22LR AR-15 Conversion Kit Reliability Tip: use buffer and spring

[Radom Guy]

“Short” story: My CMMG 22LR AR-15 Conversion Kit ran great in my AR carbine with near perfect reliability. However, once I put it in my new, built by me, dedicated 22LR AR, it was not nearly as reliable, with zero to 4 malfunctions per 25 round mag, regardless of ammo type and brand.

Knowing that the conversion kit is blowback operated that does not function with the AR platform buffer and recoil spring system, that this firearm would be a dedicated 22LR, and that I want this gun to be lightweight, I left the receiver extension/buffer tube hollow. I did NOT install a buffer and buffer spring.

Long story short: I have now put a standard AR-15 weight buffer (3.0 oz.) and recoil spring, and the gun works perfectly (damn near it anyway). Before I put the buffer in, it malfunctioned around 12% of the time. With the buffer and spring, I shot 600 rounds this weekend and had only one malfunction (a single cartridge nosedive). CMMG should have this information front and center like RightToBear-dot-com does on their site (see below), or at the very least very available in a Troubleshooting section. As a matter of fact I plan to write about this to them. They’ve been very responsive in the past when I have contacted them (for other reasons).

For those who are curious, I am of course using the same ammo now that was malfunctioning before I put the buffer in. Those two ammos are CCI Mini-mag 40 grain Copper Plated Round Nose, as well as Aguila Super Extra copper plated 40 grain RN.

I discovered this fix by accident. I had tried many other things before this, by the way. I was on the Right To Bear vendor’s website. I read what you can see below in the screenshot. Ultimately the buffer and spring help to stabilize the 22LR bolt carrier. Looking at the bolt carrier and the way that it inserts into the receiver, it looks like it will not move during operation. However, when it cycles back, it moves the carrier ever so slightly such that it can cause malfunctions/jamming.

If there were a rimfire forum here or an AR forum, I would have posted there. There is not either of those so I posted in this general topic forum.

I hope this helps someone!

 

[NIGHTLORD40K]

I found exactly the same thing with my Colt kit. Ran so-so without the buffer and spring, perfect with it.

 

[Radom Guy]

I find it very confusing that the kit instructions never indicated this necessity. It took me 10 months to figure this out because my range time has been very limited. All that time I could have been enjoying it. Thanks for commenting!

 

[NIGHTLORD40K]

I actually thought about drilling and tapping the upper for a set screw to secure the bolt more, uh, securely (and cuz Im cheap), but in the end just caved and put a buffer in it, lol.

 

[Radom Guy]

I actually thought about drilling and tapping the upper for a set screw to secure the bolt more, uh, securely (and cuz Im cheap), but in the end just caved and put a buffer in it, lol.

Haha! For myself, I waited to order a new buffer spring until I needed other items from MidwayUSA so I could get the free shipping offer; it was only $3.99 for the buffer spring. I had an extra 3.0 oz buffer sitting in my gun parts box, too, so an extra couple bucks saved there, too. Gotta do it as affordably as possible, as it is so easy to overspend on pet projects like this!

 

[12Bravo20]

This is actually a well known fact and has been for a long time. Taccom has been making a pressure plug that sits in front of a standard buffer for years. It works by adding a little forward force to the back of the 22lr bolt, holding it against the barrel. And yes they work quite well and eliminate a lot of light primer strikes/failures to fire. Bore Buddy is another company that makes a pressure plug. I run a pressure plug in all of my AR22 builds that have a buffer tube installed.

I use a buffer tube plug on my 4.5" AR22 pistol build and it too keeps the bolt from moving backwards.

 

[Radom Guy]

This is actually a well known fact and has been for a long time. Taccom has been making a pressure plug that sits in front of a standard buffer for years. It works by adding a little forward force to the back of the 22lr bolt, holding it against the barrel. And yes they work quite well and eliminate a lot of light primer strikes/failures to fire. Bore Buddy is another company that makes a pressure plug. I run a pressure plug in all of my AR22 builds that have a buffer tube installed.

