I have posted some of my concerns in other threads but wanted to start over fresh.

Once I decided to SBR my 15-22, I did some research here and a prevailing thought was a 4.5" barrel was the best, for the main reason such a short barrel would allow one to use easier to find high velocity ammo, with it still staying subsonic. Logic being, such a short, pistol length barrel, would not allow HV ammo to get up to the speed of sound... as it normally would. This would give the SBR a nice advantage as it could shoot any 22lr ammo and not have to worry about the sonic crack.

So I sent my barrel off to Adco and had it cut down to 4.5" and threaded to the specs for a Sparrow. Looks nice but danged if I don't have failures to fire. Seems when I shoot subsonic rounds thru it, such as Norma or CCI SV, I get multiple failures per magazine. Lately after the first shot, the next round loads but the gun fails to fire. I assume that means the trigger is not being reset.

I have a spare 15-22, so in testing I have tried all sorts of things, such as cleaning out the firing pin channel & even swapping in the new bolt assembly. No matter what I do or try, subsonic ammo will not always reset the trigger. A few weeks ago I put the 16" barrel onto the SBR gun and since then have had no failures. I have shot well over 500 rounds lately with not a single failure. So today I brought down the 4.5" barrel & its handguard & installed them back onto the SBR rifle. First magazine was CCI SV and the gun shot once but the trigger again failed to reset. Thinking subsonic ammo didn't have enough power to reset the trigger when used with such a short barrel, I then switched to CCI Mini-Mag HV ammo, and then the gun performed flawlessly again.

So seems to me, with my setup, subsonic ammo will not work properly with such a short barrel. Guess I could continue to use it with HV ammo but sure seems considerably louder when firing it plus every few rounds one is very loud... like it is going supersonic.

I use a CMC trigger & keep my gun properly cleaned. Originally some around here thought the issue was with the bolt or firing pin but after all my tests, I know that is not the case. When I drop in the 16" barrel everything works perfectly, as my gun always has. Drop in the 4.5" barrel and the gun fails with SV ammo.

Anyone else has issues with such a short barrel? You notice when shooting HV ammo that it is louder than when using a 16" barrel and subsonic ammo? You have any of your HV ammo going supersonic thru the 4.5" barrel?

So for now I am back to shooting with the 16" barrel. Maybe one day I can swap barrels with someone who wants a 4.5" barrel so that I can try again at say 10" or so.

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A #1. I have not experianced problems because I use the JP reduced hammer springs. I was considering milling some weight off the bolt like S&W did with the 15-22P.

JP Enterprises Trigger Spring Kit AR-15 3-1/2 lb Reduced Power



A. #2. Yes. HV is louder with the 4.5" barrel too.

Remington Golden Bullet has more powder and creates bolt bark and the cases rupture more often. Remington subsonic is under powered and the case fails to seal against the chamber so it is louder than any other subsonic ammo I've tried.

A #3. Not with anything I've tried. I've heard that Stingers might. I did loose velocity but not accuracy with CCI Standard Velocity ammo. I do not run "subsonic" ammo as Standard Velocity or Match ammo is subsonic.

I love making firearms smaller and quieter. For those who tweak firearms, we know new problems will come up. It's part of the challenge. We enjoy problem solving.

I would trade you a standard barrel in a heart beat if I had one. Sorry for your problems. I've always enjoyed reading your post with the bump stock.

Did you try the bump fire stock on the 4.5" barrel?

I contacted S&W about purchasing a new barrel but they don't sell them. However if I send the gun in, they will replace the 4.5" barrel with a 16".

Seems odd to do it that way as I was prepared to purchase the barrel. But then again, they may charge for this. I have no idea but will find out pretty soon.

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Have you tried the stock FCG in the SBR?

If you want to try the JP springs PM me and I'll drop them in the mail.

I too have an SBR 15-22 (the one in my avatar) but with a 5" barrel and I also have the CMC trigger. Every other magazine or so, I chamber the first round out of the magazine and the second round won't be picked up and chambered...once I get that round chambered by hand, all subsequent rounds chamber and fire no problem. Ammo used is Norma Tac-22...

This is the only trouble I encountered...except for my new (in jail) Warlock not threading onto my barrel...the other jailed cans (Sparrow and TacSol Cascade) thread on perfectly...

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M&P's and K Frames Pleeze!

I haven't but maybe I'll give that a try. If that helps I'll get with you on the springs or are you saying adding the springs might help the issue? Or do they simply lighten trigger pull?

I wish more folks that shoot the 15-22 SBR would tell their experiences. What length barrel, what FCG & if they have any added issues because of the shorter barrel. My 15-22 with CMC trigger just never, ever fails with a 16" barrel. Granted, I only shoot the good stuff, such as the Norma & CCI but soon as I switch to the 4.5" barrel, I have failures.

