Does anybody know how to properly tune BoreBuddy Weights to work with a Rare Breed FRT-15 in a dedicated 22LR AR?

Yesterday I function tested the lower with forced reset trigger using 5.56 and 9mm uppers. The trigger is fun.
Today I'm trying to get it working with 22 upper, but having hammer follow issues, which I contribute to bolt bounce. I am seeing FP mark on unfired rounds.

Registered SBR;  
PSA Lower, H3 Buffer, standard carbine spring;
Taccom3g pressure plug;
Redi-Mag Better Mag adapter;
Rainer Arms 22 upper, Taccom3g barrel, Taccom3g barrel collar, CMMG Dedicated Bolt Assembly, CMMG Sear Trip;
BoreBuddy Bolt Weight.

The 22LR barrel is 4.5", and running a SilencerCo Sparrow.

Without BB Bolt Weight, one round would fire, eject, and new round would load. Dead trigger, safety could not be rotated, meaning hammer was not cocked. This continued with BB Bolt Weight housing installed with no weights, and continued with aluminum weights installed in BB.

Started getting occasional bursts after swapping out one small aluminum with small stainless weights, but most of the time it was single shot with hammer resting on fresh round. Got a little better after swapping out one large aluminum weights with stainless weight.
Will try swapping the remaining small aluminum rod with a small stainless weight, and will continue playing with the weights as needed, to include working into the tungsten weights that came with the BB Bolt Weight set.

At the moment I'm running the lower without Redi-Mag Better Mag adapter to insure it isn't interfering with anything. Ammo is loading and ejecting properly. Not having any FTF, or FTE.

I'll report back what I learn, and I'm hopeful others who are getting these forced reset triggers to work in dedicated 22LR AR will share their experiences.

Using CCI Mini Mags, but I did briefly try CCI Standard, Stingers, and Federal bulk box.

Stopped for the day. Tried:
Bolt assembly without additional weights. Single shot, eject, load, hammer resting against firing pin.
Installed Bore Buddy Bolt Weight, but with no weights installed.   Single shot, eject, load, hammer resting against firing pin.  
Installed all aluminum weights (two small and two large) in BBBW. Single shot, eject, load, hammer resting against firing pin.
One aluminum small weight, one stainless small weight, two large aluminum weights. Had a burst, as well as single shot, eject, load, hammer resting against firing pin.
Two small stainless weights, two large aluminum weights. Had a burst, as well as single shot, eject, load, hammer resting against firing pin.
Two aluminum small weights, one large aluminum weight and one large stainless weight.  Had a burst, as well as single shot, eject, load, hammer resting against firing pin.
One aluminum small weight, one stainless small weight, one large aluminum weight, and one large stainless weight. Had a burst, as well as single shot, eject, load, hammer resting against firing pin.
Two stainless small weights, one large aluminum weight, and one large stainless weight. Had a burst, as well as single shot, eject, load, hammer resting against firing pin.
Two stainless small weights, two stainless large weights. Had a burst, as well as single shot, eject, load, hammer resting against firing pin.

Using CCI Mini Mags, but I did briefly try CCI Standard, Stingers, and Federal bulk box.

Tomorrow I'll try installing Fostech Extra Power 22LR Recoil Spring, and I still have two small and two large tungsten weights to experiment with.

One detail I didn't mention above, the CMMG Sear Trip is timed to my lower with Rare Breed installed. It fires when bolt is closed, and will not fire when bolt is 0.028" OOB.

Using my wife's simple food scale that reports grams as a whole number (no decimal), I recorded the following weights for Bore Buddy Bolt Weight kit:
37 grams Bore Buddy Bolt Weight with no weights installed
43 grams Bore Buddy Bolt Weight with 4 aluminum weights installed
51 grams Bore Buddy Bolt Weight with 2 small Tungsten weights installed, and no large weights
54 grams Bore Buddy Bolt Weight with 4 stainless steel weights installed
55 grams Bore Buddy Bolt Weight with 2 small Tung weights, and 2 large Aluminum weights installed
58 grams Bore Buddy Bolt Weight with 1 small SS weight, 1 small Tungsten weight, and 2 large SS weights installed
62 grams Bore Buddy Bolt Weight with 2 small Tung weights, and 2 large SS weights installed
62 grams Bore Buddy Bolt Weight with 2 small SS weights, 1 large SS weight, and 1 large Tung weight installed
64 grams Bore Buddy Bolt Weight with 1 small Aluminum weight, 1 small Tung weight, and 2 large Tung weights installed
66 grams Bore Buddy Bolt Weight with 1 small SS weight, 1 small Tung weight, 1 large SS weight, and 1 large Tung weight installed
70 grams Bore Buddy Bolt Weight with 2 small Tung weight, 1 large SS weight, and 1 large Tung weight installed
70 grams Bore Buddy Bolt Weight with 2 small SS weights, and 2 large Tung weights installed
72 grams Bore Buddy Bolt Weight with 1 small Aluminum weight, 1 small Tung weight, and 2 large Tung weights installed
75 grams Bore Buddy Bolt Weight with 1 small SS weight, 1 small Tung weight, and 2 large Tung weights installed
78 grams Bore Buddy Bolt Weight with 4 Tungsten weights installed

This reads to me as insufficient bolt velocity.

