So looking at the cost of building an AR-45 and wanted to see who had the best price on the uppers?

I'd also like the advice of you to know what is the most optimal barrel length for the 45 ACP bullet out of an AR-45? Going to also do the research but thought I'd ask and see what you all thought also! Thanks!

As to barrel length:

http://www.ballisticsbytheinch.com/45auto.html

http://www.ballisticsbytheinch.com/megraphs/45auto.html

I personally have been happy with my 16" barrel length build which allowed me to mount a full A1 stock with rifle buffer tube + took apart a rifle buffer and filled it completely full of tungsten weights + used an AR-10 rifle spring.  Got it tuned just right so the bolt never goes all the way back under blowback and the buffer never bottoms out.  Thus no jarring impact like a normal blowback PCC and it just lazily cycles nice and smooth.

If I made an AR-45 pistol I think based on the ballistics by the inch research I would want about an 8"-to-10" barrel length or so to still get near top end ballistics.

Rudy aka MadMachinist from Macon Armory. Go DI! think he said 8" is the minimum he recommends.

Factory ammo, or reloads?  I ask because if you reload, you have some control over your powder burn rates which can affect velocities depending on barrel length.  You won't see significant increases with slower powder and longer barrels, but you can squeeze a little more out of it.  Velocity gains in longer barrels are limited mainly because of overall total powder capacity; even slower powders will get consumed relatively quickly.  Ergo, chasing ultimate velocity means something along the lines of a 14" to 16" barrel.  If you look at the "Velocity by the inch" link above, you'll notice a correlation across nearly every pistol caliber listed.  14" to 16" is the sweet spot for top velocity with the exception of 10mm and the +P loads.  10mm produces its best velocities at 18" because it has a higher powder capacity...so do the +P loads.

Pros for the longer barrel:  top velocities...and pistol calibers arguably need all the FPS they can get for effectiveness.
Cons for the longer barrel: you lose all the advantages of a compact pistol build.

If you're going to build something with a 16" barrel, why would you choose a pistol caliber when something like 5.56 is going to be way more effective?

If I were to build one in 45 ACP, I would go with an 8".  In every load listed on that site, an 8" retains anywhere from 91% to 97% of the top velocity listed.  If your upper can run +P loads, all the better.

Anyway, that's my pragmatic advice, but I will caveat that by saying, if you're building it for fun or a range toy, go crazy and do what looks fun.  Even though I build my own from a utilitarian perspective, I certainly appreciate unique builds regardless of how useful or effective they may be.  Shooting isn't always about how powerful or gut splattering a round is, sometimes, they're just fun to shoot.

I just finished up a Macon Armory DI 45, 16".
First trip to the range, and am very pleased. It took any ammo I fed it, 230 ball, 185 hollow points, and 185+P.
No issues, None...
And get this, no heavy buffer banging around, I have a 2oz buffer, with Strike carbine flat wire spring.
For an 8" I would talk to Rudy.

I had a Camp Carbine in 45 ACP with a 16" barrel which is a blowback gun and my 5" 1911 shot the same loads to faster velocity than the 16" rifle, so there is a point of diminishing return.

I can see that with a Camp...
No way to tune it for hot loads, fairly light spring on the rather light bolt.
That's why I went DI AR.

This.

Just got my DI upper in, super happy with it. Need to take a couple pics. I went 12.5"

Paging @Mad-Machinist

What are you planning to use for the lower? MGI?

That is a VERY good question.  Not all lower setups are compatible with all upper setups so you need to consider that when shopping for an upper or upper parts.

I personally bought my barrel & bolt for my AR-45 all at the same place and chose all my own parts from there because I knew I was making my own heavily modified lower to use magazines for which no off the shelf AR PCC lower is made to use.

If I had not been doing that I would have wanted to buy a matching lower as well that I knew would be compatible with my barrel & bolt.

Also consider what magazines you intend to use or have to use to be compatible with the rest of the parts you have chosen.

This all especially applies to any sort of DI or delayed blowback or even over-barrel gas piston setup you might consider.  The straight blowback guns are not all compatible but are far more so than anything NOT-straight-blowback which tends to be more specialized and nitch.

Or if you have the skills it is possible to heavily modify a standard AR lower to use a particular magazine.  I basically cut a bunch of flat sheet metal plates out with a jig saw and sandwiched them inside the standard magwell with pins through the whole mess kind of like how masterlock padlocks are made to make a magwell that fit the mags I wanted to use along with figuring out a system to work as a magcatch.  Making the magcatch parts also stack in that stack of plates in recesses to move within again like the tumblers in the old masterlock padlocks stack of metal sheets construction.  Sandwiched in a hardened shark fin ejector the same way.  So long as your chosen mags aren't wider then a standard AR magwell and you do a good job it doesn't even look bad since it's all hidden inside the magwell and you only see the ends of the pins/rivers/screws/bolts on the outside sides of the receiver which if you put some effort into it can look fine.  For fat mags where you have to actually cut the receiver walls to accommodate their width and strap plates on the outside as well - well that does end up looking a little redneck cosmetically and 45-ACP is were you can get into some fat mags that won't fit without cutting into the sides of the receiver.

So, yah, you got to plan around your lower receiver and what mags it uses as well.

Macon .45 uppers lock back on last round using standard lower bolt catch.
Mag adapter drops out with the removal of 2 set screws.
So fits in ANY AR15 lower.

You can make this as hard, or as easy as you want.

Yeah, no kidding...

I built a AR-45 pistol with a Joe Bob Spartan lower
Joebob Spartan Lower

Then I got a 45 upper receiver from somewhere (can't remember)
Attached File


Then I picked up  a 10.5" Wilson stainless steel barrel, and the rest of the parts (BCG, 10 oz heavy buffer) and put it all together

Attached File


Nothing special or fancy about it, so far no issues or problems with either cast or jacket bullets. I mainly shoot lead reloads because I can make them
cheaper than factory loads, and I have a large amount of loaded ammo courtesy of my Uncle Sam from when I was in which I am saving for when the shit
hits the fan.

My first 45 acp build was similar to this but with a 16" barrel, and I sold it to because I am more into pistol builds than rifles.  The cost difference
between a regular rifle build and a 556 build is mainly in the BCG, upper and lower receiver costs.

Got a couple pics of my build this far. Its a 12.5" DI upper from Rudy (Macon Armory). Also using his adapter block and mags.

Muzzle device is a Griffin Armament Minimalist Flash Hider, with a Griffin Blast Shield.

Here is Rudy's DI upper with a 5" barrel and CNCguns Grease gun mag lower. Oh, and yeah, and a DEAGLE .50...

This thing shoots slick...

To answer some questions to help you all out to help me out. I'm not sure of what lower I'm going to use. I would like a lower that uses Glock magazines.

I have about 15 magazines that I bought a long time ago. I might be willing to go with a different magazine if they can be found cheap.

Are all 45 ACP uppers that expensive? I could build a few ARs just for the price of one 45 ACP Upper.

Mostly want this because most of my carry guns are 45 ACP and I reload along with cast for it also. Though it would be nice to have a carbine in 45 ACP also.

Rudy's D.I. upper is one of my favorites. Just say'n...