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Posted: 1/11/2015 2:35:59 PM EDT
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I have put together a new AR with 20 inch rifle length gas port, Syrac Gen 2 adjustible gas block on a lower that came with a Magpul ACS stock and carbine length stock inclkuding buffer I assume is a carbine.
No matter how much gas I give it the bolt will not cycle or lock back. I assume I need a rifle length stock tube and buffer. (A2 extension tube, recoil spring, buffer assembly, stock spacer and screw.) Can I still use the ACS stock and what kind of buffer should I buy? Any buffers that should work with the carbine length stock tube? Rookie questions but I appreciate the help. |
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You absolutely may use your carbine stock and buffer.
Make sure its a Carbine buffer and not an H, H2, H3 etc. make sure your ammo is not weak. Make sure the carrier and bolt are wet. But in all likelyhood its probably an install issue with the gas system, most likely the gas block is not aligned over the gas port hole, or the port isnt entirely open. I'd remove the gas block and tube and start checking things. Make sure the gas tube is seated in the upper properly. While things are apart go ahead and measure the gas port with calipers if you have them. A rifle a2 stock is not required in any way with a rifle len gas system and 20" barrel. A normal collapsible stock with a 3oz carbine buffer should be slightly overgassed with the adj gas block fully open. If everything is installed correctly and aligned, rifle is wet and ammo is 556 nato, and gas block is machined properly, then Id be asking who's barrel you have because the gas port may be undersized. |
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I am running a CS flatwire spring with a H3 buffer and my 20” has no problem with AE 223 ammo.
If the bolt is not cycling at all most likely you have a blockage. If it is partially cycling then most likely you have a leak. It could be the gas block since it is adjustable. Undersized ports are very rare. |
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Ammo is not weak. I was usiong IMI M855 green tip and Hornady 75 grain. Also checked operation with AE 55 grain and M193. All NATO spec.
I have a Lothar Walthar barrel, varmit tactical profile, about 3 pounds with blue printed bolt that comes with barrel. 0.750 diameter block. New Syrac gen 2 gas block fit snuggly. BTW, my reloads with Remington 7 1/2 primers had light firing pin strikes and would not fire. WSR and military primers worked fine. Wylde chamber. Thanks for advice ona tube length and buffers. An experienced small arms trainer suggested I change gas tube to one of the actonel steel tubes, but I cant find it on line. He said it cured his departments SBR issues when buffers did not. Kind of looking like a blockage? |
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Seeing As how millions of rifles over several decades have worked just fine with the standard gas tube that does not seem like a solution for your problem.
Unless there is a blockage in the tube, in which case a standard gas tube fixes your problem. You did not say if the BCG was moving at all. Most of the time these problems are leaks often at the gas key. You might try a standard gas block to eliminate the Syrac as a problem. |
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PFC,
the bolt carrier is not moving. there is a small amount of soot in front of the gas block but not too different from my previous rifle. I measured the length of the firing pin and it is about 4/1000 shorter than my other two. May be reason I got light primer strikes? 3 ounces is std carbine weight, correct? I usually run a Surefire SOCOM suppressor and would like a combination of gas block and buffer that allows me to turn down the gas so I dont over gas the BCG. |
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Quoted:
PFC, the bolt carrier is not moving. there is a small amount of soot in front of the gas block but not too different from my previous rifle. I measured the length of the firing pin and it is about 4/1000 shorter than my other two. May be reason I got light primer strikes? 3 ounces is std carbine weight, correct? I usually run a Surefire SOCOM suppressor and would like a combination of gas block and buffer that allows me to turn down the gas so I dont over gas the BCG. It's called carbon, not soot. Perhaps some pics and a more detailed explanation is required to help you solve your problem. |
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Chrome308, Wagonwheel, Pfc, Turbineguy,
I pulled the buffer and spring. Buffer is is stamped H. It weighs 3.8 ounces. 3 1/4 inch long. Sounds like a std carbine buffer is 2.9 - 3.0 ounces, correct? Spring is 10 1/2 inches long (on buffer). It has 36 or 37 coils! (30 sounds std?). Buffer and spring together weigh 5.7 ounces total. This sounds like it is a carbine spring length but super heavy for a heavy buffer. http://www.ar15.com/forums/t_3_4/452815_rifle_vs_carbine_buffer_spring_length___.html The spring and inside of the stock tube are very, very slightly oily feeling. Is this normal for corrosion resistance or should I wipe it down with gun scrubber or brake cleaning fluid to remove any and all grease? To be safe, should I just buy a completely new standard set of buffer and spring? If so do you all have a favorite brand? Can 0.8 ounces make this much difference in BCG???? Thanks very much for your help! |
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Quoted:
PFC, the bolt carrier is not moving. there is a small amount of soot in front of the gas block but not too different from my previous rifle. I measured the length of the firing pin and it is about 4/1000 shorter than my other two. May be reason I got light primer strikes? 3 ounces is std carbine weight, correct? I usually run a Surefire SOCOM suppressor and would like a combination of gas block and buffer that allows me to turn down the gas so I dont over gas the BCG. Reread your post. Do I understand you correctly ? When you fire a round the BCG does not move ? |
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I gotta ask, you do have the gas tube installed and it is a rifle length tube ? Should extend into the receiver an inch or so ?
