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Posted: 8/8/2009 3:40:42 PM EDT
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Took my first build out to the range today, ran into a bit of a problem. This rifle hasn't been fired before. Here is the sequence of events:
Function test at home, with the muzzle pointed at the dirt, it cycled the ammo just fine. This was done with Wolf .223 Hollow Points, Steel jacket. At range, insert mag, chamber round, safety off, pull trigger, gun fires After this it gets dicey Sometimes the bolt cycles and ejects the case, sometimes it looks as though it dosent cycle all the way back, and it ends up not ejecting the case. If it does cycle enough to eject the case, it does not go back enough to load a new round. I dissasembled the bolt and carrier, gas rings look OK. Put a bit of lube everywhere and reassembled the bolt... still same result as above. A bit of JB Weld carbon solvent stuff down the gas tube, it drips out of the barrel, so that looks fine.The tip of the gas tube in the upper reciever turned black after a while, so i gather that gas is coming through. Borrowed a mag from someone else at the range with an AR, still same problem, so its probable not the mags. Only thing left is the buffer spring. Can this be too strong, so that the bolt isnt being allowed to cycle all the way back? The buffer spring I have came with my Vltor Emod stock, everything as a complete set: Model AEBK-M. IIRC the M is for Mil spec. I was using PMC 55gr .223. Since some of the cases were being ejected and some weren't, I have a feeling that the slight difference between the amount of powder in each round was causing that. Also this made me more convinced that the buffer spring is the culprit. Guy in the booth next to me suggested I try a gunsmith, but I dont want to go that route right now, especially if its as easy of a fix as a new spring. So here I am looking for suggestions. If there is any more info required, just let me know |
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Buffer and everything stock-related shouldn't be mismatched. It all came as part of a complete kit.
The box that the stock kit came in says "Carbine Model" so it should be a carbine buffer. Extractor and spring look fine and function ok when i push down on the extractor. I did not scrub the heck out of the chamber before shooting. Was I supposed to? Barrel: Daniel Defense 16" Midlength 1/7 http://www.rainierarms.com/?page=shop/detail&product_id=1495 Gas Block is the low profile block you can order from RRA. I am sure I got the gas block hole and the barrel gas hole lined up. RRA gas block mounts with two set screws. There is some discoloration of the gas tube about 1/4 inch from the gas block. Could the problem lie here? Will an inadequate seal between the gas tube and gas block cause this kind of thing? Gas tube was also purchased from RRA. |
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You sure the gas block is in the right place and the gas port isn't obstructed? Definetly sure on this, because the bolt does cycle after the shot, but only sometimes does it cycle enough to load the next round. I also tried pouring a bit of the carbon solvent down the gas tube from inside the upper, it poured out of the muzzle. |
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You sure the gas block is in the right place and the gas port isn't obstructed? Definetly sure on this, because the bolt does cycle after the shot, but only sometimes does it cycle enough to load the next round. I also tried pouring a bit of the carbon solvent down the gas tube from inside the upper, it poured out of the muzzle. That could mean that the gas block isn't lined up perfectly. I saw this exact problem a week ago at the range, as a matter of fact. Edit: Stop pouring crap in your rifle. Edit 2: How far from the shoulder at the posterior end of the gas block shelf do you have the gas block? |
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You sure the gas block is in the right place and the gas port isn't obstructed? Definetly sure on this, because the bolt does cycle after the shot, but only sometimes does it cycle enough to load the next round. I also tried pouring a bit of the carbon solvent down the gas tube from inside the upper, it poured out of the muzzle. That could mean that the gas block isn't lined up perfectly. I saw this exact problem a week ago at the range, as a matter of fact. Edit: Stop pouring crap in your rifle. Sorry but i dont understand how it could still do that and not be lined up. Also the rifle was malfunctioning this way from the very first round ever that I loaded into it.Sorry if that wasn't clear. |
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Yeah, you need to move it forward about 1/16-1/8".
