I built this AR and it failed. AR15 scientist help much appreciated!!!


PDA






Mohave-Tec
June 29, 2013, 03:07 PM
I finished building my first AR 15 yesterday. Here it is in its earliest carnation.

http://i414.photobucket.com/albums/pp230/igonator/IMGP1019a_zps8aa8b7eb.jpg (http://s414.photobucket.com/user/igonator/media/IMGP1019a_zps8aa8b7eb.jpg.html)

So even though it was 100 degrees at 8:30 this morning at 4000 feet elevation I wanted to at least get out and run the barrel in. Now I've put together numerous bolt guns before and I'm a pretty handy mechanic but my experience this morning was dismal. I couldn't get off 2 rounds before a failure occurred. In the desert I wasn't able to make any determinations as to what was going on but back here at home after cleaning up the gun I am seeing some issues. Please give me a hand if you can?!

I hand load. I've developed 2 loads for other 223 rifles I have (KelTec SU16C and a Savage Axis 223) so I started out with the simpler hand load for those guns to run the new barrel in. The load on the middle is that load. It is a Remington 55gr Power-Lokt over 24.5 gr H335 with a COL of 2.182 to mimic the factory load sold at Wal Mart. The load on the left is a 60gr VMax over 25gr of Varget with a COL of 2.250. On the far right is one of the many Power-Lokt rounds I killed in my upped receiver this morning on its way to cambering. The next picture sounds one of these rounds nearly folded over.

http://i414.photobucket.com/albums/pp230/igonator/1_zps9fd711a2.jpg (http://s414.photobucket.com/user/igonator/media/1_zps9fd711a2.jpg.html)

I know next to nothing about ARs but I know other rifles. It looks as if I am having fail-to-eject issues then I'm slamming a new round into the back of the still chambered but spent case in front of it. What is doing this? I have a couple suspicions but would love to hear your opinions.

The rifle is currently a Frankengun. I got it in my head a couple weeks ago I wanted to build an AR and though I want a certain quality, I was obliged to pick up what I could in some cases if I wanted to get this thing built in a month. Some of the hardware I believe might be to blames. Here it goes.

In this picture you see an fairly well made AR Stoner 18 inch mid gassed Wylde chambed barrel over extended into a slick sided DPMS upper. First thing that bugs me is the feed ramp alignments. Not only is the barrel's feed ramps further into the receiver than the receiver's feed ramps but clearly the right feed ramp aligns but the left ramp does not. I think both the depth and alignment issues are making my rather short reloads bounce and making it difficult for them to chamber. What do you think might happen here?

http://i414.photobucket.com/albums/pp230/igonator/3_zps149d1e55.jpg (http://s414.photobucket.com/user/igonator/media/3_zps149d1e55.jpg.html)

Also, with the 18 inch mid gassed barrel I have an adjustable gas block on it but the adjustment is wide open as I cannot tell the relationship between the gas port and the jet (set screw) that regulates gas flow in the block. This and the buffer weight is 2.9 ounces when I'm thinking something much heavier might help with this gas/barrel configuration? Maybe?

Lastly, and what scares me the most is that it is a BCM BCG that is failing to eject the spent cases from the chamber. Why would this be?

I'd appreciate any help I can get on this. Since I am in "very hungry nube learning mode" I am going to cross post this thread in another forum to see how much I can learn about all this.
Thanks again.

Oh, by the way, this rifle is majorly accurate and the most repeatable off shoulder 200 yard COM I have ever shot......f I can keep it shooting.

If you enjoyed reading about "I built this AR and it failed. AR15 scientist help much appreciated!!!" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
Omaha-BeenGlockin
June 29, 2013, 03:16 PM
Soak your bolt/carrier with Break Free----work it into the extractor---then slap it back into the gun wet and see how she runs.

taliv
June 29, 2013, 03:23 PM
Is the round coming out of the chamber and staying in the action? Or not even making it out of the chamber?

If you're picking up another live round then you've got plenty o gas. My guess is chek your extractor and ejector

readyeddy
June 29, 2013, 03:25 PM
Shoot a box of factory ammo to make sure it's not your reloads.

Mohave-Tec
June 29, 2013, 03:44 PM
Omaha, I will do that. I kinda had a similar idea already. I was going to shoot a couple rounds, clean the gun, shoot a couple more rounds then run 70 or 80 rounds through it just to limber up the gun then clean it to the core and re-lube accordingly when I got home. Other than run 80 rounds through it I did just that. I have a BCM BCG and it scares me I'd need to be looking at the BCG at all but I actually wouldn't know what a properly running BCG is supposed to feel like since this s the only BCG I've ever handled.

