Both of those choices are 7075 aluminium, which is uncommon, especially the cheaper, stock-standard looking Expo Arms.
If you are interested in San tan I would choose their standard version, not the Lite version. Saving weight on something that is already light like aluminium is negligible compared to the weight of the steel barrel. If you want to save weight do it on the barrel in either profile and/or length. Or don't fit a muzzle device, that is a far more efficient weight saving. Also, the idea you can save weight by forgoing a functional mechanism like the bolt-assist comes at a functional cost. Sure, you might never use a bolt assist...until you do. Like the old saying, 'You can't use it if you don't have it'. The more meat you have on the receiver the stronger it will be. You don't want to get minimalistic on something already cut to the quip in the original design; by that I mean AR15's in general.
I see the San Tan design is full ambi. That's to be expected for the price. The photos show a fitted offside mag release. Previously you would have to buy an extra Norgon or similar to realise ambi mag release, so that's a cost saving if they include it. That is providing you like their design that goes into the trigger guard space.
I like also how the San Tan has inbuilt QD holes for sling attachment at the back of the lower, and other attention to detail innovations like the hinge for the dust cover has one end secured by the receiver and the forward end by the handguard so no need for those fiddly circlips when assembling. This is not unique, but you expect it when paying top dollar. Bottom line, if you are paying over $400 for an AR15 receiver you want it billet, 7075 aluminium, full ambi and the top rail utterly square to the bore axis.
Mega Arms have, or at least had a fantastic reputation, until they were bought out by Zev. As a subsidiary of Mega Machine their work and machinery was enviable, but with prices to match. This Expo Arms is a unfamiliar design, more MILSPEC but they claim it is 7075 aluminium. It is a much more basic design for a receiver. Not full ambi. No bells and whistles, so you are paying for the metallurgy as far as I can see.
Depends how much money you have to invest in a plinker. Most people's definition of a plinker is a cheap and cheerful gun for occasional fun shooting. In your shoes I would go A5's advice and buy an Aero. They are good value for money. Then use the savings from the San Tan to buy the best barrel on the planet. Suddenly your plinker only looks like a plinker.
If you are interested in San tan I would choose their standard version, not the Lite version. Saving weight on something that is already light like aluminium is negligible compared to the weight of the steel barrel. If you want to save weight do it on the barrel in either profile and/or length. Or don't fit a muzzle device, that is a far more efficient weight saving. Also, the idea you can save weight by forgoing a functional mechanism like the bolt-assist comes at a functional cost. Sure, you might never use a bolt assist...until you do. Like the old saying, 'You can't use it if you don't have it'. The more meat you have on the receiver the stronger it will be. You don't want to get minimalistic on something already cut to the quip in the original design; by that I mean AR15's in general.
I see the San Tan design is full ambi. That's to be expected for the price. The photos show a fitted offside mag release. Previously you would have to buy an extra Norgon or similar to realise ambi mag release, so that's a cost saving if they include it. That is providing you like their design that goes into the trigger guard space.
I like also how the San Tan has inbuilt QD holes for sling attachment at the back of the lower, and other attention to detail innovations like the hinge for the dust cover has one end secured by the receiver and the forward end by the handguard so no need for those fiddly circlips when assembling. This is not unique, but you expect it when paying top dollar. Bottom line, if you are paying over $400 for an AR15 receiver you want it billet, 7075 aluminium, full ambi and the top rail utterly square to the bore axis.
Mega Arms have, or at least had a fantastic reputation, until they were bought out by Zev. As a subsidiary of Mega Machine their work and machinery was enviable, but with prices to match. This Expo Arms is a unfamiliar design, more MILSPEC but they claim it is 7075 aluminium. It is a much more basic design for a receiver. Not full ambi. No bells and whistles, so you are paying for the metallurgy as far as I can see.
Depends how much money you have to invest in a plinker. Most people's definition of a plinker is a cheap and cheerful gun for occasional fun shooting. In your shoes I would go A5's advice and buy an Aero. They are good value for money. Then use the savings from the San Tan to buy the best barrel on the planet. Suddenly your plinker only looks like a plinker.