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Posted: 9/29/2015 7:44:43 PM EDT
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I have a BCG that i think is an SGW/Olympic Arms Manufacture. It has an SE stamped on the chromed carrier. We'll call it BCG "A"
When I changed to a HB varmint upper with BCG "A", it short stroked. Sometimes it would feed, but never lock on the last shot. When I changed to a different lower, same thing. I changed to a different BCG and the HB varmint ran like a champ. I moved it to a different lower with BCG "A", no go. I then changed to BCG "B" and it ran like a top with both lowers. I put BCG "A" in an upper that I never had issues with and it would short stroke. BCG "B" ran in all combos of uppers and lowers. BCG :A: runs with one upper only. The gas rings are snug and it takes some effort to put the bolt into the carrier. The carrier key is snug with staked screws and shows no sign of leakage I have concluded that there is something wrong with the bolt. I'm not an expert on trouble shooting, but not a novice either. One suggestion was that the hole were the tail of the bolt goes trough may need to be measured to see if it is oversized. Any help from the forum gurus would be appreciated. Thanks gentlemen. Ripsaw |
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B/C A and B,
Swap the bolts between the two and see if the problem follows the bolt or the carrier. If bolt, the bank a Head spacing issue from the bolt itself. If carrier, and the key is not binding in the upper slot and the gas tube is aligned with the key, then suspect the key is leaking from the top of the carrier, the key entrance is too worn or large, of the tail section of the carrier in the gas chamber too large and allow too much leakage out the back of the carrier around the bolt tail instead. |
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Well,
I exchanged the bolts in the different carrier. When I put bolt "B" in bolt carrier "A" I got short stroking and failure to lock. Bolt "A" in bolt carrier "B" it worked fine in three different uppers. It is something in the bolt carrier. This BCG works fine in one rifle only. The only thing I can do is to put on a new carrier key. New key and hex bolts get ordered Monday. If it doesn't work then, I'm out $8 plus shipping. Suggestions welcomed. Ripsaw |
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Would dare to guess that the key is fine, but just leaking.
So on that note, may have to lap the bottom of the key first, the top of the carrier second, then the two together so you make sure to have a clean surface between the two to being with to solve any leaking problem between the two to begin with . Also a thin coat of Red loctite between the two after they have been lapped in when you are installing the key to the carrier with the bolts, will harden to make a good thin sealing compound between the two when the loctite dries. As for key bolts, only torque them to 37 in lbs, then stake the metal of the key into the side spines of the bolt head to hold the bolt in place (read do not mar the bolt material at all, just peen the softer key metal into the side spines of the harder bolt metal instead). |
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I see no telltale soot or carbon. That is the curious part of my frustration. This is also an older bolt with the exposed rear of the firing pin.
This bolt worked well wit the old Olympic Arms/SGW lower it came with. That rifle is long gone but I sold it sans the bolt. It worked fine for the guy I sold it to. Ripsaw |
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Could just be that either the entry to the key is worn out, or was over sized to begin with. Hence a quick check with a gas tube will tell you if the entry to the key is too large from the start.
Also, depending on the age of the carrier, a while back there was a bad batch of keys that the bottom passage exit of the keys where not aligning correctly with the top entry port of the carrier. In some cases, you could en-long the bottom of the key exit port to align the two ports, while others where so bad that the only solution to the problem was to get a correctly produced key instead. Hence the trick here, was to catch the problem before the key was installed to begin with. Lastly, double check the bolt tail passage in carrier as well, hence could be over sized as well. Here with nastly gas leak, if say a rifles gas port is over sized, even with the excess leak out the tail of the bolt, the carrier would work fine in it. |
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Solved!!
Broken screw. Chrome carrier and no visible telltale soot. As soon as I went through the staking prong, =ne resistance on the screw. Fortunately, some heat on the stub, some Kroil, and gentle turning with a vise grip, it backed out. Runs like a champo with the new gas-key and screws. Ripsaw |
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