willbird

Might help somebody sometime :-).

Before surface grinders and magnetic chucks became so good and widespread most fine finishing was done by lapping, ultra fine finishing still is. But old school was to have 3 lapping plates, and with 3 of them you can work with them and make them all flat. They still use a lapping process to come in and make granite surface plates flat again. For the receiver lapping tool cast iron might actually be a very good material choice for the portion that does the cutting once loaded with abrasive. No reason you could not have a series of laps to use on that tool, keeping one for the final finish..and others to do the rough work if needed. Bill

The problem with lapping an anodized surface is how hard the surface is. Some say it is as hard as sapphire. IMHO looking at the tool you could lay a emery cloth on something truly flat, say plate glass, and carefully dress it flat again. A lap works be embedding the abrasive into it...but there is a contest between the lap and the work, if the abrasive becomes embedded into the work (because it is softer than the lap) then the work starts cutting the lap. With a hard anodized aluminum part the anodized surface is very hard, the aluminum underneath is very soft (in comparison). So once you get through the anodize odds are that the abrasive loads into the aluminum then starts lapping the tool. One thing that will help is to make sure there is NO loose abrasive present. A lap should be loaded with abrasive then any loose abrasive should be rinsed off. There is a lot more to lapping than meets the eye :-). Many folks at first think that a huge amount of loose paste between the two parts is what is wanted/needed, the reverse is true. Loose abrasive is an uncontrolled process basically. Bill

Actually you can buy LH drills now in sets with spiral flute easy outs. LH drill quality is kind of spotty due to the fact that not a lot are made....to be fair I will say "with the ones I have used so far". With a normal drill you are trying to drill without having the drill catch, using a LH drill to get a bolt out IMHO you are TRYING to have it grab/catch and unscrew the bolt :-). The bigger an allen bolt gets the harder/tougher it seems to be, we have some 1" and 1-1/4" at work that we have to get out once broken, and they are REALLY tough to drill. Worst case you worry the point of a 1/2" cobalt drill in to full dia, then run in a center cutting endmill to make the hole flat, then use another half inch drill, then the endmill again, repeat until you are deep enough for a large easy out to grab. Half of the time your feet are 8' from the floor when your doing this, and the machine is 250F and working on slow baking you :-). Bill

Looking at pictures the Toolcraft BCG seems to have serrations. But different mfg put the FA in different locations. The PSA is like $13 if they ever get one in stock again :-). Bill

I kind of lost myself in the dissertation about tap drill sizes, but you can use that math to make sure the barrel nut is on spec. major dia - the lead of the thread will give you minor dia for close to 80% thread. Bill

I have heard that the spring is different. Once one pops up and I buy it, I will know :-).

Just some general errata about threads. The lead is 1" / threads per inch, so in the case of a 1-7/16-16 thread the "tap drill size" we would typically use is the major dia minus the lead. So again for 1-7/16-16 we would use a 1.375 tap drill. metric threads are specified with the lead typically, so for a M6 x 1.0(this is the lead) we would use a 5MM tap drill. So if you have sharp topped threads at 1.400 major dia...the nut will be sloppy as %^$#@ probably ?? Bill

30” barrel, liquid cooled, beta mag. Fixed base defense game changer hehe

Any FA will fill the hole :-), but the PSA one is somehow altered to actually work

I have Toolcraft BCG coming, and an adj gas block, and a charging handle, and an orange spring, and some tungsten buffer weights ?

Yea the cheap complete lower started that idea hehe :-). Bill

DPMS pattern is a 1-7/16 - 16TPI thread, my PSA Gen I upper measures 1.430 over top of the threads....about what I'd expect. Found this on the forum https://308ar.com/ar-10-308-ar-compatibility-reference-guide/ The barrel nut and upper receiver threads follow along the same lines as the

A barrel with a water jacket (engine coolant actually, pumped) might be helpful for the 100 shot string ?

