Recently got a Raptor 50. It's set up with a new lower, Magpul PRS-S stock, Vortex Diamondback scope. Only thing I need is a Bi-Pod.  Looking at Atlas, or a Serbu. Serbu is less expense, looks to be well built, doesn't have adjustable legs. I dn't know if adjustable legs is a dealbreaker.  Atlas can be locked in at different angles fore and aft. Is that really needed?

I'm not really thinking I need tilt and pan. not on this beast. Single shot, bolt action. just a solid piece.

Serbu is in stock, but I don't know about the reputation.

looking for input from users of both or either.

No experience with the Serbu, but I have 3 Atlas bipods. 2 PSRs and a 5H.

If you're looking at the Atlas PSR bipods, they really aren't designed for .50BMG. They can potentially be used with a 50, but how they hold up will depend on the way you shoot (braced vs free recoiling. Bench vs prone. Skis vs spikes etc.).

The Atlas 5H is their bipod designed for .50BMG, but it's in a different ballpark price wise.

Other .50BMG bipods worth considering are the Accutac HD50, the Sierra S7 and the Elite Iron.

The leg angle adjustability adds flexibility for different shooting environments. Whether that's important, again depends on you. If you know that you'll only really be shooting from X position, the added flexibility may not be important.

If you meant 'cant' when you said 'tilt', that's potentially something you DO want, especially if you plan on shooting further out. Even on a bench, cant adjustability can help to level the rifle+scope. The further out you shoot, the more any off-axis cant will skew your shots.

It's one of the reasons I really like my Elite Iron bipod. The over-the-barrel apex adds stability, and the cant adjustment is like nothing else. With the other bipods, I have to crank down on the knob/lever to lock the cant (and the 5H adjustment isn't very smooth, making fine adjustments a bit more tedious).

Even with the cant tightened, some of the bipods still have a little play/slop. Not the Elite Iron. That cant ring is smooth. Doesn't really care about the weight of the rifle (the cant on the under-the-barrel axis bipods are affected by the rifle weight), and the knob is quick to loosen and holds fast with just light tightening, without needing to crank on it.

The biggest downside to the EI is the price (the Elite Iron 50 also forgoes leg angle adjustability and pan capability. They didn't want to compromise the strength of the leg interface or deal with customer complaints about the legs panning/twisting from .50BMG recoil).