Aftermarket Product Reviews
Not necesarily the opinions of the site manager
Barrels
Expansion Chambers
Rear Velocity Adjusters
Double trigger frames
Replacement bolts/hammers
Barrels A barrel can improve accuracy quite a bit. On a Pro/carbine, though not needed, it is the first aftermarket item you will want to get.

-The Dye aluminum barrels are very high quality barrels.  They have a very smooth boar(inside of the barrel) which decreases ball breaks in the barrel and increases accuracy and are rather quiet.  They are one of the best barrels you can get.  I highly recommend them.

-Armson Stealth: Good barrel? Yes and no. This is a very good barrel compared to the stock barrel.  Compared to other barrels, it is not the greatest.  There are better barrels out there but if you absolutly have your heart set on this barrel, then get it. But remember it takes small bore paint.
-I own the Armson and on your website it said that it takes small bore... I found that to be incorrect. I have run all sorts of paint through it and it works fine. The stock barrell is smaller than the armson.
Jimmy
-Lapco Bigshot: This is THE most accurate barrel there is. Many independent tests have shown this, my own
test showed this as well. It may be a little louder than most aftermarket barrels, but who cares. The accuracy makes up for noise, so does the price. Isusually around 50$'s.

Expansion Chambers An expansion chamber is essentially a place for liquid co2 to have more time to expand into a gas.  The pro/carbine does not need one at all but it will give you better shot consistency and you usually get a few more shots per co2 tank.  It is a good Idea to have one in cold or cool weather(-50*).

-ACI makes good expansion chambers which are also pleasing to the eye.  They do a fairly good job of keeping liquid out of the gun.  However, in long strings of fire in cold weather I experienced non-gasious co2 exiting the barrel.  They do their job well under normal firing though.

-CMI's x-chamber is not flashy like ACI and in my opinion doesn't do as well of a job but does help. 

-The ProTeam Intruder Assult x-chamber, though made for the model 98, can be used on the procarbine(see pic in gallery of first out's rig).  This chamber does not have stages like the others do.  Instead it is one stage but does just as good of a job as the others do.  

-The Psycho Ballistics X-core x-chamber ( now the D.O.P Dead On Products) is a great chamber. It has 8 stages and worked well in rapid fire situations. With an anti-siphon tube it is incredible.

Rear Velocity Adjusters These replace the end cap and actually adjust the drive spring tension rather than blocking the flow of air to the ball which is what the stock adjuster does.  They also help with gas efficiency and make it easier to adjust velocity, especially if you have a vertical adapter installed.

-Air-Tipps RVA's are the best one on the market.  They have the most adjustment range and are the most appealing to the eye.  They are self locking so they are tournament legal.  They also carry an extra tank o-ring. 

Double Triggers/ Frames Double triggers help speed up your rate of fire by letting you use two fingers.  Thier frames make them field and tournament legal.

-APP double finger trigger.First The entire handel piece is made out of total aluminum and the other pieces like the,trigger,springs,guard,and saftey just drop into place(some times it may be difficult to replace parts due it thier position.But I have had no problems with it.It's really dependable and rugged like the gun is.).It is really worth the money about 60.00 right from APP www.allenpaintball.com.It is lighter than the stock and is alot more omfortable.Very nicely made and crafted along with alot of APP products.This is really the only double finger
trigger ive ever seen so you really cant compare it to anything else.

Replacement Bolts/Hammers  Replacement bolts can help performance.  Mostly rear bolts/hammers.

-If you own a pro/carbine and are looking for a serious upgrade, this is it! Smooth, quiet and a hell of a lot lighter than the stock bolt. To install the new (reducing your trigger pull), saftey you have to widen the saftey whole with a drill. The great thing is that Air-tipps will do it for you for free if you purchase the part! This new bolt will really make your tippmann a better gun.

-Air Tipps Custom Hammer: I highly recommend this. It may be a bit costly, but it is worth it. Air Tipps makes some of the best upgrades for Tippmanns.

-The AirTipps Custom Polished Bolt works very well. It's quieter than the stock bolt and the over-travel mod that's included with the kit shortens the trigger pull and does make it feel lighter.  My assistant, who plays on an amatuer team, seems impressed with the overall change.  The install took less than 15 minutes.  I believe it's the next best mod you can make to the Pro/Carbine aside from changing out the stock barrel.  The cost may not be the most affordable for this tier of marker but I'm very satisfied with the results.  For those on a stricter budget I saw some polished bolts for the P/C on eBay that may work just as well.
Dramen68

-Pro/Lite Starr Fire Bolt.It goes to the front of your gun.I belived that it improved my accuracy a good amount.
It's plastic.

Regulators  Regulators can add consistency and accuracy to a marker. 

-The Palmer Stabalizer is the best regulator for .CO2.  While most regs will freeze up when using co2 the Stabalizer was designed for it.  They also work with Nitogen/HPA.  This is a very good addition to the Pro/carbine.  The velocities of my gun are much more consistent than without.  A bonus result is that ever since I put the reg on I have not needed to adjust velocity before play.  It always chronos in right around 280fps, what I originally set it at and the operating pressure is lower(650psi) which is easier on a paintball resulting in fewer ball breaks.  It is recommended that anti-siphon tanks are used with it.  I highly recommend them to anybody for any marker. 
first out
regulators