With a normal two stage trigger and barrel weight, I can get hammer follow from some subsonic ammunition with a ten inch barrel.  A 4.5 inch barrel may not be getting the bolt up to speed.

I don't have an FRT, but I understand it to use bolt inertia to force the trigger to reset.  With an FRT, your bolt is already doing more than it does with a normal trigger.

I'd start with no bolt weight, the BMA installed, no bolt weight and the suppressor (if you are going to use one), with no pressure plug buffer and buffer spring in the receiver extension.   If you are getting hammer follow after that, could it be that the bolt just doesn't have the energy to make the FRT do its magic?

I appreciate you taking time to reply, and will try your suggestions to remove pressure plug, and run it with no bolt weight installed. Yesterday I tried no bolt weight, it was with the pressure plug installed.

I'm finally getting really good results, and it was after I removed buffer pressure plug and bolt buffer.

Really consistent 3 to 5 rounds bursts, with the following setup:

Lower- Registered SBR
Rare Breed FRT-15 trigger
H3 buffer with carbine spring (NO buffer pressure plug)
Redi-Mag Better Mag adapter and using S&W AR22 mags

Upper- Running SilencerCo Sparrow SS
4.5" Taccom3g 22LR barrel
Barrel collar Taccom3g
CMMG dedicated bolt assembly
CMMG sear trip
Fostech Extra Power Recoil spring
72 grams Bore Buddy Bolt Weight using 1 small Aluminum weight, 1 small Tungsten weight, and 2 large Tungsten weights installed.

Ammo- CCI Mini Mag Copper Plated Round Nose, 40gr, listed on box as 1235 FPS

Not using buffer plug or bolt buffer. It became more stabile after removing these.

Bolt is not holding back on Better Mag when last round is fired.

Try taking out the H3 buffer and spring.  Leave the receiver extension empty.  You want the top of the BCG, that little square part, touching the lower when you close the rifle.

The BMA needs time to rise under pressure from the S&W magazine spring.  If the H3 is pressing the bolt frame forward, you are reducing the time the BMA catch has available to rise.

I found with my 4-1/2" pistol build, the bolt would not come far enough back to reset the hammer when the any additional weight was added to the carrier.  Even the little plastic recoil pad would do the same thing.  I removed them one at a time and the gun would still not run.  Removed both and it has been problem free for many miles.  Oh yeah, I've got the BMA as well.

Removed the spring and buffer, but the sear trip has to be retimed because it wasn't engaging RB locking bar, so I reinstalled the spring and buffer. Will order another sear trip, because I really do not want to go bending on this one.

My son and I shot 200 rounds mini-mag through this SBR yesterday. Most mags were only loaded with 15 rds to conserve ammo, lol, and a couple were loaded with 20 rounds. Used four S&W mags for this function test.

Almost all loadings had a failure or two of some kind, maybe three times I was able to empty a mag without any failure.
My son was not able to shoot a mag without failure, which makes me wonder if some of our problems are from holding trigger to hard, &/or too far back.
We were only squeezing and releasing for a shot. It always shot at least 2 to 3 rounds, with an occasional 4 to 5 rounds per pull.

At least six rounds were duds, dented by firing pin, and would not fire when reloaded into chamber. The others would show firing pin mark, and would fire when reloaded into chamber.

Bolt hold open did work several times. Next time I take this out I'll run tests to determine is bolt hold open is only working on specific mags, and do the same with hammer follow failures.

I never did try a mag dump.

This trigger is a blast to shoot. Briefly installed CMMG Guard 9mm upper, and it functioned without a failure using an endomag.

If you're on Facebook I made a write-up on getting these to work in this group: Fostech Echo, BFS Binary and Rare Breed FRT trigger group.