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That happens to me too & curious what is up with that? 2nd round will not fire, no matter what magazine used.

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The JP springs should offer a bit less resistance against the bolt moving reward. Since the issue seems to be not quite enough blowback umph with the shorter barrel, they might help.

Is that happening only with full mags? Or is the 2nd round no matter what?

Can you narrow it down to a specific mag, or couple of mags? If they're 25rd, does the same problem happen if you just load 20? What if you just load 2-3?

JP springs can't be used with the CMC trigger though. Unless he's willing to change to another trigger that uses a standard spring set, using the JP springs won't be an option. And with how much he seems to like the CMC, I'm guessing he won't change, even if it would lead to better reliability with the short barrel.

Phil initially mentioned trying the stock FCG and to use the JP springs with it. I have my original FCG plus have a spare 15-22 with stock FCG.

As you state, I have my doubts if I will like going back to a stock FCG, even with the JP springs. But who knows & testing it out will be interesting.

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You may find this info interesting.
I used an Innovative Arms 4.5” barrel with silencer for this testing. I did a little research and it seems a silencer does not have an appreciable effect on velocity although I did not test without the silencer.
So here are the chrono results for Federal Champion 22LR 36grain listed as 1260fps:
1055, 1083, 1089, 1130, 1111, 1041, 1077 (the rounds over 1100 had a louder crack but all the rounds had some noise that prevented me from hearing the bullet hit the dirt)
Here are the chrono results for CCI SV 40grain listed at 1070fps:
865, 914, 878, 883, 870 (these were obviously more quiet and I heard the bullet hit the backdrop each time)

Both brands cycled the action without a hitch and I have a CMC trigger too.

Did you shoot your with the Sparrow or is it just threaded for one?
Maybe some backpressure from the silencer is what you need.

Always shoot suppressed with the Sparrow.

Your test matches up to what I have been hearing when I shoot. The HV ammo is rather loud, much louder than subsonic, plus occasionally some appear to give off the sonic crack. They might not do so in the summer but seem to do so when chilly.

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We arent allowed suppressors in Canada. So I went with a 10" barrel for less weight.
I hope it wont be crazy loud with SV ammo.

It is loud... relatively speaking. Just got done shooting using the Norma subsonic ammo, and let off a few shots without the suppressor. Was so loud, almost wet my pants. Was not wearing hearing protection, as not needed with the suppressor.

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Well it is a beautiful day here, in the upper 50s without a cloud in the sky, so I took a half day off work to do some tests. I'm still confused.

So I started shooting the 4.5" barrel using the stock FCG. Trigger felt surprisingly good but on first two magazines, the second round would not fire. The trigger did not reset after the first round and the gun would not go to safe. Rack in a new round & in both situations, all other rounds went off perfectly. Then the next 4 magazines shot perfectly.

So went to the house to reload those magazines & get some more. Before trying the CMC trigger, I decided to try a magazine with just 5 rounds in it & danged if I didn't get the same failure on the 2nd round. Odd thing is, the next 6 magazines with the CMC trigger fired perfectly.

So I'm wondering something. Why is the 2nd round not resetting the trigger? Has to be something to do with not enough pressure, as when I shoot HV ammo, I have no issues, but why on the 2nd round with subsonics? I have a theory & it might explain my results. I know many suppressors, such as the Sparrow have a noticeable first round pop (FRP), especially when shot using a pistol barrel. I get almost none with a 16" barrel but on my pistols & this SBR, it is noticeable. So I wonder if whatever causes the FRP, which I think has to do with more oxygen inside the suppressor, could likewise cause less back pressure? Might also explain why the problem went away after the first 2 magazines, as I was shooting rather quickly with quick magazine changes.

I did note, on my second trip down today to shoot, that the FRP was loud on the first shot on that magazine with 5 rounds in it. And as I stated, I did get a failure to reset the trigger on that shot.

This make any sense or anyone have any other ideas? I think next time I shoot, I'm gonna try squirting some water in the suppressor to see if I can remove the FRP and to see if that allows the trigger to reset.

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FRP is caused by the oxygen in the can. After the first "explosion" it's usually burnt up. I don't remember enough from honors physics 20 years ago to tell you if that would cause the problems your having or not.

In case you missed it, I asked a question earlier about the 2nd round not loading. If you don't mind, will you scroll back and answer it? (The one about full mag vs partially loaded mag)

I have not had an issue with loading, only with the trigger not resetting. I saw your question and that is why I stated I ran a test with 5 rounds in the magazine. As I stated, I had a failure to reset after that 1st round.

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That's interesting.
What does it do without the can?

I went back & looked at your video from your SBR project, where we noted the FRP on your first round shot suppressed. When looking at your video, there is obviously a lot of "energy" leaving the suppressor as opposed to the following rounds.