Mohave-Tec
June 29, 2013, 03:48 PM
taliv, I do figure I have plenty of gas. Part of me thinks I may be over-gassed. Anyway, more often then not the spent rounds is never being picked up and is staying in the chamber. Again, a second reference to what is supposed to be the best quality part in this rifle. Hmmmmm.....

Mohave-Tec
June 29, 2013, 03:53 PM
reddyeddy. I haven't owned a box of factory ammo in 5 years. LOL. But I will pick some up and I do think I know what you are getting at. When I was in the desert this morning I was beating myself up for not bringing some of the VMAX rounds with me which are built to more traditional 223 dimensions and are not blunt nosed.

Several goods thoughts here already everybody. I will try all these things right away but I won't be going back into the desert until next weekend. It's supposed to be 118* here tomorrow.

taliv
June 29, 2013, 04:16 PM
sounds like an extractor problem or maybe yes overgassing, but that's a little unlikely with an 18" mid-length.

try a heavier buffer. make sure your extractor has a lot of tension. you shouldn't be able to move it easily with finger pressure. i'm assuming you didn't take it apart and futz with it alread. but try the little black oring that probably came in the package with it.

HOOfan_1
June 29, 2013, 04:24 PM
Umm...nevermind I was wrong about he feed ramps...Those are M4 feed ramps on both the barrel extension and the receiver

gotigers
June 29, 2013, 05:06 PM
When it does eject, where do the spent casings land? 3 o'clock, 4 o'clock, etc?

Mohave-Tec
June 29, 2013, 05:24 PM
taliv, I am unable to move the extractor with my fingers or fingernail but I can push it out a little with a screwdriver. I don't remember anything about an O-ring. I don't see one. What is this about?
Oh, and I haven't taken the BCG apart or messed with it in any way.

Walkalong
June 29, 2013, 05:31 PM
The feed ramps do not look like they line up well and that the barrel ramp is higher than the upper receiver ramp. This is an easy check with a fine dental pick etc. Run it up the ramp and see if it hangs at the junction.

Mohave-Tec
June 29, 2013, 05:31 PM
gotigers, very interesting question. In my shop when I pull the charging handle back, loaded rounds will eject at 5 0'clock. When I was in the desert this morning I had a couple guys beside me watch the ejection pattern and the spent rounds would eject at 2 o'clock. And for this purpose I would remind everybody that this is a slick side anf there is no deflector behind the ejection port.

Mohave-Tec
June 29, 2013, 05:36 PM
Walkalong, I know it does. You are correct. This is why I put the photograph in in the first place. The depth and alignment are not in sync. Along with ejection issues, I suspect feeding issues as well but the barrel staking pin had no play between it anf the receiver and this is how everything settled.

Walkalong
June 29, 2013, 05:41 PM
his is how everything settled. Yea, it's a matter of tolerances.

You will need to do some work on the barrel ramps, or find a receiver that matches the barrel or vice versa, which would be expensive. Me? I would make the barrel you have match that nice receiver.

jdh
June 29, 2013, 05:55 PM
First look at the extractor and see if there are any obvious defects like missing chips.
With the bolt in hand take a piece of brass, Not a loaded cartridge, and push it into the bolt, straight in, you will have to work against the ejector spring.
Does the extractor snap over the cartridge rim?
If it does, does it hold the rim?
If it does pull straight out on the case. Does the extractor let go easily or hang on to the case rim?

Krusty783
June 29, 2013, 05:58 PM
You have a pmag, so that's probably not the issue.

It sounds like the gun is short-stroking/failing to feed? I didn't see a clear description of the malfunction.

- Are you sure the gas block is aligned correctly? A small misalignment can make a big difference.

- Get some commercial brass ammo. If you're gonna hand load for your rifle, start with rounds that are closer to 5.56 NATO Spec, which is higher pressure than .223 and makes a difference in some rifles.

- There should have been a small black o-ring ("donut") that came with the BCG. It goes over the extractor spring to provide some extra strength for extracting on over-gassed systems.

mtrmn
June 29, 2013, 06:16 PM
Does the extractor tear a chunk out of the rim?

Given a choice, I get upper receivers that have no feed ramps so I can match the receiver to the barrel myself.