Once you join, open this link to my post (also found under Announcements): https://www.facebook.com/groups/846909159411487/permalink/976930253076043

If you're not on Facebook, here's a link to a spreadsheet I compiled of all of the successful FRT .22 builds I've found: https://docs.google.com/spreadsheets/d/18LoQ3-tV3gtSNURjyPtqmbc3S23pfA5PSwMuz3ByWEk/edit?usp=sharing

I'd bet the timing on the sear trip tab isn't set correctly. I'm still testing mine since I just switched from a conversion kit to a dedicated upper, but I will update this once I determine the exact amount of bolt gap required while the trigger can still be pulled to get the timing correct. Currently I suspect the tab on the CMMG sear trip should be bent so the trigger can still be pulled (but with more effort then usual) with a 0.010" gap in the bolt, but any gap greater than 0.010" the trigger won't pull at all. I do know for the conversion kit the maximum gap is slightly wider at 0.015", but found it is smaller for the dedicated upper.

Unfortunately since my account is new I have a 2000 character limit, so I must break down my post into multiple replies...


-Don't use the Bore Buddy plastic bolt buffer pad thing (but DO use the pressure plug, you need that).
-Since you have a dedicated 4.5" suppressed barrel, you'll likely want to try using all Stainless weights or refer to my spreadsheet to compare to the other successful 4.5" barrel builds.
-Also, you'll want to get it working 100% with the regular CMMG mags first before using the Better-Mag S&W adapter since it interferes with the sear trip, but here's a possible solution I found for that but currently my CMMG mags are still more reliable then the S&W mags with the adapter:

"Here's the modification needed to get the Better-Mag S&W Adapter to work with the CMMG Sear Trip, just file off that little bit of unnecessary material that interferes with proper function when it contacts the Sear Trip (not my photo, just found it online)"

Here's the main content of my Facebook post for additional info:

So far the only people on the entire internet that I've been able to find that were able to get it successfully running are the following Youtube users:
spzrace https://www.youtube.com/user/spzrace/videos
bench175 https://www.youtube.com/user/bench175/videos
Heineken https://m.youtube.com/user/heineken42069/videos
JayDub https://m.youtube.com/user/JohnWhite84/videos
According to their recent videos and comments you'll need:

---Required Parts---
CMMG Auto-Sear Trip with the tab bent slightly forward enough to time it correctly so trigger can only be pulled once the bolt is *almost* closed. The timing is VERY picky and the tab should be bent exactly so the trigger can still be pulled (but with more effort than usual)* with approximately a 0.015" maximum gap of space before the bolt is fully closed for the conversion kits, and approximately 0.010" maximum bolt gap for dedicated uppers (if the timing is set correctly the trigger should be unable to be pulled with a bolt gap higher than the specified maximum):
https://cmmg.com/auto-sear-trip-22arc
*Use proper snap-caps to test timing to prevent damage from dry firing.
-Also watch these videos by bench175, spzrace, and JayDub for info on timing it:
https://www.youtube.com/watch?v=aDKfOJtctPU
https://m.youtube.com/watch?v=yG5CceXTa8g#
https://m.youtube.com/watch?v=ZopS_Kr6iyk
Bore Buddy Gen 3 Adjustable 22lr Bolt Weight (for 16" barrels/supersonic ammo use all tungsten weights, for lower velocity subsonic ammo and/or shorter barrel lengths stainless weights will likely be necessary):
https://borebuddy.com/product/22lr-bolt-weight/
Bore Buddy 22lr Pressure Plug (there is also a LAW Folder compatible version available which can easily be modified to work with an Armaspec SRS, more details in comments):
https://borebuddy.com/product/22lr-plug/

---Optional Parts That May Increase Reliability---
Fostech .22 Extra Power Recoil Spring which may further reduce bolt bounce:
https://fostech.com/product/22-lr-extra-power-recoil-spring/
Bore Buddy Extractor Kit in case of stove pipes (500% spring appears to work best):
https://borebuddy.com/product/22ar-hardened-extractor/
Taccom3g Firing Pin which is slightly longer than the CMMG firing pin and should reduce light primer strikes:
https://taccom3g.com/product/firing-pin-ar-22/

I'm reading through the FB post comments now, and have looked at the spreadsheet.

Check timing with feeler gauges, and my kit seems to be timed almost properly. The trigger can be pulled with a 0.009" feeler gauge. It can not be pulled 0.010" feeler gauge.

I'll look into the extractor for future should issues arise, but not having any extraction issues at this time.

Already running the Fostech extra power recoil spring.

Hmm, I have a Taccom3g firing pin, so I'm going to install it the CMMG bolt and try again.

Edited to add: Installed T3G FP. It is longer slightly longer than stock, and requires BBBW to be slide in place before inserting firing pin. When already installed, the T3G FP will not push into housing enough to allow Bore Buddy Bolt Weight to slide into place or to be removed.

The BM Adapter mod pic was very helpful. I had already rounded the upper rear corners to allow sear trip clearance, but this pic showed I could take off more material, which I did. Thank you.

The only 22LR mags I have are the S&W. I'll need to order CMMG or BD Mags if I want to try any others.

