Remarkably, one of the best cartridge cases ever designed to shoot 7 mm LDFs is over 60 years old! The 284 Winchester and it’s derivatives. No factory ammo though. It’s little brother the 6.5 x 284 Norma is no slouch either, if you are after a creed more killer. The very first rebated rimmed case. The choice of F-class!
The SAAMI standard COAL (cartridge over all length) for LONG ACTION CARTRIDGES is 3.34”. The 30’06, 270 Win, 300 WIn Mag, 7 PRC etc. etc are all max 3.34”. Obviously, the reason is ammunition compatibility in production rifles. Some production rifles have a certain amount of “slop” built in for hand-loaders who want to optimize their loads to their particular rifle. The magazines are longer for these rifles as well. However some production rifles are “tight” to the SAAMI COAL standard. The Tikka T3 is very tight with a maximum action length of 3.5” and a magazine maximum length of 3.37”.
Shooting LDF bullets is a paradigm shift over shooting shorter, bonded bullets. With the LDF bullet, the nose, OGIVE design is quite different. The bullets are very long and typically heavier. The barrels require a faster twist. The barrel chamber throats are typically long as a result. The 6.8 Western is near perfect in case design and efficiency for shooting LDFs. Short, squat cases with optimized shoulder angles are what is needed to shoot LDFs. You have to seat the bullets long, or the bullets stick too far down into the case and infringe on powder capacity. Also because of the bullet design, the bullets need to get closer to the lands to be accurate. Some LDFs tolerate a good bit of jump but some other bullets aren’t as accurate either. The “real estate” has to come from somewhere.
I have a Tikka T3x in 300 win mag. I love the rifle, it shoots lights out and is very comfortable to shoot. It shoots Accubonds very well. I am trying to get a 200 ELD-X to give me optimal perfromance but the jury is out if it is possible. The LDF bullet is too long and sticks way down into the powder column. Also, the OGIVE jump is very long. I need a cartridge length of about 3.52” to optimize this bullet In my rifle. But the magazine is maxed out at 3.37”. Bottom line is I need to use the shorter bonded bullets to optimize my rifle. Which I don’t mind Since I can reach out to 500 yards which is where I am comfortable.