I bought one of these uppers years ago and was never able to get it to run reliably. I know they need lightened hammer springs to run, which is a little bit inconvenient.  Even though, I never could get more than maybe two or three shot bursts out of it. I was convinced it had just some problem with it. I recently sent it back into Eric at BSG gun works to have it run through. He upgraded to the latest X1 top cover.  I'm curious if we have any members that have the razorbacks functioning reliably? I'd love to hear what you did to get it to run or what I should do.

The main key to any 22lr conversion is smoothing out the action.  The round has very little power and all of it must be available to cycle the action.  Anything that rubs, has burrs, etc. must be smoothed out.  My LM7 had a raised spot on the flipper cam that would bind up just a bit every few rounds, just enough to cause a light strike on full auto.

Remove the recoil spring and gently move the bolt back and forth looking for high spots and rubbing.

Belts have to be well broken in (loose) and it’s really picky about ammo. I can go 1-200 rounds then it’s so dirty it starts to malfunction.
When it works it’s amazing.

I sent it back to Eric at lakeside to have him run through the upper. I didn't want to start troubleshooting it until I knew for sure the upper was in good working order to start with.  I followed his directions regarding my lower.  I installed a 4 o'clock hammer spring to reduce the pressure.  Then I stoned and polished my hammer face.  Then I radiused, stoned, and polished my auto sear to remove hammer dip.  I also polished and stoned all of the engagement surfaces.  I ran into an issue with the bottom of my razorback bolt galling up from the hammer riding against it.  This occurred just after the hardened pin which I assumed was meant to take the impacts to reset the hammer.  I relieved some of the aluminum from behind the pin to hopefully prevent it from riding, but I'm not exactly sure how far that hammer rides back past the pin.  After relieving I can see that there's still some galling forming behind the pin, so I assume the hammer must ride past it to some degree. I'm not sure if I'm going to be able to fix that or not, or if that's just normal operation.

I slowly was able to get the upper to function better, with more polishing and optimizing.  The best run of the day was a 100 round belt from start to finish. Most of the time I'm getting 1 to 2 malfunctions per 100 round belt. Granted, these are different belts of varying usage, and I tried two different kinds of ammo. My go-to ammo is Blazer, but I also tried some federal bulk pack which Eric said should work.  I couldn't really tell much of a difference as far as reliability goes, but it seemed to like the blazer slightly better. I also experimented unsuppressed and suppressed.  Usually my 22 uppers always function better with the suppressor given the added pressure.  However, I was having issues with the suppressor on it and I wasn't exactly sure why. I took the suppressor off and it started to run pretty well, but after I installed it back on it seemed that it was just in my head.  After about 600 plus rounds I started getting occasional malfunctions and I couldn't tell if it was just the ammo, the belt, some issue in the action, or just the fact it was dirty from 600 rounds.  At the moment I'm going to clean it really well, look over all the components, and try again.  

One issue I have is I don't know anybody that owns one of these uppers, and I really haven't had the opportunity to speak to many people that have functional razorback uppers.  The problem being, I don't know how reliable these things are supposed to be. I don't expect it to run a thousand rounds like Eric's did in the YouTube video we've all seen, but it would be nice to have it get through a hundred round belt somewhat reliably.  I bought 20,000 rounds of 22 after that last shortage, and unfortunately it seems like I'm probably going to run out during another shortage.  This thing definitely eats ammo, especially when you turn an entire brick into just belts.

Provided I can get it to run a little bit better, I always found those auto belt loaders rather interesting, but I know Eric only made 10 of them. I've considered emailing him or calling him to ask if I could possibly get his drawings for that loader, but I'm not sure how he was would receive that. I think with current technology, and I have all the machinery and tools to make them, I might try making one for myself.

I dropped my Lakeside upper and Colt M16 off with Eric, way back when.  When he was finished it just runs and runs.  It is finicky with certain ammo and cloth belts work well.   Never tried the plastic links.

I bought a Razorback for parts when Eric decided to shut it down.  Never used it, so I don't know about the Razorback, mines the original version he came out with.  Got enough parts to hopefully keep it running and a spare barrel or two.  

It really is pretty cool.  I should get it out again, it's been awhile.