I'd like to echo some previous comments: it is very, very loud.
I'd like a 10mm like you have, though, Mark! Magnificent weapon with King Kong ballistics.
Maybe I should shoot one outdoors before being so dismissive. Indoors it was brutal.
For all around shooting and if cost is a factor, I would consider 7.62x39"What caliber, what is the intended use?"
“The caliber would be .556 and the intended use would be all around shooting. I am not trying to be a smart aleck with shooting for the answer but I hate that question. It is like asking intended use for an automobile.”
I guess it’s probably a good thing I didn’t suggest something like my dedicated 22lr home built.
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Those pistols in the pictures you posted look incredible.I would start with a budget. I look at it as building your own will usually cost a little more up front but, cheaper in the long run. Starting out with better components will raise the cost. If you don't want or won't ever do any upgrades. It'll be pretty close to buy vs building price wise in this current market.
I prefer an 11.5" barrel but, a 10.5" is fine too. I recommend a blast forwarding device on the muzzle with shorter barrels. They make a difference with the blast and sound but, are still louder than a longer barrel. It will add a little length overall. The plus side is you can go with a little longer forearm. The added real estate is nice for adding accessories or keeping your hand further away from the muzzle. I also like the look which is less important to me.
Here's an 11.5" with a cut down BFD.
10.5" with the same look and overall length as the 11.5"
While I know it’s not on your list I just bought a IWI Zion pistol. 12.5 inch barrel mid length gas system with with free float 11.5 inch hand guard. SB Tactical SBA3 Brace, B5 Grip.
I’ve only had it out once but I love it. Worth a look.