45_auto
June 29, 2013, 06:42 PM
taliv, I am unable to move the extractor with my fingers or fingernail but I can push it out a little with a screwdriver.

Take the extractor out of the bolt and make sure it's assembled correctly. I went and checked on 4 different AR15's, and on every one of them I can easily pull the forward end of the extractor out (like it has to do to snap over the case rim) 1/16" to 1/8" with the tip of my finger reaching through the ejection port. I'm a pretty puny guy, I doubt if my fingers are that much stronger than yours!

Mohave-Tec
June 29, 2013, 06:58 PM
walkalong, the receiver was $86, the barrel was $260. HAhahahaa

Mohave-Tec
June 29, 2013, 07:02 PM
jhd, I never played with a bolt to actually know what was going on in there but in your little test I think I learned everything there is to know about bolts (not really) and everything seems to work just fine. with some work the case drops right in. The extractor snaps tight over the cartridge rim and holds on to it when I pull staright out bu flips it readily when I let go.

Mohave-Tec
June 29, 2013, 07:08 PM
Krusty, I don't have a great description of the issue. This is almost the first time I've fired an AR and I left the range after a few minutes in discust. : )
I just took the gas block off. I'm very well aligned on the tube.
I don't see an oring anywhere. I'm going to run up to a gun store in a minute and take the bolt group with me.

Mohave-Tec
June 29, 2013, 07:10 PM
mtrmn, this sounds like a fine idea. I could easily machine the ramps.
For your question, no, the extractor isn't doing any damage to the cartridge rim.

Walkalong
June 29, 2013, 07:22 PM
walkalong, the receiver was $86, the barrel was $260. HAhahahaaYep, but if you work on the aluminum receiver you will get down below the hardened surface to bare soft aluminum. The barrel is the way to go. FMJ is rough on soft aluminum. :)

SpentCasing
June 29, 2013, 08:27 PM
Guys the feedramps are fine and not the issue. The issue is Failure to extract. The fired case isnt ejecting and the bolt is cycling, picking up the new round, and mashing into the old.

As Taliv suggested, take the extractor out and inspect. OP seems to believe because he spent a lot of $$$ on a BCM BCG it is impervious to failure. BCM is quality kit, but every co. can make a mistake. Heed Taliv's advice and we will go from there.

jdh
June 29, 2013, 08:40 PM
Has the head space be checked? Your extractor seems ok. My next concern would be that the bolt is not going far enough forward to let the extractor pick up the case.

Mohave-Tec
June 29, 2013, 08:41 PM
Walkalong, that certainly makes sense. Drimmle and I have work to do tomorrow but I'm a little iffy about the stainless steel. What the hell, it's only money, right?

Mohave-Tec
June 29, 2013, 08:51 PM
Spent, "OP seems to believe because he spent a lot of $$$ on a BCM BCG it is impervious to failure." I appreciate the assistance but I can assure you this is not the case. I head up Special Projects in a mechanical engineering department. I did little research on AR mechanics before I started this project but when I had issues I certainly understand what to check when made aware. I just read a small article on the mechanics or AR 15 BCG and this one is just fine. Right now everything points to over gassing and my extremely light buffer weight but I'm not sure yet. I'll head back out to the desert again Friday morning to test for lock up after last round...which I forgot to check this morning.

kimbernut
June 29, 2013, 08:54 PM
Put in an o-ring or d- ring kit and I'll bet your problem is solved.
I had the same problem 2years ago on my first build. Ordered and installed an o-ring kit from Dillon Precision and never had another problem. I too shoot nothing but handloads.

SpentCasing
June 29, 2013, 09:13 PM
Spent, "OP seems to believe because he spent a lot of $$$ on a BCM BCG it is impervious to failure." I appreciate the assistance but I can assure you this is not the case. I head up Special Projects in a mechanical engineering department. I did little research on AR mechanics before I started this project but when I had issues I certainly understand what to check when made aware. I just read a small article on the mechanics or AR 15 BCG and this one is just fine. Right now everything points to over gassing and my extremely light buffer weight but I'm not sure yet. I'll head back out to the desert again Friday morning to test for lock up after last round...which I forgot to check this morning.

I didnt mean that as a slight against you, Bud. I just got that feeling from what I interpreted from your wording. Its hard to interpret context over the internet, so if I misunderstood, my apologies.