I use a buffer tube plug on my 4.5" AR22 pistol build and it too keeps the bolt from moving backwards.

Not very well known to people who don’t know it, haha!

As I said in a comment above, CMMG, who is by far the biggest producer of the conversion kits, does not mention this in an instruction manual, nor did I see it on their site. But I certainly believe that they should mention it somewhere up front as a simple thing to check when troubleshooting.

I knew about the pressure plug too, but it is billed as “reliability enhancing” along with some other goodies. Since my bolt was already working great in my carbine, I did not think any of those would be necessary. I was actually correct because I do not need a pressure plug/bore buddy. But I can certainly see now how they would be helpful and might even get one someday. For now, I don’t need it as the buffer and spring work great as a solution.

 

[12Bravo20]

I knew about the pressure plug too, but it is billed as “reliability enhancing” along with some other goodies. Since my bolt was already working great in my carbine, I did not think any of those would be necessary. I was actually correct because I do not need a pressure plug/bore buddy. But I can certainly see now how they would be helpful and might even get one someday. For now, I don’t need it as the buffer and spring work great as a solution.

Not every single AR22 will need a pressure plug. A lot depends on how everything fits together. You have to take into account the bolt itself along with how the upper receiver and lower receiver fit together. Here again we have to deal with tolerance stacking between parts that are made by different manufacturers. IF your bolt is oat the minimum specs for length and your receivers are at the maximum specs for length, then there is a good chance that you will need to use a pressure plug.

And this is not unique to the AR22. This also goes for all AR's, which is why some uppers fit tighter or looser on different lowers. Using aftermarket parts in Glock frames and/or Polymer 80 frames also have to deal with tolerance stacking.

 

[lostchild]

I've got a folding brace on my ar pistol, I just cut a 3/4" dowel or pvc pipe about 2 long, notch it for the buffer retainer pin and use as a spacer between the folder and the cmmg. On my ar rifle I use the same set up but cut the plug about 3/4".

 

[Radom Guy]

Not every single AR22 will need a pressure plug. A lot depends on how everything fits together. You have to take into account the bolt itself along with how the upper receiver and lower receiver fit together. Here again we have to deal with tolerance stacking between parts that are made by different manufacturers. IF your bolt is oat the minimum specs for length and your receivers are at the maximum specs for length, then there is a good chance that you will need to use a pressure plug.

And this is not unique to the AR22. This also goes for all AR's, which is why some uppers fit tighter or looser on different lowers. Using aftermarket parts in Glock frames and/or Polymer 80 frames also have to deal with tolerance stacking.

Yes, all good facts, thanks.

My post was actually just meant to be something simple to do when first using the 22LR conversion kit on an AR-15.

I joked above about that info not being known to those who don’t know it, because this information was harder to find than it really should be. I never actually discovered about the necessity of a buffer and spring when searching for it; I came across it by accident.

 

[NIGHTLORD40K]

Yes, all good facts, thanks.

My post was actually just meant to be something simple to do when first using the 22LR conversion kit on an AR-15.

I joked above about that info not being known to those who don’t know it, because this information was harder to find than it really should be. I never actually discovered about the necessity of a buffer and spring when searching for it; I came across it by accident.

My Colt kit (from the 90s) didnt have any instructions at all in the blister pack, lol.

 

[12Bravo20]

I'm probably showing my age here. My first experience with a 22LR conversion kit was the M261 conversion kit in my M16A1. We didn't get much if any training or have manuals for the conversion kits. We never ran them without a buffer installed, NCO's would have a cow if we took the buffer and spring out and then misplaced either one.

 

[wesmonster]

This is actually a well known fact and has been for a long time. Taccom has been making a pressure plug that sits in front of a standard buffer for years. It works by adding a little forward force to the back of the 22lr bolt, holding it against the barrel. And yes they work quite well and eliminate a lot of light primer strikes/failures to fire. Bore Buddy is another company that makes a pressure plug. I run a pressure plug in all of my AR22 builds that have a buffer tube installed.

