The PMI-I is the big brother to the PG / PGP. With a 10 round top tube and longer barrel for better accuracy, the PMI-I was an extremely popular and customizable gun. It was also available in a rarer direct-feed. The PMI-1 served as the prototype for the later P-68 and P-68sc.
The Sheridan PMI-1 is newer, so it should be commonly available, both new and used.
PGP- The shorter version, 'rimfire' bolt system.
PGP2k- Newest and last Sheridan actually made from brass, longer barreled than the original PGP, speed gate for quicker reloads and more aggressive threads on the Co2 knob to make that faster as well.
McMurray and Sons Annihilator- Open class Sheridan style marker, longer barrel than the PMI-1.
Palmers Pursuit Shop Pug- Basically Palmers version of the PGP, with all sorts of Palmers hotrodding.
'The Legend' Phantom, made by Josh Grasby of Avratech.
Avratech Falcon Pre-production model. 1-10.
Nelspot Challenger II.
See review for details.
Stock form drawbacks, see review for details.
The Sheridan PMI-1 is most definitely and 'old guard' marker. One of the first paintball markers out there to reach popularity as both a renters holy grail and the owners rifle. Built as the bigger brother of the PGP pistol, and later being the middle of the family when the P-68SC and AT hit the market.
The main selling point of the PMI-1 over the PGP relied on the fact that during the early days of paintball, the longer the barrel you had, the more accurate and further range you could hit targets at. This is true to some extent, however not nearly as much as was assumed in the early days. It was more accurate at range because the paint was impacted from directly behind it and hard a longer barrel allowing the paint to stabilize from the blast before it was out of the barrel. On average 8 inches is the minimum needed to allow paint to do so, so the PMI-1 was indeed a bit more accurate.
It was also the basis for many, many modifications both in the garage and shops, as with most Sheridans, the brass and solder were easy to tear off and modify in all sorts of ways.
In its stock form, during its day, the PMI-1 had no real weaknesses, since all markers had just about the same limitations, which is why the home-brew arms race has left so many of them in curious forms.
However, in todays world, a stock PMI-1 is a slow and cumbersome marker to reload either paint or co2 powerlette on the field, and its easy to loose the stock feed plug if you dont have a leash on it or have it replaced entirely. The co2 knob threads are incredibly long, and take a long time to fully release, load and tighten back down. Stock models also did not, like most early paint guns, did not have an easy way to adjust velocity through a rear velocity adjuster or bolt defuser. This means that the only way to adjust the spring tension is by either clipping it down, or shimming it in order to raise it, but this can lead to problems with cocking the marker.(Later models of the PMI-1 did seem to come stock with a bolt with a defuser screw in it, but Im not sure on this.)
The PMI-1 is a relic of earliest days, and its becoming more and more rare to find one in good shape.