Barrels are machined to leave room for a handguard cap, if you don't have the handguard cap, you need to move the gas block away from that shoulder as if it was there. If you take the gas block off, you should see a round carbon mark on the barrel. You'll be able to figure out from that mark how far forward you need to move the GB to align it with the gas port. |
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He meant barrel.
How many total rounds do you have through the gun? I wouldn't start troubleshooting "possible problems" until you had at least 100 rounds through it to wear in the moving parts. Lube it and shoot it. Work through the FTF/FTE issues until it's worn in. ETA Edit for spelling |
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He meant barrel. How many total rounds do you havd through the gun? I wouldn't start troubleshooting "possible problems" until you had at least 100 rounds through it to wear in the moving parts. Lube it and shoot it. Work therough the FTF/FTE issues until it's worn in. I like your answer. Going back out there tomorrow 
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He meant barrel. How many total rounds do you havd through the gun? I wouldn't start troubleshooting "possible problems" until you had at least 100 rounds through it to wear in the moving parts. Lube it and shoot it. Work therough the FTF/FTE issues until it's worn in. Dude, if the gas block is against the shoulder on the barrel, that's the problem. There's no "break in" when that's the case. |
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He meant barrel. How many total rounds do you have through the gun? I wouldn't start troubleshooting "possible problems" until you had at least 100 rounds through it to wear in the moving parts. Lube it and shoot it. Work through the FTF/FTE issues until it's worn in. Dude, if the gas block is against the shoulder on the barrel, that's the problem. There's no "break in" when that's the case. Dude, I agree it may be a problem. But it may not. I have two low profile gasblocks that are designed to be butted up against the shoulder on the barrel because the makers know there isn't going to be a handguard cap there. I have another that needs the gap. A new gun needs to seal the gasport to gas block gap with carbon, so the first several rounds are going to get some blowby, which equals varying amounts of gas to operate the action. The OP reposrt sporadic functioning. But, it's possible to chase phantom problems and end up making things really fouled up by "repairing" or "tweaking" a problem that didn't exist in the first place. There are several posts weekly here where somone takes a brand new build to the range and experience feed problems with the first magazine they ever shot through the gun. Not realizing things need to wear in and get settled down. Running ammo through the gun won't hurt it, it needs to wear in anyway. If it turns out the gas block still needs to be moved, then the OP has already eliminated one more issue. |
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Yeah...however, for me at least, firing up to 100 rounds to see if the rifle works...that's $50 worth of ammo I'd be out.
It's a simple matter to slide the gas block forward and see where that carbon mark is on the top of the barrel. And that's free. No tweaking or repairing involved. You can put it right back where it was. Also, I've never experienced short stroking as a "break in" issue; frankly I've never experienced any break in issues with ARs. If I had a problem from the outset, it needed to be fixed. The OP stated that the rifle worked fine at home, so it isn't a "gas block/barrel seal" issue. Most likely the gas block was moved, or it is in position to barely provide enough gas to cycle the action, sometimes. |
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I don't know about your gas block. Maybe take it off and use a caliper to see how far the hole is from the back of the G block inward and on the barrel how ar from the shelf?
I have one rifle that does the exact same thing with Wolf, but fires UMC 223 fine. Wolf is slightly underpowered ammo. I know I could drill my gas port larger, or trim a coil off the recoil spring to make it work, but decided not to bother. That gun has a USGI M16 upper, so I know is worked before. Try good american ammo first, if it works them you know what's going on. |
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Sometimes the bolt cycles and ejects the case, sometimes it looks as though it dosent cycle all the way back, and it ends up not ejecting the case. If it does cycle enough to eject the case, it does not go back enough to load a new round. My AR did the same exact thing, I was using a YHM low profile specter gas block and it had worked itself loose, we took it off and installed it back with some Red loctite. It has held up just fine since. What ever your issue is, it is certainly gas related. |
| Go to the auto parts store and buy 1.5 - 2' of vacuum hose. Slip the hose over the end of the gas tube. Blow through the gas tube and loosen the set screws on your gas block. Move the gas block around and check to see if you are "pinching" off your gas path. I'd say your gas port isn't quite lined up. |
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Not sure if this helps, but.
