* Take away .... Likely these guns ALL get the same internals inspite caliber and in .177 WAY OVER SPRUNG !!!

NOW THE UGLY   Accuracy or a lack of 
Spiral ... SERIOUS spiral and not much better after trying @ 10 different pellets in brand, size and weights. ( All shot in the 800-950 fps range )
Cleaned and scrubbed bore ( No better )  Torch flame to a Red Cherry and quenched in oil the muzzle end creating a slight choke .. tad better but still throwing fliers.  End feeling a GARBAGE Chinese barrel. -1

Cure, Expensive but customer wanted it to SHOOT, so it got a Weihrauch / HW .177 barrel custom machined to fit & an oversize LDC.  Now shoot incredibly well and makes for a REALLY SWEET little bullpup.

Sadly the cost to fix what was wrong, update barrel etc was over 1/2 again the initial cost of the P15  ... but in the end the customer is getting what they wanted with accuracy worthy of the investment.

Your mileage may differ.

Scott S

[Gear_Junkie]

Thanks for the writeup Scott!  I really liked the Diana Skyhawks when they came out, especially when Diana claimed that hey were going to QC check these rifles.  Lo and behold, it appears they did nothing except slap a nice stock on the gun...  what was your term - lipstick on a pig    I just kept reading report after report of poor accuracy from these barrels.  I know that there are aftermarket options, but the cost didn't seem warranted to me given the quality of the gun in general (except for the stock - that part is very nice!!!).  If I was going to spend that much money, I may as well fork out a bit more for a Veteran 

[lennyk]

Have you used that torching method a lot to any success?
I have an old barrel which is a bit loose and want to experiment with that.

[Motorhead]

Have you used that torching method a lot to any success?
I have an old barrel which is a bit loose and want to experiment with that.

a VERY old school technique to create a choke.       You need to get the last inch of barrel Red to going straw colored and then quick quench in cool to cold oil.  This causes the "Tube" aka barrel to quickly contract.
Some barrel steels react more than others, but in most instances if you were hot enough and quenched correctly you can get .001 - .003" of uniform constriction.
Oil type also comes into play in that YOU DON"T WANT a low flash point oil that with flash ignite or one that will burn within the bore leaving carbon from the surface contact ignition. 
Test first ... If Carbon is forming on the O.D. of barrel, same is happening on I.D.

Read up on heat treating quenching oils and you will get on the right track to experiment with this technique.

[lennyk]

thanks for the info

[anti-squirrel]

Good info, Scott

Not surprised about the results... it all boils down to barrel quality.  also not really surprised about the regulator needing some clean-up.  After my time in the Navy, especially shore duty in the HPA and Hydraulic shops, I found a thousandth of an inch of scoring or marring on a surface can be the difference between a big smile and an undesired loud noise or explosive decompression.  Regulators are every bit as sensitive, perhaps more so, given the way they work.

I tried flame-shrinking a barrel a while back and yeah, I never mentioned my results because they were NOT desired  .  I achieved good results on that particular barrel finding the tight spot and cutting off there, then re-crowning.

[MB]

Thanks Scott great write up, I am currently building a custom p15 putting a CZ Barrel on it, will update with progress...

[MB]

Thanks for the writeup Scott!  I really liked the Diana Skyhawks when they came out, especially when Diana claimed that hey were going to QC check these rifles.  Lo and behold, it appears they did nothing except slap a nice stock on the gun...  what was your term - lipstick on a pig    I just kept reading report after report of poor accuracy from these barrels.  I know that there are aftermarket options, but the cost didn't seem warranted to me given the quality of the gun in general (except for the stock - that part is very nice!!!).  If I was going to spend that much money, I may as well fork out a bit more for a Veteran 

I have noticed small cosmetic changes in parts on the Skyhawk compared to P15, the Valve port is now machined to a higher quality and steel as opposed to brass, the cocking lever is also better finsihed and more refined, other than that its all the same, sans stock...Diana should have spent more time on barrels

[Lani52]

Diana really dropped the ball on this gun.

