I'm looking to buy a DD upper and lower, then build a rifle from there. I don't particularly care for the government profile barrels, I'd rather have a barrel that falls between a lightweight and government contour. I would just go with a lightweight, but Illinois could be legalizing suppressors this year, and I'd like something lighter than a standard govt barrel, but stiff enough to not give a large POI change when a suppressor is attached. I've seen the Spike's "optimum profile" barrel, and the BCM enhanced lightweight barrels that claim to fall within that range. Not sure which is better, the Bravo is only 22oz while the Spikes is 26oz (pretty much the same weight as the DD govt counter barrel which is at 27oz). The Spikes also claims to be double chrome lined to M249 specs, also not sure whether that makes a difference. I'm not looking for barrels to necessarily be a tack driver, this rifle is going to be purely a SHTF/HD weapon for close to mid range, so service life is the top concern. Do melonite treated barrels last longer than CL? Which melonited or CL barrels do you guys think would work?

BCM, because it's 4 ounces lighter. Who cares what the coating is when you're pulling the trigger? Neither company is known for putting out garbage.

PSA makes a "modified A2" in their premium line, and a "lightweight" profile on their CHF line, both are mid-length, but both are also usually part of a complete upper, not stand-alone barrels.

I have the CHF barrel, very nice & light without being a pencil profile.

I'd don't think there is anything (the result of actual testing) that shows the POI is more with a lighter barrel suppressed.

You...do understand how physics works, right?

Look up "Moment of Inertia."

I own 7 suppressors and a variety of different weight barrels, and the POI shift does not correlate to the barrel thickness in any way.  The suppressors that have lined up clips shift more across all the barrels.

There's clearly other factors involved. On a particular lightweight barrel, you may have less POI shift than on a particular heavier barrel.

However, keeping everything else the same, a heavier barrel is a stiffer barrel. A stiffer barrel will deflect less than a less stiff barrel. This is not something that can be debated, this is physics.

The BCM ELWF 16" middy was 22.1873 ounces on my scale, you should be good either way you go, there are a few 16'' mid's out there that hit the 19 ounce mark but the quality is unknown.

The BCM enhanced LW middy is probably what I'll end up going with. In regards to the question about their finish, I had just heard that the finish they had on their KMR rails weren't as hardy as most which made me wonder if their barrels had the same "issue".

Also not sure if I want to go 14.5" or 16". I don't really have a problem with a pinned flash hider, though I would want the ability to change it out for a suppressor quick attach style muzzle device down the line if Illinois pulls through with legalizing suppressors. It's a miracle we got Rauner in, but I'm not counting my chickens yet.

Anyways, a secondary question for those more knowledgeable. Since I am not buying an off-the-shelf rifle, what low profile gas block do you guys recommend? DD has 4150 steel gas blocks, but I'm not certain of their compatibility with BCM barrels, the clamp-on method they use, or whether they'll work with slimmer free float handguards. They have a neat looking 416 hardened stainless block, but I'm not certain of SS's durability compared to 4150 steel or if it'd even be compatible with a non-stainless barrel.

ALSO:

I just got an email response from Bravo Company regarding my dilemma. What's surprising is they say a 14.5" barrel is a possible no-go for suppressors. I honestly don't have a clue what they mean about crush washers, I don't even know what a crush washer is or why I'd need one, as I'm a total noob...

"Enhanced lightweight barrels are made to milspec like their lightweight and government profile counterparts however, they have less mass where it is not needed and larger mass in crucial areas.  This results in a reliable and durable barrel with much better harmonics that the standard handguard cap encompassing profile.  If it is you desire to go suppressed, we would recommend a 16” upper group for one reason, muzzle device interchange.  With many suppressors, the mounting system is proprietary in nature and requires a specific muzzle device.  If you receive a pinned and welded muzzle device, you can remove it however, it will most certainly require the aid of a skilled gunsmith to grind away the welded and remove the pin.  You also do not want to have a crush washer with a suppressor, a crush washer may make the muzzle slightly off center which could result in a baffle strike."

Any thoughts on whether this holds weight? I wouldn't have figured pinning and welding a suppressor quick attach style muzzle device would be any more problematic than a standard A2 bird cage...

I have this DD clamp on steel gas block. It is an excellent block of typical DD quality.
It is very compact and was the only one I could find that would truly fit under my DD Lite Rail III which has very little space.

It will work on The BCM barrel if it is .625 or .750 dia same as it would a DD barrel.
If this block won't fit under the rail you choose I doubt any block would.

I prefer clamp on style blocks and these are rock solid.

BCM KMR rails are made of magnesium alloy, not straight aluminum.  Comparing the finish on them, you need to take that I to account.

So how does that come into play with welded and pinned suppressor quick attach device? How is it any different for a 14.5" vs 16" barrel?

You don't want to use a crush washer with a suppressor muzzle device as they aren't guaranteed to crush evenly and can lead to a misaligned suppressor.

I guess I just don't get what the point of addressing that in their email really was. Is the only way to attach a muzzle device (which is pinned) to do it with a crush washer? Isn't this a problem that can be avoided simply by having a competent gunsmith do the work?