Is the fat end, the part the hammer strikes, flat, conical or rounded?



You might try the original recoil spring.

Trying CMMG recoil string is basically the same results.

Taccom3g hammer end is flat.

Try bending the tab the tiniest bit possible forward so the trigger can barely be pulled (there should be some extra resistance) with the 0.010" feeler gauge, but can not be pulled with a 0.015" feeler gauge.

Once you do that, compare how it performs to how it currently is and if it's not running reliably yet then you'll likely want to continue adjusting the bolt weights.

OK, I'll lightly bend the tab forward until the trigger can be barely pulled with 0.010" feeler gauge gap. Will report back my findings.

I gave it a slight forward bend. Before 0.09" would fire, and 0.010" wouldn't. Now it will release the hammer at 0.012" (although much harder to pull), and will not release the hammer with 0.013" gap.

Function test, two hammer resting on bolt with live round in chamber, and the other rounds could be burst. Mag had fifteen rounds in it.

I'll try again in the morning buffer plug installed. After, will try re-installing Fostech Spring.

Current weight is two large Tung, one small tung, and one small aluminum. See my third post above, weight is approximately 72 grams total, which is where I've had my best luck, although 70 grams is similar results.

I lightly bent the tap forward this evening, removed the H3 buffer and spring, but tab still isn't engaging locking bar. Will definitely wait until I can obtain another sear trip to bend more forward for this test.

Install the Fostech recoil spring, re-install the buffer, buffer spring, and pressure plug, and be sure to time the sear trip with the pressure plug installed as you will always need the pressure plug to prevent the bolt assembly from moving around (which messes with the timing) while firing.

I vehemently disagree. In the last eleven years I've shot thousands of rounds of .22LR full auto (in a couple of M16s) and semi auto (in at least four AR-15s) using four different .22LR conversion units (in connection with at least eight different 5.56 uppers) and three different dedicated .22L uppers and have never had the need for a pressure plug or the like. Never ever.
In any case, if a pressure plug is always needed, how do you explain all the AR-15 .22LR "Blaster" pistols (from CMMG, Gibbz Arms, Cantos Arms, to name a few, as well as home builds) that don't even have a buffer tube to put a pressure plug into?

Disclaimer:  I have no affiliation with or financial interest in any vendor or manufacturer; and I am not a competitive shooter or a blogger who receives any form of compensation for endorsements or favorable public or private comments.  Use of vendor and/or product brand names, if any, is for informational purposes only.

Best of luck.
MHO, YMMV, etc.  Be well.

If the bolt velocity wasn't enough to re-set his hammer and the bolt travel wasn't long enough to allow his BMA to work, how does a heavier recoil spring and reduced bolt travel help him?

If the BCG already reached the top of the lower receiver, how could the BCG be moving around?

This thread is specifically about getting the CMMG .22 upper to work with the Rare Breed FRT, which the FRT does not have as forgiving of a functional tolerance range that an M16 auto sear's timing allows for due to the FRT being extremely particular with the timing, especially when using it on .22, and the auto sear trip isn't necessary for regular non-FRT semi-auto's so using the pressure plug to maintain consistent timing won't apply to those.

See here's the data I've been collecting and all of them require the pressure plug (the one that doesn't has a folding brace in place of it which should still serve the same function):

I believe the more powerful recoil spring helps reduce bolt bounce, I'm not sure the exact physics behind it but it does appear I'm the only poster attempting to help OP in this thread who actually has an FRT and has spent hours researching and compiling info on successful .22 FRT builds to get mine to work, and my personal experience getting mine to work along with the data I've been able to collect so far points towards the stronger Fostech recoil spring helps the FRT reduce bolt bounce (which causes light primer strikes).



If bolt velocity is too slow then the bolt weights need to be reduced, but the exact bolt weight will vary depending on ammo used, barrel length, suppressor used, etc.

The BCG needs to be 100% held in place and unable to wobble or move at all when firing, as in not 99% still but 100% perfectly still as the timing on the FRT required to function reliably with .22 is literally that picky. Without a pressure plug the CMMG bolt assembly does move around slightly bit when firing which negatively affects the FRT's extremely picky timing, so the pressure plug hold it completely still for timing consistancy.

It's great that you are trying to help.

The physics behind bolt bounce involves bolt velocity.  Higher velocity on closing will result in additional bounce.  The weights both decrease velocity in both directions and can act as a deadblow hammer dampening bounce at both ends.  Unfortunately in this instance, the additional weight also soaks up some of the velocity that would be available to get the hammer far enough back to catch the disconnector.  The recoil spring really takes up a slight amount of recoil energy, but in a marginal case, one where the hammer isn't cocking, it makes sense to look to eliminating parts that spend recoil energy.



