Ar15 Lower: Jumping In

[n3480h]

The depth requirement only affects licensed manufactures. Home builder don't even need to put any ID'ing marks on a lower. If i can find the copy of a letter a friend recieved from ATF I will post it.

Bob

Thanks Bob, that is absolutely correct. However, it is recommended: If I were at a public range and someone saw that my 300 had no SN, they might not know the regs and create a problem. Also, in the very unlikely event that someone stole the weapon, I will have a record of identifying data that I can submit to LE. Cheap insurance to prevent "complications". BTW, I will etch a matching number onto the upper (because I can).

Tom

 

[unioncreek]

Tom,

Ditto on your own identification marks. I also put them on the lowers that I finish. I found a local engraver who can laser etch anything I want for $20. Where did you get your 0% lower? I have a HF mini mill setup just like yours even with the igaging.

Bob

 

[n3480h]

Tom,

Ditto on your own identification marks. I also put them on the lowers that I finish. I found a local engraver who can laser etch anything I want for $20. Where did you get your 0% lower? I have a HF mini mill setup just like yours even with the igaging.

Bob

Bob, I think I got them from RGUNS, 2-3 years ago after Blackhawk mentioned them in a post here. Seems to me I paid about $20 each. I like the minimill and what it can do if close attention is paid to its idiosyncracies. The Igaging DRO had been perfect on this machine and I would not try anything so precise without a DRO. For example, getting the pin locations for the trigger and disconnector off just a little in X and/or Y will affect sear engagement. The only problem I had with the minimill is that when I drilled the hole for the rear pin detent, using an R8 chuck, there was only about 3/8" clearance in Z between the choked up drill bit and the buffer plane. This does not allow "pecking" to clear chips. See above. Won't make that mistake again.

Tom

 

[unioncreek]

Tom,

Thanks for the info on the 0%. I have a 4" vise on mine and with the drill chuck clearance is very limited. Been thinking of making a 2" riser block to see how that would work. Yes, the igaging make the jobs so much easier and enjoyable.

Bob

 

[n3480h]

Got started on the freefloat tube for the 300 today. Making use of the lathe and the minimill today, and using the rotary table to position ventilation holes. It's just a start, but it's fun to be able to position features accurately circumferentially. At 12.5" long, the tube is just about to maximum length on the 7x14 lathe, and only half the length can be machined at one time on the mill when using the rotary table (aligned with Z axis). But, it works. The tube is an inexpensive commercial unit that I am resurfacing and "customizing", which saves me from trying to cut the internal thread waaaaay out there on the end. A 5° tapered spud was turned with a centered countersink so I could run the live center on the lathe's tailstock. Got away with it.

Tom

 

[n3480h]

Started the electro-etching tonight. Pretty pleased with the result. Depth is .005" and detail is good. I used the swab method, with the battery charger set at 12VDC and 2 amps. Electrolyte is just white vinegar and non-iodized salt. Hope to etch the driver side tomorrow and the freefloat tube soon after that.

Tom

 

[dave2176]

Please share the process you used for the etching. Looks good. Did you do the template or have it done? What size is the font? I have a friend with one of those vinyl cutters but its smallest font is 1".

 

[n3480h]

Please share the process you used for the etching. Looks good. Did you do the template or have it done? What size is the font? I have a friend with one of those vinyl cutters but its smallest font is 1".

Dave, the process I used is very similar to what is shown in the tube video I referenced above, but instead of building a dam I attached the negative clip to a rolled cotton bore patch soaked in the electrolyte and swabbed the open areas of the vinyl mask. The mix for electrolyte was about a cup of vinegar with maybe two rounded teaspoons of salt dissolved into it (not precise, but it works well). My artwork was done oversized in CorelDraw and CorelPaint and then sent to my daughter-in-law who reduced it to final size and cut it into the vinyl. She has the same cutter as the guy in the video. Some of the tiny details in lettering were too small, such as the center of the A in SAFE, so I painted in that detail with enamel and a VERY fine brush. When etching was done I pulled the vinyl mask, wiped off the little paint detail with acetone, and scrubbed the black out of the etched areas with hot water and a fine brass brush. Font size for the ser.# and SAFE/FIRE is 12 point. Total time spent for the snake eye and surrounding type was about an hour, with about half of that actually etching. Takes a little patience to get it deep enough. I'll try to remember to take a pic of the etching in process tomorrow.

Tom

 

[n3480h]

The etching swab is just 1/2 of a cotton patch, rolled, put into the clamp, and then dipped in the electrolyte. The yellow is the vinyl mask. Plain masking tape was used to protect the surrounding area. The swab is gently rubbed over the exposed lettering and small bubbles indicate that current is flowing. A small single line like the serial # took about 10 minutes to etch .005" deep. The swab and the etched area are blotted every minute or so to remove most of the black (spent) electrolyte and the swab is dipped into fresh electrolyte before continuing, and about half way through the battery clip is rolled to use the opposite end of the swab. When peeling the vinyl off, small areas like the center of the R may stay on the receiver, but they are easily removed with a fingernail. In the SAFE and FIRE pic you can see the depth of the etch. Hope that helps to explain the process a little better.

Tom

 

[n3480h]

Aaaaand . . . . the machining and etching on the lower receiver and freefloat tube is done. All in all a good learning experience. Thanks again to Rick Leslie for getting me fired up about etching, and to all who have contributed their thoughts. Now it's on to Cerakote in FDE - hope I don't screw it up now, lol.

Tom