As others have already said the O/U double rifle is fine for deer hunting, and is far cheaper to buy than a side-by-side double rifle. The O/U is far easier to mount a scope on, and is usually lighter than a S/S in the same chambering. This is where the advantages end, IMO!
I have both types, but I prefer a S/S to all other double rifles, even in a drilling I want the S/S double barrels on top to be the RIFLE chambering, and the bottom single tube to be the shotgun barrel. In this case the drilling can be made as a DGR (dangerous game rifle) with the proper chambering and still be used for birds, or with a slug as back-up for the two rifle barrels.
The O/U double rifle is not suited for dangerous game use, IMO, and there are several reasons for this. One is that most O/U double rifles are fitted with a single non-selective trigger. The Single trigger is one thing you never want on a double rifle that will be used for hunting dangerous game. Most O/Us not only have the single trigger, but the rifle only cocks the bottom barrel when opened, and the top barrel is cocked by the recoil of firing the bottom barrel.
NOW! If the single trigger fails, in any way, the rifle becomes an 8 lb club! If the single trigger is pulled on a dud, and the bottom barrel doesn’t fire, the rifle becomes an 8 lb club. This also applies to S/Ss with single triggers, and I don’t think even the rankest novice would not want to be left to fight a cape Buffalo with an 8 lb club.
The properly fitted double rifle is nothing but a pair if single shots on the same stock, one completely indipendant from the other. If one side fails in any way, you are left with a working single shot. The double with one trigger, and a bolt action rifle are both in tha same canoe if anything it the fireing mechanism breaks, the rifle is out of service till it can be fixed. Really all you have to do is ask the bufflao to wait till you can fix the rifle, or clear a jam!
The O/U double must be opened very wide to load the bottom barrel, that is true, but the real sticker in the saddle blanket is the barrels are one above the other, and it is almost impossible to re-load both barrels simultaneously, while the S/S double rifle is easily loaded in both barrels at the same time, because with two cartridges between the forefinger, and the middle finger, of the fore hand. The barrels sit side by side, and all one has to do is bring the left hand (rt hand shooter) round to the top of the open rifle, and simply place the side by side BULLETS of those cartridges in the open side by side chambers, and release. The cartridges will slide into the chambers, and your right hand (the trigger hand never leaves the pistol grip.
The cartridge’s natural weight lowers the cartridges S/S into the chambers, while the O/U, trying to load both barrels at the same time the natural weight of the cartridges tends to try to lower both cartridges into the bottom barrel, and usually it is much faster to load an O/U one barrel at a time.
This means the O/U is much slower to get of shots 3, and 4, than with a S/S, and if you have hunted Cape Buffalo much you will know they are rarely stopped by the first two, and if not and they decide to charge, that re-load is critical!
Some say here, "why not just use a bolt action that holds 4 or 5 shots?" That sounds like a real good idea on the surface, but in the field you rarely get more that two shots before the animal is out of sight, and/or hits you with a double rifle, and only one with a bolt rifle, in a close charge.
The double rifle is far, and away quicker for the first two "AIMED" shots, and is about the same for the third shot as is the bolt rifle with a skilled rifleman, and far ahead of the bolt for the fourth shot. This is only the case when using a S/S double rifle after the first two, the O/U is slower than the bolt for the 3rd and 4th shots,but faster for the first two, and the bolt is slower than the S/S double rifle,for all four, even if the bolt guy doesent get a jam while working that bolt as fast as he can.
This was accidently proven at the PH classes for rifle handleing at the Zimbabwe PH school for class members getting their dangerous game rating. They changed the rules because one applicant was useing a double rifle to make it more even for the double rifle user, they changed them back when the double rifle guy smoked the bolt action guys, for four AIMED hits in the kill zone on the target, in less time. This was printed up in African Hunter Magazine by one of the teachers at the school, a few yrs ago.
You will notice that you rarely see an O/U double rifle chambered for anything larger than 9.3X74R! There is a good reason for that fact. That fact is the Over under was designed for deer hunting, and is why most are sold to hunters who hunt Europe. The nearest thing they have to dangerous game is a wild boar, or in some places large bears, and the 9.3 will handle them quite nicely. Rarely will you see an over under double rifle in the hands of an African PH,I've only seen one in 30 yrs of African hunting, or even a client hunter, but a full 99 % of the O/U doubles you see in Africa, will be in the hands of client hunters, mostly from Europe.
Both types will kill dangerous game if the cartridge is right, and is placed in the right spot. However when the first two doesn’t do the trick, and the animals has decided to take issue with you poking holes in his hide, that little fumble prone O/U design may get you killed.
The cost difference is in the building of the rifle! The O/U (what you call “EXPRESS”) is far less skilled labor intensive than a side by side. Virtually all O/Us are built on mono-block barrels, and the barrels are much easier to regulate than a side by side. The O/U is a design that is much more forgiving to most of the fitting done by machines, and this cuts down on the SKILLED man hours needed to build one. Besides that with most not cocking both barrels on opening, there are fewer moving parts to fit and finish.
The phrase “EXPRESS RIFLE” more often used to describe a rifle chambered for the old EXPRESS cartridges. For example 450 NITRO EXPRESS, or 500NITRO EXPRESS, and most O/Us are chambered for small cartridges like the 8mms, or 7mms with the largest usually being the 9.3X74R, which barely makes the EXPRESS list of cartridges.
My advice is, if you want an O/U double rifle, and you intend hunting nothing larger than a bear or moose, then buy one! It will certainly save you some money, but if you intend hunting dangerous game with it, spend the extra money and get a good field grade S/S double rifle chambered for something from 450/400NE 3” up with the absolute minimum being the 9.3X74R, S/S with ejectors, to speed your re-loading of the chambers for shots three, and four, with a non-automatic safety, and double triggers. The S/S will get more valuable the longer you have it, and will out last you and your grand children. The O/U, is like a used car, it will be just a used rifle when it comes time to sell.