If you are telling the OP he must choose between having a functioning BMA with full bolt travel or a functioning FRT with precise bolt location, I don't agree.  A pressure plug doesn't keep a bolt from moving; it allows the buffer spring to exert pressure on the BCG so as to keep the BCG short when the bolt is closed.  The BCG still moves and you can hear the buffer spring resonate.  That matters quite a bit in a conversion where the collar is apt to move off the tenon on recoil and require a lot of hammer energy to be able to both shove the collar forward and strike the firing pin. A pressure plug save the hammer the trouble of putting the chamber insert of a conversion back into place.  (If you read old directions for conversions, you will see lots of recommendations to stick with mil-style triggers to deliver greater energy).

If what you want is a static BCG, then you want a static BCG support.  The lower itself provides static support where the top of the backplate meets the lower.  If you also want support lower down on the backplate that support should come no farther forward than the top of the lower where the top of the backplate rests against the lower.  A dowel cut to precisely the correct length can be used, but it also works to use two dowels with a bolt threaded into one of the dowels.  The bolt can be turned to regulate length.  I use polymer rods in my rifles.

This will permit uncompressible support of the BCG and allow the fully extended length so the BMA has the best chance to work with the S&W magazines.

I'm telling OP how to get his .22 dedicated CMMG upper to work with both his FRT trigger AND his Better-Mag adapter because I literally have a dedicated CMMG .22 upper with the Better-Mag adapter and the FRT, and mine actually works including the LRBHO feature. I actually already addressed how to get the Better-Mag to work with the FRT/auto sear trip in my previous post:

"Here's the modification needed to get the Better-Mag S&W Adapter to work with the CMMG Sear Trip, just file off that little bit of unnecessary material that interferes with proper function when it contacts the Sear Trip (not my photo, just found it online) "

And I literally just checked my dedicated .22 upper after removing the pressure plug and I can very clearly see the bolt assembly move when pressing it back and forth (I have a LAW folder so the rear of the bolt assembly is exposed when folded), which that amount of movement is certainly enough to interfere with proper timing of the FRT, which the pressure plug prevents.

Also, literally every single functioning FRT .22 build that can be found online including mine also uses the pressure plug (or an equivalent plug to restrict any rearward movement of the bolt assembly).

If you read upthread, you'll see that with the pressure plug in place Tripntx was getting poor BMA function and better function without the pressure plug.  Like any bolt catch, the BMA requires enough time to rise and meet the bolt.  Compress the BCG against the barrel with the relatively considerable force of the buffer spring, and you reduce the time available for the catch to rise enough to work.



Emphasis added.    That conclusion would only be correct if the buffer spring were incompressible.  Because the buffer spring is a spring, it is compressible.

When you press the back of you BCG, you are moving the frame by compressing the recoil spring.  That the buffer spring and pressure plug can compress the recoil spring doesn't mean that the buffer spring doesn't move under recoil.

The other difference your analysis misses is the absence of your finger moving the BCG when the rifle is operating.  If the top of your BCG meets the top of your lower when the rifle is closed, the frame isn't going to move back and forth because there will be no pressure plug moving the frame back toward the barrel.  The frame stays in place, located by its contact with the top of the lower.

The Bore Buddy pressure plug is a great improvement over the prior Taccom plug.  Understanding what projecting the force of the buffer spring into the upper does will be necessary to get the system balanced.

In this case, there is:
-a short barrel that may serve to decrease bolt speed.
-bolt weights that further decrease bolt velocity.
-a trigger that isn't resetting unless bolt velocity is increased.
-a BMA that works best with low bolt velocities and full bolt extension.
-a trip that can be frustrated by the BMA in its original form (and for which you've found the fix).

Running into some similar issues myself.

New M4 dedicated build with 16.1" BBL
CMMG dedicated BCG & Auto Trip
Bore Buddy weight with all tungsten rods installed
Bore Buddy buffer plug and recoil buffer

Was nothing more than a single shot so removed both the plug and recoil buffer.  Now it runs for 3-5 rounds and then stops with the hammer resting on the firing pin.  CCI Mini Mags run the best; Federal Auto Match and Aguila Super Extra won't run at all.  Stoppages are due to hammer follow.

Hammer will drop on 0.010" bolt gap but not on a 0'011".

This is a brand new setup so wondering if it just needs some break-in?  Any other ideas?  I certainly cannot go heavier on the bolt weight because it's already maxed.  Yes, I know that .22s are extremely finicky but I'm thinking this should be running like an angry woodpecker.

Emphasis added.

I love the BB weight.  It slows the bolt so it can't outrun my bolt catch.  In your rifle, I think it works against the FRT.  You want that bolt coming back with lots of force because it is doing more than just cocking a hammer and stripping a fresh round from the magazine.  You could split the difference and take out all the internal weights.

