Canadian Airgun Forum

Woke up this morning with the need to build one of my last stock XP4 pistols (clone of the Beeman P17). I had an adjustable piston lying around, and also a brass sleeve for inside the valve (to reduce volume and increase pressure). I cut 1 1/2 coil off the valve spring, polished all trigger/hammer mating surfaces and lubed with WS2 paste, then polished the barrel breech face and re-crowned the barrel. Had to notch the upper receiver for the piston's rod to have enough stroke so the Oring clears the air inlet hole. I did the ''no-longer-automatic'' safety mod by removing that small lever underneath the cylinder. Also sanded the molding edges smooth on the grip, especially the back strap. Don't get me wrong, the gun has excellent ergonomics, better than the P17 IMHO, but it's kinda ''unfinished''. Adjusted the piston to have 1/4'' cam over and the Oring just clears the inlet hole when the piston rod butts against the receiver. Before I started on the gun this morning, I ran a ''control'' chrony test: 323 fps (1.7 fpe) with JSB RS Exact 7.33 grains domed pellets . Now another chrony test with the pistol built up:

JSB RS Exact 7.33 grains 4.51: 439 fps (3.18 fpe)
JSB Exact 8.44 grains 4.52: 414 fps (3.23 fpe)
H&N FTT 8.64 grains 4.50: 411 fps (3.24 fpe)

Much better, and this is with the stock barrel!

Haven't checked accuracy yet, but this barrel has very nice rifling, pellet fit is good and in my experience, these barrels are as accurate as P17 barrels can be. The plastic FO sights are decent and usable, there's no slop in the rear one for once LOL! With my first XP4 I got 1/4''-3/8'' groups @ 10 yards with the FO sights, I'm expecting the same with this pistol. Never tried the FTTs yet in the Stoeger though, curious to see how they'll do on a target .

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If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

Nice results! Lots of added power after the mods.

Well~ adding 100+ fps proved how bad it was~ [emoji38]

Without touching the barrel and give the HW40/P17/XP4 that power on a 8g+ pellet is amazing!

IMO, this is called a 'finished' product after the treatment and mod~

Wondering if similar could be done on a FAS 6004 platform?? I hesitated so many times on buying a SIG Super Target for that 'paper penetration prevented' power... If it can do a power like this, I believe much more ppl would throw their pocket money for one...

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~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

Thank you Ken .

I don't know about the FAS 6004 unfortunately, but I wouldn't be surprised that some ''hot-rodding'' could be done to it . I do have an older Webley Nemesis SSP pistol, I think I'll have a look at it .



Thanks Todd! Yes they respond pretty well to tuning, using the same methods as with the P17.

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If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

My mods to up the power are so efficient I ran into a new issue. The OEM poppet Oring started to extrude and tear because of the added pressure in the valve, and also stuck on the seat, so the gun wouldn't fire. This happened after about a dozen shots. I didn't want to make a entirely new poppet, so I decided to try a different material for the seal. I used duro 90 urethane to make a conical seal instead of an Oring.

The round bottom of the Oring groove in the poppet head have been re-machined flat and the edges rounded, width of the groove is 0.080'', slightly less than the thickness of the new seal. The new seal is about 0.015'' bigger on OD than the OEM Oring (-006 I think), 0.085'' thick and has a 45° bevel, same as the valve seat. Center hole is 3 mm. I coated it with silicone grease and installed it, very good tight fit. Put the gun back togetther, pumped it and the valve sealed immediately. Best of all, the gun fired LOL! Will see if the new seal stand the test of time.

_________________
If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

BTW, I noticed a detail that may be a way to de-tune these pistols , I suspect maybe because of the weaker design of the upper slide: please note the difference in the position of the bigger Oring, just under the brass threaded piece, between the XP4 and Beeman P17. The lower position of this Oring in the XP4 lowers the pressure in the valve chamber by adding ''lost head space''. The closer to the spring the Oring will be, the higher pressure you'll get in the chamber. This difference may also explain the rumors circulating, saying that this pistol has no power potential. It DOES have power potential, but the upper slide is weaker than on the P17 and will easily bend under added pressure.

_________________
If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

Looks that's much better than an o ring~ no doubt the factory won't take this design in order to lower down the cost...

_________________
~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

I agree Ken! Don't make them too good or they'll last too long .

Mine has already started to yield a little, see the bend indicated by the red arrow in the pic. Also I bought a ''parts'' XP4 from a good fellow which suffered a bent upper after installing an adjustable piston. Need to find a way to reinforce this weak area now. Meanwhile I now cock the gun by putting the entire width of my hand over the slide, this helps quite a lot but it's harder to close the slide.

_________________
If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

;) do we need to detune it?!

Couldn't think about one day the government will set the limit again from 500fps to 300fps something??

_________________
~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

As a final note for today's update, I added a minor mod to the piston to help the intake of air.

I started by adjusting the piston so that there's almost no ''cam-over'', no more than 1/4'' - the Orings were removed during this. Then opened the slide to extend the piston to its maximum ''open'' stroke, then scratched a light mark exactly where the comp. cylinder stops. Then scratched the underside of the piston through the air inlet hole with a dentist pick while cycling the piston (axial mark). I took the piston out and by aligning scratch marks I saw that part of the front Oring and the front piston lip were in the way of the inlet hole. So I ground a small notch in the lip in-line with the axial scratch mark, and now the inlet hole breathes freely.

_________________
If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

LOL! I hope not!

I meant, this could be a way from the factory to lower the pressure needed to close the slide so it doesn't bend under pressure, due to the weaker-than a-P17 design .

_________________
If everything's so lovely yeah, then why don't I, why don't I, why don't I, why don't I feel lovely?

Best way to fix is giving it a metal construction ~

Like a HW45 I think~

_________________
~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

I was an active member on the American yellow airgun forum when the Marksman 2004 was first introduced (year 2004). This was the first Chinese copy of the HW40 and a predecessor of the P17 (aka Beeman 2006). The Marksman was low priced and quickly became popular. However, the bending upper frame became a problem due to plastic thickness. The Marksman 2004 was discontinued and then reintroduced as the Beeman P17 with improved plastic thickness. Some of the Marksman owners posted pics of the common workaround for the bending. They would tape the fake loading ports and fill the barrel channel with JB Weld. The entire barrel was epoxied into the frame to provide support strength to the flimsy upper frame. Apparently the idea worked.

Hmm! Filling up the space between the barrel and the up cover with JB Weld is really a good idea that so easy to apply and have good result both doubt~ :thumbs:

_________________
~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

I always wondered why all Top straps were not made of alloy as in the case of the FAS which does not yield in OEM unmolested state, or when fully modified in a similar way to the original post here.

The early Webley Nemesis (single stroke) managed to keep costs competitive to the HW40 by employing alloy for the entire lower frame…..so it cannot be just a cost issue that you can have no metal in the gun, once you have established the tooling.
I still thought Webley had got things buttock about face with this layout (all the force being applied to the plastic top strap) but at least it was an effort to have some some semblance of metal in the gun, and giving it a better heft than its competitors.
Thinking aloud, maybe because the metal frame was of a cheap die casting, they realised it would not have taken the force like modern plastics might….leaving us with this flexing, but not cracking issue.

I concluded that FAS went the way of more expensive alloy, rather than die cast metal to get around this problem, but then passing on the extra cost to the customer.

One day maybe a manufacturer will offer a reasonably priced all alloy gun of this type, but sadly not so far they aint…