Re: FS SWFA SS 5-20x vs. VIPER PST 6-24X50???
I've had both.
The SWFA has the edge on glass clarity and durability-- I've killed 2 6-24 FFP PSTs just from recoil on a braked .338 winmag hunting rifle. Debris inside the scope happened first and then the POI wouldn't hold as the reticles came loose. They've been perfect after being cleaned and repaired (quickly!) by Vortex here in the USA.
The PST has a more "conventional" reticle that appeals to me a little more than the SWFA mil-quad although the SWFA does give you some interesting options for shooting small targets as you can dial one mil up or down and use the little dot in the middle of the diamonds. Ranging/holdovers on either reticle is fine but there's a little more memorization required for the SWFA. It's more an issue with spending enough time to know it rather than a limitation. The turret markings are more widely spaced and easier to read on the PST; if you do a search on the SWFA the majority of the bitching stems from the knob to turret interface having 60 splines where the actual erector mechanism has 100 clicks/marks per rev. What this means is that depending on where your zero ends up the turret might index in between hash marks.
If illumination matters to you the PST is full illumination where the SWFA is only an illuminated center dot; the PST does the better job here.
If you pick up both scopes the additional heft of the SWFA is the first thing you notice; the PST feels like a toy in comparison because it's so much lighter.
Both the SWFA and post-repair PSTs have tracked well.
My suggestion would be to snag a new or very lightly used 5-20HD off the classifieds here and save a few bucks over new. However, the PST is still a very good option and will save you a few bucks over a used SWFA.
While you didn't ask, in my experience a better comparison to the SWFA from the Vortex line is the 5-20 Razor HD. Given the choice between a PST and the SWFA I'll choose the SWFA every time without hesitation but ask me to choose between the Razor HD and the SWFA and the choice is much more difficult. Having spent a lot of time behind my 5-20 and a friends Razor HD, money no object I'd give the edge to the Razor but if you factor in the "special" prices available on the SWFA in the past and what you can snag lightly used ones for the SWFA wins the price/performance contest and really doesn't give up much IMO.