I decided to start a new thread to hopefully get more people to read this.
I have a RRA style (same parts but not bought from RRA) 9mm upper, VM Hytech mag block and a Bushy lower. 9mm hammer and buffer.
Originally I had only USA Magazines. Even with them the gun worked fine for a few hundred rounds.
I really want to stress this:The gun worked fine for a few hundred rounds.
This is why from the start I wasn't too convinced that this was a magazine issue.
How could the mags become an "issue" suddenly after first working quite well?
Anyway, that seemed to be the only explanation anyone could come up with, so I spent some serious time, effort and money to get better mags and ended up with Mec-Gar ones.
I tried them finally today and the problem still persists.
Sometimes the gun will fire up to 20 rounds without problems. Sometimes it misfires several times in a row. Most of the time I get maybe 4-5 misfires for 20 rounds.
When it misfires, the primer will have a light strike mark.
When I pull the bolt open after a misfire, the cartridge usually sort of stays halfway in the chamber, the extractor doesn't pull it all the way out. If I then let the bolt slam closed on it again, it will usually fire.
I noticed today that at least some of the misfired cartridges have had the bullet pushed a bit into the case - some kind of partial misfeed which takes enough velocity off the bolt to keep it from closing properly?
Couple of other points that may or may not tell someone something:
I can't see anything wrong with any of the parts of the gun when I take it apart, including nothing I'd interpret as unusual wear, scratch marks or anything like that.
The mag block is an extremely tight fit in the lower, takes force bordering on violence to insert and take out.
The USA mags are very difficult to insert, they don't want to lock properly. I tried to file the mag catch hole on one, but it didn't help. After I filed a bit more, the mag now misfeeds 100% of the time.
The Mec-Gar magazines are also a bit tight fit in the sense that it takes a bit of force to get them to lock, but not nearly as much as the USA ones.
To me it would seem that something keeps the bolt from closing properly sometimes, and then the hammer hits the bolt and not just the firing pin, and the gun misfires. But what causes it and what to do about it? Or could it be something else?
I'm all out of ideas and getting so fed up and frustrated I'll soon be tempted to just bury the damn upper in my gun safe and try to forget it exists