I figured this was the best place to ask, so here we go.

I have a dedicated CMMG 22LR upper with A LOT of rounds through it. It ran just about everything I put through it with the exceptions of subs without any issues at all. As of the last several hundred rounds, it hasn’t wanted to run Federal Automatch very well but is still running CCI mini mags without fail. I figure this is just a matter of the springs being a bit fatigued and the plan is to go ahead and replace them. I’ve got spare parts from CMMG that I can toss in now and I’m sure they’d get me back in business, but I’m curious if the hive has found a better option for replacement guts for these rimfire ARs for when I’m replacing parts the next time.

Picture because I love this thing

Not sure if they're objectively better than CMMG, but I've had good luck with BoreBuddy parts.

AR22 Recoil Spring Kit

I’ve never replaced a spring on my CMMG pattern bolts except maybe a firing pin spring once.   In my experience Federal rimfire ammo quality control has been pretty bad the last few years.   If the mini mags run in your AR-15 your springs are fine.   My bet is the Federal ammo is really inconsistent.   A chronograph will tell you for sure.   It won’t hurt anything to change the main bolt recoil spring but I bet it makes the Federal ammo less reliable.  The Federal ammo probably has such a weak impulse a new spring will probably be heavier than an old spring.

Thank you. I’ll give them a shot on my next go-around.




I would guess that there is somewhere around 15-20k rounds through it at this point. Almost all of them suppressed. I’ll have to borrow one, but I’ll get the automatch chronographed. Assuming that I’m getting underpowered loads every couple of shots with the automatch, a lighter spring should help it run more reliably?

A lighter recoil spring would help if you want to shoot subsonic ammo.   Lakeside used to or does sell various weight springs for the Atchisson, Ceiner CMMG pattern bolts.



http://www.lakesideguns.com/title1/spring.html

Thank you, yes. That’s why I was wondering if going with a lighter spring would be better for the Automatch, if it is showing me wildly different velocities. I figured lighter would run it better, but my logic may well be flawed.

I have plenty of subs, but I don’t generally use them in a barrel as short as this (4.5”).

I can’t have a suppressor because I live in Illinois.  Everything I’ve read indicates most bulk pack high velocity 22 LR is subsonic out of a 4.5” AR-15.   I’ve fired tens of thousand 22 LR in various semi auto pistols and rifles.  They all perform more reliably when they have been shot extensively and springs wear in.   I’ve read the suppressors back pressure tends to help 22 LR blow back actions reliability until they get filthy.

That has been my experience. I suppose I need to try out a few different loads of 22lr and see what’s what. As you said to begin with, it could be as simple as Automatch not being as reliable as it was when I began buying it in bulk years ago. I used to be able to run thousands of rounds of Automatch through this thing without a cleaning, and without issues. My first thought was that it was simply too dirty, but I put it through my ultrasonic cleaner and got it as clean as it’s ever been. The issues persisted despite trying shooting from several different batches of Automatch. After having no luck with Automatch I was able to run 500 rounds of CCI without a single stoppage, even with the binary trigger.