I, however, dont think it is overgassing. Syptoms over over-gassing would include bolt over-ride (or, failure to pickup new round as well as, as you seem to know, failure to lock-back). As taliv said, 18.5 middy is highly unlikely to be over-gassed. I think you prob lies in the BCG. As others have said, look into what is referred to as a "Crane O-ring". Good luck, and keep us posted.:)

Mohave-Tec
June 29, 2013, 09:48 PM
I may have to back up a step. I bought go/no go gauges when I started this assembly. Without taking the bolt apart, both gauges served their purpose admirable. The bolt closed on the Go gauge and did not close on the No Go gauge. Good enough.
But just now, on everybody's prompt, I just disassembled the BCG less the ejector. I don't have a punch here that is small enough for that; I left it in. With mostly disassembled bolt, bolt closes over the Go gauge and is flush with the receiver in the back. With the No Go gauge, bolt less extractor, cam and firing pin, bolt closes on the No Go gauge and is still flush with the back of the receiver.. So, what is that?

Mohave-Tec
June 29, 2013, 09:49 PM
Spent, I didn't take it that way.

Mohave-Tec
June 29, 2013, 09:50 PM
Kimbernut, I must need this O Ring kit because I don't see an O Ring in the BCG anywhere.

carbine85
June 29, 2013, 09:52 PM
Fail to Feed is the magazine. Fail to extract is usually bolt related. You might be damaging the case when it feeds. Your ramps don't look right. They look like standard ramps on the barrel extension. I would try some new ammo, a different mag and possible changing the feed ramp.
My RRA with a wylde chamber is picking with reloads.

SpentCasing
June 29, 2013, 09:56 PM
Crane O-ring would be on (over) the extractor spring.

As far as the gauges. You have a .223 Wylde chamber. Slightly looser than 223, slightly tighter than 5.56. What gauges are you using? 223, Wylde (do they make these?), or NATO?

Knightsofnee
June 29, 2013, 10:06 PM
Your BCM bolt likely has a 5 coil BCM extractor spring. It is "stiffer" than most extractor springs. BCM says you "most likely" will not need the o-ring with that spring (that may be why it didn't come with one). Your set up may need it though.

Mohave-Tec
June 29, 2013, 10:12 PM
I feel like this is being narrowed down.
Now it makes sense I don't see the Crane O-Ring. It is under the extractor OR in the bag the bolt came with. Unfortunately I can't recall an O ring in the bag and it isn't over the extractor spring so I shall pursue one immediately indeed.

Carbine, I vaguely remember fail to feed once or twice but mostly when the spent case ejected I was able to get off another round right behind it. I just look at the ramps and they tell (I assume) I am going to have feeding problems. I haven't really gotten that far yet but I'm pretty sure you are right. :banghead:

Spent, I have been thinking that the only difference in a Wylde chamber was that the neck was longer. Am I incorrect or incomplete in my thinking? If so, then maybe I have the wrong gauges or my findings are within spec? I have Forsters Go/No Go. Go at 1.4636 and No Go at 1.4666. I can't verify with instruments I have at home but I can at work this week. Anyway, I'm betting they are NATO.

Man, if it weren't 115 degrees outside (literaly) I might not be getting this wonderful education right now.

Mohave-Tec
June 29, 2013, 10:18 PM
Knights, I just read that. It's probably why I don't have one. Anyway, when it is supplied it is usually not installed and only given as an option for the installer if I've read correctly. And it said it is less likely needed in my longer barrel. I've putting in an order anyway so I'll pick up one of these too.

Carbine, I knew when I went to the desert this morning I should have brought a different round I have developed. These short and blunt Power-Lokt loads have to do some radical moves to chamber. They did fine in my shop but not so much at speed.

Mohave-Tec
June 29, 2013, 10:22 PM
Everybody or anybody. Am I using the wrong word when I talk over gassing? What I think I've read is that by using a heavier buffer weight I can slow the cyclic rate down ever so slightly which in turn will alow everything a little more time to do what it has to do thus smoothing out operations. Should I just get un-hung from this train of thought? I do hang on to things sometimes.

SpentCasing
June 29, 2013, 10:39 PM
223 Wylde will have longer LEADE than 223 but shorter than 5.56 NATO. Kinda sorta longer neck in laymens terms but I may be out of my lane on this. Handload mod Walkalong could probably clarify this better than I. (I also am a reloader but all of my chambers are 5.56)

A heavier buffer will increase dwell time as well as slow cyclic rate, so ,yes, you are correct on that. But Im not entirely convinced at this point, that it is the cause of your problems.

