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Old November 12, 2019, 05:33 PM   #1
Join Date: November 6, 2018
Posts: 35
Build a versatile .308: gas systems & hand loads

(Apologies: I'm asking this question here because it straddles a lot of categories and I expect "The Smithy" to have the most educated people who might have enough experience to provide a good answer)

Let's say I build a .308 AR in such a way that it would be heavily over-gassed (suppressor, light bolt carrier group, maybe a short gas system) except for the fact that I put an adjustable gas block on it so I can dial back the gas and make it operate properly. Suppose it's one of the click-adjustable varieties like Odinworks or SLR Rifleworks makes that have ~20 positions.

Assume that on click ~3 (out of 20) the action runs great with standard power .308 ammo. Now, if I reload weaker ammunition I expect I will have to open up the gas to keep it cycling reliably.

Let's say I keep reloading weaker and weaker ammunition until I get to the point where I have to adjust the gas block nearly all the way open for reliable function.

How weak are my loads at that point? Say I'm shooting 125 gr bullets out of an 18" barrel? How low do you think I can get the velocity? Can I get all the way to 7.62x39 performance?

To push this idea even farther. What if I built a rifle in such a way that it was over-gassed without a suppressor but it ran well when I turned the gas way down. From the previous thought experiment I have loaded weak ammo that runs reliably with full gas. Now if I put a suppressor on it pressure will be increased and I should be able to load even weaker ammo and get it to cycle reliably. Again, how weak are my loads at that point? How low can I get the velocity? They'll certainly be less powerful. It's only a question of how much.

Maybe this idea is far-fetched and won't work (which is why I'm asking) but surely you can see the appeal: 1) build an over-gassed, super-light .308 AR, with a suppressor and a click-adjustable gas block. 2) End up with a rifle that behaves like both a thumper .308 battle rifle and also a soft shooting suppressed modern sporting rifle in an intermediate cartridge with nothing but a few clicks on the gas block and an ammo swap.

Other important questions: can you foresee any other problems with this idea, and, if so, can you think of different way to accomplish something like I'm describing?

Thanks for any advice.
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