First off we are not talking about 6mm Plastic Airsoft Guns but rather 4.5mm Steel BB versus .177 caliber Pellet.
Same but Different:
Generally speaking a BB CO2 Pistol and a Pellet CO2 Pistol are very similar, they just shoot a bit different types of ammo, that will determine a couple mechanical differences in both guns. You may come across a CO2 Pistol that can shoot both Pellets and BB's but these are not as common.
The fist main difference is usually the magazine design, since lead pellets don’t stack on top of each other very well compared to steel BB’s, action CO2 BB and Pellet pistols will have a very different types of magazine designs. Pellet CO2 Pistols will generally use a rotary type magazine while BB Pistols will use a stick or stacked ammo magazine. In terms of realism, a stick or stacked magazine is better suited than a rotary magazine. Some Action Pellet Pistols will have what looks like a stick magazine, but the stick will actually have two rotary magazine on either side. You will often find higher capacity magazines in BB CO2 Pistols since Rotary magazines usually only offer around 8 rounds (16 on a double sided stick style).
Another downside to a rotary magazine is knowing when you are out of ammo, a rotary magazine does not allow for this, it will just keep turning around and around no matter if there is ammo in it or not, so you need to listen to the the sound of the CO2 gun to determine when a rotary type magazine is empty. BB Action shooters do not have this problem since in most cases the magazine BB spring follower acts exactly the same as real steel gun follower locking back the slide on the last shot, stopping any follow up shots from happening.
Steel BB’s traditionally only come in 4.5mm which is the same as .177 caliber. Lead pellets can come in a myriad of sizes, the most comma being .177, .20 and .22 caliber but they can go as large as 50 caliber for PCP air rifles used to hunt even large game.
Another common difference between BB and Pellet CO2 Pistols is the rifling inside the barrels. Lead pellets need to spin in order for them to shoot straight. Steel BB’s on the other hand fly pretty true thought the air weather they spin or not. Rifling is most often not used in steel BB pistols because the hardened steel can damage the rifling and since there is little to no benefit in adding rifling to a BB guns barrel in terms of accuracy, then why even have it. Pellet pistols with their softer lead ammunition need to have the rifling in order to create the spin that keeps the pellet true and straight while in flight.
Even though many BB CO2 Pistols can shoot accurately at close to medium ranges, they are not as accurate as a Pellet CO2 Pistol, especially as the distance become greater to your target. Not only does the spinning of the pellet help accuracy, but also the added mass of the lead pellet keeps them from being as effected by cross winds and airborne debris.
Hunting and/or Pest Control:
In most cases I do not recommend using a pistol for pest control because, plain and simple they are harder to shoot accurately. This is because there is no stock on a pistol to help steady the gun, and the front and rear sight are much closer together on a pistol than compared to rifle sights which means there is more margin for error when signing in a target. Pistols are generally lower powered than rifles which also plays a roll when considering a pistol for pest control since it may not have enough power to get the job done humanly. That said, there are pellet pistols deigned with power in mind, usually these are spring piston, or pressurized air powered air guns which can have a lot more power than a standard CO2 BB or Pellet Pistol.
Pistols versus Rifles:
This is not the forum for a full pistol versus rifle comparison. I can tell you that you will find a lot more pellet rifles than your will find BB rifles, they both exist but for the most part rifles are geared more towards target shooting and hunting. Most of the BB rifles available would be styled after replicas so the focus is not necessarily on power and or accuracy in these models.
In terms of Replica Action Shooters, BB Pistols outweigh the Pellet pistols by a land-slide. BB’s just work better in action pistols because the round hard steel ammo operates much easier and more reliably than the softer lead pellets, at least for action shooters. And the point of Replica Action Shooters is not so much power and accuracy but more so towards rapid fire good old back yard fun shooting.
Which is Best?
Well… Neither one is best, it just depends what you are looking for.
- Do you want accuracy at longer ranges - if so maybe get a Pellet CO2 Pistol.
- Do you want more realism in terms of magazine loading and your slide locking back on the last shot - then you may be in the market for a BB CO2 Pistol.
- Do you want more power down range - heavy pellets are going to hit harder and truer than lighter Steel BB’s.
- Do you want trouble free shooting - hard steel BB’s rarely miss-feed or misfire compared to softer Lead Pellets especially in action shooters.
The best is what’s best for you and not always what's best for me…