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9/22/2017 12:11:25 AM
Posted: 1/17/2006 4:04:33 PM EDT
I have Bushmaster 16 inch upper that I'm getting threaded for a Phantom 5C1. My question is, When it goes to a gunsmith what parts are needed to take off before they start the threading, ie. receiver from barrel, gas tube, front FS post etc..?? If that is correct, I would like to get a flat top gas block for a folddown front sight put on while the barrel is being serviced. Would this be a good time to get it done as well? Whats is a good gas block and folding front sight also?
Link Posted: 1/17/2006 5:26:56 PM EDT
Well, if you remove the barrel from the upper yourself (instead of the gunsmith doing it), you'll need an action block, barrel wrench, torque wrench, vise, moly lube, and 1/16" pin punch.

If you also want to remove the front sight base, you'll need a hammer and a 3/32 nail set to drive out the two taper pins. I would assume that the front sight base can be left in place for barrel threading though.
Link Posted: 1/17/2006 10:53:20 PM EDT
[Last Edit: 1/17/2006 10:56:07 PM EDT by Randall_Rausch]
Link Posted: 2/2/2006 1:24:01 PM EDT
Good info. thanks everybody!!
Link Posted: 2/2/2006 1:46:03 PM EDT
agree that the pri is one of the better fsb and i would choose it over a railed gas block and sight combo.

also some require removal of bbl. but adcofirearms does not, think there are some that can actually chuck up a whole upper and thread.
Link Posted: 2/2/2006 2:02:19 PM EDT
Link Posted: 2/2/2006 2:02:56 PM EDT
I have an adapter that allows me to chuck up the assembled upper. But, I really prefer to work on a stripped barrel. Less problems and less that Mr Murphy can screw up. Charles the Gunsmith.
Link Posted: 2/2/2006 2:07:16 PM EDT
Link Posted: 2/2/2006 3:17:52 PM EDT
[Last Edit: 2/2/2006 3:24:20 PM EDT by 1911builder]
I never have figured out how to do pics. The adapters are featured in Derrick Martin's "Accuracy Speaks" catalog. I bought one from him when I ran his gunsmith shop while he was in Iraq.

You really have the right idea as the adapter is a steel cylinder the exact OD of a bolt carrier. There are 2 drilled and tapped holes in the cylinder that allow a clamp with 2 matching non-threaded holes to have hex head allen type bolts inserted and the clamp bears down on the bottom of the upper receiver.

This is a really useful tool on occasion. But, as you said the muzzle is centered on either a live or dead center and the crown needs to be recut. This can be done by using a steady rest without removing the upper from the chuck. This allows you to stay on the same axis and center line that the threads are cut on. It does save some time. Hope this helps.


EDIT TO ADD: No real need to engage the barrel extension with this cylinder and clamp.
Link Posted: 2/2/2006 3:53:31 PM EDT
[Last Edit: 2/2/2006 3:54:51 PM EDT by AR15barrels]
Link Posted: 2/2/2006 5:18:38 PM EDT
[Last Edit: 2/2/2006 5:20:30 PM EDT by 1911builder]
Actually, the bolts in mine are 3/8 x 24, IIRC. This allows you to torque them down enough so that there is no danger of them coming loose when the barrel/chuck is spinning at 600+ RPM. I indicate it in to 0.0003 inches or less off the cylinder using a 4 jaw chuck. Works very well. Charles.
Link Posted: 2/2/2006 6:50:18 PM EDT
Link Posted: 2/6/2006 2:43:07 PM EDT
I'm not a machinist but I am a woodworker and have a basic understanding of metalworking.

So, why can't you fix the barrel in a chuck/jig and spin the cutter/die around the barrel?

Just curious.
Link Posted: 2/6/2006 5:23:31 PM EDT
While the barrel is installed in the chuck the threads are cut with a single point tool. A conventional die is generally not used. This helps to ensure concentricity of the bore and threads. Charles.
Link Posted: 2/6/2006 5:54:20 PM EDT
Link Posted: 2/6/2006 7:34:27 PM EDT
Nice looking threads Randy. Charles.
Link Posted: 2/6/2006 7:45:31 PM EDT
[Last Edit: 2/6/2006 7:45:46 PM EDT by theshootersden]
Yeah Randy, very nice work, real clean...
Link Posted: 2/6/2006 7:46:01 PM EDT
Link Posted: 2/7/2006 7:49:14 AM EDT
Thanks for the lesson guys. Very informative...and the pics are great!

One more question: In order to make multiple passes at thread cutting, both the material and the tip of the cutter would have to be returned to exactly the same starting point each time. Is this a feature that is built into the lathe?? I could see how getting the cutter back would be fairly easy (linear motion) with stops, but how is the timing (axial motion) reset so precisely for the proceeding cuts?
Link Posted: 2/7/2006 8:07:24 AM EDT
[Last Edit: 2/7/2006 7:15:04 PM EDT by AR15barrels]
Link Posted: 2/7/2006 8:23:26 AM EDT
Once again, thank's for the informative lesson.
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