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The few I shot without the can were on the gun with the 16" barrel. I shoot very little on my property without a suppressor as it spooks the horses & makes getting them in the barn that evening just a load of fun.

I assume the problem would only get worse, with the reduction in back pressure. My reasoning is that shooting subsonics suppressed with a 4.5" barrel is right on the edge of where a trigger can reset, as demonstrated by having the same issue with the stock trigger & the CMC. I note dullh has exactly the same issue. We all know every gun acts a little different so maybe some never have this issue. I sure woud like to get a lot of data from lots of folks regarding barrel length, ammo used & which suppressor used.

The 15-22 was not designed to operate with such a short barrel. Obviously it can do it but the question is, what barrel length allows 100% functionality? My observation is 4.5" is too short.

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Oxygen accelerates the burn of the unburnt powder in that first shot. That's why the first one sometimes looks and sounds different. I guess if you were right on the edge of a tolerance required to reset your trigger, it may be just enough energy difference to cause the symptoms you're seeing. I'm not sure there's an easy fix...unless you find somebody with a barrel that's 8+ inches that may add just a little extra oomph to that first shot.

I agree there appears to be no fix, since I went back & tried with a stock FCG. I sure don't want to keep playing around with triggers. If I had it to do over again, I would certainly go longer... probably 9-10". That would get the gun back down to carbine length, with suppressor attached, and I bet that extra 5" or so would give that extra oomph needed.

My purpose here is not to necessarily fix my issue but to bring to the forefront issues when cutting down your barrel. 4.5" was suggested to allow using HV ammo without hearing the sonic crack. That is true & nice. What wasn't really discussed was functionality with such a short barrel nor was how loud HV sounds in that barrel. They may not crack but they are very noticeably louder. For me, if I'm gonna shoot suppressed, I want the gun as quiet as possible. That means shooting subsonics... period.

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The lighter JP springs might be enough to overcome that first round issue. If that doesn't solve it lightening the bolt or playing with the bolt return spring might be worth considering. There's got to be a solution for that barrel length. Heck, I guess you could start every mag with a MiniMag since you get a FRP anyway but that's not really a solution. If I were close by id like to try my YHM Wraith can which has a lot more volume than the Sparrow. No FRP.

I will try your springs & see what happens. I'm not interested in those other options. If the springs don't work and if no one wants to trade barrels, then I will just send the gun to S&W & let them put a 16" on it.

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Before you send it back, let me know. I'll see if I can find somebody that wants to just swap you out, either with a ~10" or factory length.

I would like to trade, so please check around. Even an unthreaded barrel will be fine as I will send it off to be cut & threaded for the Sparrow specs.

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RJ- you could give it a blast of CO2 to help reduce the FRP. Also after the CO2 you could put a piece of electrical tape over the can, it would seal in the CO2 for a while and would give"slight" increase in back pressure?? Enough to reset the trigger??
I have a 10.5 on 15-22 with an Innovative arms integral suppressor, it is incredibly quiet ( action noise) use Fed bulk 36 gr 1250, cycle and runs great. I have tried Rem subsonics and CCI "quiet" rounds and now I do not remember which one cycles the gun ( senior moment) I will check it later today and let you know. Also I had tried a slidefire on it with the HV loads and the can is so effective that it will not run. If I change uppers to stock it runs great. I would be curious what the tape will do. Be Safe,

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I read through the post and have some good news for you. I think there is a very simple item that everyone has overlooked.

I regularly shoot my 15-22P suppressed with no problems. I usually run CCI standard velocity and it is absolutely silent, feeds and fires every time.

The difference is in the bolt spring. Remember these are blowback operated. Reduced chamber pressure and dwell time has detrimental effects. Full bolt cycle & trigger reset has very little to do with the FCG springs. The 15-22 rifle that you used for the SBR's starting point has a blue bolt spring. If you open up an M&P15-22P pistol that comes factory with a 6" barrel, you will find that it has a reduced pressure white spring.

Call Smith and order a pistol spring and I think you will be pleasantly surprised.

Happy shooting!

Is that the only difference? I thought others have said the bolt itself was lightened.

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Shots sound louder with the short barrel because the muzzle is a lot closer to you.

I've got a couple guys that sound interested. One even willing to swap handguard as well if you shortened it. Another one already has F1 approved and just hasn't made the move, yet.

You want to try the white spring first? If so, I'll let them know.

No. I'd prefer to start over & go with a 10" barrel. I'll swap handguards too, as no big deal cutting one down.

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Redneck_Jim
You are correct that the bolt in the pistol does have more material removed to lighten it. Figured a .50 spring would be the best place for him to start.

