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Page AR-15 » Troubleshooting
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Posted: 9/29/2015 7:44:43 PM EDT
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
Link Posted: 9/29/2015 9:27:17 PM EDT
[#1]
Link Posted: 9/30/2015 7:15:37 AM EDT
[#2]
Thanks.
I should have swapped bolts last Sunday when I had it all out at the range.
Bought ought to be interchangeable for the most part shouldn't they?? If a custom build, I could see issues with the very close tolerances.

Ripsaw
Link Posted: 10/3/2015 4:28:45 PM EDT
[#3]
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
Link Posted: 10/3/2015 5:42:48 PM EDT
[#4]
Link Posted: 10/4/2015 9:32:26 AM EDT
[#5]
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
Link Posted: 10/4/2015 2:14:37 PM EDT
[#6]
Link Posted: 10/27/2015 12:57:10 PM EDT
[#7]
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
Page AR-15 » Troubleshooting
AR Sponsor: bravocompany
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