I have the 22 Skyhawk  and it had a bad barrel.

JSAR put. Huma regulator and LW Polychoked barrel in it and the results were astounding.

My next improvement is a to send it to Lee 545 for a 25 caliber plenum  and a lengthened shroud.

My barrel is now 20 inches long and for me that makes the shroud too short, not to mention the threads are machined off center on the shroud.  So Lee545 is making me a new shroud from a 20 inch tube I ordered from China.

It is still ismply a 1 holer with Crosman Hp’s and yes for the money I could be shooting a Veteran.

I think the best way to get into these p-15’s is to get either a used Artemis or Skyhawk from a frustrated owner on the cheap in 25 and  first do the Huma plus reg extension.  That way you can rebarrel with a Mrod/Gander mountain  barrel and save some money.

The Skyhawk stock is a lovely addition, it suffers from being to dry, but hand rubbed Trueoil fixes that.   Too bad the  high end pups don’t use such wood.

Thanks much for the info Scott.

Roachcreek

[KnifeMaker]

Well written and worded Scott. Thank you for your efforts on this AG.


You mentioned PEEK for the seat. What is in the Huma. I have peek on hand, and the reg is starting to drift.


Knife 

[Motorhead]

Well written and worded Scott. Thank you for your efforts on this AG.


You mentioned PEEK for the seat. What is in the Huma. I have peek on hand, and the reg is starting to drift.


Knife 

HuMa uses what looks like disks cut from acetal sheet, tho never have asked Huub what it is exactly ?

[oneshot61]

Been wondering about the p15 as a low cost bull pup option. Very nice write up. Can you elaborate on the reg bypass ? How is that done?

[Motorhead]

Been wondering about the p15 as a low cost bull pup option. Very nice write up. Can you elaborate on the reg bypass ? How is that done?

When you back out the set point adjuster screw the seat never seals or does so at pressure beyond normal pressure the plenum / valve operates at normally and what ever pressure is within the tank is also within the plenum space.
In doing so you can now fill tank to a measured pressure, vary said pressure and see how hammer spring changes effect power etc ...
Once you get a handle on "At what pressure" the system operates best, pull the reg back out and adjust the set point to that pressure.

[oneshot61]

Didn’t know that could be done, but I know very little about regulators. Thank you for explaining that. Essentially, I could potentially shoot it as a non regged gun.

[KnifeMaker]

Thank you for your reply Scott. Appreciated!


Knife

[Gear_Junkie]

So we start clipping the hammer spring, until when @ 3/8" shorter than we started the speed started to flatten out, peak and slowly fall away +/- @ 1600 psi. 

With hammer springs, do you still need to heat, close, and grind the spring ends?  Or is this less critical than the main spring in a springer?

Thanks!

[Motorhead]

So we start clipping the hammer spring, until when @ 3/8" shorter than we started the speed started to flatten out, peak and slowly fall away +/- @ 1600 psi. 

With hammer springs, do you still need to heat, close, and grind the spring ends?  Or is this less critical than the main spring in a springer?

Thanks!

Just nip the spring and belt sand the end so it's not sharp, place cut end on the vel adjuster end.  K.I.S.S.

 PS,
Just did a Diana Shyhawk in .177 earlier in the week ... it was far nicer having no reg issue and a decent barrel.

[Scotchmo]

So we start clipping the hammer spring, until when @ 3/8" shorter than we started the speed started to flatten out, peak and slowly fall away +/- @ 1600 psi. 

With hammer springs, do you still need to heat, close, and grind the spring ends?  Or is this less critical than the main spring in a springer?

Thanks!

For small wire diameter springs, I often close the coils, but don't grind.

I have a gas stove, so I heat the end (last one or two coils) until cherry red, and then push the hot end of the spring against something handy that is flat and heat resistant (flat piece of metal or maybe Corning ware).

[Gear_Junkie]

Thanks Scott & Scott!