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Posted: 6/27/2016 5:37:35 AM EDT
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Hi guys,
I finally got to take my M16A1 build to the range today to sight it in. It was a fun day overall, with a lot of retro goodness going on. For starters, after getting settled in I realized that the guy at the first table on the left was shooting a very nice M1 Garand. Next to him was gentleman shooting an M1A (he said he bought it because it was closest thing he could get to the M14 he carried in Nam). Then there was me with my M16A1 clone. It was like looking at a display of the evolution of US small arms!  Wish I could have gotten a picture!!
Anyways, the real reason for this post is my A1 clone is giving me trouble. I'd load a mag, chamber a round, then it was....bang....bang...click! Empty chamber. Pull back the charging handle to load a round and once again....bang...bang...bang...click! I'd do this enough times to empty the mag, but, it would not lock back after the last shot. To make matters worse, every once in a while, it would jam with the nose of the bullet just starting up the feed ramp, but the bolt would be stopped about halfway down the case (bolt over base?) Tried multiple magazines (couple of old adventureline 20 round, PMag 10 round, D&H curved 20 round. All of which work great in my other guns) same results. I even tried swapping out the BCG with the WMD nickel boron one from my TactiCool carbine (which runs like a sewing machine), also same results. It seems to be short stroking, but, I can't figure out why. My other two builds work perfectly, but, both of them are carbines. This is my first rifle, with fixed stock and 20" barrel. Anybody have any ideas what might be going wrong or what to look for? I'm really bummed as besides the aforementioned problems, the rifle is proving itself to be very accurate. Here's what I was shooting..... Lower: Anderson Upper: Brownell's A1 BCG: DelTon (ar15 profile) Barrel: ar15sport.com, 20" lightweight, 1:9 twist, non-chrome bore. Buffer/tube/spring: ar15sport.com, fixed rifle stock (buttstock screw is the correct A1 length) FCG: DelTon, standard GI style Ammo: mix of PMC bronze and freedom munitions reman, 55gr .223 Rem (both of which work well in the carbines) Here's a pic of the misbehaving rifle.... 
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| My advice, get some good ole M193 (5.56 55 gr. FMJ) ammo and try it again. The weaker .223 may be causing it to not cycle completely. Try the 5.56 ammo and see if that does the trick. If it does, run it for a while and then try the .223 again. I helped a young man build his A1 last Fall and he used an AR15.Sport 1/9 barrel. We used M193 ammo in it and it worked great. |
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Would it serve if you put the entire finicky upper on one of your carbine lowers that run well?
What I'm thinking is it might help you determine if the rifle's lower spring and buffer combo are giving you issues. You have done all the other troubleshooting suggestions, mags, bolt carrier etc. I have a number of carbine builds in various end configurations, and almost all of the have an abundance gas pressure and bolt speed, my rifle builds are usually close to evenly gassed, but certainly not like the bolt speed of the carbines. I built many more carbine and always erred on too strong a spring, and too heavy a buffer, and have to "tune in" a solution. I don't have any experience with that company's springs though: In the shorty carbines, sometimes the bolt is too fast, and bounces off the back of the recoil tube and travels forward too fast to allow another round to come up. I haven't really seen that in my rifles except when I had a very very weak spring from an RTI kit. |
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I use three ammos:
-Federal Lake City M193 -Independence M193 (sometimes IMI, sometimes LC) -Personal reloads with 25 grains 4064. I have use some factory reloads that didn't work, when all of the above did. Also PPU and Aguila are not consistantly as hot. Get some Federal Lake City (or PMC X=Tac M193), lube it, and shoot it. Nice build, by the way. |
| I agree with the hotter ammo theory, but in all honesty, you have a modern components rifle there and it should shoot everything without trouble. I would shoot it more and see if things get better. It's a long shot, but there always a possibility that the ar15sports barrel gas hole was drilled off center or too small or there is a tiny obstruction in that area. If the hotter ammo and more shooting don't work, you may want to look at those things. |
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All of the above is great advice.
I'd add, and encourage everything to, when trying to trouble shoot an issue like this to bring a note book with you, number your mags, and test for malfunctions using the same batches of ammo. Also, trouble shoot using one remedy at a time to try and isolate issues and possible fixes. I would suggest strictly only loading 1 round in to a mag while test firing. I had a barrel that was so on the edge of short stroking that it would pick up a round almost all the time but only lock back a few times. You could fire a string and thing everything was good until it short stroked too far. As catching the bolt hold open is the farthest stroke the bolt has to take, you'll find out every time if it's short or not. Using 1 mag or at least tracking malfunctions per mag will help you figure out if 1 mag is worse than another, too. I would shoot a group of something around 10 rounds, single loaded, from a numbered mag and record your results. Repeat with different brands of ammo. That should give you a very very good insight in to what is going to work for your rifle and what needs tending to. Switching to another lower is also not a bad idea to rule out some other issues. |
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I've had similar issues before and discovered that the buffer spring was the issue, I changed the spring out and it ran perfectly after that. I agree with lubing the tube too, I use green grease from the auto store in mine and they are much quieter as well. On a side note, that old spring works very well in my 762x39 rifle just not when I snap on a 223 upper even with 193 it short strokes
Glod luck! |
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So, I had some time to look it over some more and here's what I've got so far....
Yes, the roll pin is in the gas tube. 