In the nicest possible way :-). Why are so many parts always shown as "out of stock" ?? The PA10 forward assist and charging handle as a couple examples ? Bill

I would be curious to see the velocity numbers used in the test. To properly build statistics about SD and ES it takes more than just a few rounds. And temperature control of the gun and the ammunition would factor in too, maybe humidity and atmospheric pressure too. Here is a really good article on the subject. I see folks getting axle wrapped about SD calculated from a 5 shot sample a lot. https://www.shootingsoftware.com/ftp/Perverse Nature of SD.pdf

At a past job I was a "tool room technician". We had 18 CNC horizontal machining centers and I set all the tooling for them. Changed out dull tools, replaced inserts, measured the length and put a tag on the finished tool build. Ordered all the stuff we used and dealt with the tooling vendors we bought from and who sharpened diamond inserts. So when it came to changing diamond inserts, I did hundreds a day, and hundreds the next day. Most used allen screws, a few used torx. Doing that you will quickly see the quality of a brand of allen wrench. A good Bondhaus or Eklind might last a week...the use kind of breaks the rules too because you wind it BOTH ways, stuff like car axles fail way more quickly if torsion is ever reversed. A CHEAP no name import may only last a day, and will start to wind up and do all kinds of weird stuff before it fails. So...use good allen wrenches. For the 1/4 hex bits and all types of Torx wrenches and bits Wiha tool is hands down the best out there that I found. Some tool mfg seem to have their own standard for the Torx so I held onto the ones that came with tools, and would try a few different types if I had a stubborn one. For gun stuff I'd do the same with the tools the mfg of the base or whatever provide, MAYBE they have chosen one that works really well with their screws. Again between the WIHA and a poor quality in 1/4 hex bits , you will see the poor quality bit wind up when you try to use it...it is is winding up and unwinding each time you tighten or loosen, it is dead on it's feet :-). When gun stuff moved away from allen and into Torx I was overjoyed really....some of the allen screw scope bases really sucked no matter what kind of wrench you used. Brownells sells Torx scope base screws that are worth keeping on hand, I do not even mess with allen head scope base screws any more. There are two styles, one called "oval" has a sort of rounded socket the screw seats in, and the other is a conventional flat head screw socket. Bill

There is some weird stuff that goes on with first firing :-). With my 6-284 the primer pockets get DEEPER on first firing of the brass. If I uniform the primer pockets in virgin brass, then fire form it (really the case body is not changing shape any to speak of with 6-284) the uniformer will never touch the bottom of the pocket again, does not do a good job cleaning the pocket. If I fire them first time without uniforming, then uniform, on every subsequent reload the uniformer cleans the pocket nice, and will even shave a little brass if you pull the powder measure handle a little too hard :-). Have not seen that with any other cartridge. The 357 AR which is made from 223 basic brass from starline (easiest way, people did use 223 brass before the 223 basic was avail) if you do not expand the body with a custom made expander that goes deep into the case they shorten up a whole bunch on first firing, which is not good because they headspace on the case mouth. Bill

I searched for something or the other, maybe more than one something and ended up here :-).

I am from NNWW Ohio as I say it, cannot get much more N or Much more W without getting into IN or MI :-). Bill

It is interesting to see how many ctgs will work with 7.0 Unique too. John Ross has mentioned that some older Dupont handouts they had at gun stores listed fairly slow IMR powders in say 44 magnum for "rifle loads". Bill

Another thing worth mention, if Amazon DOES delay shipping on a prime item they said was in stock you can dig around and find a place to complain, and they almost always give you a free months Prime. Brownells Edge is a great program too, it gives you *free shipping, and some discounts. https://www.brownells.com/aspx/store/edge.aspx It is well worth the $49.95, especially because you can order a thing today, one tomorrow, and one the day after tomorrow and not have to try to hit some minimum for free shipping. It does not cover shipping on say 1,000 rounds of ammo, but it DOES cover shipping on Aerosol cans of stuff. Bill

Nothing like seeing a part locked inside a length of metal bar stock, and freeing it from it's prison :-).

Ok after some convo with 98Z5V I made up a steel buffer body. The stock PDA buffer appears to have Tungsten weights. Finished buffer is on the right, new steel body with the PSA guts 5.65oz or so.

I think it shoots great. I have not went nuts with trying to get down to 1/4 MOA or anything. I have one of the Burris AR332 3X scopes on it. At 75 yards (you will see that distance a lot in my post because my backyard range easily achieves 75 and 100 requires moving the bench every time I shoot) it seems to hover around an inch with the el cheapo federal 55 grain fmj ammo. Within that inch will be tighter clusters too :-). I have not shot any extended strings to look for walk with barrel heating either. But I’m over joyed so far :-).