LOWERED GAS BLOCK INFO

I have two builds to do this summer.

I want to use lowered gas blocks. Does it make a noticeable difference which gas block I use?

One is an M4 but I am going to use a YHM SPECTRE RAIL. This is for a first AR15 for my son. I am using a CAV ARMS Mark 2 for the lower and it is complete. I am working on the upper. The barrel is an Adams Arms M4 with a 1:8 twist with an M4 flat top upper receiver. I need to decide on BUIS and a GAS BLOCK for this carbine. For BUIS I am leaning towards the Magul MBUS. It will have a scope mounted on a Burris PEPR mount.

The second one utilizes a billet lower (TI-BDX.) I need a billet upper that matches and a gas block to fit under a PRI carbon fiber rail. The barrel is a 16 inch LW50 stainless from Spikes Tactical with an SPR contour that I am having fluted simply because I like fluted barrels.

I have looked at the PRI stainless steel gas block and Larue gas block and want info from folks that have used these gas blocks or others. I am sure there are other gas blocks but I am not familiar with any of them. For BUIS i am going to use Troy BUIS or PRI BUIS.

Any knowledge, advice or experience that you can share with me will be greatly appreciated.

Thanks