Get one in 45/70 and have a Savage type breach plug installed. They make a very nice fast twist 45cal. If you just want a 50cal, i would opt for the Accura MR instead. Its quite a bit lighter and a little cheaper than an Apex. They are very similar in design except the Apex has a steel receiver.
I shoot a 50 cal apex. Great shooting gun. A little on the heavy side. I do agree with GMB54, if all you want is a 50 cal ML, then go with the Acurra MR. Either rifle will shoot great.
Yes, if weight is a concern you will enjoy the Accura MR more. Its also offered in a nitride finish over the stainless barrel. The Apex has one other minor draw back vs the Accura MR. The Apex does not have a firing pin bushing. The bushing in the Accura MR can be adjusted to take up some primer head space with a cheap shim kit. Properly adjusted/shimmed it will be virtually blowby free.
If you decide on the apex. You can buy some small metric sized rubber O-rings (1mmx4.5mm) and place in the breech plug. In the primer pocket. This will take away the blowback problem for the apex.