My reasoning for removing the pressure plug, buffer and spring from tripntx's rifle pertained to his BMA.  If you don't have a working bolt catch, I am not clear on why removing the pressure plug helps your FRT function, unless removing the plug helps keep your GCG in one place.

Successfully resolving the hammer follow issue by adjusting the bolt weights to obtain the proper bolt velocity needed to fully reset the FRT should conveniently also resolve the mag catch issue, though it's also possible something may be out of spec as my BMA doesn't always catch the bolt in another lower of mine (even when activating the bolt catch manually).

But...that's just not true at all though as various forces do move the bolt assembly between firing, hammer striking, FRT's locking bar, bolt cycling, etc, and in the FRT's case it requires the timing to be as consistent as possible when activating the FRT's locking bar, which is why 100% of successful FRT builds involve a pressure plug or an equivalent measure to limit bolt assembly movement while the locking bar is activated.



My point was simply for OP to use a pressure plug or an equivalent measure to hold the bolt assembly in place, regardless of whether it's by spring tension or just physically restricting any movement as either way works for the FRT.

The small plastic recoil buffer bad restricts the bolt movement from cycling fully to reset the FRT, so don't use that, but the pressure plug is necessary for consistent timing. Did you adjust timing on the auto sear trip tab to release the hammer with a 0.010" gap/not release with 0.011" gap with the pressure plug installed?

If not, do that and report back with your results.

EDIT - One other idea I'd toss out for consideration is try different hammer springs.  It can be surprising how much bolt inertia is spent just cocking a normal AR hammer, and how much harder a 22lr will cycle with lower power hammer springs.

I don't know whether that will screw up FRT function.



Too high a velocity will do that too.  Remington Golden Bullets aren't something I shoot lots of, but they would routinely cause my bolt to outrun the BMA.  This was before Bore Buddy made bolt weights, so I just avoided very high velocity ammunition.  I had settled on subsonic by then, so it was no real sacrifice.



Emphasis added.  When you were pressing the back plate of the frame with your finger, you were moving the frame, and moving it in the same way the pressure plug would.  The frame stays in one place unless you introduce buffer spring tension into the upper so the frame moves back and forth during firing.  That the hammer and bolt move during operation isn't pertinent to how you keep the frame in one place during operation.  The hammer and bolt also move during operation when you've a pressure plug in place.

Yep.  Timing was set with plug installed.  Honestly though, it seems to run the same whether the plug is installed or not.

I also tried just about every combination of weights that I could think of and the only one that ran the best (if you can call it that) was with all 4 tungsten weights installed.

Tried another 20 rounds before it got too dark and had 5 stoppages.  A 25% failure rate is pretty bad.  Not ready to blame the ammo yet because CCI Mini Mags are typically very reliable.  Still, even those can have a bad round but not even close to that percentage.

Have you seen my spreadsheet with all the details on successful builds I could find? This one All successful builds utilize a pressure plug or an equivalent, and everyone with 16" barrels found best results with all tungsten weights so don't change that. I do suggest trying the Fostech recoil spring, but also the timing measurement I suggested is what I personally found worked for me, but that's still a total sample size of 1 so it's very possible you may need to further adjust the tab a tiny bit at a time until you get it to work.

I have.  I've also considered that the hammer might not be fully resetting but ejection is pretty stout.  Empties typically land 8-10' away.  Perhaps the stronger recoil spring will tame it enough to make it run reliably.

Sorry for the highjack OP but hopefully this is helping you as well.

Update:  This project is toast!  I've tried everything that I can think of (and what has been suggested by others) to get this to run and it's just not happening.  Spent waaay too much money, wasted too much ammo, and used up whatever patience that I had left trying to get it to run.  This FRT will be hitting the road!

-I'll have to split this up in 3 posts

I wouldn't consider a thread that was active less than a month ago dead, but I wanted to chime in and say this entire thread has been monumental for me. I'm in a similar situation, where I decided I'd like to shoot 22lr like a madman for cheap and decided to build an ar15 pistol with a cmmg bravo 22lr conversion. I'm having a ton of issues with light primer strikes, I think, might be stupid old ammo that's gone bad since there have been a few that will not fire even in the ruger 22, and I've tried a ton of different things from videos and this thread. Currently, my goal is one successful mag dump with a 25 CMMG 22lr mag, and I have the 50 round from black dog which still ran pretty well when it did run. I'm currently running a:

