I am curious if it’s common to have just 1 lower that can be swapped to multiple uppers?
I am wanting to build a lower with the Vltor A5 system and a CMC trigger and have it work reliably with a 16" 5.56 mid length upper, 18" .223 wylde precision upper, possibly a .204 upper and finally a 9" 300blk upper.
Is this idea possible?
Is it possible? Yes. However, I am here to tell you that empty uppers grow lowers, and spare lowers grow uppers. It is not a question of having a single lower that can be utilized for multiple uppers, it makes sense, same stock, trigger, grip, for everything, the question is can you stop yourself from buying another lower to build for that lonely upper.
If the 16" will wear an Aimpoint and the 18 and 204 a scope I would say no. The cost of the additional lowers will be insignificant compared to the uppers. I would rather have 3 complete rifles for 25% more $$$. If you do a 9" the lower will have to be registered as an SBR. I wouldn’t want it to be the only lower I owned.
I started with one lower and three uppers. While it worked reliable with each upper, I quickly realized I would much prefer each to be a complete rifle. You can get quality lowers pretty cheap these days. I think you will be happier in the long run with complete rifles.
THIS!!!
Boy, I try, but somehow all those uppers grow little magwells, RE’s, stocks, milspec triggers turning into Geissele magically overnight…
Now I’m thinking “Oh I’ll just get another AR308 upper, something nice and light and short…don’t need a new lower for that right?” :jester:
Glad my wife thinks they’re all one rifle. They all look the same sort of.
Good luck…if you manage to stick with one lower you have will of steel, grasshopper!
I’ll have to make it work, haha. My wife shoots all the guns I own. She’ll know if something new shows up.
Yep - you’re in trouble. Your budget got cut in half. Ammo, gear, everything.
Me, I like it when she prefers going to Yoga. Much cheaper.
I have done it for years. My “main” lower is a DD SBR, so it is registered. Then, I can throw any upper I want on it. I have a 14.5 (not a pin and weld) so I can change the muzzle device as I choose. I also have a BCM MK 12. Very versatile that way. Since I had to register the SBR, it didn’t matter much.
I’ve done it with limited success…
My last build started as a 3 prong M16A1 surplus muzzle break, and the other parts just started getting ordered. Now I have a retro pseudo-SP-1.
If you can control the purchases, you CAN use one lower for multiple uppers, except maybe 9mm.
I hope you do better than I did…good luck!
Commonly, no. Possible, very much so, if gassed accordingly to the action. Practical, no.
I can’t keep a spare bcg and charging handle without having to complete the build.
I personally think it’s much more convenient to get at least another lower for a couple complete rifles. That said, I switch out 4 SBR uppers on two registered lowers. Works just fine for me.
I know I can make it work. I’m just concerned about it being able to function the uppers that I specifically want.
I already have the Vltor A5 system on my current AR but will use it on this new lower. My old lower will be given to my wife.
I’m leaning towards the Rainier forged lower. Then I’ll buy several of their forged uppers and build off them. Figure keeping it manufacturer specific will help. Or am I thinking to much into keeping it manufacturer specific?
If you are using good equipment, that is kept within specs, no worries about manufacturers names. The trouble starts when one manufacturer is out .01, the next manufacturer is out .02, etc. you can end up with “stacked” out of spec parts. That can lead to issues. I would guess there are a GREAT number of fine rifles around here that are sourced from different manufacturers.
I’ve been doing it for over a year now. I have three uppers and two complete lowers. The only reason that the extra upper hasn’t sprouted it’s own lower is that I don’t want to deal with the pain in the ass that is purchasing serialized components in the state of California. I’m only stationed here for a bit longer, and then its off to a free state (and a five-pack of stripped lowers, if I get my way).
Yeah, that’s what people say, but in my experience it’s only a general rule. I have found that VLTOR MUR uppers are an unreasonably tight fit (pounding the pins in with a mallet) with Noveske gen2 lowers. Not only are both VLTOR and Noveske considered top quality brands, but Noveske actually sells some rifles with VLTOR uppers. I’ve had similar issues with some other combinations also. I would say maybe 80% of the receivers I’ve dealt with are perfect mix and match, but the other 20% includes some quality names.
However, I have found that lowers made by Mega Machine Shop and Charles Daly (which is long out of business) will fit easily with every upper I’ve tried. I’m guessing they held their dimensions to the center of the tolerance range.
FYI, if OP isn’t familiar with NFA, one big reason is that an SBR can’t be taken out of your home state without BATFE permission, and you can’t lend it, and various other restrictions.
All of my uppers end up growing lowers, no matter how often I tried the efficiency approach lol
Yup. Happens every time. 
I know the NFA rules…that being another reason for 1 lower. The only concern I have is if the Vltor A5 will cycle the 204 and 300blk. That being the big issue with owning one lower. Now, after the uppers are completely built, then I can foresee more lowers in my collection. But I can use the money for other lowers into building the uppers I would like. Take the extra minute to take off one upper and putting on another is not an issue for me.
It should, assuming both barrels are properly ported for their length and chambering. And worst case is that you might need multiple A5 buffers to swap around while you swap uppers - adding what, 20 seconds?