I put together a 22 upper this weekend and I’m having lots of issues.
I’m using a CMMG left hand conversion kit, and LH extension. Barrel is 12.5” Beyer barrel. LH Stag receiver. Raptor charging handle with Bore Buddy insert, and Silencerco Sparrow.
Lower is my SBR, A5 with Bore Buddy insert, Better Mag adapter with S&W 25 round mags. Trigger is G2S.
Ammo has been CCI SV and semi auto quiet.
It’s basically a single shot. Failing to fire with obvious strikes on rim. Failure to extract same unfired cartridge.
Also the mags don’t like locking in. Is that normal for the better mag adapter?
CMMG mag seems to lock in to my lowers.
Lastly, how does the forward assist adapter install?

The forward assist adapter slides in behind the bolt and I believe there is a stud which fits in a corresponding cut out on the rear plate of the conversion kit.   I suggest you try to get your gun running with a CMMG mag or a Black Dog Machine mag first.   The BMA can take some tweaking to get it to function.   The CMMG mags have nubs on the spine of the mags that require filing to permit a proper fit to the mag well.  Make sure your CMMG mag is being inserted far enough into the mag well to seat and lock into place.

I also suggest you try some high velocity ammo.  Normally 22 conversions take a little time to wear in.   Once you have some ammo run through the rile and have it functioning you might try some sub sonic ammo.   I wouldn’t trim the conversion bolt recoil spring until you have several hundred rounds through the upper.  I’d only trim the recoil spring as a last resort to get proper function with sub sonic ammo.   Some forum members have had luck polishing the conversion bolt and rails.   I never did this but I run my conversions well lubed with CLP and high velocity ammo.   My CMMG dedicated uppers run near 100% with Federal 525/550 bulk and Winchester 555/333 bulk ammo.

Normally a suppressor adds back pressure which helps 22 rimfire semi autos.  I’d test your new upper with and without the suppressor with a couple different kinds of ammo.   The CMMG  conversion kits were designed to work with High Velocity 22 ammo but most will function with CCI standard velocity after the conversion kit or dedicated upper is worn in.

I’d also check the extractor and how it seats into the barrel collar for proper fit.  Most conversion kits and dedicated uppers have difficulty extracting live ammo and even fired brass can be difficult to extract using the charging handle.   I would clean and lube your upper and try it without the suppressor and high velocity ammo with a properly fitted CMMG mag.  If the kit fails to cycle load one round to see if it will fire.  If it fires and ejects try two rounds.  Many times with a completely new upper or conversion kit they won’t cycle with a full magazine and sub sonic ammo.   A full mag with high velocity can still have added drag by the pressure from the rounds pushing up from the mag onto the underside of the bolt.

Once you get the upper running you can try adding the suppressor.  Once you know the upper functions you might get the BMA adjusted to where you can use the S&W 15-22 mags.   If you continue to have failure to fire inspect the firing pin and spring.  Many times a failure to fire is caused by the bolt not completely closing into battery.  Many times the extractor will not snap over the loaded case’s rim.  If the extractor is not fitted properly the rim might not be able to slide under the extractor hook.  Many CMMG extractors have limited engagement surface to grab the cartridge case rim.   An improperly fitted or shaped extractor will only add to the difficulty of extracting a cartridge out of the chamber.

I’m unfamiliar with the bore buddy but have used mil spec charging handles with CMMG conversions and dedicated uppers without issues.   If you continue to have issues it is best to try milspec parts like a standard charging handle and FCG.  I have used RRA NM and Geissele G2S triggers with my dedicated uppers and conversion kits.   If yo still get a lot of failure to fire and your sure your bolt is in battery check for proper firing pin protrusion and try a mil spec trigger/hammer.  Some hammers don’t interface with the rear of a 22 rimfire style bolt to where the hammer is able to strike the firing pin squarely.

Everything Vascar notes is correct, but  have additional notes on my specific experiences.

The Bore buddy is a great part, but take it out for now.  It's an additional variable you don't need while figuring this out.

Many guns find "quiet" CCI a problem.

That is not normal.  The BMA depends on being inserted to the correct depth to work properly.  Polishing and lubricating the bolt catch part of the BMA can smooth things out.

