New AR15 build failure to extract, and failure to feed.

[pastprimitive]

I just finished my first AR15 build. I was pretty meticulous about each step, made sure my gas block was aligned, proper torque for the barrel and buffer tube nuts. Assembled it all from individual parts. Didn't have a single pre-assembled part. So I am intimately familiar with every part of the gun, it's function etc... Anyhow... take my pride and joy out, and fire's beautifully, accept I go to pull the trigger, and nothing... cycle it to find the spent case in the chamber still, ejects no problem, and the next round feeds fine... Anyhow after 25 rounds of bolt-action-style firing, and scouring forums for areas to check where I may have gone wrong in my build, there are only two stones left unturned.

1. I fell into the Tula Ammo trap, and bought their steel cased .223 for $6.50 per 20 ends at wally world. From the vast forum reports this ammo is notorious for cycling issues. Already went out and bought some brass rounds to feed it. Will see tomorrow if that greatly helps with the extraction issues. Towards the end of my 25 rnd sadness I'd have sporadic extremely difficult to manually extract rounds after firing them. Although I had gone from the first 10 ends that I fired with a sane amount of lubrication. Which for me means mostly dry, except for a drop on all contact surfaces which is lightly wiped with a dry cloth.... to pouring the lube on.... So I may have been having extraction issues at the end in regards to running to wet, and too much oil finding it's way into my chamber.... Combined with the decreased expansion of the steel rounds, allowing for more gass to mix in the chamber with my lube... anyhow... I have learned my lesson, no more steel cased ammo for me.

2. I notice when I charge it, that about 2" into the pull I feel the friction suddenly increase. Feels like it's coming from the buffer tuber area, verified that my BCG and charging handle slid smoothly with out the buffer spring in place. And they slide beautifully on their own. Even cycled the bolt a bunch to break it in... Feels nice and smooth. When I pulled the buffer spring out, I noticed that on the inside wall of my mil spec buffer tube (and I am positive about the mil spec portion) that I had what seemed like an extremely odd ware pattern, and that the buffer had some where on one of the edges. It almost looks like my buffer tube was a defective extrusion. (I assume that's how they manufacture them) because the ware battery honestly looked like the side walls of my buffer tube had a ripple on one side. I slid the buffer no spring back and fourth in the tube, plenty of room to move, moved easily through... Of course under load from the buffer spring I am sure it pushes up against the buffer tube wall somewhat...

I guess my question is... Does this picture look normal below? And would this be a major issue for short stroking... I did verify by watching the bolt as I fired it, and could confirm that it was indeed not coming back all the way. (and yes I checked the gas tube, gas port, alignment at every point, etc..)

I have no problem picking up a new one, but I want to be certain this is an abnormality before i start rebutting every possible suspect.

Thanks for dealing with my long winded description.

Below you can see the dotted line wear pattern... After 25 rounds seems a bit odd.


And just for reference here is the rifle itself. I know it's nothing fancy, if anything it's low end... But I like it:)

[nivlak]

What buffer spring?
What buffer weight?
lube?

Are you sure you lined up the gas block correctly with the gas tube? You can easily break it down and pull the block and look where the soot is to check. Sometimes the gas block needs to be pushed forward...sometimes one to two credit card widths (not much) to get proper alignment.

Also list of build parts?

[italydad]

So in my limited experience, I know that steel cased stuff can build a lacquer up inside, and with already tight specs... I would take it on down to Frank at Protection First, if anyone is going to see something not running right, it will be him. Good luck and congrats on your first build, it will work out.

[Low Trq]

Take you buffer weight and spring out and try putting your BCG inside the tube.

It would help if we knew the maker of the following parts: BCG, buffer tube, weight and spring.

[eph411]

It's really hard for me to tell much from your pictures, but there's a few places I'd look in terms of potential short stroke problems. Ammunition is a possibility, although I gotta say I've run many, many tens of thousands of steel cased ammo through a lot of different rifles and found it to work just fine. It may be that your buffer weight and/or spring are too much for the stuff, but it should still run with pretty minimal adjustments. So I'd try a fuller powered ammunition first as you've suggested, and then if you find it'll cycle that you can always go back to tinkering with the buffer and spring configuration if you want to make it cycle the steel stuff.

Beyond the ammo and buffer, I agree with others that it's worth checking your gas tube and gas block again to rule it out as a possibility. You might be certain you installed it all correctly, but it really doesn't take much misalignment to start causing gas problems. I'd also check your bolt carrier and bolt as well, making sure your key is staked well and your gas rings on the bolt are properly installed. That's where I'd start, and then if you rule out each of those you can always move on to other areas as well.

