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Durkin Tactical Franklin Armory
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Posted: 5/2/2015 9:42:50 AM EDT
building another 6.8 using an ARP 18" barrel/bolt/brake. decided on the Mega megalithic upper which arrived yesterday. in their tool instruction the say to torque the barrel to 65 ft/lbs and the additional offset of their barrel wrench will yield a total of 75 ft/lbs applied. seems a little high to my thinking, but as this is my second 6.8 build i'm not as up to full speed on this type info. any thoughts? usually i'm an anal operation manual adherent, but i just don't know about this. and i use bold font cause my old eyes aren't what they once were
Link Posted: 5/2/2015 10:33:57 AM EDT
I would go with what Mega Arms says.

They come from the aerospace industry.

They know what they are doing and are one of the best machine shops out there.

Link Posted: 5/2/2015 10:37:35 AM EDT
I have 6 of their monolithic uppers and that is what I did
Link Posted: 5/2/2015 11:46:00 AM EDT
My MKM Maten had the same torque value and I had no issues. I am not a mechanical engineer or materials expert but if I had to guess I would think it has to do with the female reciever threads vs the male threads of a standard reciever. Either way mega is a reputable company and their instructions should be followed with confidence.
Link Posted: 5/2/2015 1:55:54 PM EDT
Fwiw, my mega was not even hand tight after about 800 rounds when it was pulled apart.  Get it tight enough, 75 sounds about right.
Link Posted: 5/2/2015 9:39:56 PM EDT
thanks for your collected experiences, 75 lbs it is. this will be my second 6.8 build and first time i've used mega parts,,,won't be the last. was putting what i could of the lower together and it's a pleasure to work on nicely machined parts. will install the barrel tomorrow, had to go buy a better torque wrench
Link Posted: 5/2/2015 11:05:29 PM EDT
Apples and oranges compared to a standard AR15 barrel nut. The fact that the barrel nut is a larger diameter means you need a higher level of torque to achieve the same "tightness." Also, as mentioned above, it's a different design. Torquing the Megalithic barrel nut at 65 lbs feels just fine, not like doing that on an ar15 and thinking you're about to twist the thing in half.

Link Posted: 5/4/2015 11:25:43 AM EDT
don't mind saying that seating the barrel in this 1 piece upper/rail made me as nervous as a working girl in church (my old mom used to say that, but used more colorful language)
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