Copied from the Colorado State Patrol Website:
Is it Legal to Carry a Weapon in Colorado National Forests?
While visiting National Forests in Colorado, you may carry a weapon. However, in addition to state laws, you must comply with Federal Regulations pertaining to the use of a firearm on National Forest System lands.
A firearm may not be discharged in the following National Forest areas:
- Within 150 yards of a residence, building, campsite, developed recreation site, or occupied area; or
- Across or on a Forest Development road or an adjacent body of water, or in any manner or place whereby any person or property is exposed to injury or damage as a result of such discharge; or
- Into or within any cave. [36 CFR 261.10 (d)]
So... there you go... follow the above and whip it out and crack it off.
Now... with that said... many Forestry Officials, County Mounties, Local PD's and the Public At Large are not aware of these regulations.

I know, I know... hard to believe, right? Well you had better BELIEVE IT!
I was cited in a National Forest (Off of Road 550 outside of Buffalo Creek before the fire) because some putz could HEAR my SKS and it was frightening his F#%*$ing Prescious Brats. I was over 400 yards and two valleys away from them. Long story short... I SPANKED 3 Forest Service Pukes (I say "Pukes" because they should have known better), 6 Jeffco Sherriffs Deputies (copped a pretty bad 'tude with me... almost went after badges and cash had they not Apologized in Open Court) and a Federal Prosecutor (Judge threatened him with Contempt) in FEDERAL COURT here in Denver. Never did get them to charge the putz that harrassed me... which is what the regs state is what SHOULD have happened.
So, go ahead... but be ready to stand up for your rights... out in the field (They {Jeffco Sherriffs} threatened to confiscate my weapons and engrave them with the case number... warned them that that would get quite expensive as I would be going "all out" to correct this egregious behavior... that they had better be certain of their actions. Don't be a smart-ass, but do not "roll over" either.) and IN COURT!!! SIX Sherriffs Deputies and NOT ONE Had Stones Enough, Out In The Field, To Defy The Feds AND Get His Fellow Deputies To FOLLOW THE LAW and not the emotional outburst of some idiot who hasn't bothered to teach his children that the National Forest Is For Everyone AND Has Many Uses... INCLUDING the DISCHARGING of FIREARMS.
Serve & Protect? WHOM?!?
Sorry if any Law Enforcement Types Out There Are Offended By My Disparagements or Vitriol Concerning Their Brothers in Uniform. But when Y'all Screw Up, It Reflects Badly on ALL of Y'all. Best thing to do? NEVER EVER LET IT HAPPEN AGAIN.