IMO, you seem to be getting insufficient tension on the case rim, and your extractor is "hopping" off of your case rim during cycling.

This chart should give you an idea as to where you stand on buffer weights:
http://i37.tinypic.com/14av5o4.jpg

Walkalong
June 29, 2013, 10:40 PM
Guys the feedramps are fine and not the issue.Agh, I finally waded through the whole post and yes, you are right. The feed ramps do not match up though, and will cause stoppages eventually, or occasionally.

Mohave-Tec, do you have an extra bolt or bolt carrier group you can try in it? A BCG from another rifle perhaps? If that runs you will know where to look.

If you have a heavier buffer it won't hurt to try it.

G.barnes
June 29, 2013, 10:50 PM
Try a heavier buffer. The could be moving to fast and trying to pull the case out before it has contracted.

Mohave-Tec
June 29, 2013, 11:09 PM
You guys are most appreciated. In an area where it is important that I learn or very costly if I don't, I've probably doubled my AR leanings in this thread today. I recall that I ran into an unusual number of brass that didn't want to fit in my shell holders when reloading or they were very tight. Not much of an issue when you shoot bolt rifles like I've been doing for years. I imagine this can also be critical when high speed extraction comes into play.
Ok. We've got get a Crane O-Ring, check rim depth on my cases, try H2 buffer, they a more traditional shaped/sized hand load and fix the feed ramps.
I also think that being most of my components are of reputable quality that I may just move to a better make upper before I mess with the ramps. The upper I have is well spoken of in it's circles but if I have to guess who is at fault there I'd have to say DPMS or my match barrel. If this thread continues, so be it. If it dwindles I will certainly return to let you all know how things turned out. Again, I appreciate this most valuable input more than I can express.

Mohave-Tec
June 29, 2013, 11:11 PM
G, barnes, I have read this many times. I will invest in an H2. Anyway, with an H2 and a carbine buffer, I can concoct any intermediate buffer so I'm going to buy one 'cause I wanna buy one. LOL.

Knightsofnee
June 29, 2013, 11:13 PM
And you can play with the buffer spring. Companies like springco make buffer springs of different compression rates, and with the Tubb square wire spring you can whack off a coil at a time till everything works (with that particular load anyway). Seriously though, you are working with a lot of variables there. The adjustable gas block alone has driven men crazy. Patience will reward you, that's a nice looking rifle.

SpentCasing
June 29, 2013, 11:18 PM
Mohave-Tec -

Either/or the Crane O-ring and H-H2 buffer would probably solve your problems. Buying both, I would be shocked if the issue wouldnt be fixed. Get both, lube well, enjoy. Good luck!

I personally use a Spikes Tactical ST-T2 buffer which is right in between H and H2 weight. Rather than solid weights it uses tungsten powder to give a "dead-blow hammer" effect. Has worked great for a PSA 16" middy gas length, FNMI A2 20" rifle gas length, and KAC SR15 proprietary gas length (longer than mid, shorter than rifle). Any of the 3 options would be an improvement over your carbine buffer.

Mohave-Tec
June 30, 2013, 12:25 AM
Spent, don't give me any more ideas. "Dead blow hammer effect."
I put this rifle together with a rather odd premise. I like 60gr bullets. The lower has a set screw to wedge it against the upper to take the rattle out of the gun. The buttstock cams into the buffer tube to take that rattle out. Since we are heading in the direction of smoother action I chose a muzzle break instaed of a flash hider. I am also thinking about the captured buffer spring if I ever get a warm fuzzy about what I'm already working on. Why not a buffered buffer?

taliv
June 30, 2013, 01:32 AM
look, the AR is a "system" and there are many things that could be close to their tolerance limit and be causing a failure together whether any one of them alone would not.

overgassing normally means too much gas. like, the port in the barrel is too large. or too close to the chamber. it's possible but unlikely in this situation.

the overgassing problem people USUALLY experience is when you have a carbine length gas where the port is closer to the chamber. that causes the gas to act on the BCG faster than normal. which in turn tries to open the bolt while the chamber pressure is still high and the brass is still stuck to the walls. in this case, the extractor can slip off. putting an o-ring inside the extractor along with the normal insert and spring can help. but it is really treating a symptom of a poor combination of parts.

another thing people do is use a heavier buffer, which also slows the bcg down a wee bit to give the chamber pressure a little more time to drop before opening.


