Thanks to everyone that posted comments to my request for proposed ideas for my next rifle project. I want to take a minute and point out that this is for a build project. Thanks for some of your thoughts on buying M1As, SCARs, or LaRue rifles, but I am not looking for suggestions on BUYING a factory made rifle.

I am building one using what was an 80 percent lower*. I have a number of lowers that have been machined already, and are thus already legally owned firearms. They are waiting to be outfitted with parts and accessories. Building rifles has become a bit of a hobby in itself. Here are the posts on my last build:

This will result in an off paper, one of a kind rifle that I built myself. Since this is a build on an AR10 receiver, I am looking at a Faxon barrel and a good scope. Trying to play with some other pieces/parts to get a 2 MOA rifle. The last build is hitting 4 MOA with factory ammo. Maybe I can get 2 MOA with the one I have, if I get some better ammo. My direct supervisor at work is a precision shooter that builds his own rifles and handloads. He is hitting 4 inch groups at 700 yards and has said he will give me some of his hand rolled .308 to try out. That should tell me if it’s an ammo issue.

*Note to the fellas at the ATF: This was an 80 percent lower that was purchased and machined prior to you changing the law. As of the date that you passed the ban on homemade lowers, this was already legally a firearm, according to your own definitions. Since ex post facto laws can’t be made and they were legal to create at the time, I am within the law.

So don’t even think about killing my dog, my son, or shooting my wife in the face. Likewise, please don’t come and set fire to my house with everyone inside.

Categories: Arts and Crafts


Wild, wild west · October 13, 2023 at 10:54 am

Good equipment/ammo, a solid and repeatable position and good wind reading skills are what is required for hits at long distance. Strongly recommend you spend at least as much on the scope as the rest of the rifle for a “good” one, more for “better”. LaRue QD scope mount and MBT trigger are good stuff in my experience, well satisfied with several of each. Wind reading skills for long shots are as important as the equipment, if not more so. Several good books on wind at Champions Choice and Creedmoor Sports.

For handloads, the 125-grain Speer TNT bullet fly well thru 300, easy on the shoulder and economical in bulk. Past that, 175 Sierra Match King outshines their 168 (which is still a good bullet) or any number of Berger will get the job done. I’ve heard good things about the new Hornady bullets but have no personal experience with them. Worth a look.

It's just Boris · October 13, 2023 at 11:03 am

Re improving accuracy of your existing .308.

Some people swear by using a retaining compound like Vibra-Tite 538 or Loctite 609 to remove any play between the barrel extension and upper. Of course that also makes any future disassembly more interesting. (This stuff is like thread locker in that it comes in different strengths, etc, but intended specifically to lock up cylindrical assemblies. Some people use thread locker in this application, but the “right stuff” isn’t that pricey. I think the thing to watch would be the temp range; but have not done this myself so wouldn’t make a specific recommendation as to whether and what to use.)

Lapping the upper receiver will square the ends of the threaded section with the axis, helping to ensure uniform contact between the barrel extension lip and upper.

You might try one or both, if you haven’t already done so, and don’t mind disassembling your existing upper. If it notably helps your accuracy without needing custom ammo, it might be worth it in the long run.

    SmileyFtW · October 14, 2023 at 8:58 am

    Rocksett is designed to take up thread play and mitigate motion between parts after assembly and also to be able to disassemble, unlike lok-tite

Moe · October 13, 2023 at 12:30 pm

“Note to the fellas at the ATF: This was an 80 percent lower . . . . . I am within the law.”

Divemedic, you have an analytical mind and I really wish I could agree with your reasoning in this
instance. But alas!

If you squint carefully at the ATF’s Great Seal hanging prominently at their headquarters you’ll
see a small embroidered Latin phrase that translates roughly to “Heads we shalt win, Tails thou
loseth”. 🙂

McChuck · October 13, 2023 at 12:35 pm

Have you tried Tubb’s “Final Finish” bore polishing bullets? They really do seem to improve accuracy. As far as using hand loads goes, they are generally better than factory, but really need to be tuned to your rifle. Thousands of an inch of headspace make enormous differences in accuracy.

