[Squawk]

I have a standard Milspec lower. I know there are multiple uppers in different calibers that are compatible with standard lower receivers. Which one is best for long range shooting past 500 yards but ammo isn't too expensive?

I looked through stickies and didn't find this in them.

[locutus]

Get a 24 inch heavy-match barrel and feed it 77 grain match ammo.

No cheap ammo will do what you want, so suck it up and buy the good stuff!

Or even better, handload the good stuff.

[hmh]

You could go 204 ruger depending on how expensive is to expensive. That being said I went with a 5.56 floated fluted 1:8 ss bull.

[Squawk]

I was interested in other calibers. Like 6.8, 6.5, .458, etc. calibers that can be used with a standard lower but different upper.

[AgentTikki]

Because you ask i think you should start with a .223 wylde 20" precision stainless barrel. It will take you out to past 500 yards with the right bullet and glass. It is a relatively cheap caliber to learn on and widely available.

Once you've understood the ballistics of the .223 remington/5.56 nato and have outgrown the caliber and mastered the fundamentals of precision shooting, then I'd do some research into other calibers and then go for more

[Txhillbilly]

A 223 caliber with a 1/7 or 1/8 twist shooting 75gr or larger bullets will get out to 500 + yards easily,but in most cases the rifle will be turned into a single shot rifle with the length of the cartridge being too long to fit in a magazine.
The 6.5 Grendel would be the best choice for that type of shooting,but the ammo won't be cheap if you don't handload.