M&P 15-22 cut barrel to 4.5" SBR?

The reason I cut my .22 LR barrel to 4.5...

Subsonic ammo help suppressors do their job.
Subsonic ammo is quieter.
Subsonic ammo is more accurate.
SBRs are lighter.
SBRs are more maneuverable.
SBRs can use both subs and HV.
SBRs are sexier.
SBRs are more fun.

You won't miss the extra 11.5" :)
 
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vipermd said:
RJ: Any follow up on accuracy, function after cleaning the bolt?? Be Safe,
Click to expand...
Just shot this weekend & still had at least one FTF per magazine... from a gun that historically just doesn't have failures.

I'm bringing my upper from my spare 15--2 to work tomorrow, so as to remove that barrel. I will then put it on my SBR build to see if anything changes. If necessary, I can drop in the new bolt group, if I still have failures but will change one thing at a time. As of now, the only thing that has changed since these failures cropped up, is the 4.5" barrel.
 
RJ: Sorry to here the problem is still present. I agree only changing one variable at a time. Keep us posted. Good Luck. Be Safe,
 
I have no problem with mine but I bobbed the hammer.

S&W removed a small amount of material from the top and bottom of the bolt to reduce weight on their 6" 15-22P. If I did it again, I would do the same.

mp3.jpg
 
I can take pictures or measurements of the pistol bolt if you need them. I'm going to try shooting my pistol project suppressed this morning.
 
vipermd said:
RJ: Sorry to here the problem is still present. I agree only changing one variable at a time. Keep us posted. Good Luck. Be Safe,
Click to expand...

Made the failure to fire go away.

So I have a brand new, spare 15-22 due to that great price Palmetto offered a while back. After completely cleaning my bolt & firing pin channel but still having failures, I decided to try some new parts from the spare. First thing I did was to lubricate the rails on the new bolt group & installed it into the SBR. After the first shot, the hammer did not reset. Kept shooting & had this to happen a few more times with the same magazine. I reinstalled the original bolt and then installed the spare 16" barrel and gave it another try. 6 magazines later... not a single failure.

I am no firearms expert but this tells me that a 4.5" barrel reduces the back pressure enough to cause issues. Every gun is different, so might work for some but not for others. I use a CMC trigger, which hits hard & has never caused me a single issue. I am shooting CCI SV, which is about as good as you can get IMO. I tried this with a cleaned & lubed bolt group as well as with a brand new bolt group. As long as the 4.5" barrel was in there, I had issues. As soon as I went with the 16" barrel... none.

I only went with the 4.5" so as to be able to shoot HV ammo subsonicly but that is no big deal for me, as I have many thousands of rounds of subsonic. My preference, for a SBR would be a 10" or 10.5" barrel, so that the rifle stayed carbine length with suppressor attached. If someone wants a 4.5" barrel threaded for the Sparrow, send me a PM for a barrel trade. I will even trade for an unthreaded 16" barrel.
 
Darnit!!!! I wish you had posted this two and a half months ago!!!
Only issue is getting a barrel imported from the US is a pain if the paperwork isn't filled out and they check the shipment.
I've been trackin your threads, this is why I ordered a 10" barrel from Suffolkrifle. I'm hoping 6" off helps.
I had an 8" barrel on my 10/22 and thought it was too loud. It will be interesting to see what 2" more does for noise.

Please message me with a price if you want to sell the 4.5" barrel!!!!
 
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little_airwolf said:
Darnit!!!! I wish you had posted this two and a half months ago!!!
Only issue is getting a barrel imported from the US is a pain if the paperwork isn't filled out and they check the shipment.
I've been trackin your threads, this is why I ordered a 10" barrel from Suffolkrifle. I'm hoping 6" off helps.
I had an 8" barrel on my 10/22 and thought it was too loud. It will be interesting to see what 2" more does for noise.

Please message me with a price if you want to sell the 4.5" barrel!!!!
Click to expand...

I shot the 4.5" barrel first, followed immediately by the 16". The 16" is noticeably louder than the 4.5", as expected, but nothing horrible. Most of my suppressed shooting has been done with a 16" barrel anyway. I'll take a tad louder gun that shoots perfectly any day over a quieter gun with lots of failures. I bet I could get the 4.5" to work by shooting Mini-mags or other HV ammo, but that doesn't interest me. I'd say a 4.5" shooting HV is about as loud as a 16" shooting subsonic.