occasionally, you also see some guy who reloads bolt guns in 223 try to use the same powder, which burns too fast for an AR, and will cause similar symptoms. so try some factory ammo here and make sure you're using a powder with the right burn rate.

again, in this situation, the fact that the gas system is mid-length means it's unlikely to be trying to open the bolt too fast. but that is what it sounds like, so who knows?


another possibility is a rough chamber. run a cotton ball in and out of the chamber and see if it snags on anything.

you should be able to move the extractor with a screwdriver but have difficulty with your fingers. so it sounds like yours has a normal level of tension.

also, i know it sound stupid, but does it extract when you hand cycle it? i mean, (point the gun in safe location and put the safety on) just use the charging handle with a full mag and pull it back and let it go several times. do the rounds come out ok by hand?

jim in Anchorage
June 30, 2013, 02:01 AM
Swap it for a mini 14:evil:
Quit messing around with the gun and go shooting!

Mohave-Tec
June 30, 2013, 08:03 AM
taliv, the rounds eject every time when I pull the charging handle and let it fly. No problem. I also had a professional AR builder check out the BCG yesterday and the BCG checked out just fine but I expected it would.
I will do a close examination of the chamber this morning but rounds that do fire and eject look just fine.

dprice3844444
June 30, 2013, 08:25 AM
http://www.brownells.com/rifle-parts/extractor-parts/extractors/ar-15-m16-extractor-upgrade-kit-prod24635.aspx

here ya go. i do this on every ar-15 i own before i even fire it.never trust the lowest bidder on parts.

Walkalong
June 30, 2013, 08:28 AM
If I read "adjustable" gas valve, try turning it down, and do check the chamber for roughness.

Mohave-Tec
June 30, 2013, 09:39 AM
Top-o-the-morning to you all.
It's 86 degrees in Las Vegas this morning at 5:30AM. I'm packing up again for the desert before it reaches 117 degrees. Right now I'm doing an experiment to try to establish where the jet is about to meet the port on my adjustable gas block. I didn't have a wrench for it yesterday and it was wide open. I've exchanged my gen2 PMAG for a gen3 and an aluminum magazine. The only store bought 223 I have is Hornaday Tap, a couple very expensive boxes leftover from pre-reloading days so I'm taking that. I'm leaving home my 2.120 COL Power Lokt over H335 and taking 2.250 COL Hornaday VMAX 60gr over Varget. Gas block wrench in hand and chamber snag test passed. I'll let you know how it goes in a few hours.

Skyshot
June 30, 2013, 09:59 AM
Have you tried using a small base die.

Mohave-Tec
June 30, 2013, 12:13 PM
No. I don't have any reason to. I can all but pull the spent cases out of the chamber with my fingernails and the newly formed hand loads drop right in the chamber just as they are supposed to. I don't know much about the small base dies, probably because both my Lee and RCBS do just fine as is. Am I missing something?

