It looks like the "groove" will serve the same purpose as a "crimping groove" or "cannelure groove". There might be another (more industry specific) word for it. But at this point.... "I'm comfortable".
Some people might say that the grooved or the more pronounced cannelure style of bullet is "less accurate" than a smooth side bullet. Of course quality control has a lot to do with all that. Then, you'll note that a smooth sided bullet is usually found on Match Bullets. So probably.....there is something to that?
And, there is always the issue of possible deformation of the bullet when it's "crimped" into a brass case. Yeah.....one could go with a light or heavy. Or even, a barely there (say close to "slip") fit into the cartridge case.
Of course remember......
Recoil and feeding (from magazine or just placed into a chamber) will dictate much of what you're doing (trying for).
ME.....I don't want the bullet "telescoping" into the case or moving just a little (to change things up).
YES, Yes, yes.....there are many ways for different people to Get-R-Done.
ME....I stick with the two die sets. I use the 2nd die supplied (combo seater/crimper) with a moderate crimp for my semi auto ammo. Same for my ammo being put through my bolt action. LOL....KISS or just lazy. Whatever. It's usually "Good Enough" (for me).
But then......some people might insist......about using a third die - the FCD (Factory Crimp Die). They may just say that it's THE way to go (with a moderate to heavy crimp) with every cartridge produced. Especially, if/when loading for a semi auto or full auto firearm. They say that it adds to consistency. Like, trimming and annealing with every firing.
Which groove and/or what COAL (cartridge over all length) to use?
OK......that's where the "EXPERIMENTATION" comes in. And, keeping good notes.
As I said before......
The cannelure is (for me) a "suggestion". Though, normally a good one. Then, there is something to be said about just copying the COAL from a factory cartridge. Hummm......a cartridge that has the same or close enough bullet. Wink, wink....
Since I normally have only one die set per caliber. YEAH, fussing (even a little bit) with the settings or playing with different bullets, etc....etc...... is a slight problem with getting consistency. For me......I'm normally happy with choosing to get it set up "just right or close enough" to the last time. Assuming that the last batch that I made passed my expectations.
Remember, I'm lazy. Not to mention that I ain't shooting for a Gold Medal here.
Others will probably disagree. Whatever. That's OK too.
i am at minimum powder 18.000 lil'gun i had data for 125 gr @ min 17.8 and 115 gr @ min 20.2 so i went low guess and set @ 18.00 figured .2 more for 2gr lighter projectile. (if i take the min 17.8 for 125gr and 20.2 for 115 gr and the bullet weight was 10gr dif gives me a rough # of 0.24 of powder per gr it seems) so i went 0.20 more for the 123gr to start thinking i was prob 0.2 on light side of min load.So I wouldn't change course mid stream, probably ideally I may have started with the lapua recipe from the start but its also just a guide.
That being said, Its not a big deal.
*Edit: .050" under isn't crazy just so long as you follow safe practices. As long as your "downloading" some and not going straight to max load. Generally people do want to load as long as possible to get max velocity and max case volume so you can get the most powder and most velocity potential for longest range in the end ultimately.
What's your recipe?
Is it a standard load out of a book? Are you starting at min load and working up like you should? I assume your current COAL is the one recommended by the book load your using? Or at least loading max MINUS 10% if either of the latter two I wouldn't worry there's quite a bit of safety margin built into loading and that's why you start with minus 10% etc.
What's your increments?
case length is 1.350 on the min 1.355 on almost all the rest. (converted 223/556 brass)
and of course the 123 lapua fmj