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Posted: 1/5/2024 7:34:42 PM EDT
[#1]
Most uppers I have measured come in at around 1.000" to 1.001". Maybe for a tight fit?
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Posted: 1/5/2024 7:36:46 PM EDT
[#2]
Did you get it out of the receiver yet?
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Posted: 1/5/2024 7:39:57 PM EDT
[#3]
Quote HistoryQuoted: Most uppers I have measure come in at around 1.000" to 1.001" maybe for a tight fit? If most uppers come in around 1.000" to 1.001" I should be able to thermo fit one to my oversized barrel extension. I am assuming the combination of a 0.001” oversized barrel extension and milspec upper receiver will act the same as a 0.001” undersized upper receiver (BCM M4) and a milspec barrel extension. |
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Posted: 1/5/2024 7:50:29 PM EDT
[#4]
Quote HistoryQuoted: If most uppers come in around 1.000" to 1.001" I should be able to thermo fit one to my oversized barrel extension. I am assuming the combination of a 0.001” oversized barrel extension and milspec upper receiver will act the same as a 0.001” undersized upper receiver (BCM M4) and a milspec barrel extension. Thought you were using one of the undersized BCM uppers. One I have only measured around .998" or maybe a little smaller when I just checked it. How much an upper would expand from heating I have no clue. Also I did not say most uppers I said most that I have measured. |
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Posted: 1/5/2024 8:15:23 PM EDT
[#5]
Quote HistoryQuoted: Thought you were using one of the undersized BCM uppers. One I have only measured around .998" or maybe a little smaller when I just checked it. How much an upper would expand from heating I have no clue. Also I did not say most uppers I said most that I have measured. I was using a BCM upper. That's the problem. It will not work with an oversized barrel extension. I did not know that Compass Lake installed an oversized barrel extension. |
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Posted: 1/5/2024 10:40:12 PM EDT
[#6]
The one thing I have yet to hear is what temperature you bringing the upper up to.
Until I hear that number, I am not giving up on completing a thermal fit. |
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Posted: 1/6/2024 12:37:13 AM EDT
[#7]
Quote HistoryQuoted: I was using a BCM upper. That's the problem. It will not work with an oversized barrel extension. I did not know that Compass Lake installed an oversized barrel extension. Ya, it appears that you are on opposite ends of the tolerance stack. I'd expect there are a few uppers out there of equal or better quality that would accept that barrel. Post it up in the EE if you aren't happy with it. Some guys would pay a premium to have such a "problem". |
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Posted: 1/6/2024 1:00:28 AM EDT
[#8]
really necessary to make two post about this issue?
edited |
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Posted: 1/6/2024 1:05:48 AM EDT
[#9]
Quote HistoryQuoted: really necessary to make to post about this issue? It's a tech forum 
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Posted: 1/6/2024 1:16:27 AM EDT
[#10]
Quote HistoryQuoted: It's a tech forum Quote HistoryQuoted: Quoted: really necessary to make to post about this issue? It's a tech forum really necessary to make a 2nd post about this same issue. |
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Posted: 1/6/2024 1:20:10 AM EDT
[#11]
Quoted: Compass Lake built a barrel for me using a oversized barrel extension that I measured to be .9990" at the barrel extension face and 1.0000" just before the index pin. I see that milspec is .9979” min to .9987” max. I did not request an oversized barrel extension when I ordered the barrel and I do not understand why they supplied one. Unfortunately Compass Lake decided this week to end commercial sales and I have not been able to find out what my options are. Does anyone here know why oversized barrel extensions are used and are there upper receivers that will work with them? I would secure the upper in a vice with blocks, then recruit someone to drive the barrel out with a 1" dowel as I heat the threads. Considering you have an undersized upper with an oversized extension, it sounds like two people would make it easier. Honestly, I don't think you need a thermal fit upper for that barrel or most barrels for that matter. |
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Posted: 1/6/2024 1:20:53 AM EDT
[#12]
Quote HistoryQuoted: really necessary to make a 2nd post about this same issue. Quote HistoryQuoted: Quoted: Quoted: really necessary to make to post about this issue? It's a tech forum really necessary to make a 2nd post about this same issue. Your first post didn't indicate it was in regards to the OP creating two threads on this issue (I see now it was a typo). Regardless, that point was addressed in the first thread. |
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Posted: 1/7/2024 2:04:17 AM EDT
[#13]
Just go buy an Aero upper receiver. You may have to hit it with a heat gun but it'll go.
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Posted: 1/7/2024 2:26:29 AM EDT
[#14]
Stripped uppers aren't all that expensive. Grab a new one and save the BCM for future use. No point in fighting it.
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Posted: 1/7/2024 6:54:36 AM EDT
[#15]
Quote HistoryQuoted: Stripped uppers aren't all that expensive. Grab a new one and save the BCM for future use. No point in fighting it. That's what I would recommend, except this time stay away from BCM. |
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Posted: 1/7/2024 11:09:51 AM EDT
[#16]
Quote HistoryQuoted: That's what I would recommend, except this time stay away from BCM. Quote HistoryQuoted: Quoted: Stripped uppers aren't all that expensive. Grab a new one and save the BCM for future use. No point in fighting it. That's what I would recommend, except this time stay away from BCM. This. Start with a standard receiver, not an undersized thermal fit. |
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Posted: 1/7/2024 11:14:19 AM EDT
[#17]
That’s not really a problem…just buy a standard mil spec upper receiver. A Colt would work.
Heat it up, use a wooden block to backstop the receiver and tap the barrel into it with a mallet. Easy day. |
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