Would a tactical barrel fit in a USP .45? Could i just buy one and drop it in? Are they better quality than a 3rd party 5" threaded barrel?

Yes, and yes, and no.  For aftermarket you may want to check out Jarvis and CCF.  Usually they need no fitting but some might be needed if you are unlucky.  If you go with an o-ringed barrel then make sure you polish the barrel opening on the slide or you may have your slide eating those $5 o-rings.  Directions for this are on CCF's web sight.
IMO HK barrels are not one bit better than those match grade barrels produced by Jarvis and CCF.  The only thing you get extra with the HK barrel is it says HK on the side and you CANNOT shoot cast bullets in the polygonal bored HK.  The Jarvis and CCF barrels are land and groove rifled so you can shoot cast all day with no problems.

CCF no longer sells barrels So the only O-ring setup I could get would be from HK I guess. Is the O-ring setup that much better?

Jarvis does the o-ring on the full size Tactical barrel don't they, or did they quit also?  And no, IMO the o-ring really does not do all that much.  From a solid rest with match ammo I can shoot my Compacts and USPs damned near as well as I can my Tac, Expert, and Elite.  IMO those shoot better because of the trigger, not the o-ring.  I think the o-ring gives you better slide to barrel lock-up over a longer period of time but other than that I don't really buy into the o-ring being the end-all of all things.  Maybe from a machine rest they will give better accuracy but not in the hands of most mortals.

Quoted: Would a tactical barrel fit in a USP .45? Could i just buy one and drop it in? Are they better quality than a 3rd party 5" threaded barrel?

FYI - A tactical also has a different spring. They look the same, but are different part numbers.

I'll just buy a Jarvis tac replacement barrel.

Now how would I go about upgrading the trigger? Maybe I should do this before the barrel?

The real tactical spring is for suppressor use.  Unless you are going to suppress it don't worry about the recoil spring assembly.
The trigger upgrade to a Match trigger IMO is the number one thing you should do.  Also IMO I think you should send it to HK to have it installed and set up correctly.  While often said to be a drop it kit, it really is not.  The only problems and complaints I have ever heard about match trigger installs have come from people who dropped it in themselves.  The odds are about 85% that you would drop it in and have no problems but why not get all you can get out of it and know that:
1. you have gotten it set up correctly and are getting all it has to offer,
2. you have not voided your warranty by doing it yourself-if that matters to you.

What’s the difference of the Match trigger compared to standard? Does it get rid of the 'mushy' SA take-up and creep? I just got done w/ a Todd Jarrett class and he commented on the trigger of the USP 45. I know it's not a speed trigger like he is used to shooting but it was allot sloppier then a stock Para or SA 1911.

He also talked about 'over compression' in the chamber. We noticed that primers on the cases were flat and had the markings from the firing block face on them. He stated it was from having extremely tight chambers that did not allow any blow by per say. He fired his 'competition' gun and the primers were rounded like b4 being shot and only had the dimple from the firing pin. Oh, and can the guy shoot!!!!!!!hock.gif

Quoted: The real tactical spring is for suppressor use.  Unless you are going to suppress it don't worry about the recoil spring assembly. The trigger upgrade to a Match trigger IMO is the number one thing you should do.  Also IMO I think you should send it to HK to have it installed and set up correctly.  While often said to be a drop it kit, it really is not.  The only problems and complaints I have ever heard about match trigger installs have come from people who dropped it in themselves.  The odds are about 85% that you would drop it in and have no problems but why not get all you can get out of it and know that: 1. you have gotten it set up correctly and are getting all it has to offer, 2. you have not voided your warranty by doing it yourself-if that matters to you.

I can't find anything on the HK site about trigger upgrades. Where would I go to set this up? I should have them throw on some night sites while they have it too...

If you get night sights, get the fiber optic kind instead of the tridium. They dont seem to loose there effetiveness and they are smaller in diameter so you shouldn't have am aiming issue.

Not according to the CCF web site!

Quoted: CCF no longer sells barrels So the only O-ring setup I could get would be from HK I guess. Is the O-ring setup that much better?

It will not be listed on their web page.  Call their customer service line and inquire.  They will give you a price and maybe a RA number.  Then you can send them back the pistol and they will install the trigger kit as well as do the sights if you so wish.  They will not install aftermarket sights and will only do their own.  Any smith worth a crap can install sights and I have done most all of my installs myself.  It is not rocket surgery so long as you are careful and use the right tool for the job.

redsled brought up a question I was wondering about, too: What exactly is a match trigger?  How does it help?  Could somebody even throw numbers in there to help me see the diff between a match and standard?  Also, what does an O-ring do, exactly?  I understand that it's already been established in this thread that the answer to that is "not much," but what is it *supposed* to do?ETA: One other question while we're on the subject of USP tacs - do the raised tactical sites still have the three-dot configuration or are they more like regular American-style iron sites?

Weight of pull wise there is little difference although it will feel much ligher.  The match trigger has a smoother DA pull and a SA pull with absolutely no creep or excess overtravel.  The trigger breaks so crisply that it feels at least a full pound lighter than what the scale says it is.
Most standard triggers have a little creep in them after you get the take-up removed but before it breaks.  The match trigger will not have any creep at all and between no creep and no movement of the trigger after it breaks, over travel, this is where you get your better groups with the match trigger.

Quoted: Not according to the CCF web site! Quoted: CCF no longer sells barrels he

It shows them on the site, but I called to place an order and the guy told me they no longer sell barrels. I don't know why he would be bullshitting me...