Great looking rifle, you are lucky to own such a nice example.
Now, to keep it nice, I recommend reloading for this rifle and not using modern off the shelf ammunition. Port pressures will over accelerate your bolt and cause rail damage. I would advise anyone using these rifles to not use heavier than 150 grain bullets, keep velocites around WW2 levels (2700 fps) and to use powders no faster than IMR 4895. I have shot a couple of pounds of IMR 3031 in the M1a, our Club President uses it all the time in 30-06, so it should work just fine and as it is faster than IMR 4895 and the pressure curve should drop sooner. High residual breech pressure will beat up a gas gun.
This is a lot of information about M742's in this thread, most of it taken from Wisner's web page. Wisner's deleted their excellent advice and observations but someone copied and retained it.
Another 742 post?
The important information about rails from that thread:
One of the most common problems with the Remington 740 & 742 is that after much use the receiver rails will get worn. These rails guide the bolt lugs on the movement both rearward & forward. The receiver is made of a soft metal since the bolt lugs engage the rear of the barrel for a positive lockup. The receiver simply holds the parts together.
This movement is under gas pressure on the rearward movement & spring pressure on the forward movement. At the rearward stop position the inertia of this bolt lug exerts extra pressure caming it against the receiver rails, pounding them enough that they get worn. There is a bolt latch on the 742 (this latch was not on the 740), this latch is supposed to lock the bolt head into the bolt carrier to help keep the front from over-rotating at the most rearward inertia's movement, but after wear on all parts, things seem to get sloppy & do not function as intended.
When this happens the bolt lugs, now slightly out of time, having been moving back & forth, may also chew up the front of the rails. Then the bolt carrier & lugs can get bound up & in extreme circumstances actually stop the bolt unit from cycling when the gun is fired, or binding it on the return stroke enough to stop it before it completely closes.
Under some circumstances the operating handle may drag, usually on the bottom of the receiver slot that the handle operates in. If this happens it is usually related to the above rail problem.
Since there are no new receivers available & the only used ones could be questionable in that may possibly be worn also, A GOOD gunsmith/welder/machinist familiar with firearms can usually salvage the receiver by welding the worn rails with a special long nozzled wire feed or heliarc welder. This receiver can then be re-machined to factory or tighter dimensions on a vertical mill using special long cutters. This is not a job for the average "gunsmith" however.
It is my opinion, understanding I don't own one, that the absolute first thing to do is not use high pressure commercial ammunition, but to use reloads that are low pressure during combustion and during unlock. Also use 150's or lighter bullets. All of this is to slow down bolt cycling so the lugs take longer to chew up the rails.
And, keep the chamber clean. Get a chamber brush clean the chamber each and every time you come back from the range. Clean the chamber, oil it, oil the lugs, the carrier, and get all the carbon out of the gas system.