I had the exact same problem on a build, and it was related to the buffer tube. The buffer was binding in the tube for some reason or another. I was using a cheap commercial buffer tube that came with a stock I purchased. One of the symptoms was when you used charging handle to pull bolt all the way onto battery, the bolt would momentarily stick before returning. When bolt was released from battery it would snap into place. But when slowly released with CH it would slightly stick. All I did was take off the buffer tube and re-install it and it started working. I noticed that when the buffer tubes was screwed into the receiver it had a decent amount of play, which disappeared when castle nut was tightened, but if castle nut was tightened with tube slightly off, the bolt would bind. A week later I installed a mil-spec buffer and tube, which had a much tighter fit in the receiver. |
I would agree that it is most likely the gas block being out of alignement or the buffer. However, if you don't think that these are the issues, could it be the wrong length gas tube. If it was too short I would think that this could cause short stroking and a lack of power for the ejection. How far does your gas tube stick out in to your upper reciever
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He meant barrel. How many total rounds do you have through the gun? I wouldn't start troubleshooting "possible problems" until you had at least 100 rounds through it to wear in the moving parts. Lube it and shoot it. Work through the FTF/FTE issues until it's worn in. Dude, if the gas block is against the shoulder on the barrel, that's the problem. There's no "break in" when that's the case. Dude, I agree it may be a problem. But it may not. I have two low profile gasblocks that are designed to be butted up against the shoulder on the barrel because the makers know there isn't going to be a handguard cap there. I have another that needs the gap. A new gun needs to seal the gasport to gas block gap with carbon, so the first several rounds are going to get some blowby, which equals varying amounts of gas to operate the action. The OP reposrt sporadic functioning. But, it's possible to chase phantom problems and end up making things really fouled up by "repairing" or "tweaking" a problem that didn't exist in the first place. There are several posts weekly here where somone takes a brand new build to the range and experience feed problems with the first magazine they ever shot through the gun. Not realizing things need to wear in and get settled down. Running ammo through the gun won't hurt it, it needs to wear in anyway. If it turns out the gas block still needs to be moved, then the OP has already eliminated one more issue. and now there are barrels with an extended shoulder to take the place of the handguard cap. causing more confusion. |
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Dude, if the gas block is against the shoulder on the barrel, that's the problem. There's no "break in" when that's the case. Dude, I agree it may be a problem. But it may not. I have two low profile gasblocks that are designed to be butted up against the shoulder on the barrel because the makers know there isn't going to be a handguard cap there. I have another that needs the gap. and now there are barrels with an extended shoulder to take the place of the handguard cap. causing more confusion. Which is why I use the Raininer low pro gasblock dimpling tool. 
It locates properly over the gasport and centers with a conical screw. It is perfectly setup for the Vltor gasblocks, I used it with two other blocks (a YHM LP and GHB aluminum) with minor adjustments to locate the second dimple.. |
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+1 on this. I do it this way with a piece of clear tube from a fish tank. Also you might check and make sure you put the roll pin in your gas tube. I had the same thing happen at the range after a build and it turns out I didnt put my gas tube roll pin in and after the first shot it pretty much did what yours is doing..
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Go to the auto parts store and buy 1.5 - 2' of vacuum hose. Slip the hose over the end of the gas tube. Blow through the gas tube and loosen the set screws on your gas block. Move the gas block around and check to see if you are "pinching" off your gas path. I'd say your gas port isn't quite lined up. |
| 100 rounds break in before the gun works right? Huh? Put together right they work right from the first shot. I'd go with the old mechanics rule, " Start your diagnostic with the last thing you 'fixed'" i.e., You changed the gas block, everything else is "factory assembled". I'd be checking the gas block for proper alignment and function. |
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