Max Wiley · October 13, 2023 at 3:42 pm

I can give you loading tips for magazine fed semi auto rifles, but it sounds like you have the assistance of an experienced loader so I will avoid writing a book.
Suffice it to say:
NEVER use someone else’s custom loaded bolt gun ammo in your semi auto
NEVER use bolt gun loading techniques like neck sized brass and/or loading close to the lands for your semi auto.
Slam fires ARE a real thing with AR platform guns and you don’t want to be monkeying about with the ease of fitting the cartridge in the chamber.
The nice thing is that the AR design doesn’t really seem to care much about such finicky loading methods anyway.
The place to pay attention is with neck tension. I use a neck sizer (after body size and shoulder bump) and then a mandrel to set somewhere around .0025″ neck tension. The mandrel is required because of the differences in neck thickness. A very light Lee factory crimp afterwards may improve consistency.
On parts:
I know the Geissele trigger is expensive but it is worth every penny on a precision rifle.
Get the Tubb AR10 buffer spring or someone else’s silicon carbide spring, but you want a spring that rapidly takes a small set and then changes very little over thousands of rounds. This is important for both accuracy and reliability, much more so than in the AR15 platform, so don’t skimp.
I also suggest an adjustable gas block AND an adjustable weight buffer for fine tuning.
If you end up where I did, you will want to be able to shoot 308Win loads for distance while retaining the ability to shoot 7.62NATO without malfunction. This will result in the rifle being slightly overgassed with the 308 ammo, and the buffer can help tune it a little better.

Gryphon · October 13, 2023 at 3:45 pm

Sounds like a fun project, but Accuracy much beyond the Mil-Specs for 7.62 / AR Platform is going to be a Challenge. Two things to Consider, IMO, are the ‘rough handling’ that Precision-Made Cartridges get from that Action, and also, the Dirt that a Direct-Gas Action inevitably builds up.
When you Hand-Load Ammo to Thousandth-Inch Tolerances, it takes very little Dirt or Damage to throw them ‘Off’. Good Luck with it…

karl ushanka · October 13, 2023 at 4:15 pm

It is good you have a buddy with precision rifle experience. I jumped into the hobby a few years ago when I belonged to a private range with a 600yd range. It took a full THREE years to get sub-moa, with most of the effort at the reloading bench (but also I custom barrel). I then competed in their varmint tournaments and took last place all three times – with <0.5MOA shooting. Those boys know how to shoot! Needless to say, there is no such thing as too much info on the subject.

For your rifle: have you considered zeroing with two optics? Perhaps a red-dot for short range and a high-end scope for long range. I've done this with an AR, with both optics mounted on quick-detach mounts. That rifle project's name: What if I could only own one.

Danny · October 13, 2023 at 4:58 pm

I guess a lot of people can’t accept that you’re a mad scientist who wants to torture himself with all the stress of building a “Frankenrifle” 😀

    Divemedic · October 13, 2023 at 6:24 pm

    That it is. The project that I linked to, above had the objective of being the lightest AR10 I could build. This one will focus on precision.

John in Indy · October 13, 2023 at 8:06 pm

You should be able to get <2 moa out of a semiautomatic, with proper ammo. As recommended, after barrel break in (5 rounds, clean, repeat x 5+), get several makes of good ammo, and test them the same way, but use a fouling shot first.
The match rifle I had (M1A, 7.62) shot 2" with Sierra bullets, and 1" with the same weight Noslers, with the same lot brass, charge, and loading techniques. That brass had all been neck-turned to the same thickness and matched for weight. I wish I hadn't sold that one, but I didn't have time to compete any more. Now my eyesight isn't good enough. 🙁
Decide on bullet weight first, then buy a barrel with twist optimized for it.
When you find an ammo or load you like, get lots of them. 🙂
God luck with your build.

Ditchcritter · October 13, 2023 at 10:19 pm

When assembling the barrel/upper receiver, I use brake clean to clean everything up and make sure that the threads and mating surfaces are immaculate. Tension the barrel nut to the manufacturers specs, loosen, repeat. Goal is the top end of manufacturers torque spec, and getting the barrel seated so that nothing is moving about unnecessarily. Should be able to get under 2 moa with a quality barrel and a free float hand guard.

Vitirbi · October 14, 2023 at 3:35 am

I don’t know if this would meet your accuracy requirements, but I build something like what you are thinking about. I built a DMR type AR10 in 6.5mm Creedmore, not .308. I got a Faxxon Match series Big Gunner 20 inch barrel, and built the rifle around that using mostly Aero Precision parts.

I haven’t been able to take it out and really see how accurate it is, as there isn’t any place local I can get out further than 200 meters, but it cycles fine with S&B 140gr stuff, and I got it sighted in at 200.

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