Eric

[Nievo]

Yep, the others have covered it pretty well but without knowing exact parts used it's kinda hard to tell. Also, what length barrel and gas system?

[Low Trq]

Yep, the others have covered it pretty well but without knowing exact parts used it's kinda hard to tell. Also, what length barrel and gas system?

Looks like mid gas and 16 inch barrel.

[pastprimitive]

Wow, thanks everyone! This is some great input. Ok to answer the questions about the specs of my gun.

Chambered in 5.56 Nato, 1/7 twist, 16" mid-gas Anderson Manufacturing barrel, plane jane, no frills, non chromed, etc...
Anderson Manufacturing Upper, and Anderson Manufacturing BCG (came preassembled, I lied, that part I did not assemble myself. Although I took the BCG apart, and made sure it was properly cleaned and lubed.)

The buffer tube is mil-spec, the buffer spring and buffer were claimed as a standard carbine buffer and spring. Cheap eBay purchase from US seller. So no guarantees that it is indeed what was claimed. But I have no reason to necessarily disbelieve the claim. I believe 3 oz was the stated weight. I'd need to weigh it to verify though. (update, weighed and verified it's a 3oz buffer.)

I'm using an Anderson Manufacturing High Rise Picatiny Gas-block, and a standard stainless steel gas tube. I verified the Gas port on the barrel was clear, and I removed the gas block twice in between shootings and verified that the burn mark was over the gas port, all best a little off center towards the rear of the barrel, but the burn mark completely enclosed the gas port on the barrel.

I will have to check out the gas key to see if it's properly staked. I'll need to read up on that, as I have not yet dealt with installing a gas key on the BCG.

On to what I did with it today. I tinkered and had an opportunity to take it out shooting with some 55 grain Brass FMJ.

Before I did that though I realized my buffer retaining pin was binding on the buffer tube. It wouldn't depress easily or at all. If I threaded the tube on one more turn it was too far on and would interfere with the upper closing, if I threaded it a turn backwards it would retain the pin, but just barely. I realized looking at the buffer tube that I had quite the significant amount of tube hanging off the threads before it started, around 1/16" of non threaded tube. So I took it out to the grinding wheel, and ground off the tube at an angle so the longer portion would be over the buffer retaining pin, This allowed me to install the buffer tube an additional turn further into the lower, while still allowing the upper to mate with no interference, and now my pin was captured by the buffer tube, but was silky smooth, and not binding at all when depressed.

Hoping this was the culprit, I took it out, and no love, same issues as before... And I had even forgot my newly purchased .223 55 Grain FMJ Brass ammo. So Took it back in and decided that possibly I needed to inspect/clean my chamber better. So I used a 9mm copper brush chucked in a drill , and some powder solvent to give a thorough sub to the chamber. Ran that for a few seconds, and thoroughly swabbed clean, and used compress air to blow any fiber, etc clear of the chamber from the cleaning process. Being adventurous I decided to use a 9mm cleaning swab--the kind you soak in powder solvent before you run your cleaning brush down the barrel-- and put a decent amount of rubbing compound, and chucked that in a power drill and spent 10 - 15 seconds polishing the chamber. I know that's a controversial thing to do, but I figured 10-15 second of rubbing compound was just going to knock down rough edges, if it really did much of that at all.

Took it out again, remembered to bring the brass ammo this time, and I had some stove pipe jams, and some good ejections. But regardless all of them failed to feed a new round... Although occasionally there was a enough force to cock the hammer. Followed that all up with some more steel rounds to see if I had fixed the extraction issue. What I noticed is that the first shot or two the steel rounds were manually easily cleared via the charging handle. But progressively became more difficult extract, until I could almost not accomplish ejection with the charging handle alone.

Not wanting to push my luck, having already in the first shooting session having to clear a spent steel case via a cleaning rod, I called it a day. I made sure to collect my shells to inspect, and I did notice something really interesting. There are two deep scratches up on the shoulder of the shell... Which seems like an so place to have scratches, especially as deep as they seemed to me.

So I included a picture of those two deep scratches... But this sort of makes me think my chamber needs to be cleaned up more. They are present on all the shells fired from it. Although with varying degrees of depth.


Here's a link to an album of pictures of the gun from all sorts of angles, and stripped down etc... Hopefully that helps some of you good samaritans out there;)

https://plus.google.com/photos/11319828 ... 1006700737

I am guessing I have a tight chamber, plus some burrs to clean up... But it's really hard to see in the chamber without removing the barrel.... Which I suppose I need to do if I am going to really diagnose it well. Plus the whole reason for me building an AR was so I could learn to fix it myself, and know the system intimately.

