Colt Gold Cup series 70 National Match

I am interested in Bullseye competition but am new to pistols.  I recently bought a Colt Gold Cup series 70 National Match.  I was told this is a hardball gun which is good for EIC matches, but not so much so for Bullseye.  I was told that the pistol should not be used with SWC ammo since it was not made for it.  Can someone explain to me the reason a hardball gun should not use swc ammo?  If one wants to compete in both EIC and indoor Bullseye, does one need two pistols?

Thanks

It can be set up for bullseye.  The issue would be switching it back and forth. It can be done but will require a bit of work.
Hardball loads are completely different from SWC so the recoil spring would need to be changed.  The barrel would need to be cleaned well when switching from FMJ to SWC.  
The biggest issue IMO would be if you want to shoot a red dot on the gun for bullseye.  EIC matches are iron sight only.  Whatever type of mount you use would have to be removed for the ball match.  Your mount would have to be set up to not interfere with the iron sights, which some shooters here have done. 

Every EIC match I have shot (Perry being the exception) is done at the end of the day when you are already a bit fatigued from shooting a 2700. Your time before the EIC match will be better spent relaxing and doing prep than rushing to convert your pistol over to hardball.

I never have copper or lead fouling issues with my barrel so switching for me is as easy as changing a recoil spring and removing my scope rail to reveal my iron sights.

It is important to make sure your recoil spring is stiff enough for the ammo you are using.

SemiWadcutter ammo is almost always loaded with LESS powder than hardball, so try shooting it with some SWC and see if it functions ok.  The worst that can happen is your gun won't cycle as well as it does for Hardball.

There are a lot of bullseye shooters who shoot series 70 gold cups.

I'll just add that you shouldn't use a max load on SWC to avoid the spring change as this can add to leading of the barrel.  You may will have to play with the OAL to get the SWC to feed well.  Start out at 1.255 which works well in my Series 70 & 80 but I did end up using different mags than I do with my hardball loads and this seems to vary by gun too.

Get some good magazines and shoot that Gold Cup!     Don't kid yourself thinking that you have a match grade 1911 though.    You'll be fine for a while but plan on a full accuracy job somewhere down the road.  Back when I was an active shooter in the 70s and 80s the pre series 70 NM and the series 70 Gold Cup were routinely seen on the line in the hands of master class shooters with welded up and fitted barrels with solid bushings or Kart barrels and Bomar rear sights.  I personally shot one for a while until I traded for a old well worn Clark custom that I had rebuilt and rebarreled with a Kart barrel.  That was the year I broke 2600 shooting as an expert.  Got my master card and Distinguished badge that year!