willbird

That little lip along the top edge where upper mee ts lower is an Palmetto state armory Gen 2 or gen 3 attribute ?? If you are buying a complete working gun I am not a bit afraid of PSA, I have a gen 2 lower that I put a gen 1 upper onto. BUT parts interchange as far as other uppers will be an issue, and PSA gen 2 stripped uppers seem to be chronically unavail.

Does not look like an Aero to me ?? Close up of both sides would be helpful.

OK here we are mocked up with Faxon pencil 18" 308. Lacking a gas block. The rules say for total weight it needs sights or scope and a magazine...but without those. Lower 2lb 6.6oz Upper 5lb 3.9oz Total 7lb 10.5oz. So 2.5 oz heavier than projected, 6mm bore will add a litle weight unless I pare it off in the lathe :-). The rail and nut actually weighed in at 13oz, guntec claims 10oz :-(. (Total Weight Including Barrel Nut Is 10 Oz!!). A smoke composite would 8.53 total...not gonna go nuts over a few oz :-).

People get way way too twisted over twist :-). Good barrel and good bullets in 6mm as one example a 1/8 will still shoot under 1/2" with 75 grain bullets. Crappy barrel and crappy bullets does not shoot worth crap anyway. I would not lose a wink of sleep going 1/10 instead of 1/11.375 ;-). Bill

16" carbine gas are avail too, maybe a safer bet. Again that would chop and re thread pretty nice. You would have like $83 in it plus shipping, and the chop and re thread.

You could look at buying a 16" mid gas barrel and having it chopped and re threaded to 13" if that is where you want to be. This example might chop back pretty nice ?? Bill

Here is how mine came out. Trying to find the EXACT length of many rails can be almost mind boggling. Bill

milling a deep pocket into aluminum, with a hand held router, even guided by a jig is maybe one of the more demanding machining operations ever conceived :-). Add into there the fact that many are using cutting tools designed to work well in rigid cnc machines and it gets even more amazing that it actually works out decent :-).

Yea the profile thing will be fine :-). So far I have never set anything up where half of it was on the rail and half was on the upper. I was just spinning it and seeing that shaving 2 oz from the rail was going to cost $200 more or less, $100 an ounce is usery hehe. Bill

Building a pile of parts. Bought a 308 faxon 18" pencil so that I can document the barrel contour. Here is where things are headed Have........ Aero M5 lower Aero M5 upper Faxon Pencil 18" (just for measurements and weight) Aero LPK minus FCG Brownells BCG... PSA nickle boron 2 stage trigger Magpull MOE grip BATTLELINK Minimalist Stock AR-10® 6 POSITION RECEIVER EXTENSION KIT (NO STOCK) – AR10REKIT01..includes spring and buffer. White oak precision gas tube rifle minus 1" That totals up to 6lbs 7oz Coming in mail.... Guntec 15″ AIR-LOK SERIES M-LOK COMPRESSION FREE FLOATING HANDGUARD WITH MONOLITHIC TOP RAIL (.308 CAL) This is specified as 10oz complete which is fairly light...not many other fairly light M-Lok options that are not $300-$400 Surefire PROCOMP 762 So that supports 7lbs 8oz or lighter...which makes me smile :-). Not ordered yet gas block, probably going to be BATTLE ARMS DEVELOPMENT LIGHTWEIGHT LOW PROFILE TITANIUM GAS BLOCK-RAW TITANIUM FINISH

Actual bore sighting works great :-). Where I grew up neighbors had a basketball backboard in their driveway. I would set up way back in the room so as to not cause panic, align gun or upper so the basketball backboard was centered when the two rings (bore and exit) were aligned, then adjust the scope until it agreed with the bore sight. Always got me onto a normal target at 100 yards. Bill

From my fixture building days I know it is poor practice to try to reference two datums, will not work long term because no two parts are the same, the two lowers I did were close enough to identical that it worked out tho :-). I did reference the proper one when I picked up location.

OK, so they are not referencing the rear pin at all. I referenced both, but when/if I encounter a receiver that the pin to pin dimension is out of spec I'll have to make a diamond shaped pin for one end :-).

I made a set of jaws for my Kurt mill vise to hold the lower in each position. I used two pins to align to the takedown hole, one from each side. One could perhaps use a sacrificial aluminum or brass pin that could just be cut away to machine the entire pocket. Bill

I have noticed on 80% that the upper did not mate with lower before the FCG pocket was fully milled. This was due to the corner radii in the front end of the small pocket included in the 80%. Bill

Also if you ever "needed" a field gauge you could find the equivalent dimension and cut a disk of shim stock and affix to to the rear of your no-go with some grease. Looks like "Field" is an extra .004 for SAAMI 308 and an extra .006 for milspec M14 7.62 nato. SAAMI 308Win: GO 1.630" NO GO 1.634" FIELD 1.638" 7.62NATO (M14 US MILSPEC): GO 1.6355" NOGO 1.638" FIELD 1.6445"

The only downside is that they HATE semiwadcutter bullets. Looking at how they work I think it is because of how far the barrel drops to come out of battery compared to John Browning's original design. Bill

I have had an XD45 for years, recently added XD® MOD.2® – 3″ SUB-COMPACT MODEL 9MM. The round count on the double stack left me a lot happier than the S models. Bill

The Brownells tool is a good one. I have one for AR308 but not yet for AR15 :-). The punch for driving in gas tube roll pins is handy :-). Bill

Fedex just brought my Labradar and this tool from Brownells. :-).

The issue with DB readings is how they are taken. There is a specific instrument that should be used in a prescribed manner. And even on an indoor range with totally controlled conditions for the most part the data differs from day to day, probably small changes in humidity.

The ones we had at the tool and die shop were in drawers, kind of a "library" if gage pins. So in one spot would be .001 and .0005 increments in both plus and minus tolerances, from .06 clear up to at least .750. Some of our hole tolerances were +.0005" minus 0 too, and with all 4 pins surrounding that target size you could be pretty sure you were in there :-). having a lot of them we ended up with gage pins and gage blocks that were past life for precise work. So we used those to put in a hole when the part was clamped up for another operation. A part might have a .750 - .751 hole in a 1" part, slide a precise pin in and you could clamp without crushing that hole.

Ohio is good :-).

The idea was good enough for a guy named "moleman" to develop the 357AR. He started with 223 brass then Starline released a "223 basic" case that made things a lot easier, it is a 223 case before being necked down. The slightly bigger base dia of the 350 legend is no doubt an improvement :-). I have a custom 357 AR barrel and a 350 legend CMMG barrel. I have always been a 357 maximum nut since Ohio made it a legal ctg, the 350 legend is pretty much a 357 maximum for the ar15. The 265 grain subsonic looks interesting :-). https://winchester.com/Products/Ammunition/Rifle/Super-Suppressed/SUP350

Gage pins are nice things :-). I worked in a shop that probably had 30 sets of them all over the place. They come in .001 and .0005 increments, and in + and - tolerance. The plus pins the whole tolerance is above the marked size, the minus pins are the opposite. if you have whole and half and plus and minus you can nail a hole size down to within .0002". For general purpose use the .001 minus pins will be fine. I have them from .015" clear up to above .750. They were all cheap import sets....at that time I could go get the top quality ones if I needed them but the import cheapies were fine for a lot of stuff. Some of the benchrest gunsmiths use them that are sized in .0001 increments, they find the perfect fit for a barrel minor dia then indicate the pin prior to threading and chambering a barrel. Bill