AR Sponsor
Posted: 10/13/2012 6:22:24 PM EDT
|
Finally got a chance to take my dedicated build to the range today. I took 100 rds of 40gr RN, and 100 rds of 36gr HP Mini-mags with me.
Here's a photo re-posting of the build: 
Beyond the furniture/normal components, the guts are a CMMG dedicated barrel, CMMG SS Bravo kit, the barrel collar is actually the park'ed version (came with the barrel, but a SS is in the future), PSA LPK with JP reduced power (yellow) springs, and a TACCOM plug. Out of the 200 rds fired, I had 10+ light strikes. Interestingly enough, most occurred on the first round chambered after inserting a new magazine. When this occurred, I dropped the mag and pulled the charging handle back. The round would remain chambered (not extracted), and then I'd release the CH/let the bolt snap back. Pull the trigger on this second attempt, and it would fire every time. I'd re-insert the mag, chamber a new round, and then happily snap through the other 24 rds. Overall, I'm hooked. I should have built a 22LR a long time ago. 
My concern is regarding the light strikes, and specifically why it occurred on the 1st rnd chambered almost every time. (There were 2 or 3 mid mag light strikes early on.) Something amiss? Possibly the JP springs? ' 
|
|
If the bolt doesn't close that last little RCH or 1/16" to 1/32" after you reload and charge the bolt, the first time you pull the trigger it takes up the slack. That's just enough lost kinetic energy that the firing pin won't set off the round. Make sure you get absolute bolt closure. There are other parts that have to wear in as well, but that's the one that caused me the most trouble figuring out. |
|
Yeah, after thinking about it some more, I think you've both made good points.
Based on the way it was acting, I agree that the bolt may not be closing completely on that 1st round. And that's something more wear-in/break-in time should help to resolve. I'll pay closer attention to that on my next range visit. To that, I was under the impression that the CCI Mini-Mags were one of the better rounds to use for break-in. Is there a better choice? Velocitors or Stingers? |
|
My CMMG 22 uppers and conversion run great on Federal 36 grain bulk HP. It is possible the bolt is dragging on the bolt catch slightly. Look for finish wear on top of the bolt catch. It is best to pull the charging handle to the rear and release to get the most forward momentum. If the bolt doesn't move forward smartly the bolt may not go completely into battery. Also make sure the firing pin moves freely and retracts. If the firing pin doesn't move freely remove the cross pin and inspect the firing pin. These have been known to break and can lead to erratic ignition.
The JP yellow spring might be a little light for a new gun. As the gun wears in the failure to fire may go away. |
|
CCI ia a better ammo. I stay away from the super hot loads mentioned. Accuracy deteriorates with the extra speed.
Read here: http://www.ar15.com/forums/t_3_15/526872_How_to_make_your_AR_22_run_smoother_NOW_with_pictures.html And here: http://www.ar15.com/forums/t_2_145/176451__22_Conversions_Trouble_Shooting.html Dave S |
|
A TACCOM firing pin was on my future purchases short list, so I'll go ahead and pick one up. (I have the plug in place already)
I had done a cursory read of the tacked run smoother topic awhile back. Now that I've re-read through the entire thread it seems I need to break out the dremel and power drill for a little polishing work. Thanks for the reminder.
|
|
Just a suggestion, wait a little longer to see if you really need to buzz the chamber.
Sometimes the issue isn't the chamber at all and there is no putting metal back once it is removed. A detailed cleaning a close look is definitely a good idea, but run some more plain rounds through the rig first to see if she breaks in. If you get several hundred more rounds down range and still have the problem, then take a look at your brass very carefully. Try to notice if there is any difference between normal function brass and failed-to-function brass. Your rig shouldn't need Stingers or High Velocity rounds to function. Standard Velocity CCI or some of that new Tactical 22 is all you should need energy wise. Mine cycles perfectly with sub-sonic match ammo or std vel. Watch for that closed bolt issue if there is a click and no bang, but make sure you follow safety first, keep it pointed down range and wear your eye protection. |
|
Interesting that you have multiple "first round" light strikes. I would definitely look to see if there is any undue resistence preventing the bolt from fully closing that first round. My build (w/CMMG bolt, collar, and dedicated bbl) had a light strike issue as well. I would get at least one FTF with each 26 round mag...randomly, beit the first, the middle, or last shot. My rig had roughly 600 rounds through it and at first it happened so infrequently that I just figured they were dud rounds. However, once I took a close look at the spent casings, I realized that I had very light strikes on ALL of them! I was amazed any of them were firing! Investigating the problem I discovered that the hammer did not come into contact with the back of the bolt when fired. It was close, maybe 0.15", but would come to rest on the back of the bolt catch instead. I don't know if this was just an upper/lower receiver machining deficiency or other, but I felt this caused undue stress on my lower as the bolt catch was catching the brunt of the hammer fall, not the bolt and subsiquent firing pin.