I checked the gas tube and it is centered and does not appear to be dragging or catching on the gas key. The bolt carrier came out of another one of my builds and has about 500 rounds on it already. The rails are smooth and shiny and it slides freely in the upper (already tried swapping the bcg out for a known good one when I was shooting, same results) I lubed the bolt inside and out with some light oil before going to the range, but, just a few drops on the rails and a drop or two on the gas rings. It wasn't sopping wet. Didn't see an unusual amount of carbon around where the FSB meets the barrel or where the gas tube enters the FSB, so it doesn't seem to be leaking there. One thing I did notice is the bolt is noticeably harder to pull back than on my carbines. Checked the buffer tube for dents or other obstructions and didn't find any. However, there was a small amount of sticky sludge inside the tube. Stuffed a rag down there with some CLP on it and the rag came back with a dark brown, sticky substance on it. Almost looked and felt like cosmoline, but, being as this is a new buffer tube, I don't know why it would be in there. After cleaning it out and putting a little lube down there, bolt is easier to pull back with charging handle. It's still harder to cycle the bolt by hand than my carbines, especially once it starts camming the hammer back. The bolt really seems to be dragging a good bit on the hammer (even when the hammer is being held back by the disconnector). I'll try shooting some hotter 5.56 out of it, but, I really don't want to have to rely on hot ammo for it to run. I'd like it to run on cheaper .223 also. |
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Do you have another full length build that works? I'll assume you don't.
Swap the upper with your carbine build that works (swap both, full length upper on carbine lower & vice versa). Which component (i.e. upper or lower) did the problem (difficulty cycling by hand) follow? |
| Get a can of el cheapo brake part cleaner (Not carb cleaner) and hose down the inside of the buffer tube. If there's still gunk there, it'll jam things up. You didn't mention, but is your gas tube new or used? If it's a used tube, it could be partially blocked. |
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Quoted:
It's still harder to cycle the bolt by hand than my carbines, especially once it starts camming the hammer back. The bolt really seems to be dragging a good bit on the hammer (even when the hammer is being held back by the disconnector). As you stated, the carrier moves freely in the upper. So the drag seems to be on the hammer. I would check to see if the pivot pin holes in the lower are drilled to high, or if there is some other interference that is keeping the hammer from dropping down. It could be a poorly machined hammer. I'd remove the fire control completely and try to cycle the bolt. If it still binds then it might be bore misalignment between the upper and lower. |
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Well, I have followed everyone's advice and tried all the different "checks".
Here's the results.... Removed bolt from carrier and checked gas tube fitment.......bolt slides easily in and out under own weight. No restriction from gas tube. Sprayed out buffer tube to remove "mystery gunk"......... bolt is easier to cycle by hand. Still extra stiff when riding over hammer. Removed fire control group and cycle bolt..............hmmm, very easy to cycle bolt (duh! no hammer resistance! ) Carrier does not appear to be dragging on side of tube, receivers seem to be aligned.
Changed out hammer for another............Ahhh! Now we are getting somewhere. Slight resistance at beginning of bolt travel as hammer cams back, then much easier to move. With removing the gunk from the buffer tube (seriously, I swear there was some sticky old cosmoline in that thing!) and changing the hammer out, cycling the bolt now feels like my other AR's. No more gritty, stiff feeling when cycling the bolt by hand. Unfortunately, I won't be able to check it at the range for a couple of weeks. Can only get there on the weekend and I'm not going to bother trying to get in to the range on Independence Day weekend (rather stand in line at the DMV!) |
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Finally got a chance to shoot it today, and it seems that I'm on the right track.
When I first got there, before even setting up my target, I let her rip with a rapid fire mag dump (which, unfortunately for me means 10 rounds  ). Went through the whole magazine with no problems and the bolt locked back when it was empty.
After that, I slowed down a bit and enjoyed myself. It's actually quite accurate (much more accurate than my old eyes are capable of) and a very soft shooter compared to my carbines. Now, after about 60 or 70 rounds, it started acting up again, but not as bad as before. First it failed to lock back after the last round. Then, halfway through the next magazine, it short stroked and closed on an empty chamber.  Racked the charging handle to finish the magazine, short stroked two more times and again, no lock back on empty.
I pulled the buffer out and wiped it down and squirted some lube down the tube. After that, it seemed to work fine again. However, when I got home, I noticed something odd...... 
All around the edge of the "rings", it seems to be wearing the anodizing off. At a few points, it's down to bare aluminum. Mind you, this is after only about 100 rounds, with the inside of the tube dripping wet with lube. I cleaned everything again (inside tube and buffer itself) , removed the spring and installed the buffer. I can feel it dragging on the inside of the tube, especially near the mouth of the tube. When the spring is in, if I push back the buffer with my finger, I can feel it stick and drag for the first 1/4 inch of travel. This buffer has always been very difficult to install and remove. To get it to go in, I have to line up one of the flat spots with the retainer pin and slam it home. To remove it, I have to hold the retainer pin all the way down for both the first and second ring (is that normal?) I tried inserting a carbine buffer that I know is good, and it doesn't drag whatsoever and was much easier to get past the retainer pin. Did I just get a bad, out of spec buffer? I'm thinking it worked OK at first because it was lubed up enough to reduce the drag. As the lube dissipated with use, the drag was enough to short stroke the bolt. Re-lubing the buffer made the problem go away. I'm thinking I should get another rifle buffer and see if it helps. What do you guys think? |
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