Some (if not most) commercial carbine barrels have gas-blocks either welded or brazed in place. Universal took to seriously welding their blocks in place at some point in time. I have ran-across a couple of posts' in other forums where shooters have reported failures in this particular design of gas-block attachment. Does anyone know of, or have any comments concerning this method of gas-block attachment as opposed to the USGI design of the integral or swagged block?
Every time I consider the purchase of one of the better commercial carbines, this always haunts me. Out in the jungle, there seems to be a native behind every bush....
That is why when a USGI block fails from someone over tightened the castle nut means the barrel has to be replaced. Welding and brazing doesn't work. Might last for a box or two of ammo but it will finally crack again.
I've seen pictures of a few that were cracked due to nut over-torquing. My question was more directed to the physical attachment of the block to the barrel. The integrity of that particular method of attachment to the barrel and the block itself. The pictures of cracked blocks I've seen have been on barrels with the block welded/brazed in place. I'm sure there have been GI barrels cracked for the same reason, I'm just wondering if the quality of the block itself used on this type of attachment is weaker and more prone to cracking.....for whatever reason.
You could get the commercial carbine and replace the barrel with a GI-spec one (assuming, of course, that the commercial carbine would accept a GI-spec barrel). Sarco has one listed for $149. For a couple oddball projects, I purchased barrels from Criterion (Krieger) and from Auto-Ordnance. They were more expensive than the Sarco barrel.
You also could just shoot the commercial carbine until (or if) the gas block failed before rebarreling.
USGI gas blocks did not use any brazing or welding to be attached to a barrel. Some were machined from the same steel as the barrel at the same time. Others were slipped on the barrel under great pressure then rifled along with the barrel. But they were not attached by welding or brazing.
AB I have owned 3 Plainfield carbines and never had any problem with brazed part of the gas cylinder. I am thinking the problem is over tightening the piston nut and/or trying to loosen a piston nut that is frozen in place. To much pressure on either USGI or commercial gas cylinders with the special wrench can damage the cylinder. SM