What did I do? I fabricated a new, slightly longer pin from a std 5.56mm firing pin. Result = solid, deep, well defined rim strikes, and I haven't had a FTF since in roughly 400 rounds. If you don't have the plastic case deflector on your rig, you can easily see if yours has a gap between the hammer and the back of the bolt when the hammer is in the fired "fwd" position. I suspect this is the issue with many of the "light strike" complaints I have seen in this forum.
|
|
Quoted:
Finally got a chance to take my dedicated build to the range today. I took 100 rds of 40gr RN, and 100 rds of 36gr HP Mini-mags with me. Out of the 200 rds fired, I had 10+ light strikes. Interestingly enough, most occurred on the first round chambered after inserting a new magazine. When this occurred, I dropped the mag and pulled the charging handle back. The round would remain chambered (not extracted), and then I'd release the CH/let the bolt snap back. Pull the trigger on this second attempt, and it would fire every time. I'd re-insert the mag, chamber a new round, and then happily snap through the other 24 rds. This (bold/underlined) is significant, IMHO. Although the 22lr is blowback operation, so that no extractor is "needed" (normally, blowback kicks empty case free of chamber), in order to remove a un-fired round, a functional extractor is a necessity, IMHO. 1st: If you remove the bolt from the weapon, and insert a 22lr cartridge under the extractor (as if it were sitting in the chamber ready to fire), does the cartridge stay in place? there should be enough tension on the case rim from the extractor/spring assembly to keep the round in place. 2nd: and this is harder to determine, when assembled, and a round chambered, the extractor should only just barely rub against the extractor notch in the barrel extension at the front of the chamber. if there is too much "nose" or protrusion on the extractor, so that it cannot get full contact with the case rim, it won't be able to pull the un-fired round from the chamber as well as it should. dirt in the bolt's extractor channel, or in the recess for the extractor spring will add to this. the bolt assembly should pull a live cartridge out of the chamber, consistently. safety factor!! Also, the interference of the "nose" against the extractor notch could be interfering with the 1st round functioning properly. just some thoughts. raffica |
|
We replaced the JP Yellow Hammer springs on a bunch of our guns and the light strike problems have ended on both conversion kits and dedicated .22LR uppers. I also installed the Taccom Pressure Plug after most of the light strikes stopped to give additional help keeping the bolt closed tight and I seldom have a problem any more.
As a test I reinstalled the JP Yellow Hammer Springs and the problem resurfaced. It makes no difference if you leave the JP Yellow Trigger spring in,,,,,,the problem appears to be with the hammer. |
|
If you are using JP yellow hammer springs......you need to cut the back of the hammer off. I like to say.....the part that looks like the "woody the woodpecker" hair style. If you do that, and still have light strikes, and have the pressure plug.....the problem is'nt the hammer.
Tim |
|
Quoted:
We replaced the JP Yellow Hammer springs on a bunch of our guns and the light strike problems have ended on both conversion kits and dedicated .22LR uppers. I also installed the Taccom Pressure Plug after most of the light strikes stopped to give additional help keeping the bolt closed tight and I seldom have a problem any more. As a test I reinstalled the JP Yellow Hammer Springs and the problem resurfaced. It makes no difference if you leave the JP Yellow Trigger spring in,,,,,,the problem appears to be with the hammer. The ammo you're using isn't resetting the hammer. The springs will help with the occaisional weak blowback. I just went through this last week. I could open the lower and see the hammer riding the bcg. |
AR Sponsor