FRT 15, none of the springs are crimped or anything, it's fine
NBS Slick Side 7.5" 5.56 Upper
Anderson Lower with no bolt catch anymore, since it slightly improved my light primer strikes
CMMG Bravo 22lr conversion BCG with
- Bolt buddy adjustable weight with all tungsten
- Not using the polymer bolt buffer that came with the weights, tried with and without but didn't get any ground breaking results
- CMMG trip kit, which I've timed to not trigger fire with a piece of printer paper folded twice stuck in, so it's timed right probably
- Bore buddy firing pin, which seems to be working just as well as the stock firing pin, which is a ton of light primer strikes
- Hardened extractor from bore buddy, since the stock one chipped around 200 rounds in, with 500% power spring in it
Phase 5 pistol buffer tube with a carbine spring and two carbine buffers stacked back to back, was using the bore buddy pressure plug but two buffers seemed better I guess
CMMG's 22lr mag's

I've run every combination in between, and my problem ALWAYS comes back down to light primer strikes. I've ordered the Taccom firing pin, Fostech's upgraded bcg spring thing, a hammer spring based off of https://www.youtube.com/watch?v=ga--SjoD5O8&ab_channel=2ACollective, and really nice ammo, even though I 100% believe the ammo type should not matter and this thing should be able to chew through everything. Money is not an issue, and I will, WILL, have this thing running flawlessly. Once all these come in, I'll start running different combinations, starting with just adding in Taccom's FP, and I'll post what new results I get.

When I first put together the rifle without the FRT15, but with the conversion stuff, using just the basic stock trigger setup that came with the lower kit, I chewed through around 300 rounds of Remington Thunderbolt's with 1 fail to feed, and that was because the mag lip got stuck on the last round. I could shoot as fast as I could pull, and that was without the adjustable weights or sear trip or anything, but the moment everything came together for the FRT15, it started looking bad. To date, this https://youtu.be/xspFXrmdQW4 is the best and closest to a mag dump I've gotten, and that was Remington Thunderbolts, and it seems to have only gone down hill from there. I think I might have warped the sear trip way too much, as the corners show severe warp and sometimes, when either putting in or pulling out the bcg, I get it caught on the sear trip.

I always lube the important bits before I shoot, and I do a damn well good job cleaning after I get home, so I haven't considered mistreatment a possibility of why it's not running well. Someone briefly mentioned that Taccom's firing pin is a tad bit longer, so I'm hoping that will nip my problem in the butt. I've also considered getting a heavy piece of metal put before the hammer in-between the spring and hammer for added 'oomph' on the hammer action, so the spring is under more tension and should swing harder, and the weight of the hammer would put more inertia into the firing pin for better bullet smacking.

On a side note, I've gone through old Thunderbolts, old Federal, old Blazer, old Fiocchi blue, old Fiocchi orange, old Armscor, I basically ransacked my dad's old 22lr storage cans, and I've gone through brand new Thunderbolts, which overall gave me the best performance. However, the orange Fiocchi gave me the closest, I only had 50 rounds of it, but both mags almost did a full mag dump, one had a fail to feed and one got a shell split in half on the bcg itself, so I figure these would have completed a mag dump had nothing gone bump in the night. Federal gave me the worst performance, with almost a 95% failed to fire, but if you put the rounds back in and shot it from a fresh rack, they would still shoot, so the ammo wasn't bad, if only they were harder to set off than the others.

Also can someone explain why a heavier buffer is needed to cycle? In my mind, it would make sense that a lighter piece of metal that needs to move backwards would be able to be moved more and faster, so it would lock the hammer down and load a new round. A heavier buffer would mean you would need a stronger round to cycle correctly, but it seems to work the other way around.

I suspect you are having either hammer follow or the timing is still off (possibly both, read my post above for more info on timing), but start by trying the Fostech recoil spring along with lighter weights (perhaps all stainless steel and go up/down from there). The Taccom firing pin will also help since it's longer and has a lighter spring.

You don't want to use a stronger hammer spring because that will make it harder to reset the hammer, which is already tricky enough as it is due to the forced reset function.

Also, take a look at my spreadsheet and you'll notice the people using all tungsten weights have 16" barrels, while those with shorter barrels use lighter weights: https://docs.google.com/spreadsheets/d/18LoQ3-tV3gtSNURjyPtqmbc3S23pfA5PSwMuz3ByWEk/edit?usp=sharing

I had that same determination but never could get mine to run.  Tried every aftermarket gizmo and combinations thereof and still no luck.  Got rid of the FRT and installed a Franklin Armory binary.  Much happier with it now.

I sincerely hope that you have better luck than I and get that thing singing.

My phone has a 960fps mode for videowing super slow mo, with a tolerable amount of motion blur, next time I go out I'll try to capture a video to see if the hammer is actually being locked back or not.

