Back in the late ‘80’s, I lucked into a trade for one of the rarest military semi-autos in existence, the Sig Stg 57. The one I had was imported by Sarco (IIRC), and was in mint condition, but was lacking all the accessories and box. I got it for a fraction of what it was worth. There is so much on the internet about this rifle that just isn’t so.

To look at it, it’s an ungangly, rather odd looking rifle. Kinda like someone stuffed an FG-42 and an MG 42 into a blender, and out came the Stg 57. But the rifle actually had good balance and pretty good human engineering (Much better than an M14, but not nearly as good as an M16). With your hand on the tiny rubber forearm, your arm was extended just the right amount. The straight line design of the rifle had the bolt traveling right directly back to your shoulder, which resulted in an extremely smooth, full powered battle rifle. Recoil was much like a 7.62 AK that has a ’74 style muzzle brake, which is to say, nearly non-existent. Now I’m sure if you flicked the selector from individual to “group therapy” that smooth “non-existent” recoil would probably quickly become unmanageable. But then consider that you only have an aluminum 24 round magazine and the rifle has a bipod like a GPMG, so before things got too out of hand, you’d probably be out of ammo.

The bipod was rather unique and interesting in itself. It consists of aluminum legs with some sort of measuring marks on the inside (never did find out what they were for, kinda like a ruler). The bipod could be locked in two locations at either end of the aluminum (most say it’s steel, it’s not) ventilated barrel shroud. And when on the bipod, you can rotate the rifle 360 degrees. Still the bipod didn’t have positive locks, and it was very easy to begin to collapse one of the legs. Not that I had much opportunity, because in the whole year I had the thing, I doubt I put more than 80 rounds through it because I just couldn’t afford to feed the thing. Back then, the Stg 57 was still very much in use, having not been replaced by the Sig 550. So surplus ammo was nearly unheard of, and the only ammo I cold find was Norma match at around $35 per box and I was a very poor, lowly Paramedic in the days when Paramedics were horribly under paid (though I’m sure most Paramedics would claim to be under-paid now, but believe me, it was MUCH worse at one time).

The first 5 rounds that I fired out of that rifle with open sights dropped into a cluster of .78 inch; aaahhh, the days of youth and 20/10 vision. One of the few times I wisely, unloaded the rest of the magazine, put the rifle away and called it good, because I knew I wasn’t going to repeat that feat; and I don’t think I ever did. Still, I don’t remember shooting a group of over 1.5 MOA with that rifle, and I did shoot many sub MOA groups with it using the issue sights.

I did flirt with making my own ammunition when a friend let me borrow his 7.5 Swiss dies. The body of the case is larger than the .308 so I had to use .284 Winchester brass that was re-formed into 7.5 Swiss cases. With that recipe, I struggled a bit to find the right load that would function the rifle, but not give too much stick in the chamber, because the extractor didn’t have the best purchase on the rebated rim of the .284 parent case. Still, accuracy with Hornady 168 grain match bullets was excellent.

And speaking of extractors, the Stg 57 had a most interesting and unusual extractor that doubled as a “controlled round ejector”. The extractor / ejector would slightly spring one way (extractor mode) and cam the other way (ejector mode). The extractor / ejector was pushed (in the ejector mode) by a scallop in the stamped receiver when the bolt travels back giving the case a gentle push rather than a sheet metal tab that kicks cases out like nearly every other rifle in the world. Kinda cool in a typical block head Germanic-Swiss over-engineered sort of way. The consistency of ejection and the design means it’s REALLY built for the long run. Since it’s an easy push, than a slamming, jarring action, I can’t imagine this is a system that fails often if ever.

Disassembly was very easy, just push a lever, twist the stock, pull one pin, and the whole thing falls apart. Internal machining could be a case study in how machining is done. Many parts exhibited a high degree of polish, much like the internals of a fine sidelock shotgun. The sights were both excellent and crappy at the same time. Adjustment was very easily done for elevation, but you need a tool for windage, however; the sight picture was excellent and resembled target sights. The real weak point was the fact that both front and rear sights fold down, and it didn’t take much for them to begin folding. One little bump in the field and they snap down; that was annoying.

There was a very slick winter trigger system that consists of a lever that folds up parallel to the trigger housing. When wearing gloves or mittens, you just fold the lever down that extends far beyond the trigger guard and pull with multiple fingers.

On many of the Sig’s, if you look just above the trigger guard, about half way up the receiver, you’ll see a small white rectangle. That rectangle is the semi-auto conversion. Basically, it’s a small sheet metal tab that you wedge between the upper receiver and the trigger housing and it simply prevents the selector from moving to the full auto mode. If you ever need it as a full auto, you just pull the pin that holds on the trigger housing, slip that off, and it’s a selective fire weapon again. Of course the US versions lacked the “happy button” parts, but they still put the little white tab on there.

Also, if you look closely at the trunion section of the rifle, you’ll notice there’s a “C” clip on either side. The “C” clip holds in the locking blocks for the trunion. So when you wear one out, you pull the “C” clip, drop in new one’s, check headspace and you’re done. Essentially, a gun rebuild in about 2 minutes; very slick.

Just a few more brain droppings for those who may be interested in such things.

Sounds like just the thing for a rifle squad, allowing flexibility in a choke point. One person or a group, some can use it as LMG and some as a rifle.