You could read more about the weapons of Star Wars here: http://www.partsofsw.com/index.htm , mine is BlasTech E-11 Stormtrooper Blaster Version C (also used by Han solo in shooting the comm panel in the detention cell bloc scene). Or you can look here in the Behind the Scenes section: http://starwars.wikia.com/wiki/E-11_blaster_rifle
Quote: "The E-11 blaster rifle prop was built from a British-made Sterling L2A3 sub-machine gun. To give the actors something to react to and to give rotoscoping artists timing reference when animating blaster bolts, the E-11 rifle props in the original trilogy—which were still fully operational firearms—were loaded with blank cartridges that were then fired to provide a practical effect. Because of this, expended 9mm casings can be seen ejecting from the props in several scenes in A New Hope, particularly during the assault on the Death Star's detention level. This can also be seen briefly in a closeup of Lando firing one in The Empire Strikes Back."
The pic below shows a real Sterling and an ROTJ E-11 blaster (mine is ANH).
Now a short comparison of the blasters I have: Sterling SMG, MR (I have 2 MR blasters, one complete with everything, and one loose), SDS, and Hasbro (unmodified).
The Master Replicas version is quite cool, but is about 90-95% accurate. The cocking mechanism (handle) and the spring on the right side of the real SMG is completely missing on the MR, that part is just a bit dented as a shape to what it should have been there, but no real hole. I know there were 501st customizing it and cutting that out, but is a hell of a job to do it since MR is metal too.
The weight is almost identical on both SMG and MR, thus quite impractical for 501st for trooping - heavy and not very comfortable. Trigger on MR is not working, neither is the A/S selector switch. The folding stock is one of the cool things MR could have done to make it work - I've seen people upgrading MR E-11 to have folding stock and seems it was not very difficult. Since MR is a static prop is understandable on all these points. It is a bit tricky to completely unfold the stock on SMG, but once you get the trick it is really fantastic - you need to push the end cap of the blaster in and also push the underside button (they both have springs) and only then the stock will open up completely and fit in the back perfectly.
My T-tracks seem more accurate than the MR ones, so is the scope (original M-40). But still the MR scope seems to be an exact copy after M-38/M-40 tank scope anyway (so quite accurate), and not after M-19 (which also were used on E-11 blasters), of course the MR blaster scope has that red computer targeting grid, which is very cool on its own. The MR blaster is cleaned up looking very pristine, also having all the specific numbers and codes removed (maybe because of the gun laws).
The SDS E-11 is copied after a similar real Sterling which belongs to CfO, and thus is very accurate, on some components even better than MR (SDS does have partial cocking mechanism and even a spring like tube inside, plus a Hengstler counter copy and metal cylinders), on others it looses some sharpness, but being made of plastic is kind of understandable. After all the SDS blaster, as being made of PVC tubing and plastic/resin, is excellent for trooping but will look cool on display as well.
The Hasbro Stormtrooper blaster is what you see LOL, unmodified it looks very inaccurate, but with some upgrading kits it may look cool too. Of course there are other fan made blasters or kits like hyperfirm or doopydoos which are very accurate, but more expensive than Hasbro version.
In the end both MR and the SDS are quite accurate on their own, some work may be done on both to make them even more accurate, but they are very cool nevertheless. But none is even close to holding a piece like the real SMG. The seller told me I won't let it off my hands and he was totally right. Now just to get a cool stand for it - working in progress already
It seems there as many as 6 or even 8 different versions of E-11 in ANH (according to different scources), some with all greeblies (Hengstler counter and cylinders on the magazine - like SDS), some with just the Hengstler, some with just the cylinders (like Han's - and mine) and others with nothing (like MR).
Mine just looks like this one:
Or here: http://www.partsofsw.com/index.htm it is like the BlasTech E-11 (Stormtrooper Blaster) ANH Version C aka Han Solo's blaster from the detention cell block, when he is shooting at the comm panel. It seems the seller intention was indeed to make it like that, that's why no Hengstler on it, just the 2 cylinders.
BTW an interesting read about how deactivated guns are allowed but not replicas LOL. Really stupid...