New to modding my Ruger AR556 carbine.

Installing a ALG handguard so I have to install a Low Profile gas block. Looking online there appears to be 3 different mounting methods for gas blocks. Pinned, "jam screws" on the bottom, and the "clamp style gas block. I realize the pinned it likely best as it exerts no force on the barrel. Since I cannot pin a new LPGB on using original pin holes in barrel, and would prefer to keep the remved A2 sight block unmolested, I will have to use the jam screw or clamp on style.

Which style would be better to go with? Either one better than other concerning forces placed on the barrel. Either affect barrel accuracy?

Just curious as to which is more popular among the marksmen.

I always do set screw and pin if there is the option.  Otherwise, I dimple and set screw.  Set screw style gas blocks may not work for you depending on where the original pins are located as they could interfere with getting a good bite with the set screws.  In that case I would go clamp on.

Clamp on is generally considered the best for precision work since it places equal stress on the barrel and doesn't affect stress or harmonics like set screw pressure, dimples, or pins.

I generally think that your air temperature and humidity are more likely to affect your actual measureable accuracy so it's not something I worry about.

Pinned is the way to go for durability.

Imo the best system is what KAC and Q use, especially with the AN fitting style gas tube on the KAC, but sadly that's not an industry standard at all yet.

A dimple or two and the CORRECT knurled cup grub set screws and you'll be fine. I use blue locktite but once you really heat up the bbls then it's toast as it's failed with me(with smooth cups screws). I have since staked all my current gas blocks, once things are good. Pinning a LPGB is the way to go, for reliability, mainly even if it's under a FF rail. Here's my thread on staking and pics.https://www.ar15.com/forums/AR-15/Why-I-now-stake-set-screw-gas-blocks-/118-728442/

IMO:

1st : virgin drilled and pinned GB
2nd : cut down pinned GB from above
3rd : clamp on GB
4th : dimpled set screw
5th : other

I believe the clamp on is the best for accuracy.  I only use set screw type, but dimple my barrels for gas block.  I only use rockset on setscrews.  I look at AR's as a battle rifle not a precision rifle.  Good shooting

For a rugged use rifle..noting beats drilled an pinned.

For range toys under a handguard, I use set screw type. I make sure I use knurled set screws that "dig in" a little.  And I NEVER use anything other than blue loc-tight. The first time you have to take something off that's been red loc-tighted you will curse the day you were born.

For range toys with gas blocks outside the handguard, I use clamp on type.

I don't dimple or stake anything, and I have never had either style shoot loose, move, explode, or cause any issues, in fact, even with just blue loc-tight they are PITA to get off when it's not heated up.....but like I said, these are range toy rifles. My home defense setups all have drilled and pinned FSB's

I do the set screw ones. One of them I dimpled though I find it unnecessary. Just wanted to do it. Clamp-on style is also a popular option. I don't know about some folks claiming it makes for a more accurate barrel. Perhaps in a lab.

I personally like pinning the gas block as it is the most secure. If this isn’t an option I go with with dimpling your barrel and set screws. You can stake the set screws, red loctite or rockset. But if they are knurled set screws, dimpled barrel and torqued properly you shouldn’t have to loctite, rockset or stake. The set screw gas blocks are also still able to be staled as well.

Also with a dimpling jig it is possible to get a perfect alignment over the gas port with the set screw gas block.

The rifle already has a pinned fsb correct? Why not just cut it down and have a pinned gas block. Probably the cheapest option as well

I have used the clamp on style for many builds.  Mainly because they can be spread slightly for ease of installation.  I've never had a problem with them coming loose, moving, etc.

I have had problems with set screw types if tolerances stack the wrong way and you end up with a loose fitting gas block or one that can't be installed.

Clamp on, on all.  Many set screw and pin on's leak tons of gas, enough to cover that area of the hand guard.

Nothing but clamp on.

That's probably the route I'd take but the OP states he prefers to keep the removed FSB "unmolested" for some reason.

LOL..I hope he doesn't do what I did when I started out. I just threw them in a box without even a thought they were specific to the barrel.