Ran some Federal Auto Match tonight. 80% reliability via the CMMG mag. Same previous issues with S&W mags. It’s like something is keeping the round from igniting. I’m getting pretty good strikes on the rim, but obviously not good enough. Bummer, I’m pretty invested in the S&W mags. Hopefully this things works itself in.

What hammer/FCG are you using?   If there is any movement of the rimfire bolt assembly in the upper receiver this can contribute to failure to fire.   TACCOM used to sell a pressure plug which set in front of the buffer.   The pressure plug put forward pressure on the rimfire bolt assembly to remove any excess movement.  You can achieve the same thing by taping quarters onto the front of your buffer in the lower receiver.

There have been issues with QC on CMMG firing pins.  I’d inspect the firing pin and ensure the FP protrude far enough.   It might not be a bad idea to remove the retaining pin and inspect the firing pin channel for free firing pin movement.  I’d inspect the firing pin and firing pin spring.   I have seen firing pins break but still stay in the bolt but give erratic ignition.

I have a TACCOM pressure plug in my rifle. I had some FTF issues until I put the pressure plug in. Definitely check the firing pin, spring, and channel.

Bore Buddy sells a pressure plug.

G2S trigger, and I have a Bore Buddy pressure plug installed.

And your FP looks OK?

It's incredible what a shattered mess the FP and return spring can be, yet still give reasonable function. I never know that mine is done until I get feed problems.  I could see a shattered rebound spring jamming a pin.

Well your trigger should be good to go and I didn’t remember the new pressure was bore buddy.   If you can have someone watch you shoot they might be able to see if the bolt is completely closed when you get a failure to fire.   It doesn’t take much for the bolt not to be completely closed to get a failure to fire.   Make sure the end of the barrel and the collar are flush together.   If the fitting is off between the collar and the barrel you could get failure to fire.

Sometimes the collar is loose on the bolt rails or the detent on the collar permits to much movement of the collar on the barrel stub.   Only other thing I can think of his the bolt is dragging on the bolt catch or magazine zapping just enough energy you get an occasional FTF.    Some case rims on 22 rimfire don’t play well with the extractor hook or the  relief cut in the collar for the extractor.   I’d try a hundred CCI Mini Mag round nose ammo or Agula Super Extra plated round nose.   If you still get fail to fire your getting tolerance stacking causing an issue.   You might have an out of Spec CMMG bolt face or other issue.

It would be interested to run some two or three round drills to see if you get any failure to fire.   I’ve gotten batches of rimfire ammo that had the priming compound not evenly distributed in the rim.  Some rounds would fire on the second or third try other ammo would never fire.  I’d pull the bullet, dump the powder and there would be no priming compound in the rim.  Some lots of ammo are worse than others.   Once in a great while I get a box of CCI Mini Mags that has four or five FTF with improper priming compound distribution.  I may shoot several hundred rounds with 100% function then get a bad box.

I’d still pull the firing pin and inspect it and the spring.  If all else fails call CMMG.   Let us know if you get it sorted out.

Pulled the firing pin and spring. It looks fine. Protrusion looks about right.
Loaded 25 mini mags in the CMMG magazine and got 1 fail to fire that refused to fire after 3 tries.
Had about 4 failure to fire and would not extract, did fire on second try.

So, better but still not good and your BMA isn't allowing magazines to seat.

I can only suspect a dimensional problem in the bolt face, barrel breach face, or collar.  Those all need to be right for the rim spacing to be correct.  Do the face of the collar and barrel breach face look like a single smooth surface?

A failure to extract a live round isn't a huge indicator in itself; when chipped, my extraction on a live round is marginal, but it only comes up when a ceasefire is call in the midst of a string.

Sometimes posting excellent close up pictures can help people figure out what is going on.  Photography isn't something I can do, but if it's within your ability close ups may prompt a better dx.

I built a similar upper for my daughter to shoot 4H with and had a few issues. The FTF problems seemed to be an ammo issue for the most part.

I used Wolf Match Target to sight it in and ran a few round with no issues but when I got her on the range with a new box it was FTF almost every round.

I came to realize Wolf switched from SK to Eley for their manufacturing and the gun just did not like the Eley.

Going back to SK ammo reduced the problems significantly but they continued to exist.

I played around with it and the firing pin protrusion seemed sufficient but the spring felt a little stiff so I found a spring pulled from another old conversion bolt that felt softer and swapped them. That seems to cure the issue until the bolt gets a little dirty.

