Drumsnguns, I can share my experience with my .22 Impact. I have both the FX Slug Power Kit and the NSA Pin Probe. I also modified my stock probe and TP. Glem.Chally has it right about a DIY modifying the TP port.
I elongated my TP 1mm on both my .22 and .25 (Dreamline), smoothing out the edges to increase laminar airflow the best I could.
All said and done, there were some good points and not so good points about all 3 of them.
Lets start with the first one I purchased, the NSA. I wanted to try the FX "pin" after I modded my original just to compare, of course I hemmed and hawed a week to long and they vanished, dang, now I have to wait for the next batch. But wait, my friend Rick from rmp_airguns says "did you see the new NSA Pin Probe for $80 @ UA?" Boom, I was on it and had one in 3 days. Install is straight forward after you break loose the Black Loctite with iirc 2.5mm allen. Have a good new allen key of high quality or it's over, just say'n. After installing the probe and doing a depth adjustment with blue tape as my guide I was ready. There is an .018 difference in the cam arch movement to max depth and set depth after cocking.
I found that when the NSA pin was adjusted to "maximum slug depth" it was determined by the pin placement, after being cocked to insert the magazine, flush with the backside of the magazine slot. This flush reference point is the "Maximum" depth possible. The difference in depth after adjusting for the magazine insert baseline between the NSA and my stock probe was .050 in favor of the NSA.
The story continues...
Problem #1 with the NSA I discover is that at that max adjustment the taper at the back of the NSA probe is now encroaching on my newly ported TP!!! What have I gained now? I readjust the probe back out so the taper clears the TP. All good.
Now I am tuning for a Slugs. There are 4 I have in mind.
FX Hybrids, NSA 23, JSB KO, NSA 27.5. All very different base depths.
Now is where it becomes interesting.
As you can see the probes offer different depth options in the way it moves the Slug/Pellet into the liner. What you see here is an .075 difference in set depth between a Pin and a modified FX Probe with these slugs. Looking closely you will see that the standard Probe will seat any projectile at "maximum" depth because of it seating from the rim base, whereas the "pin" depth is determined by the center concave depth of the slug/pellet which varies from "0" flat to ".075" FX Hybrids in my collection.
My original probe mod taking only 50% of the diameter away for the mod gave me a 20fps increase and after the TP mod was another 10fps. I will take 30FPS for free as would we all. This 50% amount allowed the slugs to move through the magazine with no glitches and over the oval TP was not a problem for 23gr slugs "dropping" into the TP.
What I learned about the NSA Pin probe is that trying to adjust the large grub screw in the back to set the whole pin probe for a particular slug is, well, that's not going to happen more that once, pick a slug and live with it. The idea that is promoted for "larger and stronger" is a mute point for me. No advantage that I see. It was a challenge to get the grub screw to "catch" the Pin and "jam" it before it turned and changed your depth, was trial and error. Not user friendly. Instructions were frankly non existent other than photos for reference. Installing the new NSA probe did not change my FPS at all over my stock mod with oval port .
Second problem was that my new Saber Tactical cheek riser no longer worked because the probe block was so large it interfered with the screw mount. Oops! bummer.
Opinion: The NSA is well machined, and that is very much appreciated.
I finally received the "FX Impact Slug Power Kit" , took out the NSA and installed the FX with the original probe holder with blue and NO black Loctite. Knowing you could adjust the pin probe depth without moving the main probe body gave me more adjustability for the pin where the probe taper could be adjusted behind my TP and give better flow. 2 adjustments instead of one, Yes!!!. Bingo!!
Did I say you get a .25 sleeve as well !!! FX Rocks.
I will say that I could not install the FX spring and ball part of the kit as I have a Gen I converted to Gen II that had it's Valve spring adjuster " Black Loctite" on so I will need to replace the whole assembly in order to install the new spring and rubber ball, not FX fault but a 3 party that I wont mention...next on the to do list and to test.
So my experience in both my Dreamline and Impact is that the DIY Probe and TP Mod are a great bang for your buck/time. If I needed to purchase a kit, the FX "Impact Slug Power Kit" as a great value for "plug and play"
As we know YMMV.
I hope this helps.
Be safe,
Patrick