Mohave-Tec
June 30, 2013, 12:52 PM
OK everyone. The hard work has paid off.
I wrapped a piece of cellophane around an air tube on a can of compressed air and placed it in the chamber side end of the gas tube. Then I put an expanded/spent case in the chamber. I wanted to see if I could judge the degree of valving I was getting with the adjustable gas block. I tried this yesterday but I was trying to feel how much air us being released at the muzzle end. I just couldn't tell.
This morning I tried it again but this time by sound. I gave the air can a very short burst with the gas valve at what I believed to be nearly closed. It took about 3 seconds for the "bleeding off" sound to dissipate. I opened the valve a quarter turn and it took 1 second to dissipate. open another quarter turn and a shorter time to dissipate until It only took about an eighth of a second for the bleed off sound to dissipate. Fantastically, this sound test works very incrementally and I was very able to judge the degree of jetting the gas valve was doing. I then closed the valve until it took about 2 seconds to hear the air bleed down then I went to the desert. I took a different ammo with me than I used yesterday but I also took some of the same ammo. This morning I started by putting two of the same reloads in the rifle as yesterday. BANG, eject, feed, BANG and the bolt locked back. I repeated this a couple more times with 2 rounds. The bolt didn't lock down only one time. I closed down on the valve 1/8th more turn and the rifle ran perfectly on subsequent tests. They I loaded the magazine to 28/30 rounds and let it rip. Never a failure. It ran perfectly with the short hand loads and the rough honed feed ramps. Then I filled it up with the VMAX loads I developed for my Savage 223 bolt rifle. These are the finest bullets I have ever reloaded consistently making compound holes at 100 yards. The AR LOVED them and I was hitting a piece of typing paper off shoulder at 220 yards every time I pulled the trigger......with a red dot. What a fantastic workout.
I'm still going to but an H2 buffer. With a carbine buffer and the H2 I can configure any common buffer weight by mix matching parts from both buffers. I want to see if this will let me be able to make even more intricate adjustments at the gas block by leaving a little more of the port open. Other than this, I'm going to clean up the feed ramps then commence with some better optics and a few other toys to finish dressing it out. Again I thank you all so very much.
I want to add an un-related peice of information before I close. I had to buy a lower parks kit in order to build this rifle. Almost nothing was available and I certainly didn't want a bottom floor trigger in the rifle as I have always put aftermarket triggers in my guns. I was un-happy that I couldn't get a known trigger for the gun but I was happy to find something that called itself an improved trigger. I never heard of this before but out of nesesity I bought a lowly 'Del-Ton Enhanced Lower Receiver Parts Kit with Two Stage Combat Trigger Assembly' for a modest $124 from Midway. I am here to tell you that this is the sleeper value trigger of the decade. It doesn't break like glass or drop the hammer at .25 pounds. What it does do is stop and a very disernable second stage at nearly the end of the trigger pull, drops at about 4 pounds then resets in the same place every time. I think this trigger is the new gotta have it trigger for the duty bump and crash rifle. If you ever what to make just a budget rifle I highly suggest you look at this trigger. I may not even replace it in this rifle when "better" triggers become more available.
Now, off to optics but that's another thread.

Mohave-Tec
June 30, 2013, 01:00 PM
Oh, price, I thank you for the link. A search didn't produce the O-Ring for me and I fully intent to pick one up regardless of immediate need or not.

Mohave-Tec
June 30, 2013, 01:14 PM
Spent, SOLD. Spikes Tactical ST-T2 buffer. I'm buying this buffer. Any idea how I might find one?

taliv
June 30, 2013, 02:07 PM
i had missed that you had an adjustable gas block. so that still doesn't make sense to me as full-open on the gas should be limited by the port size in the barrel, which should be the 'standard' and still not 'overgassed'. especially on a midlength. if you ever take the thing apart, it would be interesting to measure the size of the port and see if it is normal or super-huge or something.

Mohave-Tec
June 30, 2013, 02:49 PM
Yeah, I really haven't processed much of the science of it yet but I will. I have indeed been told on numerous occasions that a heavier buffer weight is needed in a mid length mid gassed barrel and that an adjustable gas block would do some of the same thing. I will divulge if things become clearer to me.

SpentCasing
June 30, 2013, 03:29 PM
Glad to see you got it sorted.

Spent, SOLD. Spikes Tactical ST-T2 buffer. I'm buying this buffer. Any idea how I might find one?

I got mine from AIM Surplus.

http://www.aimsurplus.com/product.aspx?item=XSTSLA00T2&name=Spikes+Tactical+ST-T2+Heavy+Buffer&groupid=576

Knightsofnee
June 30, 2013, 04:12 PM
Does your gas block have a way to "lock in" that setting?

Mohave-Tec
June 30, 2013, 04:44 PM
Knights, I don't. Not that I have specifically put into practice. Right now I have gummed it up with blue loctite but I don't know if that will be the end answer. There are ways. I don't actually recall how tight the screw was when I bought it but I don't think JP Enterprises had anything in there for the purpose either.
A favorite is screw against screw.

Walkalong
June 30, 2013, 04:55 PM
Don't get too carried away with the Loc Tite, especially on fine threads. Ask me how I know. ;)

Mohave-Tec
June 30, 2013, 07:26 PM
Blue LocTite. I know too.

MarshallDodge
July 1, 2013, 01:42 AM
I just got done reading this thread and the first thought that came to my mind is that the gun is overgassed.

By no means am I an expert but I have been playing with ARs for over 20 years in one form or another.

There are quite a few manufactures that ship ARs and barrels with large gas ports to deal with folks that like to run the cheap steel cased ammo which is typically is loaded light. This higher amount of gas will insure that the bolt will still cycle.

The other issue you may be having is the fact that the barrel is an 18" with a midlength gas system. This is the same issue that people see with carbine length systems. The carbine system was designed around a 14.5" barrel but the barrels ended up being lengthened to 16" for civilian use. This can affect bolt dwell time because the bullet is in the barrel a little bit longer after it passes the gas port keeping the chamber pressure up, and making it harder for the bolt to extract the case.

