I have built several 10.3 - 10.5" pistols/rifles and can recommend the Seekins/Spikes BAR rail which, despite lacking keymod/M-lol, is extremely robust and lightweight. I also have a Seeking MCSR rail, which I cannot recommend highly enough. It lives on a 10.5" pistol with BCW keymod furniture. I also really like the Samson rails for lower-profile builds and the Daniel Defense Lite Rail III and RIS.