My taccom came in, but not the fostech springs. Comparing the bore buddy firing pin to the CMMG one, they were very similar with bore buddies having the round tip, but taccom's firing pin is wildly different, from length of the pin to the amount that the hammer impact point doesn't sit flush and sticks to the more room it can slide around while the codder pin is in, I have a great feeling it'll work better. I'm going to try it by itself, then reduce weights, and then maybe mess with the timing. I have feeler gauges on the way too, so I'll get a more accurate time adjustment.

I would try a reduced power hammer spring, if it was me.
I believe the hammer rate is keeping the bolt from coming back far enough in cyclical.

Just a guess.

CMMG firing pin with both stock fp spring and  CMMG fp spring, from all tungsten to mix and matching with steel and aluminum, it ran worse than ever. I'd even say that the light primer strikes were worse than the stock firing pin. Still waiting for the hammer spring replacement and fostech recoil spring.

I tried to record it today, and since 960fps is only 10 seconds and only does slow mo for 2.5 of those seconds, I have to time it, so I did 240 fps. Not only does this thing cycle fast, I can't even see what the hammer is doing because of the bore buddy adjustable weight blocking the view, so next time I go I'll have to ask a friend to video tape directly in front of the ejection port to get a good video.

The first cycled round fired 100% every time, but the second one almost never did. The longest burst I got today was 4 rounds, twice, after going through maybe 200 rounds. My gun was effectively a bolt action 22 that wasted every other round.

I was so sure the taccom pin would have made a huge difference, but I guess I was wrong. And I fully believe a weaker hammer spring would only make things worse, I've felt the pressure needed to push back the FRT-15 and a stock lower parts kit hammer, and the stock hammer was way harder to push back, but it did every single time. I might see if I can somehow force the stock hammer spring into the frt 15.

I'll head back to the range Tuesday, I should have the springs ready by then.

I strongly suggest trying the Echo recoil spring and adjusting the timing on the auto sear trip first before even thinking about trying the heavier hammer spring (assuming its the POF one) due to the increased risk of hammer follow and extra dry fire damage. I loaded 1 round to see if it would hold the bolt open with my S&W Better Mag adapter which it did not, but what it did do was cause a visible amount of damage to the firing pin after it attempted to fire the non-existent second round.

I went to the range for about 2 hours today, with better but not satisfactory results. For most of the time, the Remington Thunderbolts were giving me 2 - 6 round bursts every other fail to fire, and Federal had a 2 round burst twice, all the others were fail to fire. I've -

Installed the fostech spring, I bought two, the stock CMMG spring is almost a centimeter shorter the the fostech ones, but both springs I got from fostech were also different lengths, one was longer by a few millimeters so it doesn't intsill confidence that all of our springs are the same.

The remington thunderbolts did not care, what little the federal rounds worked no longer did, they wouldn't even cycle a new round.

After that didn't work, I installed the POF hammer, which was a tight squeeze but fit the dimensions to work in the FRT. I could feel that the pull on the charging handle was tougher, so I decided to remove 2 large tungsten weights and kept the two small ones. Thunderbolts didn't seem to change at all, while Federal performed even worse.

I then swapped for all aluminum weights, thunderbolts still acted the same while federal were at least loading.

At one point, I thought I might be getting hammer follow, but I extensively checked by loading one round, and then the CMMG empty mag would prevent the BCG from closing, but it still should have set the hammer back, so I would take out the mag and the BCG would close the rest of the way, then I could tell from a trigger pull if the hammer was actually being reset. At first, it didn't seem like it was resetting, so I kept removing weights to make it lighter, until I eventually removed the BBAW, and it still wasn't setting back the hammer. Then I realized that, if you pull the trigger down while the BCG is coming back to battery even if it's not anywhere near the trip, it will fire regardless on BCG close, so you could effectively load a trigger pull and fire by loading a round. Very dangerous, it happened to me one time, when I decided to swap the empty mag for a 1 round mag, and as I let the charging handle go it let the hammer go free as soon as the sear tripped, my fingers weren't even on the trigger. Luckily, I always keep it pointed down range at the target, but it still gave me a scare. It's possible to get around this by, pushing the trigger back forward and then letting the BCG close, which would let you dry fire, confirming that my hammer was indeed being reset after a fire. In fact, I did this around 30 times just to make sure the hammer was being reset every time, and even using all tungsten weights, thunderbolts would reset the hammer.

For more proof, I carefully noted how far back the bcg needed to travel to set the hammer, and I recorded a ton of 960 fps vid's of the ejection port, and every single one showed that the BCG traveled far enough back to reset the hammer, with thunderbolts at least, on every weight config and with the upgraded spring, although with the heavier hammer spring it didn't reach the back of the BCG but still went past the reset point by half a centimeter. So, I guess it now comes down to the issue, with light primer strikes.