45 lc hot loads and gas checks

If you can find the load in the book! You are talking close to 454 loads.
 It will be  hard (but possible?) IMAO to push any 300 gr bullet through the crony that fast out of a Vaquero, I load a 45LC 300gr FAFP or an XTP mag "full blow" and out of my 7-1/2" FA 454 they chrono around 1300+, 1250 or so out of my 4-5/8 Blackhawk. Also have shot the same load out of (Someone else's) first gen Vaquero, but not through the chrono. Lead should go a little faster, but like the book says, start safe and slowly work your load up. Let us know your results. And if you think you are doing something crazy, make sure and have the camera running! Can't speak to the gaschecks, never used them, but never had a problem going 1200-1300 with non gas checked "Dry Creek's" out of any of my revolvers.

Thank you very much I will let you know my results, but I plan to start very low. I like my gun.

You can't safely get anywhere near 1,500 fps with a 300 gr in that Vaquero.
FWIW, I need no gascheck on any properly sized hardcast bullet I shoot in my 7.5" Blackhawk, be it a 250 gr @ 1,340 or 325 gr @ 1,180 fps...

The latter requires a firm grip btw...

No No No No Nope!
First of all, if someone is determined to drive at 125 mph, one does not choose a skateboard as their platform. If one really, truly must have a ridiculous level of velocity, it's pointless to stick with any mass produced sixgun.
Second, if one absolutely must run modern centerfire rifle pressures to squeeze the last drop of velocity out of a cartridge, then why use a sixgun  cartridge at all?
No, the Ruger is not capable of withstanding such a load.
No 45 Colt brass is capable of holding up to such a load.
A sober review of published data for full house Ruger loads would bring the velocity expectations back down from the stratosphere. A sober recollection of bullet behavior will clarify that published data is pretty much in synch with bullet design, and that conventional bullets will simply fail at 1500 fps, if they grip the rifling at all.
To anyone who reads this, manuals, such as Speer, Lyman, and Hornady, etc. offer the best guidance for load and bullet combinations. Get them. Read them. DO NOT EXCEED THEIR MAXIMUM!!!!!
Finally, the new midsize Rugers of which the Vaquero is one, are NOT capable of digesting loads published in the Ruger section for the .45 Colt. That data is only for the full sized guns on the 44 frame size!

http://www.customsixguns.com/writings/dissolving_the_myth.htm

Worth the read

John Linebaugh is probably the one guy most associated with hotrodding the .45Colt cartridge in the field of high performance sixgunning. The careful reader will note that his references to his high performance loads are all with the proviso of OVERSIZE CUSTOM CYLINDERS!!!!!!!
Note that his references to case strength and longevity are all in regards to HIS CUSTOM CHAMBERS!
What most folks don't know is that even though the cartridge is straight walled, the factory chambers are tapered. This is great for loading and unloading in less than pristine conditions, but a really poor mix for souping up the round. This accounts for the primary reason that the .454 came into existence-rifle like pressures were achieved with good case life in a cylinder happy to live with very tight tolerances.-and why so many adamantly state to live with the Colt at reasonable pressures.
Factories have been literally all over the place with dimensions of their 45 Colt cylinders. I've owned Rugers that had no more than 3 good chambers, and even when shooting standard velocity ammo, spit so much lead I had to wear gloves. 
On the other hand, the 44 magnum dimensions are all pretty good. So, yes, if you have a good gun with a correctly spec.'ed cylinder,you can get away with running hotter loads in the .45 Colt, yet for the majority of handgunners, the second magnum really does far more than the Colt, and does it better.
If you have the money and the desire, a custom sixgun can get you places no standard production gun will ever do-excepting maybe the Freedom Arms offerings. Really, the Ruger is not the poor man's FA, the Ruger is a solid production gun that can-if you have a good one-deliver greater than factory levels of performance.
The problem with stuff like Mr. L's commentary is that people will overlook the CUSTOM component in his philosophy, and think he's referring to the gun on the local dealers' shelf.

...cylinders  Linebaugh is still not at the 300gr/ 1500 FPS !

Mule;
You are talking about getting 45-70 ballistics from a case that is tiny compared to the 45-70. I once let a friend load some 45 LC for me in a Colt New Service. That's a strong gun. He used half a grain more than I told him and split the forcing cone. There are too many weak links in a revolver to try to get super ballistics out of it. In this case, I agree with MAK. If you want an Alfa Romeo 4C, get one. Don't try hopping up your Beetle.
Not dissing you. I just want you to keep all your fingers.

Mike