Gary -
Howdy, once again !
To clarify...... the 450 ft lb energy threshold, I have suggested as a guide.
( Refer my response to your post titled “ groundhog “, and other similar responses I have made
The energy guide can be useful in giving some idea of what various varmint rifles/chamberings might be capable of; energy delivery wise.
Alternately:
You can look @ your questions back-asswards....
What type for rifle do I think will suit my needs ?
A single shot bolt rifle, a repeater bolt gun, a magazine-fed
gas gun; for examples.
If you are committed to a magazine fed AR derivative, that brings w/ it certain limitations; such as: overall cartridge length, Max case diameters that the action can safely accomodate; etc. Bolt guns feeding rounds from a magazine, likewise will have cartridge oal limits.
That to me, drives the question to: whether your needs could be met shooting a single-shot rifle; especially a bolt action ? With the ability of the shooter to single feed cartridges that have bullets seated well out.
It’s possible a shooter might feel their needs would be better met by a single shot bolt rifle, than say... a falling block action; or a top break
action; or a gas operated repeater. Nice thing about the bolt action types, is that a whole bunch are offered specifically to meet the needs of precision shooters ( for example - benchrest ).
For many, use of an established benchrest action might be a reach.
Some view the use of a “ trued “ factory action, as a good fit for their varmint rifle needs. Not to say that this option is inexpensive.
In my particular instance, I intended to have Fred Sinclair make my first custom ( varmint ) rifle utilizing a sleeved and trued Remington XP-100; set-up as a single shot rifle. Fred advised that use of the sleeved action would really restrict my potential rifle stock choices/options. What Fred advised me to do was go w/ the then-new Wichita WBR 1375 single-shot benchrest action. Fred as usual, was right on-point! My Wichita is s/n 15,
and it has served as the core for a variety of rifles/chamberings; mostly as a dual-role’ varmint/target rifle; notably....as a dedicated groundhog rifle.
Application:
As others have also mentioned, you should take a clear eyed look @ what engagement distances you might have to cover. If 500 yd is the max, that’s has implications for what features the rifle and chambering might need to have ( scope, too ). If the distances might run to say... 1,000 yd, that may very well lead to a differing rifle/chambering configuration
( scope too ).
To my way of thinking...... if you are not one that re-barrels his varmint rifles all that frequently, or similarly .....don’t often have a custom varmint rifle assembled; I’d think you’d want to step out the door w/ a rifle that can cover the max ranges you might potentially be called upon to cover.
To that end, why go w/ an energy delivery system that can scarcely cover 500yd, we have you can build one to cover say... out to 1,000 ?
For example: a 24” 1-14 .220 Swift shooting 55gr varmint bullets might meet the energy guide for shooting groundhogs @ 500 yd, but it will not
for 1,000 yd. For that, the example Swift chambering might need to be
put in a 29” 1-8 barrel, and say 75gr VLDs used for distances out there ...like, the example 1,000yd.
Using the .220 Swift example..... w/ a 75gr VLD seated, the resulting cartridge oal might bias your action choices towards use of a single shot
( quite possibly ) bolt action.
Fer sher..... why spend the $$$ for a custom groundhog gun that only delivers say... 150 ft lb @ any distance ? That’s not offering very much distance capability. By extension, why limit yourself to a 250 or say
375 ft lb energy delivery capability out to any distance ? Again, you are the one best positioned to truthfully answer the question of what ranges you will need to cover; and how much deliverable energy you will be comfortable with. The 450 ft lb energy guide certainly positions one for more-favorable outcomes, than shooting combos that feature notably lower
energy levels ( IMHO ).
And yes.... longer ranges might drive you to use of a bullet that is not a purpose-made varmint bullet ( for example.... use of the 75”A-Max” in my 28” 1-8 barrelled rifle, chambered in my .22-35 Remington wildcat ).
Not my most eloquent writing Gary, but I hope it helps you w/ your varmint rifle trade studies.
With regards,
357Mag