Since others can shoot a 4.5" barrel without failures, I'm assuming that is about as short as the 15-22 can go. And because such a short barrel seems to work for most, I likewise assume a 10" barrel would work well for me. That would certainly give more back pressure. I'd sure like to try it to find out.

Makes me wonder if the CMC trigger needs more back pressure to reset than other triggers. It hits real hard so curious if it takes more pressure to reset? Anyone shooting with a CMC & a 4.5" barrel?

I'm not interested in selling my barrel, as that would leave me with 2 guns & one barrel. That is why I stated I would swap.
 
How comfortable are you with a rotor tool? I provided a link that shows how to mod the hammer. If you screw it up it'd only the cost of a standard AR hammer and cheap springs to replace.

I had the 15-22P. I saw that S&W milled the bolt to drop mass. I knew I had to shed some mass so the choice was either mill the bolt or cut the hammer/spring force. I did not want to reduce the recoil spring as S&W can be stingy with replacement parts.

I'm pretty sure this is why mine works well.
http://smith-wessonforum.com/smith-wesson-m-p-15-22/244556-trigger-job-speed-hammer-pics.html
 
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No, I wouldn't do that. It is not that important to me to have such a short barrel. I wish I'd stuck with my original thought of having a 10" or so barrel.

To me, the 4.5" barrel is too short & just looks a bit weird. I understand many like that look by I would prefer my 15-22 look more like my SBR 300 Blackout, with its 9" barrel. I like that look especially with suppressor attached.

I'm betting I can find someone who would like this short barrel, with all the work (and expense) already taken care of.
 
So it sounds like the thing that makes the CMC more reliable concerning light strikes also makes it less reliable with the short barrel. Seems like reducing the hammer spring weight, recoil spring weight, hammer weight, or bolt weight might be the only solutions for your particular situation if you were to keep the CMC trigger and 4.5" barrel. I haven't ever played around with a CMC trigger...can you remove the hammer spring at all and possibly install a JP lightweight spring? They are fairly inexpensive and if it could be changed may make the reset more reliable, even if there is a possibility of slightly less reliable ignition (light strikes).

Sounds like you're just looking for a barrel replacement at this point for reliability and cosmetic reasons (nothing wrong with that), so even if you don't have a chance to try any of the above remedies, maybe if someone else is having a similar issue they might find the ideas useful.

Also, found the pictures I had previously of the rifle/pistol bolts. Again, it's about a half ounce of weight difference.

kMsB7Tvm.jpg


N9ZASW1m.jpg


4FEPW77m.jpg


9Mr1pUsm.jpg
 
telero said:
I haven't ever played around with a CMC trigger...can you remove the hammer spring at all and possibly install a JP lightweight spring? They are fairly inexpensive and if it could be changed may make the reset more reliable, even if there is a possibility of slightly less reliable ignition (light strikes).
Click to expand...
The CMC trigger is in a drop in module. I would never mess with it.

telero said:
Sounds like you're just looking for a barrel replacement at this point for reliability and cosmetic reasons (nothing wrong with that), so even if you don't have a chance to try any of the above remedies, maybe if someone else is having a similar issue they might find the ideas useful.
Click to expand...
Exactly. What doesn't apply for me, in my circumstances, just might apply to others.

Next chance I get, I will load up some magazines with some HV ammo & then try out the 4.5" barrel again. Going by perceived sound levels, I'm thinking HV might have enough extra oomph to reset the trigger properly. I just remember a few weeks ago, when I tried out some Mini-Mags with the short barrel, that they were considerably louder than my subsonics.
 
Correct! I fond very little if NO difference with 1150fps Dynapoint and Rem Sub 1050fps
However M22 and Rem Peters @1280fps had a harder kick and was much louder.
 
FWIW, don't use Rem .22LR ammo.

Rem subsonic .22 LR ammo is under pressured so the cases fail to expand against the chamber wall and are loud with suppressors. Rem Golden Bullets are over pressured so they have chamber bark with suppressors.
 
I don't use much bulk ammo because I want the 15-22 to work reliably. I do use CCI/Speer Blazer mostly with CCI Standard Velocity and CCI Subsonic when I want to go quiet.

My .22LR submachine gun is a hungry piggy so it gets CCI Mini Mag and Remington Golden Bullet. At 900 RPM, its a lot of fun. Think of a 200 round .22LR Micro Uzi with no recoil.

15198028625_848473ede2.jpg
 
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