I use a buffer tube plug on my 4.5" AR22 pistol build and it too keeps the bolt from moving backwards.

This what I was taught. On my RTB upper I'd get occasional light strikes even with a buffer and spring, there was just a bit of front-back play in the carrier and that was enough. A Bore Buddy plug fixed that. But only the spring is needed to keep tension, I run the Bore Buddy plug and spring but no buffer. Doesn't matter either way but if you're buying parts for a new build a pressure plug is cheaper than a buffer.

 

[someguy2800]

I found the same thing. If you want to save some weight you can take the roll pin out of the buffer and dump out the internal weights. I have been thinking about 3d printing something to go in the end of the buffer tube to put tension on the carrier to save the weight of the spring and buffer but its only a few ounces so not high on my priority list.

 

[herrwalther]

I would have guessed keeping the buffer and spring in was implied. As the instructions on my CMMG kit were "Just replace the bolt carrier." Or something to that effect. It was on the box that I long threw away. I can see how Brownell's ARIC bolt took a few hints from the CMMG conversion bolt but left the beefy stuff to handle the bigger round.

 

[Bcwitt]

Ny cmmg didnt run very well until i got a dedicated 22lr barrel. Not had any issues since.

 

[Radom Guy]

I would have guessed keeping the buffer and spring in was implied. As the instructions on my CMMG kit were "Just replace the bolt carrier."

Like a lot of folks, I built this dedicated 22LR AR from scratch, so there was no buffer to keep in the buffer tube. Since I knew definitively that it is blowback operated and the bolt carrier never enters the receiver extension, I had no reason to believe that a buffer and spring were necessary.

Side note: I see a lot of AR 22 pistols with no receiver extension (aka buffer tube). I now believe those must use some type of pressure plug to keep the bolt carrier from moving backwards. If anyone here has an AR 22LR pistol with no receiver extension, I am curious to see a picture or something to see how it keeps the bolt carrier in place. Just for knowledge’s and curiosity’s sake.

That all said, the actual purpose of my post was for those who may have had the same issues as me, to be able to search this site and find my simple non-bore buddy non-pressure plug solution to try. As I said before, I searched online for a solution but never actually found it until I came across it by accident.

 

[Radom Guy]

I found the same thing. If you want to save some weight you can take the roll pin out of the buffer and dump out the internal weights. I have been thinking about 3d printing something to go in the end of the buffer tube to put tension on the carrier to save the weight of the spring and buffer but its only a few ounces so not high on my priority list.

I like it, I was thinking of something like that too. Someone above also wrote about using a 3/4” PVC pipe cut to size. Same here, not high priority, as right now I am just thrilled have it working so well. I think I said before, 600 rounds and only one malfunction; I’m psyched!! I love shooting it now especially with the pride of having built it myself to my exact specifications and desire.

 

[12Bravo20]

One needs to remember that for us old timers, we started out when only the conversion kits were available. So the buffer and spring was already in the lower. Plus if you read a lot of the AR22 threads on Rimfire Central and ARFCOM you will see that people have been using pressure plugs to help reliability for a long time.

Now to answer the question on AR22 pistols that do not use a buffer tube. Most will use a plug that screws into the buffer tube hole in the lower.The plugs stick out enough into the receiver to keep the bolt from moving enough to cause issues. Though some have still put a small piece of wood or plastic in to tighten things up a little. I haven't had to add anything to the buffer plug on my 4.5" AR22 pilots build.

Now you will find some that don't need a pressure plug while others do need one. This is due to tolerance stacking. Tolerance stacking happens when parts are either at the minimum or maximum of the allowed specifications. The more parts used from different manufacturers, the worse tolerance stacking can be. If the upper is at the maximum dimensions and the bolt as at the minimum dimensions, they you will mot likely need a pressure plug.

I can't say for sure about CMMG and why they don't include instructions to use a buffer. But if I had to guess, the reason stems from the fact that years ago most who built a dedicated 22LR upper were putting them onto an existing lower setup for centerfire use and just left the buffer in place to start with.

