Originally Posted by No Fear in Accuracy
I do have 338/416 Rigby Imp that Darryl Cassel gave me many years ago. I'll post a picture soon, just for comparison.
If I were me, I'd chose 338 Raptor over 338/416 Rigby Imp due to quality of brass.
Darryl's friend shot an elk close to 2800 yards with 338/416 Imp long time ago.
Darryl shot an elk around 2100 yards with this caliber.
The 338-416 Imp is really a dead horse today. It was made obsolete the minute that Wby released the 338-378 Wby. They are for all intent and purpose identical in capacity and performance.
I will not get into the chamber pressure issues with brass going south after only two firings but will say that when loaded to the same chamber pressures, the 338-416 Imp and 338-378 Wby are for all intent and purpose identical.
THen if one uses the 338 Kahn chamber, which has a conventional 35 degree shoulder angle for better headspace control, there is NO difference. No brass forming chores either!!!
It can be very confusing to hear someone state that the 338-416 Imp will get close to 3300 fps with a 300 gr SMK but then I state that my 338 Raptor which is MUCH larger will only get 3150-3200 fps. The difference is that my recommended loads will get you into the 10+ firings per case range and the 338-416 Imp loads will get you one to two shots per case and that's it.
Loaded to the same pressures in a 30" barrel length, you will see roughly these velocities with the various 338 magnum chamberings and the 300 gr SMK:(these are all with conventional throat designs to keep everyone on the same playing field)
338 Lapua Imp.....2950-3000
338 Allen Magnum..3300-3350
Now, all of these velocity levels can be manipulated by adding more pressure. All of these above loads should produce at least 8 firing per case no matter if their brass is known to be very strong(Lapua) or relatively soft (Edge). If you add 10-15K psi to any of these, there will be a significant increase in muzzle velocity but there will also be a dramatic drop in number of firings per case.
For example, many of my customers are shooting the 338 Allen Magnum to 3400 fps. By doing this, they drop brass life from 8 firings per case with my recommended loads(3300 fps) to around 4 firings per case at 3400 fps and they are perfectly fine with this. Getting 4-5 firings per case is my redline mark for acceptable chamber pressure. I prefer more firings per case but if your getting at least 4 firings per case, that is acceptable max chamber pressure in my opinion. Less then this, your simply pushing things to hard no matter if you blame it on weak brass or not.