The bolt seems to have almost zero tolerance for any fouling on the face. When it starts having issues now I just have to take pick tool and clean any build up and it’s  fine again.

After about 500ish rounds it started to have issues again but mainly chambering rounds. I assumed it was just getting dirty and ran a bore snake through it a few times. The next weekend it did fine at first but started back up.

I ended up tearing it down completely during the week and running most everything through the ultrasonic. When doing so I discovered the chamber was deformed pretty badly at the extractor cut and the extractor was boogered up too.

I emailed Clint the pictures and he replied back asking me to give him a call. Talking to him he said I could ship the barrel to him and they would check it out. This was on a Monday and her regional competition was on Saturday so I chose not to send It fearing that it would not make it back in time. He gave me a few tips on how to clean it up in the meantime.

A friend that owns a lgs got me a chamber iron. I used it to straighten up the chamber and lightly cleaned up the extractor cut damage with a needle file. I cleaned up and polished the extractor, put it back together and headed to the range to test it.

It ran fine for about 20-30 rounds and the chamber is deformed again.

My daughter ended up having to miss the regionals due to some school testing so it worked out anyway. I pulled the barrel and was going to send it in last week to see what they can do but the corona hit and I got side tracked. It’s in my back seat now so I’m going to try and ship it tomorrow.

I’m just not sure what caused the issue. I personally feel the extractor cut in the barrel was to deep leaving the chamber edge razor thin and the deformed areas chewed the extractor up in the process.

I don’t know if anything above will remedy or is the cause of any of your issues but it’s been my journey into a left hand 22 upper so far.

Sorry for all the spacing but it’s late and my eyes are crossing when I don’t do it. It’s hell getting old.

Got my replacement kit from CMMG.
It ran a few rounds and then back to failure to fire. The rounds ignite in my other guns.
I ordered some of the steel lip, black dog mags and it's the same.
I don't understand, the rim looks pretty crushed on the rounds not fired.

Just so I'm following...you're using the mag adapter with the 15-22 mags, right?  I've talked to a few people having problems with the ready mag adapter.  There are Catch22 adapters at Right to Bear Arms, these work.  They have been 100% in both of my dedicated .22s.

Failures to extract.  CMMG recommends cleaning every 200 rounds or so.  Screw that.  I got 500% extractor springs from BoreBuddy.  No more failures to extract.

The Geissele trigger you're running, does that have full power springs?  You need full power springs.  The CMMG firing pin spring is stout and needs a full power strike.  They do this to keep it from going full auto, in my experience.  Is the hammer notched or rounded.  .22 bolts don't like notched hammers.

Visually inspect the chamber of your barrel and look for machine marks.  You can put a bore brush on a drill and smooth out the machine marks, if they're there.  You don't need to get rid of them, just smooth them out.

Light primer strikes are either hammer falling out of battery or an obstruction in the firing pin channel.

I've been loving my .22 builds, but having put over 10K rounds through them in a matter of a few weeks, I've seen a bunch of their weaknesses.

Also watch for lead buildup on the bolt face.  This problem will manifest itself as failures to feed with the bullet looking like it wouldn't feed from the magazine.  The built up lead looks like stainless.  I didn't find it until out of frustration, I scraped the bolt with my pocket knife and a layer of lead came off.  I polished the bolt faces and feed ramps to minimize the problem, but gotta pull the bolt and tend to it every 500 rounds or so or when it starts jamming, clean the bolt face.  Since i went with the heavy extractor springs, the only malfunctions I get are either ammo related or due to lead build up on the bolt face.

Most of my FTF issues are caused by the bolt bouncing off the collar and stopping slightly out of battery (about 1/16" or just enough to have the extractor not engaged).  The hammer falling seats the bolt, but then there is not enough power to set the round off, so you'll get a slightly deformed rim, but no ignition.  Most of the times I've had this issue I was running crappy Armscor ammo.  

Rumor has it that BoreBuddy is working diligently on a solution to this problem

I had one do something similar and it was the trigger.  Try a plain Jane trigger and see if it fixes it & isolates the problem.

Well, I finished a new pistol lower today with a standard trigger. Ran a few rounds inbetween rain showers and it seemed to do better.