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MGySgt USMC (ret)
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Back in the early 70's when we first started making NM spring guides in the Marine Corps, we made them from round drill rod and silver soldered the rear of a standard spring guide to them. We put a rather long taper on the front so they would not interferre with the op rod spring functioning. We did not harden the drill rod. We silver soldered the first ones, but then switched to Tig Welding the rear part on later on. When those guides were made correctly, they lasted for a surprisingly long time. However, when they were not made correctly, they could screw up function or accuracy even the first time they were put in place.

When I find one of those older style NM op rod spring guides (ORSG's) in a rifle, I check them the same way we checked them in the 70's. First, get something that is FLAT and a good 6" steel rule works well for this. Lay the rear portion of the ORSG down flat and hold it flat on the surface of the rule. Then look at the side of the ORSG to see if the forward round section is PARALLEL to the bottom of the rear of the ORSG. If it is not, you MAY be able to file the bottom rear of the ORSG to get the front section parallel, but most of the time you can not. If the front section is not parallel, it will cause undue rubbing on the op rod spring that will harm function and/or accuracy. Best to throw it away.

The second test is to look at the ORSG along the top over the full length. If the forward part of the ORSG is not in line with the rear, then throw it away because it will also cause undue rubbing on the op rod spring and hurt accuracy and/or function.

If the silver solder or Tig weld is cracked, best throw it away. Unless you know how to do Tig welding, it will not be econonmicable to repair it.

The simple solution if you want one of the NM ORSG's is to buy one from Sadlak, Badger Ordnance or if you can find one of the older Brookfield ones. They all are/were well made.

Having written this, I have to state I'm not a huge fan of using the NM spring guides in anything but a NM or ultra long range rifle as I just don't believe they will give most folks any accuracy advantage they will actually see on targets.

I HAVE noted people saying they used one of these NM ORSG's and that they seemed to "smooth out" the function of the op rods. That may well be true, especially if you have a loose Op Rod Guide on the barrel or if the Op Rod guide has not been properly aligned so the front of the op rod is centered on the rear of the gas piston tail. But pardon me if adding a NM ORSG to make up for this seems a bit a$$ backward method to fix that. The correct way to fix that is to knurl the barrel or glue the Op rod guide on so the op rod IS aligned with the tail of the op rod piston and then you don't NEED another part to "smooth things out."

Years ago I decided to glue ALL Op Rod Guides on any semi auto M14 I built so they would always align with that op rod for the life of the barrel. I even do it on "rack grade" or "Standard Infantry Rifles" I build. The op rod is going to outlast two or three barrels or more. Gluing the op rod guide ensures you never have to worry about it coming loose or your op rod binding or not centering on the gas piston tail. It actually makes the rifle a bit MORE reliable for all future use with that barrel. So MOST of the rifles I work on, I advise folks use the standard op rod spring guide. That doesn't mean I won't install a NM ORSG on a rifle for a customer, but for many/most rifles, I don't see the need.
 
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