Side note: Im not against bringing it into a gun smith. But that sort of defeats the purpose of this exercise for me. Of course I can throw more money at it if it's necessary. But this is part of the challenge/hobby that makes these sorts of things interesting and fun.

Thanks again everyone for all the help.

[Nievo]

Check around your gas block for leaks. Do you notice any excessive carbon buildup or escape? Also, you really shouldn't ever have to grind down the buffer assembly like that, makes me wonder if it isn't maybe the wrong spring, buffer or size tube. Another thing to check is that when assembled the gas tube is perfectly straight and not angled or binding when entering the upper. I have seen tubes bind on the bcg before and cause issues. Last thing is make sure your rings on the bcg don't line up, they should be offset from each other.

[Nievo]

Couple other things to check. Make sure your mag catch is tight and there isn't any play in your mags and they are seated fully. Also, check your spring, buffer tube and buffer lengths and let us know.

If nothing else works I would contact Anderson and discuss the barrel/extension.

[pastprimitive]

No leaks around the gas block in bizarre places. And I did make sure to check gas tube alignment, and made sure it was not binding on the BCG. The mag catch is tight, mag's fully seat.

Buffer tube is 6.75" long (after grinding 1/8" off). The spring is 10.75" long. The buffer is 3.25" long, 3oz. I do think my spring is too strong. But I can't find any numbers on that other than length. And this being my first build I have no way to gauge it I suppose I need to make a trip to the gun shop tomorrow and bring my spring with to compare.

Since my buffer tube assembly was this random no name brand assembly off eBay I am suspicious of a craptastic spring here. Or perhaps a stronger spring geared towards a carbine length gas system. Also I would have loved to not grind on my tube, but it was either that or back it out a turn at which point it would not capture the buffer retaining pin.

Also I am hearing reports of guys ripping off the side of their shells when using the cheap tula ammo, where as mine does not seem to do that at all. Which Irealize could mean a gas issue, but given my extensive testing of the various gas systems in it, and them checking out, I am very suspicious of an out of spec spring that is just too much for the mid length gas system.

But what do I know... lol.





I agree that grinding the tube would

[Nievo]

Buffer spring looks correct, ok length and correct number of coils. How easy or hard is it to compress into the buffer tube?

I still aren't convinced it's not something with the the gas block though. The carbon marks are awfully off-centered.

In pic #12, why does it look like there are multiple holes in the receiver for the gas tube.

I am heading to the range over here in CDA on Monday if you would be able to make it. I've got lot's of different parts we could swap around to see if we can trouble shoot the issue.

[pastprimitive]

Might be able to make it out on Monday if I haven't figured it out by than. My brother is coming into town this weekend and will be going out again. So I am hoping to have it solved by than, but thanks for the offer, i'd love to go out and just shoot. But as of right now monday is pretty tight with work, and family... Work from home, and have a huge prototyping project due for a client... Another time perhaps? If not just for the enjoyment of shooting. I've got a 3d printer, and a small CNC router... possibly need to make you something up for sticking it out with me;)

As far as picture no. 12 goes that's because there are multiple holes. Comes like that from the factory, and i've verified that in product pics of the upper receiver.

As far as the buffer spring goes my intuition says it's way too hard to compress. I'll see tomorrow if there are any shops in town with springs on hand. I would assume so. And i'll need to pick up some more ammo.

[eph411]

Bolt looks ok to me, you can see stake marks and you should be able to tell if rhe key is loose. Your gas rings look good too as far as I can tell, so I think your BCG looks good.

It may sound silly, but did you check your gas tube to make sure it isn't installed upside down? It happens more than you might think, so it's worth checking. Easy way is to pull the upper, remove the charging handle and bolt, plug the chamber with your thumb and then blow down the barrel from the muzzle. If you can't blow then your gas tube is either upside down or obstructed somehow.

Eric

[Sawdust]

Ill bet your buffer tube interior diameter is not to spec (small). And or Spring diameter is not to spec (large). or your buffer diameter is just a little large -Milspec or not ( when a spring compresses the diameter expands )
I can take different brands (name and off brands ) put them side by side Most will be made to different so called SPECS
YES I have had this problem .
Manufactures are only as good as there Quality control .

[Low Trq]

Ill bet your buffer tube interior diameter is not to spec (small). And or Spring diameter is not to spec (large). or your buffer diameter is just a little large -Milspec or not ( when a spring compresses the diameter expands )
I can take different brands (name and off brands ) put them side by side Most will be made to different so called SPECS
YES I have had this problem .
Manufactures are only as good as there Quality control .

This was my guess too.

[to4e440]

I had a blown primer get stuck in my gas key in the bolt. I thought I was going to get rid of the gun, then I took some pipe cleaners and ended up finding the problem. Keep at it you will find the problem.

