I have 4 or so different manuals to choose from for load data. However, many times the components used are not the same I have on hand. Are the components interchangeable from one manufacturer to another? Specifically the bullet and primer brand. The powder used would still have to be the manufacturer and powder weight called for. For a fictitious load, if it calls for a 6mm 85gr HPBT by Sierra and a Remington primer could they be substituted for a Hornady 87gr bullet and a Win primer and the powder remains as called for in the manual? If so, would one start @ the lowest load called for and work up? Thanks for any help.

Within reason.
Every reloader swaps components around. And evem if you are following the receipt in the book to the letter, it is still prudent to use some circumspection in determining your starting load as each rifle is different.
I have no experience with the mono metal bullets but when using standard bullets if you wanted to exchange say a 100gr Sierra for a 100gr Hornady, you shouldn't have a problem starting with a load that was 60-75% of max. If If I had it, I would use the book for the bullet I was loading.
I've never seen too much difference in primers although many folks have reported dramatic differences. If it was me, I wouldn't worry too much about it. Just pick a primer and stick with it. If you switch from a standard primer to a magnum primer, it's said that you should back off by a couple or three grains to see how your rifle is going to like it.
All of this assumes you are using a modern bolt action rifle.

Check at least two reloading manuals to find the lowest starting load and start there. Work up by increasing powder charge by 2% until you reach first reported max load or you have some sign of max load. If accuracy is still improving, carefully work up to the second max load and pay extreme attention for any pressure sign.
If all you have is a max load, drop that load by 15% (unless the load is a "do not reduce" or the manuals tells you how much to drop from the max load) and again work up to max in 2% of charge weight increments.

I believe this is one of the most frequently asked questions on this forum . Please click the following Link an read the entire article

Everyone seems to have a method an opinion as too the correct way of reloading . Someone once said opinions vary !.

http://www.frfrogspad.com/loaddev.htm

With a known Book Load ( Component Manufactures didn't just grab that info from thin air ,it was researched and researched tried and retired ) reloads are safe an sane ADVICE !. Nothing in this world is absolute NOTHING !.

I personally have grabbed an read more than a few manuals over 44 years of reloading !, I've still got 8 fingers 2 opposing thumbs ,both eyes an uncut eye lids or brows ,along with a fair amount of Wit left !.

I jump into the Middle of a Known load ,an work up by a 1/2 Grain of powder it's USUALLY the quickest SAFEST method I know of .
I STOP when MAXIMUM ACCURACY is achieved and could care less what velocity is . I'm after PRECISION not PROOFING my actions every time I pull the trigger . Knowing the velocity of a given cartridge is USEFUL ,trying to match or exceed a book's printed value ISN'T !!!.

The key is COMPONENT SELECTION AND COMBINATIONS , one bullet an one powder DON'T ALWAYS CUT IT !!!.

quote:

The powder used would still have to be the manufacturer and powder weight called for.

Not really. Most manuals have a "Relative powder burn rate" listing which as the name implies gives the relative burn rate of various powders. Note the term "Relative" because canister powders do not burn exactly the same even from one can to the next. This is why once you have settled on a load one would typically buy enough powder, primers, etc of the same lot# to load for the foreseeable future.
Any hows if you find your loading manual has loads for H4895 and IMR4320 which you do not have but you have IMR4064 which is between the two, you can back off 5% or so and work up a load. Just be careful and check the relative burn rates listed in at least 2 manuals and always back off %5 on powder charges WHENEVER you change a component just to be safe.