HoosierQ
July 1, 2013, 08:03 AM
I finished building my first AR 15 yesterday. Here it is in its earliest carnation.

Carnation...that's funny right there :neener:

Feed ramps do not look good at all.

Ramone
July 1, 2013, 11:22 AM
Slightly off topic, (and the issue seems resolved, anyway) But I have that same barrel, and I love it.

https://lh3.googleusercontent.com/-joYUivQwN68/T8yZUKDmH2I/AAAAAAAAH6Y/y2uqz6EjD7Y/s640/_DSC9157.jpg

Mine has been flawless with a rifle length stock, and standard (rifle) DPMS Spring and Buffer.

Walkalong
July 1, 2013, 11:34 AM
Mighty nice looking rifles guys.

ObsceneJesster
July 1, 2013, 02:17 PM
Glad you found the issue and fixed it. I just saw your thread but if I had seen it in the beginning, I would have told you to not even waste your time trying to find something wrong with your BCG. You purchased one of the finest most sought after BCG's on the market. I don't know if you noticed but did you see how dirty your BCG was when you first got it? BCM will test each and every BCG to the extreme. They don't just shoot one round and assume everything is fine. They shoot multiple rounds consisting of multiple pressures just to make sure everything is in working order.

Consumers know this and it's exactly why we pay more for a BCM BCG.



Sent from my SGH-T999 using Tapatalk 4 Beta

SpentCasing
July 1, 2013, 08:01 PM
The other issue you may be having is the fact that the barrel is an 18" with a midlength gas system. This is the same issue that people see with carbine length systems. The carbine system was designed around a 14.5" barrel but the barrels ended up being lengthened to 16" for civilian use. This can affect bolt dwell time because the bullet is in the barrel a little bit longer after it passes the gas port keeping the chamber pressure up, and making it harder for the bolt to extract the case.

Bold type is incorrect. Carbine gas was actually designed for 10.5" and then kept for use in the 14.5" in the M4 system. Thats why many people find the midlength gas for 14.5"+ the ideal length. Also why many, myself included, find it sub-optimal for the even longer 16" civilian legal bbl. One of the (several) reasons I prefer many other options first over Colt. But thats probably best left for another thread ;).

Mohave-Tec
July 1, 2013, 09:34 PM
Marshall, my gut has been telling me this from the beginning. I've repaired more machinery with feel and sense than with books and wrenches.

Mohave-Tec
July 1, 2013, 10:36 PM
ObsceneJesster, The BCM BCG was the first thing I bought/traded.

Mohave-Tec
July 1, 2013, 10:38 PM
Walkalong, Ramone...thanks a bunch. I'm hoping this will be a winner. It does look very nice and shoots extremely straight.

MarshallDodge
July 2, 2013, 01:27 AM
Bold type is incorrect. Carbine gas was actually designed for 10.5" and then kept for use in the 14.5" in the M4 system. Thats why many people find the midlength gas for 14.5"+ the ideal length. Also why many, myself included, find it sub-optimal for the even longer 16" civilian legal bbl. One of the (several) reasons I prefer many other options first over Colt. But thats probably best left for another thread

You are correct. :)

My thoughts were based on the present M4 vs. civilian "M4" where issue is still something to consider.

I don't own a Colt AR either. Nothing really against them but I am a fan of the midlength gas system on a 14.5 or 16" barrel and they don't offer one.

Mohave-Tec
July 4, 2013, 08:55 PM
Spent, just to let you know, I bought your buffer weight. http://www.aimsurplus.com/product.as...er&groupid=576
It makes all the sense in the world to me and the weight seems logical as best I can process it in my mind. The rifle is working well now but I think I'd like to find some more traditional middle ground by having the buffer regulate the cycling for the most part then having the adjustable gas block to fine tune with. I'm trying not to introduce a gas line restiction as much as possible.

I bought a new Aimpoint Pro for $385 brand new this morning. No tax. No delivery. MIAD pistol grip instead of the MOE and some BUIS and I'm good to go. This will be a really beautiful rifle.

SpentCasing
July 5, 2013, 01:09 PM
Good deal bud. Im sure youll be happy. Enjoy your new stick.:cool:

If you enjoyed reading about "I built this AR and it failed. AR15 scientist help much appreciated!!!" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!