[wrfforgotten]

In the shop we check the gas system by placing a long wood Q-tip into the gas tub. Place your thumb over the chamber and blow compressed air down the barrel. If the Q-tip shoots across the room you should be good. Another problem could be if your gas rings are lined up on your BCG. If both those look to be good I would suspect the buffer system. As for the scrapes on the necks of the brass cases, they are from the sharp edges of the locking lugs around your feed ramps. Another word of advice, DON'T SHOOT STEEL CASE AMMUNITION. If you have clean your chamber with lacquer thinner. Also drop a live round down the chamber by hand. See if it will fall in and out without much help.

That is my two cents.

[pastprimitive]

So I took my AR into Protection First. First and foremost, major props to the fellas at Protection First. They were awesome! Will be going back there for sure.

Anyhow there were a number of issues that my inexperience with handling AR's led me to miss. First off my charging handle was all sorts of messed up, caused all sorts of friction that shouldn't have been there. But how was I suppose to know? I've shot a total of maybe 40-50 rounds through a total of 2 AR's before I built this, and that was months and months ago when I shot them. Anyway, now I know.

Secondly they suggested I dremel a small ramp on the inside gas port of my cheap chinese gas block so there was no chance for impingement there. If you look at the pictures i linked to above, you'll see the barrel gas port is right on the edge of the burn marks.

Thirdly my buffer was messed up from some previous experimentation in my noob hands. So I picked up a new charging handle. The difference in charging the thing was bluntly obvious when they showed it to me. Got my barrel gas port bored out to 0.070" per their recommendation. Apparently the anderson barrel gas ports are a little under spec.

After all that expected all to be well... and got rid of the steel cased ammo... (heard that message loud and clear)

And while I was indeed now ejecting every time... CRAP it was still failing to FEED! I was ejecting between 4:30-6:00 and realized it was still short stroking... fortunately now I knew I had my gas issues very well trouble shot, it was not a messed up charging handle. Having my engineer brother in town and having a Saturday morning to ourselves on my in-laws private shooting range we trouble shot it more. We weighed my buffer, and I had a 3oz buffer. His suggestion was I try increasing buffer weight...

Which I know... You google solving short stroking issues and about everything I read said that decreasing buffer weight was the way to help solve short stroking issues after you made sure it wasn't a gas issue. Well after a good discussion with him and his scientifically based knowledge.. he said that decreasing would most likely make short stroking issues worse, not better. So we cracked my buffer open, replaced the steel weight with some molten lead and increased my buffer weight to 3.75 oz. And my AR now cycles beautifully.


Disclaimer: preachy boring science stuff follows... you've been warned.

Now I know it seems counter intuitive to increase buffer weight to help with a lack of rearward movement of the BCG. But the science is really sound, and once we explored it was very clear. When you decrease the weight of your BCG and or buffer you're getting rid of mass which will severely affect the kinetic energy of the BCG + buffer combo (you can treat them as one since they remain in contact the entire time.)

Here's the equation for KE (Kinetic Energy). Energy = 1/2 Mass x Velocity(squared).

So in other words if we take a standard carbine buffer of 3oz and bump it up to 4oz you get a 33% increase in kinetic energy if our velocity of the system remains a constant profile regardless of weight change... And that's pretty likely that our velocity stays relatively constant since in a healthy gas system there's plenty of energy that is waisted once the BCG gas key leaves the gas tube.

And when we only need to come back maybe an 1/8" or 1/4" more... That is sort of a HUGE deal. Because once the gas key leaves the gas tube, you're operating on 100% kinetic energy in regards to the BCG traveling far enough rearwards. Make sense? Not that I am a genius here, but this was extremely enlightning for me when I found out. And as long as you're gas system isn't under gassed from blockages, etc... a heavier buffer is going to harvest more energy from the gas blowback to allow for a harder push on our buffer spring.

I think this is intuitively understood with ballistics on the muzzle end, heavier bullet equals more energy delivered down range when velocity is relatively equal. It's the same thing for the BCG/buffer combo. The heavier (in spec) combos are going to deliver more energy to compress the buffer spring; because they do a better job of capturing energy in our gas impingement driven system.

Now i know the velocity staying relatively constant would need to be verified, but the proper ejection of 3:00 4:30 pattern on my AR with perfect cycling is enough of an indicator for me.

Anyhow thanks again everyone for all the trouble shooting help, and I hope I don't come off as a jacktard know it all here, because the guys at Protection First were the ones who offered the extremely helpful expert advice. And they did tell me to replace my buffer.... They probably meant to use a heavier one, any way... I hope this will help someone else who struggles with similar issues down the road.