Sent three of them your contact info. Hopefully one of them works out. Don't know any of the three, but they're all fairly active members of either ARFCOM and/or CSC (Carolina Shooters Club) and I wouldn't hesitate to do business with any of them.

Thank you sir.

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To update, a member here has sent me his upper for a swap.

My plan will be to cut the barrel down to around 10", once the swap is complete.

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I just shipped mine off for a cut-and-thread to 9". It'll be sitting at the 'smith until the Form 1 comes back.

I see you've already gone another route but here goes anyway.

6" barrel
Stock trigger with JP yellow springs
Sure Fire Ryder

I havn't shot any "subs" or quite ie the really slow stuff. Ran a full mag of Gemtech with no problems at all. Have run a lot of Aguila SV, CCI SV with no problems.

I hope more folks will post their experiences, issues, configuration & ammo used. I pretty much only shoot CCI SV & Norma Tac-22 & as stated, had issues with trigger reset with a 4.5" barrel. So you have NEVER had that issue with a 6" barrel & your Surefire? That is good to know. Did you first try the stock trigger & have issues? Did the JP springs help with issues or were they used just to lighten trigger pull?

This am sent off my 4.5" barrel & short handguard to a member here. Hope he post results with his configuration. Also sent off my new barrel to Adco this am, to be cut down to 11".

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Ran probably 300rd of misc ammo with stock trigger no trouble at all. Only fired a couple of rds without the can just to function test,I'd guess I'm at about 1000rds through barrel and can. I was going to go 4.5" at first but changed my mind only because of handgaurd selection. I think most of the bulk HV I've shot is staying sub but there is a noticable diff from SV. Ran 2 or 3 mags of HV with a bumpfire,worked pretty well.

My 4.5" worked just fine with HV, but had the issues with SV. That issue only cropped up on the second round, which led me to blame the suppressor's FRP. That tells me SV ammo with a 4.5" barrel is maybe cutting it too close or right on the edge of having enough back pressure to cycle the gun properly. Your post makes me think going to 6" is a big help for those wanting to shoot SV.

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Ran two mags of bulk pack Blazer through mine yesterday. First ~15 rounds unsuppressed, the rest with a Warlock II. Not a single hiccup.

Taking my son shooting for his first time on Sat (or at least that's the current plan). We'll try unsuppressed and suppressed. Seven 25rd mags loaded, and four 50rd drums. Also have the three 22 pistols with 6-8 mags apiece. Should be a fun day.

It'll all be the same bulk Blazer, so probably won't help with this discussion...but it'll more than double the amount of rounds I've put through the SBR so far.

6" barrel could definitely make a difference. There's a reason <5" is recommended to keep everything subsonic. If you're fine with thinking about going 10" this time, maybe something in 7"-8" range would also work.

Hopefully soon you can try a batch of SV & see if your short barrel also causes you issues.

Agree. However my desire to go SBR has less to do with how short I can go, or if it allows me to shoot HV without a sonic crack (both very valid reasons to SBR a 15-22), but with how quiet can I shoot & can I reduce the length of the gun with suppressor attached back to normal (carbine) length & reduce the weight way out on the end of the barrel. With a 5" Sparrow, my 11" barrel will now bring the gun back to carbine length and better match up with my 300 Blackout SBR.

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Made your barrel swap, yet?

Yep, swap took place and my barrel came in today from Adco. It was cut to 11" and hope to test it soon. Too cold to shoot now... at least it is for me. Temp was just above zero this am when I was feeding horses.

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Took off a bit early today, since the sun is shining & it is above freezing. Tried 150 rounds of Norma Tac-22 & 100 rounds of CCI Sub-Sonic ( slower than the Norma) with the new 11" barrel. No failures whatsoever & the barrel is exceedingly accurate, so good job Adco. I am one happy camper and even the horses came up to observe.

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Glad to hear that report!

Jim, if you don't mind me asking, what do they charge to cut & thread a 15-22 barrel?

You select their AR15/AR10 barrel threading, which costs $65. You fill out the form online & checkout prior to sending the barrel. They normally turn around the barrel in a day or two. Just make sure you pack the barrel properly & really wrap/protect the ejector. I keep my double box that my 300 Blackout upper came in to ship such items. It is really strong & full of padding. I also used it to ship the lower to be engraved for the SBR requirements.

I'm thinking of sending them my 16" barrel on my other 15-22 to be rethreaded, even though it came threaded from the factory. This way I can get the O-Ring engagement, which keeps the threads clean when using a sparrow, it will shorten the threads so as to no longer need a spacer, plus that will get the barrel recrowned by them. I'm no expert, but all I read tells me the crown really impacts accuracy & they do a great job. This 11" barrel seems to be very accurate. Guess I need to bring down a rest to verify what MOA it now shoots.

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