204 Ruger AR Build - Updates and Initial Field Report
Headspace Check
I used Manson no-go/go gauges. The no/go check was good...no way it was even close. The go gauge would turn just slightly but not all the way. A new piece of Hornady sized brass worked with no issues as did a dummy round.
Magazines
Before test firing, I made 10 dummy rounds to mimic factory Hornady Superformance Varmint 40 grain ammo to manually check cycling. I already had some 223/5.56 Lancer mags and Magpul Pmags, all 20 round capacity. I decided to try those mags first before buying/trying the Stoner mags recommended by 204 AR. I've heard the Lancer mags work great too but in my Aero M4E1 lower with the Aero M4E1 Enhanced upper, the Lancer mags appeared to sit up too high. When the BCG would come backward over the top of the magazine it would disturb/misalign or almost pop the top round out of the magazine. I've also read where Pmags tend to not work well with 204 Ruger. The Pmags worked perfectly in my rifle. I'm using a Lilja barrel and they said Pmags work best with 204 Ruger (
.204 Ruger AR feed issues - Lilja). I can see where the follower guides on the inside of the Lancer mag allow the 204 rounds to move more freely where the follower guides inside the Pmags are a little tight looking up against the shoulder of the rounds. I had 2 20 round Pmags. I left one unmodified and I filed down the follower guides inside the other one; there is a good thread on PM about this (
Pmag 204 Modification). Pmag modifications made no difference in the operation of my rifle during manual test cycling or during actual firing. I only loaded my Pmags up to 10 rounds in my testing so far; unmodified and modified Pmags both worked great without any issues. I've seen some 204 Ruger specific mags available but I think I'll stick with the Pmags for now. I can see the appeal of 20 Practical vs 204 Ruger just based on magazines.
Test Firing/Velocity
After adjusting the SLR gas block, the rifle cycled perfectly with and without the suppressor and ejected brass in a nice pile around 3:30-4:00. I'm using a JP FMOS BCG and a JP SCS H2, for reference. So far, I've only shot factory Hornady Superformance Varmint ammo in 32 and 40 grain. 32 grain around 4,015 fps and 40 grain at 3,770 fps.
Target Practice
I put the ballistics info in the Chairgun Elite app for 40 grain factory ammo and used the MPBR calculator for getting the near zero range distance. Curious if anyone else uses this approach or recommends something different.
I mounted and zeroed a Pulsar Digex C50 for daytime hunting and got a few practice shots in on an Atlas Target Works steel coyote. I have a few of their coyote targets, highly recommend. I forgot to turn on the audio recording in the scope. This rifle is super quiet suppressed. Pulsar just released a software update for the C50 including integration of their ballistics app...still need to try that too. The groups I was shooting on paper at 57 yards while getting the C50 zeroed were very small. I still need to put on the real scope and shoot longer groups to see how it really performs. Looking forward to load development too.