Shimming NPSS for more power ...

[SpringerForever]

It's possible to shim the NPSS in at least the Hatsan Mod 125s for more power. Don't know what effect this will have long term so do so at your own risk.

I just swapped a NPSS from one of my Mod 125s .25 into my brother's remanufactured Hatsan Mod 125TH .177 & for some reason there was a huge drop in FPS, ~200, from the OEM spring. Even shimming the NPSS with ~5mm of washers didn't bring it back up to the original power levels. Came within ~100 FPS but compared to the Hatsan Mod 125 .25 it was originally installed in that was still ~50 FPS short of the difference between the NPSS & OEM spring in the Hatsan Mod 125 .25. I've since switched it back. But I included the same ~5mm of washers to the Hatsan Mod 125 .25 so hopefully that will bring the FPS up to the OEM spring #s in, at least, that AG.

The Hatsan Mod 125 .25 Sniper NPSS was shooting the JSB Exact King 25.39gr pellets in the 650s-660s. And in the 710s-730s (mostly lower #s) with the OEM spring. But talk about twangy! Definitely needs some break in! I'm just spoiled with the NPSS/Vortex AGs. Anyvey ... I switched it back to the NPSS but this time added ~5mm in washers so hopefully that will bring the FPS up to that of the OEM spring. I'll find out later today when I chrony it. I'll post an update after I do.

[longhunter]

the only forseeable problem with shimming is, bottoming out the ram. if the ram is compressed too far, you can, at the very least, force some gas out around the seal. at worst, you can destroy the seal completely. if you blow the NPSS, look up N-forcer. they're rebuildable and refillabe. i'm currently looking at one for my patriot. i want to re-chrony it otday, to establish a baseline, then i'll tear it down to measure the spring to match it to a " black label  N-forcer mini-forcer" ram.
on a side note, i was mistaken about the # of pins holding the breech plug on the patriot, there are three, not four. i'm also going to find out what was up with the abnormally high chrony readings i initally posted, for the patriot. i'll post my findings when i get back from the range, later today.

[SpringerForever]

Managed to get two 10 shot strings chronied today in a light rain. Just had to see whether the ~5mm of shim washers made any difference. Apparently not much. ~10+ FPS from the previous 10 shot string avg of ~660 FPS with the JSB Exact King 25.39gr pellet so not exactly worth the effort. But there's a bit of FPS variability from shooting session to shooting session due to that it's hard to pinpoint whether any changes actually produce any effect. For example, two shooting sessions previously, pre-shimming, it produced roughly the same #s as it did today. Definitely noticed temperature sensitivity in chrony #s over the 1000s of pellets I've chronied since I took up AGing again this past April. Even with a JM/ARH piston seal. An o-ring seal is supposed to reduce/eliminate that sensitivity but AFAIK there isn't one available for the Hatsan Mod 125s. And I don't have a lathe handy. Don't think it could be done with just a drill as a makeshift lathe either. At least not so that I'd trust it.

Add to that my lack of confidence in my "Shooting Chrony" F1 chrony, I'm definitely going to do a retest. Got so disgusted with the F1 the other day that I finally just ordered the ProChrono Digital chrony. Something I should've done from the beginning. The F1 has been a whole lot of time wasting. Just out of curiosity I'm going to compare the two chronies end-to-end. I'm going to place one right behind the other & compare the #s. It will be interesting to see if there are any differences. I'll post those results in a separate, newly created thread.

I've researched the heck out of doing a N-Forcer conversion but concluded that it's just not worth it for the FPE #s produced. Based on my research, lower #s than stock. I'd be more inclined to mod a Benjamin XL ram to fit in one of my Hatsans. I think that's a better solution. But even better is just sending in my AG to HatsanUSA to have it converted to the Vortex spring. IIRC it's ~$100 for the conversion. And based on my one Vortex Hatsan Mod 125 .25 Sniper it would definitely be worth it.

[longhunter]

what N-forcer did you look at? red, yellow or black(custom pressure) ? i was considering a black label. just have to figure out what fill pressure i need.
by the way, could you point me in the direction of your resarch info, please? i can't seem to find much information on N-forcer conversions.

[SpringerForever]

Largely based on the chart in this thread:

http://www.gatewaytoairguns.org/GTA/index.php?topic=27585.60

that compared the various rams, I was originally going to try the N-FORCER Mini-Forcer MF19-125 Yellow 200/260/177 bar ram but after some additional research that finally culminated in this thread:

http://www.gatewaytoairguns.org/GTA/index.php?topic=34917.msg324678#msg324678

I decided, no way, no how am I going to screw up my 125 for the equivalent power output of a coil spring. And now that I have a Vortex powered 125 that's especially so since it outputted higher #s than the N-FORCER conversion in the thread above. At least initially.

There's quite a bit of variability in velocity during an extended shooting session & from shooting session to shooting session due to temps. The highest FPE of 30+ with the JSB Exact King 25.39gr pellet was produced by the Vortex during a shooting session that started at 1415 in the afternoon with temps at 79* (feels like 80*) & humidity of 50%. That was for the middle 2 10 shot strings in a 6 10 shot string session that was interrupted with testing of another AG. Here are the #s for that session: 28.74, 29.77, 30.13, 30.18, 29.23 & 27.77. I've owned it for a little over a month now & its 1st FPE #s were 27-28 but it's currently shooting in the 26s-27s. I've chronied it 600 times & have ~620 shots thru it so far so it's nearing the # of shots that the previous Vortex made it to (~700) when its piston seal really started failing (last shooting session produced FPE #s in the 22s).

No failures otherwise on either Vortex. And that's with the stock pressure setting of ~125 bar on the OEM air spring. Max is 150 bar so it's possible to add more air for even more power. I'd like to try for 35-40 FPE out of my Hatsan Mod 125 Sniper Vortex .25 but I'm going to try to increase the pressure by 10 bar increments. Try, as my pump's pressure gauge has a range of 0-250 bar in 10 bar increments so the 10 bar increments are going to be estimates.

If you're still set on trying it here's a link:

http://www.gatewaytoairguns.org/GTA/index.php?topic=24324.0

with two downloadable docs that details the process of conversion on a GTA members' Walther Falcon Hunter (AKA Hatsan Mod 125) .25.

Good luck.

[aj.allen92]

Question for anyone familiar with the hatsan 125 sniper vortex .25 cal!!!:
 It is a serious gun and deserves that feel to command respect but right now I want to be able to make that thing as light as possible so when I go out hunting its easier to manage. Are there any deadweights in the gun that can be removed / anything that could be done to make it lighter?

Any help would be greatly appreciated!

[Privateer]

Take the stock off once. You'll see that most of the weight is the metal parts.