If so can you verify that the tube is not obstructed ? Put a piece of small tubing onto the gas tube and blow through. It seems that you are getting zero gas into the barrels gas port, through the block, into the tube to reach the gas key. I feel that your adjustable gas block may be the culprit. |
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A partial obstruction or minor assembly issue would have the bolt moving some at least. If its not moving at all you are either loosing a significant amount of gas or not getting any at all. 0.8 oz of carrier weight might cause the bolt to not lockback or might cause the occasional malfunction but its not nearly enough to stop the carrier from moving entirely. Sometimes its hard to tell if the carrier moved or not. It can happen basically faster than the eye can see yet still leave a case in the chamber.
At minimum, make sure you're getting air through the gas block. If you seal the chamber with something and blow down the muzzle you should be able to feel some air out the gas tube inside the upper. If it passes that check I'd be looking for leaks, either at or around the gas block or maybe at the gas key. A pic of the gas block and another of the gas tube protruding into the upper shot from below would help. |
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Quoted:
PFC, the bolt carrier is not moving. there is a small amount of soot in front of the gas block but not too different from my previous rifle. I measured the length of the firing pin and it is about 4/1000 shorter than my other two. May be reason I got light primer strikes? 3 ounces is std carbine weight, correct? I usually run a Surefire SOCOM suppressor and would like a combination of gas block and buffer that allows me to turn down the gas so I dont over gas the BCG. BCG does not move when the weapon is fired. You said you swapped BCG’s. So most likely you installed something wrong or something is wrong with the gas tube, gas block, or gas port. I know you are new, but I would presume you have a rifle length gas tube. For the BCG to not move either there is no gas or very little getting through. The gas tube and port seem like easy things to check which leaves the GB. I don’t know about the Syrac GB, but a standard clamp on gas block is really hard to screw up. If you cannot figure out if the Syrac is ok then substitute a clamp on for testing. |
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MAKE YOUR RIFLE SAFE
yank the syrac OFF, make sure all holes everywhere are clear,set the syrac for max flow, gas rings in bolt are spaced equally,bolt moves in carrier w minimal resistance,,remount, make sure YOU HAVE THE HOLES ALIGNED w barrel and gas block AND TEST AGAIN TO MAKE SURE AIR MOVES FROM BARREL THROUGH TUBE TO BOLT.go someplace safe and test fire. like the girl w the loose cootchie said: you aint gettin no queave!) NO GAS, NEED GAS TO MOVE THAT THANG!!! |
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Thanks guys.
I can stand bolt carrier group on a table, bolt face down and bolt extended, and the gas rings are tight enough that the bolt carrier stays in place. So I have a tight seal there. I will let you know about the air through LBE gas tube. Gotta be there or the Syrac GB, dont you think? (Or too small a hole for gas port but youd think Lothar Walthar would not screw it up that bad.) No word from Syrac or barrel maker yet. How far should the gas tube protrude inside the gas key??? LBE said it was rifle length on packaging but human error is always possible! I really appreciate your help. Youre the best! |
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Update.
Gas tube was blocked. Mu gunsmith removed gas tube and gas block. Blew compressed air through tube from gas key side forward and out popped a plug of metal shaving. We were surprised 47 rounds of 556 ddid not clear the tube but gas was going toward gas key not away from it. I am guessing it was blocked at the dog leg in gas tube? Any way, rifle works fine now! Gas port diameter was Colt spec 0.093. Gas block was .120 and fit directly over gas port. Take home lesson is to blow through gas tube before installation. thank you all for your help. |
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