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Originally posted by Lemonaid
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No the extension alignment pin does not lock into the threads on a AR -
I going to jump in on this one. This barrel was produced probably 4 years ago before we discovered that the nitriding process can reduce the torque required on the barrel extension. For the past 3 years to there abouts we send the barrel to nitride before installing the barrel extension and drilling the gas port.
Using a reaction rod seems to aggravate the situation. Barrels that would probably last for 1000's more rounds are being loosened by this method. We used to use the Reaction rod in our shop quite a bit until we had this happen on several barrels in one week from several different manufacturers. Most of these were from suppressor attachments that were rock set on. We now use another system that works better.
The extension pin is for alignment only.
Its not simply a deal where we can reinstall the pin because re torquing will place the timing of the alignment pin and the gas port about 5 to 10 degree off. We have to go through our batch of extension and try to find one that will match the barrel. Being the barrel is nitrided we cant just recut the chamber by .005 to match the gas port.
Unfortunately in this barrel's case none of the 100 extension we have in house clocked at the right place so we need to wait for the next batch of extensions next month to check if any of those will fit. If not we will discard the barrel and replace.
Mark Hostetter
Precision Firearms"Precision - The Pinnacle of Perfection."Comment
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Mark, educate me. I have always been under the impression that the barrel extension has the hole drilled after it's installed and torqued to 150ft-lbs, or whatever the spec is. Then, the index pin hole, and the gas port are drilled on a fixture ensuring they remain exactly in-line. That way the indexing happens easily and without timing issues. Am I wrong here?
I can see how the thermal and chemical properties of nitriding a barrel with an already installed extension could cause expansion/contraction loosening. But those lessons have been learned since nirtiding has become more mainstream, right?
I'm confused how a RR could cause the extension to come loose if the torque required to remove a muzzle device is less than 100 ft-lbs (which is friggin hard to do on a RR; like Grizzly Adams hard), especially considering super max MD torque should be 60 ft/lbs...
Now, rock-set is a different animal; and anyone using it should already know that it is intended to be a permanent fixture. It's like using the two part putty... Don't expect to get away with getting it apart. It can be done, but using it makes you the permanent owner of the two parts and their marriage. Don't go complaining when it doesn't come apart without damaging one or both of the two parts... Question then, why don't we rock-set the extensions onto the barrels?
If you've moved away from the RR, what have you found to be a better solution? I've been eying some bench top barrel vises.Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.Comment
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The hole in the extension is drilled to be timed with feed ramps. I think you can figure out why that is important.
Yes it has. Which is why I explained how we are doing it differently now. Out of a thousand barrels we probably only saw this type of failure like 10 times
Only a problem if the extension is torqued to 125 LBS. But Ive seen this happen even on Name Brand Barrels that start with D and B.....Especially with Suppressor mounts and locktite.
You probably could use Rockset. We use red locktite here.
We make a vise block with a accessory Picatinny Rail block that works very good. I have one unit here that has been part of the assembly process on at least 50,000 uppers."Precision - The Pinnacle of Perfection."Comment
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Footnote guys: on Rocksett, I have used it successfully and also disassembled it successfully and used the parts again. There's a trick to it, suspend the piece with the rocksett portion submerged in water -- boiling or at 200+ deg, for 20-30 minutes, it will come apart like silly putty. It is a silicate type compound that crystallizes, that's what makes it "permanent" but will dissolve in hot water. Heat alone will not faze it as the crystalline structure goes to IDK 2000 deg or so...
But let the hot water seep down to it and bingo!"Down the floor, out the door, Go Brandon Go!!!!!"Comment
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Rocksett should also come apart with the same amount of torque used to tighten it. It isn't meant to be 'permanent' like red loctite. There does seem to be a lot of misinformation that 'red' = high temp. There is also blue loctite that has the same temp rating as red but comes apart at the same low torque rating you'd expect with a "medium" strength thread locker.
Sadly the more exotic ones listed aren't available at your local hardware store.
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This. I've used this method once before on a buddy's personal Mk 18 after talking with the onsite armorers for the State Department DSS/MSD. They oversee hundreds of thousands of rounds in a short period and barrel swap on a regular basis. For removal of a Rocksett muzzle brake, they recommended boiling water, turning off the flame and then soaking the muzzle end of the barrel while occasionally rotating it in order to render the Rocksett pliable. After just under 10 minutes, I used a 1/2" drive 24" breaker bar and was pleasantly surprised at how easy it was to remove the muzzle brake.Originally posted by grayfox View PostComment
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We use the boiling water method too.
Works well most of the time."Precision - The Pinnacle of Perfection."Comment
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