Some are but I think Grant takes great pride in making sure the ones he gets are all to the correct spec.
Printable View
When I said I got it from Grant, I hope that didn't come across as a stab at him. That wasn't the case. I've never gotten anything but top-notch service from Grant, but to be quite honest it's a $3 part and I haven't lost any sleep over it not working out for me.
I may have been able to get a couple thousand more rounds out of that one but I use that upper for HD so I didn't feel comfortable with it. I replaced it with some new standard rings that I had. I may order some McFarlands from Grant and try one of them when these rings wear out. DSG has two different part numbers listed for their rings so its hard to tell what you're getting.
I run HK and.... it has gas rings :happy:
I actually prefer gas rings to wear out instead of piston or cylinder. They are easy to diagnose before they fail and then easy and cheap to replace.
BTT I had McFarlan ring installed in my Stag (it was only AR15 avaliable in Poland 7 years ago) and zero problems in several K rounds. Next owner also had no problems with it. Initially it was rather tights inside cylinder (bolt carrier), but loosened up a little in first thousand rounds and then stayed this way.
This makes prefect sense. Rings on bolt, when do not seal gases in "DI" configuration, also work as a guide to centre bolt tail inside carrier. HK uses modified bolt, with special "guide" surfaces, so does not need ring on bolt any more, but if "piston AR" uses "standard" bolt, then rings are still needed here.
From what I understand of combustion engines, rings will press against the cylinder wall under the compression stroke.
Further, with a McFarland, you have only 1 "gap". With the regular gas-rings, you have 3 "gaps". This means to me that the regular rings can have much more variance and still make up for it with expansion that, since each ring has its own "gap", will not harm function nearly as much as an out of spec McFarland---whether through use or manufacture or foreign debris.