willbird

This is what goes on at the other end of the spindle. I indicate the OD to get close, it is faster to eyeball than trying to get it close with the indicator up in the bore.

Here is how it goes up in the lathe. There are far more than 1 ways to do this, one can get stuck on dead center so to speak the first time trying to decide the "right" way. I found the way that is right for me so far :-). Final indicating here is with a .0001" indicator, and I get it .0000 runout or as close as possible.

Ok for some stuff done today :-). Left barrel at 26" for initial test work and 1.2 dia, it kind of re defines "bull barrel" hehe. Headspace is a bit longer than I want, will take the ext off and shorten that up. I used sharp corners on my gauge to measure cases and make a headspace gauge, the reamer has a radius at the neck shoulder junction. Easy fix.

to us mochinists that would be "four tenths of a tenth" which can be measured. GM engine heads we held a dowel hole diameter + - 12.5 microns. The old shcool guys would go "oh crap this hole is three thousance oversize"...and I would say "john those are microns, it is aluminum, and it is 105 degrees F just out of the wash process"....and I'd get a sheepish "oh yea hehe". Bill

The Science on those projectiles is pretty interesting too, I'm sure you know but here we go :-). At sustained high velocity like we get if we put some stank on a bullet and it retains it due to a high BC older design polymer bullets the tips heated up and they lost BC. The stated BC was "true" but not true in many real world conditions. I was looking at the 90 grain ELD X compared to the 87 Vmax (both .243) the Vmax is .400 BC, and the ELD X is .409. The Vmax probably still wins for varmints 50 lbs and under. yes the ballistics by the inch are cool. The test gun was actually a "gun" not a universal receiver so maybe the velocities by inch are calculated with Quickload ?? In my experience Hornady is pretty good about answering questions :-).

A guy could two just to balance out his load :-). arm insurgents of opportunity, good stuff like that :-). Hornady did say ... "This 6mm ARC reloading data is intended for use in gas guns (e.g. AR-15’s) and kept to a maximum pressure of 52,000 psi. Do not exceed the maximum charges. Separate data will be provided for bolt action firearms." case capacity is really close to 6ppc from what I am reading.

Buddy and I were talking about something and I decided to make a phone call and see about it. He told me after "you are sometimes really a dick in person but when you call people on the phone you turn into an ENTIRELY different kind of person". Yup, because they perhaps have what I want, and the better I treat them the harder they work to provide it to me. I do it in person too. "yes sir, yes ma'am, please and thank you" have gotten me stuff that other people could not get or get done, their work went into line BEHIND mine because they did not show some semblance of respect to the person they asked for something. Some of them, MANY of them never even consider that ASKING may get WAY more than demanding or ordering people to do stuff. Just because you CAN do that, does not mean that it is the best approach, ask and let the other person meet you way more than halfway. Bill

That data is limited to 52,000 due to being AR15 based. Put that in a bolt gun and stoke it to 62,000 and I bet it will run to the magic 3050 that many folks feel is where 6mm really starts to hum at 1000 yards. Looking like CFE223 and LeverEvolution might be "the" powders maybe. it is still doing really really good out of a 12" barrel. A 12" pencil setup built light from head to tail would be a very interesting setup. Bill

Faxon 350 legend barrel. Accurate molds no lube groove custom mold for 350 legend barrel :-).

They had a bunch of the HK AR stuff a few months back and most of us were all over those, similar prices or cheaper.

https://www.cdnnsports.com/dpms-ar308-243win-barrel-16in-hunter-threaded-g2.html Sorry, there is the 243.... They have this 20" too...for 79 it is a steal https://www.cdnnsports.com/dpms-ar-260rem-barrel-20in-hunter-threaded-g2.html

if you are half smart 🙂 and your playing G2 you will go and grab some of these barrels. https://www.cdnnsports.com/dpms-ar308-260rem-barrel-16in-hunter-threaded-g2.html https://www.cdnnsports.com/dpms-ar308-260rem-barrel-16in-hunter-threaded-g2.html They are dirt cheap and IMHO a 1 time deal, both cool calibers too. 98 Bill

https://www.amazon.com/1500pcs-Split-Spring-Stainless-Fasteners/dp/B01IACE6UE Bill

IMHO quite a few parts cross over from AR15 to AR308...so if somebody gets onto listing their parts as "mil spec" then they will use that on everything. And the materials and finish applied to say an AR308 bolt catch might indeed be the same as a "milspec" AR15 part. Bill

if you are half smart 🙂 and your playing G2 you will go and grab some of these barrels. https://www.cdnnsports.com/dpms-ar308-260rem-barrel-16in-hunter-threaded-g2.html https://www.cdnnsports.com/dpms-ar308-260rem-barrel-16in-hunter-threaded-g2.html They are dirt cheap and IMHO a 1 time deal, both cool calibers too. Bill

Testing :-). yep :-), all good, thanks :-).

Every time you post they take a long lunch hehe :-).

I tripped over this last night :-). Getting the absolute most out of the small frame platform really makes a lot of sense :-). A friend who was a local gunsmith was always a 6mm caliber devotee, the issue hack in the 80's was lack of consistently good bullets. .224" and .308" bullets were hands down the most accurate bullets made. Once that issue was resolved things started to happen :-). The neatest thing that to me kind of starts to happen with 6mm and smaller high BC bullets is when you are in the open the bullet flight noise is very easily heard, as well as bullet impacts into meat :-). The 6mm ARC should be REALLY good at that even non supressed :-).

Many people quote 75-150 fps per inch when it comes to barrel length. The higher end is more for say 22-250 or other similar calibers where muzzle pressure is higher. 98 is way more of a long ranger than I am but to me the key thing is when the bullet velocity goes trans sonic. I have been an exterior ballistics devotee since my teen age years so this is kinda old hat :-). These kind of tests here are great. http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/ There are a ton of external ballistics links and apps, I kind of like this one, but to me what is important is to find one and use it enough to get familiar. I used the 168 grain load listed in the ballistics by the inch, probably few would choose 168 for 1k yards but it just gives us a quick idea what might be going on. Just guessing at the graph I knocked off 100fps for the 16". vs 18". Another issue is that many 16" barrels use mid length gas, and quite a few of the 18" use rifle gas tube location. IMHO overall if we use the optics to support 1k work adding 2" of barrel from 16 to 18 would not be bothersome at all really.

Ok had a chance to sit down with a depth Micrometer and the barrel extension today and double check with the new BCG for this build. Wanted to see if the hard chrome made a dimensional difference. For the most part it did not. Had I used the original dimensions or were I to swap BCG the hard chrome one would .003 more headspace. revised my drawing.

I did notice the AR308 search term and almost always use it for search.

https://www.brownells.com/rifle-parts/bolt-parts/bolt-carrier-groups/ar-308-bolt-carrier-group-chrome-prod126540.aspx ??

Brownells had these hard chrome BCG on sale, Brownells brand, I am a sucker for a half off sale any day :-). Weight is 477G vs the 503G for the either Toolcraft or Brownells. I REALLY like the ejector a lot better. No concerns with plating thickness because I am making my own barrel. Here is what Brownells calls it. BROWNELLS - AR 308 BOLT CARRIER GROUP CHROME

it has no mfg markings at all ?? if not it almost had to have started as an 80%. Mfg name, city, and state are required as well as a serial number for something sold as a firearm. The 80% folks offer custom selector engraving.

is that Janet Reno at 2:56 ??