That makes sense. Since that’s the same cartridge
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You mean I’m right?
Uploading: IMG_2591.png…
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Beware. The nominal diameter of the bullet for the 7,62x 39mm is .309-.311. It’ll fire, but it’ll be tight and will likely increase barrel wear. Slugging the barrel will tell you the best bullet diameter is best for your particular barrel.
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Thank you for catching that 
7.62x39 removed from my post to avoid confusion
Interesting thread. Not that anyone asked for it, but this makes me want to express an opinion 
Honestly, there are too many calibers out there, and companies continue developing new ones. In rifle and handgun calibers, it seems like new ones get added every year. The world is full of tried and true, 100+ year old calibers (or some maybe newer, but very well established), why do we keep needing new ones? The old ones continue being refined, to where common, ancient calibers like 9x19 are extremely effective at what they’re designed for.
For me, I’ll only buy guns in very popular calibers, just because I don’t want to invest in something like a Betamax VCR (or even a VHS VCR for that matter). I’d like to know my daughter can still use my guns long after I’m gone.
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If it makes you feel any better, it is the same with most things, certainly cars and motorcycles. The call it progress, but most of it is merely change.
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That is a good question. I have to think ego plays a part. People want to put their stamp on something, have an impact, introduce a thing, etc whatever. Because there just doesn’t seem to be a need or reason behind so many.
Like really who asked for .30 super carry? And sorry Gaston but .45 GAP was a classic case of solution to a question nobody asked.
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Answered your own question.
Many of the “new” calibers/cartridges puncture more wallets than they do bad guys or game. Just like fishing lures, they catch more fishermen than fish.
AS for the original question: wouldn’t a comprehensive reloading manual contain much of the information you’re looking for?
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…merely for the sake of change.
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Happy to help. I’m kind of a stickler on double checking everything when I reload, even if I’ve reloaded that cartridge before. I hate surprises when I pull the trigger.
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This is the majority of the why of the new calibers. It can be hard to compete in the tried and true calibers when so many other manufacturers have been making them for so long. But if a manufacturer makes something few others are making they may find a niche where they can make a little profit.
Though sometimes these niches can gain some traction and make a larger market of their own. Like 300blk and 6.5 creedmoore in rifle cartridges. Or to a much lesser extent 5.7x28 in pistols and the PS90.
I’m sure there was a time when people asked why anyone would want that new fangled 9mm Luger when there were so many other tried and true options out there.
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Resistance to change; one of the universal constants.
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for the facebook crowd!
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What do you double check. Caliber?
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This could turn into a book but, to hit a few of the high points, the brass has the main focus because it holds everything together. Primer pockets are of particular interest. When punching out the old primer, some resistance must be felt. An audible POP indicates an acceptable pocket, Trim length is checked religiously and those that are not in the middle of min/max trim length are soon remedied. wall thickness uniformity was checked to the degree possible. When satisfactory combinations of projectile, powder, primer were found, the recipe was recorded and, having been proven accurate and of sufficient power to perform the desired task,
All of the above applies to rifle cartridges, as well except they are checked for concentricity, wall thickness and runout on a very old NECO gauge (with dial indicator),which checks all of these and are checked both before the casing without the bullet and after the loaded cartridge is complete. I have reloading manuals dating back to 1976 to present. Load data from then to now sometimes has deviation that needs to be accounted for. Care must be taken if you push the limits of the deviations of old to new.
If you choose to do so, particular attention must be paid for signs of excessive pressure.
These are the bare minimum that I do.
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Sharing some more info I found while 22M deal hunting.
CMJ: Complete Metal Jacket
FMJ: Full Metal Jacket
FP: Flat Point Nose
HBWC: Hollow Base Wad Cutter
HPBT: Hollow Point Boat Trail
HP: Hollow Point
JFP: Jacketed Flat Point
JHP: Jacketed Hollow Point
L: Lead
LF: Lead Free
P: Plated
PSP: Pointed Soft Point
RN: Round Nose
SWC: Semi Wad Cutter
TC: Trucated Cone
TMJ: Total Metal Jacket
And
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