I don't want to step on any toes here. I am sure I am in the minority here and this only my experience with my MP 15-22. I can see no real accuracy improvement with or without the forend cap using the same ammo for both tests. In my opinion a 16inch .22LR barrel doesn't create enough barrel vibration or heat ( the way I shoot anyway ) to make freefloating the barrel a accuracy improvement. I do know on a 24inch ( or longer ) high powered hunting rifle sometimes freefloating or a damper on the barrel can tighten shot groups. And I have had rifles where freefloating the barrel made accuracy worse and I needed just some small amount of even pressure between the barrel and the stock. Of course this is all just my 2cents worth and don't want to create a firestorm of controversy here.

My MP 15-22 is no tack driver by any means no matter what I do including different ammo, forend cap on or off. All in all it is the most fun to shoot of my .22LRs and the meanest looking also.