I've got a chop saw I can donate to the fund, and can fab a wood jig for holding the receiver/barrel combo plumb and square to the blade...
The jig can be a piece of old Norc M-14 stock that has been squared up on the sides and bottom. I'll bring one to the next meeting ... if my old brain remembers that far ahead, or someone reminds me a lot closer to the date
Just a note here to remind everyone that most of the information about Do It Yourself GUNSMITING that I hand out at these seminars, is for TABLETOP amateur smithing ... like Hungry, I am a big fan of making do with "Field expedient" tools and techniques. This may not be how a PRO, with a full machine shop would do things, but these home made tools and techniques will get the job done.
eg: why buy an EXPENSIVE full set of headspace gages, when you can get by with just a GO gage, and a few precise thickness shims cut from a set of automotive feeler gages.
The proper way to chop and crown and thread a barrel, quickly and professionally, is to mount the barrel in your barrel vice, bolt on your receiver wrench, pull the barrel out, and chuck it into your metal lathe. However, if you don't happen to have a set of proper receiver and barrel wrenches, and a lathe, the barrel chop can be done without pulling the barrel .... this is why man invented the chop saw ... to chop things.
And, with the piloted crowning tool adapted from a carbide router bit, which I showed you at the seminar, the crowning can be done very nicely without a lathe, and again without pulling the barrel. NOTE: Because the NORC bores are chrome lined, ONLY carbide will work here. Brownells sells a very nice piloted hand crowning tool with HSS cutters, but unfortunately the chrome is harder than tool steel, and the expensive HSS cutters won't last long.
As I mentioned, you know the crown is smooth enough, with no burrs, when you can drag a cotton q-tip out the edge, without leaving pieces and threads behind. You can also LAP the bore with a brass ball and some valve grinding compound, if you prefer a round crown rather than a square crown. To save time, you can start the crowning by breaking the bore edges with a Dremel and a round ceramic ball, but before there were lathes, and Dremels, old time gunsmiths used hand turned drills and brass balls.
Of course, the proof of the crowning job is not how pretty it looks, but how well it shoots ... so don't sprain you arm patting yourself on the back, at how well your crown looks, until you take the rifle to the range and try it out.
As for the barrel threading, this is possible with hand tools, and again without pulling the barrel. A piloted die adapter, with a .299" pilot that fits down the bore, will align the thread cutting die with the bore at the start of the threading. However, since many barrel muzzles are NOT concentric with the bore, and since you really want the threads to be concentric with the bore, not the exterior, this will not be precise enough for those rifles where the bore and the exterior are not concentric. While you may start the die off perfectly aligned with the bore, once it leaves the guide, the die will tend to follow the barrel exterior. This is why PRO gunsmiths use lathes for precise threading on barrels.
However, for a flash hider, which has a whopping big hole at the end, this level of precision may not be necessary. A few thou out of alignment on a flashider will not hurt anything.
Muzzle brakes or compensators, with interior passages only slightly larger than bullet diameter, are another thing entirely. These must be as perfect as possible, otherwise very bad things could happen. BUT, for those barrels where ... by luck or skill ... the bore and the exterior are concentric, the threads cut by a piloted hand die may end up as perfectly precise as those cut on a lathe.
If you are lucky ...
do you feel lucky, punk?
If VooDooMan can fab a threading die, and Laz can give us the specs for his 'recrowning' tool, maybe the group can branch out abit.
So, it might be possible to follow up on Doc's dream of shoving perfectly good M-14 rifles into the chop saw, and have them come out as shorties.
Fortune favors the brave [ and the lucky ]. The worst that can happen, is that we screw up a few cheap NORC barrels, and have all the PRO gunsmiths laughing when we bring the botched jobs into their shops for final FU fixin'.
And we've all been there before any how, haven't we??
[;{)
LAZ 1
