Here is my 2 cents worth
Decide what you want for a rifle / how much you want to spend
Factory like a TRG-42/ AI etc then 338Lapua is not a bad choice
Custom with Factory Action - Edge, 338LM, 338LM AI . Your though of going Edge because you can use a factory action is not the best logic. IF you add up the cost for the barrel / chambering / trueing up etc, probably want a new trigger, new stock....before you know it you should have just bought a custom action ( Sturgeon , Nesika , Stiller etc )
Custom with custom action - 338LM, 338LM AI
I am not trying to be disrespectfull, but your really should NOT have brass cost / availability etc as a deciding factor. I shoot lots off not to common cartridges. When you set yourself up, buy lots of brass. So what if your local store doesn't have 338 LM brass
Secondly, the brass cost of 338LM over 300UM should not be an issue if you can afford to build a long range rifle anyways. BTW comparing Lapua / Norma brand brass to Remington is an apples to oranges comparison. For example, if you think 308Win brass from Lapua is the same as the Win ( the Lapua is far more expensive BTW ) then you have not handle both
Lastly, don't forget you are going to spend some serious change on optics / mounts anyways. Keep in mind, your are not finding the 25MOA / 45MOA sloped base at your local gun store. Scope choices become much more narrow to ( need lots of adjustment for what you want to do...so like a NF NSX that has over 100 MOA etc ) When you are all done the last thing you are worried about is brass / powder / bullet cost
When you start tooling up your loading gear with all the higher end dies like the Redding Competition bushing etc the brass cost becomes irrelevant
If you also do the cost calculation on how much you would spend over the years shooting this long range gun you are building, barrel life discussions are splitting hairs. Again, if you can afford to do this, you can afford to rebarrel every couple of years
I think you should decide what you want for a rifle / what your budget is first before trying to analyze ( especially over the internet ! ) what the best if 338LM / AI / Edge is the best. \
AS you can see these discussions always get sideways
Lastly, if you think you will ever go hunting with this rifle don't get too crazy on barrel length. I lug a 26" 338LM and 28" 30-378 in the Rockies every year and it sucks
Decide what you want for a rifle / how much you want to spend
Factory like a TRG-42/ AI etc then 338Lapua is not a bad choice
Custom with Factory Action - Edge, 338LM, 338LM AI . Your though of going Edge because you can use a factory action is not the best logic. IF you add up the cost for the barrel / chambering / trueing up etc, probably want a new trigger, new stock....before you know it you should have just bought a custom action ( Sturgeon , Nesika , Stiller etc )
Custom with custom action - 338LM, 338LM AI
I am not trying to be disrespectfull, but your really should NOT have brass cost / availability etc as a deciding factor. I shoot lots off not to common cartridges. When you set yourself up, buy lots of brass. So what if your local store doesn't have 338 LM brass
Secondly, the brass cost of 338LM over 300UM should not be an issue if you can afford to build a long range rifle anyways. BTW comparing Lapua / Norma brand brass to Remington is an apples to oranges comparison. For example, if you think 308Win brass from Lapua is the same as the Win ( the Lapua is far more expensive BTW ) then you have not handle both
Lastly, don't forget you are going to spend some serious change on optics / mounts anyways. Keep in mind, your are not finding the 25MOA / 45MOA sloped base at your local gun store. Scope choices become much more narrow to ( need lots of adjustment for what you want to do...so like a NF NSX that has over 100 MOA etc ) When you are all done the last thing you are worried about is brass / powder / bullet cost
When you start tooling up your loading gear with all the higher end dies like the Redding Competition bushing etc the brass cost becomes irrelevant
If you also do the cost calculation on how much you would spend over the years shooting this long range gun you are building, barrel life discussions are splitting hairs. Again, if you can afford to do this, you can afford to rebarrel every couple of years
I think you should decide what you want for a rifle / what your budget is first before trying to analyze ( especially over the internet ! ) what the best if 338LM / AI / Edge is the best. \
AS you can see these discussions always get sideways
Lastly, if you think you will ever go hunting with this rifle don't get too crazy on barrel length. I lug a 26" 338LM and 28" 30-378 in the Rockies every year and it sucks