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Posted: Sun Feb 18, 2018 12:43 am
Brownells and several other marketers are offering 80% recievers for $40 dollars. I just say the add. Iam toying with the idea of finishing a lower this spring before the outdoor work takes control. The add says it is supplied with a plastic template, so much of the original machining is done and they are dark anodized to boot. Anybody done one lately? What is the recommended barrel twist, 12 or 7? I think it is lighter bullet, faster twist. (one in 7).
Re: 80% .223
Posted: Sun Feb 18, 2018 8:00 am
I did some a couple years ago. I had a drill fixture, and a machining template that came with part of one kit. Not plastic, but aluminum, and the drill fixture had hardened bushings.
Twist is dependent on the bullet weight. Most common is 1:9, which is best with 55 grain bullets, and what I generally shoot.
Lighter bullets, like a 40 grain, a 1:7 would be better. I don't think a 1:12 would be good until you were 75 grain or above.
Re: 80% .223
Posted: Sun Feb 18, 2018 10:41 am
You guys are reversed in your twist facts. AR's are generally one of three twist rates 1:9, 1:8, or 1:7. Not that I have ever seen or had it happen but theoretically and I have read that guys shooting light bullets out of a 1:7 twist have found the twist rate fast enough that centrifugal force can actually cause the copper jacket and the bullet core to separate. I have seen figures that show a 55gr projectile fired in a 1:7 twist at average factory loadings can be spinning in the 200K rpm range or more. A handloaded .223 round with a 55gr or lighter projectile might be more susceptible to the issue as many tend to load a bit hotter rounds than stock factory loadings. Going with a heavier bullet weight in a 1:7 twist is sufficient to slow down the velocity therefore slowing the rotation of the bullet.
With the exception of some test loadings everything I hand load for an AR is 62gr or heavier as all my AR's other than one are 1:7 twist.
In contrast bolt action varmint type rifles like a .223 or 22-250 will have a 1:12 to a 1:14 twist rate and do best with 55gr and lighter bullets. A 22-250 with a 45gr bullet can be in the 3500-3800 fps range but with a very slow twist achieves proper stabilization.
As for the 80% stuff, they are all pretty easy to do these days and right now they are cheap. 4 or 5 years ago an anodized lower would be in the 75 to 100 dollar range, now you can find them for 50 or less if you look.
You need to be aware that although there has not been any "law" changes to the building your own guns thing, the ATF has taken it upon themselves to make some determination changes. That is if you even let someone use your tools or machines to finish a lower you have crossed over into the realm of manufacturing and therefore need to be licensed. I am sure its only being done to make finishing an 80% lower alittle harder and to criminalize those who would help another person finish out a lower.
For those who do not have a mill or a good drill press with an add on mill table or etc,, there are several jig fixtures out there now that need nothing other than a good router and a hand drill to finish out an AR lower. Or as I have seen a couple guys do it, the hillbilly way, take and drill a jillion holes and then use a dremel to finish out the fire control area, crude but it works and is likely how many are getting finished out.
Re: 80% .223
Posted: Sun Feb 18, 2018 4:29 pm
Thanks Alky and Warm for your input. All the memory of this info is very old when they were dicing around with the speeds and 'stopping power' of this .223 round. I remember the claim of bullets flying apart, but mostly after striking flesh, and causing tumble and wound cavity expansion for lethality. That is what made the round desirable as a killing instrument to the military.. Beyond that dim memory of the debate and the wise guys coming out with twist rates and 5.56 and all that blather, I really dont care. First hit wins. I prefer .30 caliber for most thnigs anyway, and have a Springfield to back that up. This is a project that interests me, and would add to my experience and personal training in a slightly different dimension. Once I purchase a barrel, thats pretty much it. I am not interested in having multiple barrels for different weather conditions, or some such hokum. I intent to build an economic, (cheep?) weapon of modern thinking and manufacture.
I have turned to reconditioning my stored Lionel and prewar trains, LGB and Bachman, for running a loop around the ceiling of the lower level. I may just sell off most of my meager stock in favor of the outdoor 1.5 scale parts and pieces I have. Like a kid, I have way too many interests and get bored with some things , once the initial challenge is gone. I generally follow through though, look at ' a better looking SKS' That was mostly distastful hand work, and seemed like the hand fitting took forever.
Except for the bits and the templates, I have everything I need, and can finish in ceramcoate or anodized, whatever suits my fancy. Except for a couple of premachined black powder kits, I have not ventured far into gun building, or mods, and am totally willing to heed any advice on this wide subject.
With all the tragic news that has occured now in Florida, I think I will support my rights under the allowed laws to persue this project. Beyond the statement that 'Gun control is hitting your target' I will leave the politics alone. As far as the historic debate goes, you cant fix stupid.
Re: 80% .223
Posted: Fri Mar 02, 2018 6:03 pm
Look around there are a few places you can buy 80% lowers cheaper then brownells
I got mine threw tactical arms , very good quality and unanodized blems are only $29
If you keep watch and snag them when available .
If you watch they also put non blemmed lowers on sale for $32 quite often
Re: 80% .223
Posted: Sat Mar 24, 2018 1:20 am
As I sit here nursing my insomnia, I thought I would throw out there that I have a nice lower made by Matrix arms and have received from another guy on the board a template that I intend to duplicate. I have the needed drawings and dimensions (thanks guys!) for the vital dimensions. With a new set of R-8 sleeves laid in to my tool stock ( the originals were stolen by a miscreant) and a long reach bit for the final trigger hole, I am ready to begin the nerve wracking task at hand, that of figuring and turning wheels. All the small parts and pins for the trigger group and lower assembly are in hand. A light pull kit for 3.5 lb pull is here too. I only need the hand grip, and the buffer spring assembly.
I need to machine a set of journal boxes for some arch bar trucks for a project, and that should get me into the head game of turning the wheels to a mark.
Re: 80% .223
Posted: Sun Apr 15, 2018 7:03 pm
Wiith the easing of th eweather, I have started to duplicate the jig for the lower. That way I will have one. Today it is miserable cold and damp, having been raining all last night and into the morning. Temps are way down, and all my equipment is in unheated areas.
I have started by sawing out some plate in aluminum to make the side plates for this thing. and am using a belt sander to smooth the edges off. It will match the jig I have. Since I am using a Rockwell mill the jig plates are uneeded except for the pin hole pattern to hold the trigger group. The jig is intended to use with a router to chew out the forging with some due care and set the pin holes. I have marked out the cavity, and only have to remove the metal without blowing a dimension.
Re: 80% .223
Posted: Mon Apr 16, 2018 4:18 pm
My sister & BIL live in the UP of Michigan. Be glad you aren't up there!
Been snowin'. Like....a lot. They got another 4" of the stuff in the time it took for the NASCAR race to finish up today... a day late.
Stay dry....and warm!