 

[Radom Guy]

Now to answer the question on AR22 pistols that do not use a buffer tube. Most will use a plug that screws into the buffer tube hole in the lower.The plugs stick out enough into the receiver to keep the bolt from moving enough to cause issues. Though some have still put a small piece of wood or plastic in to tighten things up a little. I haven't had to add anything to the buffer plug on my 4.5" AR22 pilots build.
…

I can't say for sure about CMMG and why they don't include instructions to use a buffer. But if I had to guess, the reason stems from the fact that years ago most who built a dedicated 22LR upper were putting them onto an existing lower setup for centerfire use and just let the buffer in place to start with.

Thanks for the explanation about the pistols with no buffer tube. I looked up “screw in buffer tube plug” as well as “pistol plug” and found a few. None that I was able to find look long enough to stabilize the 22LR bolt carrier but I can probably find that info with a little more searching.

I’m sure you are right about the reason CMMG does not mention about a buffer or pressure plug being necessary for many or most builds. Plus, “just remove your BCG and put ours in” is better marketing, haha! However, we all know here of the exponential growth of people building their own AR’s and particularly with 22LR chambering. I do feel like they should have that information somewhere on their site at least. out of respect to the people who buy their products for custom dedicated 22LR builds. . Just like Right To Bear does as I included in my original post.

Thanks for your input!

 

[wesmonster]

I would have guessed keeping the buffer and spring in was implied. As the instructions on my CMMG kit were "Just replace the bolt carrier." Or something to that effect. It was on the box that I long threw away. I can see how Brownell's ARIC bolt took a few hints from the CMMG conversion bolt but left the beefy stuff to handle the bigger round.

Probably assuming it's not a dedicated build, if you're sharing a lower with both a .22lr and 5.56 buffer, you don't want to shoot 5.56 without a buffer.
Now on another forum a guy with a machine shop actually made his own carbine buffer but the face was thicker with the same cuts & profile as a pressure plug. Said it fixed his light strikes but still ran fine in his 5.56.
I've shared uppers on lowers for years and it can sometimes be tough to compromise a lower for multiple duty. Making a dedicated build is easier and if you're like me, you probably already have enough takeoff parts to cover most of a lower.

 

[Radom Guy]

Probably assuming it's not a dedicated build, if you're sharing a lower with both a .22lr and 5.56 buffer, you don't want to shoot 5.56 without a buffer.
Now on another forum a guy with a machine shop actually made his own carbine buffer but the face was thicker with the same cuts & profile as a pressure plug. Said it fixed his light strikes but still ran fine in his 5.56.
I've shared uppers on lowers for years and it can sometimes be tough to compromise a lower for multiple duty. Making a dedicated build is easier and if you're like me, you probably already have enough takeoff parts to cover most of a lower.

I am the original poster of this thread. I did not write the comment to which you quoted and replied. I believe that person was just making a general comment about the conversion kits and the one he bought years ago.

For me, the purpose of my post was really just to help others who may have encountered the same problem that I formerly had and resolved before I created this post. Again, this is a dedicated 22LR AR.

Thanks for writing, though. The buffer that the machinist made that you mention sounds pretty darn cool!

 

[Walkalong]

It makes sense it needs a stop of some sort, without it is sort of like limp wristing a handgun.

 

[czhen]

My DPMS 22 upper run either way fine.

 

[Radom Guy]

My DPMS 22 upper run either way fine.

With buffers and buffer springs potentially serving the same purpose as a pressure plug, to quote 12Bravo20 , “Not every single AR22 will need a pressure plug. A lot depends on how everything fits together. You have to take into account the bolt itself along with how the upper receiver and lower receiver fit together. Here again we have to deal with tolerance stacking between parts that are made by different manufacturers. IF your bolt is oat the minimum specs for length and your receivers are at the maximum specs for length, then there is a good chance that you will need to use a pressure plug.”

And to quote myself: “… the purpose of my post was really just to help others who may have encountered the same problem that I formerly had and resolved before I created this post.”