What do we know about the 338 ARC 170 gr Monoflex load?

[SD guy]

I see Hornady is finally releasing loads that seem more tailored to hunting, for the 338 ARC. Not sure how long this mono flex load has been out there. Look forward to hearing back of some first hand experience with this load on meat or at least a milk jug or ballistic jell test.

 

[SD guy]

Suppose the primary thing I am wondering is what may the lower impact velocity threshold for this Monoflex, for proper or adequate expansion on game.

Other thing that has been more of a wish than anything is would a subsonic projectile considerably heavier than the 307 grain offering, be a viable option? Was hoping for 395 grains or so. Targeting a subsonic with 1000 ft lbs muzzle energy.

 

[Oso]

I thought the primary objective of 338ARC is subsonic???

Hornady is recommending 1:8 twist barrel for 338 ARC so that you can shoot all of their existing bullets / product lines without risk of a critical failure. Traditional cup core bullet design can disintegrate as it leaves too fast a twist barrel). The potential issue is that Hornady is simply Plug&Play their existing 338 bullets designed for 338 magnum cartridges into anemic 338ARC without modifying bullet design to ensure performance as lower velocities.

In lieu of greater velocity a faster twist barrel (1:6 or 1:5) will improve bullet expansion without resulting in critical failure of majority of cup core bullets.

Only solid copper projectiles can handle the 1:3 twist barr

 

[Oso]

Suppose the primary thing I am wondering is what may the lower impact velocity threshold for this Monoflex, for proper or adequate expansion on game.

Other thing that has been more of a wish than anything is would a subsonic projectile considerably heavier than the 307 grain offering, be a viable option? Was hoping for 395 grains or so. Targeting a subsonic with 1000 ft lbs muzzle energy.

There are +300gr .338 projectiles designed for subsonic. At preset there is a jump from 300gr-310gr subsonic bullets to 340gr-350gr subsonic bullets. The 310gr class seems to be the upper limit for 338 ARC, whereas the 350gr class are designed for 8.6BO.

An educated guess is that the AR15 magazine length limits the 338 ARC from being able to use heavier bullets (too long). Perhaps in a short action bolt rifle with custom barrel (chambered for longer bullets) using either AICS Magazine or internal box magazine/hinged floor plate.

Makers Bullets offers a 8.6BO 350g solid copper expanding subsonic bullet (aka Maker REX bullet “Rapid Expansion”). A couple of specialty ammo manufacturers are using this bullet in their 8.6 Blackout ammo.

Gorilla Ammunition offers a 342gr solid copper expanding bullet in their loaded ammunition for 8.6BO.

Edit/Note: If you are wanting 400gr or larger projectiles that can still fit within AR15 platform or even short action bolt rifle then you are most likely going to need a larger caliber (diameter) bullet to accommodate the added weight. This can be achieved with cartridges such as the 450 Bushmaster, 458 SOCOM, 50 Beowolf, etc.

 

[SD guy]

I thought the primary objective of 338ARC is subsonic???

Hornady is recommending 1:8 twist barrel for 338 ARC so that you can shoot all of their existing bullets / product lines without risk of a critical failure. Traditional cup core bullet design can disintegrate as it leaves too fast a twist barrel). The potential issue is that Hornady is simply Plug&Play their existing 338 bullets designed for 338 magnum cartridges into anemic 338ARC without modifying bullet design to ensure performance as lower velocities.

In lieu of greater velocity a faster twist barrel (1:6 or 1:5) will improve bullet expansion without resulting in critical failure of majority of cup core bullets.

Only solid copper projectiles can handle the 1:3 twist barr

Apparently Hornady sees or anticipates demand for supersonic offerings as well.

Yes expansion tends to become a challenge with the lower velocity to be sure. I have little doubt the faster twist barrels may be advantageous in terms of expansion.

 

[SD guy]

450 socom has my interest as well. Bolt action is my intent as opposed to an AR offering. Currently Ruger already offers the Socom & 338 ARC may be available rather soon.

 

[dantiff2]

450 socom has my interest as well. Bolt action is my intent as opposed to an AR offering. Currently Ruger already offers the Socom & 338 ARC may be available rather soon.

Socom is not a factory option. Bushmaster and Arc are. Bushmaster is awesome!

 

[Oso]

For what it is worth on the 338ARC vs 8.6BO contemplation… if “bolt rifle” then 8.6BO makes more sense than 338ARC. The 8.6BO cartridge should (1) more reliably/smoothly feed from internal magazine or AICs mag and (2) increased case capacity should provide greater velocity for supersonic loads.

As to other larger caliber cartridges then you can have some fun going down rabbit hole watching loads of ballistic gel comparisons on YouTube

Don’t forget the 375 Raptor as well. The only other consideration is no use shooting subsonic without having a quality suppressor…. Add this to your shopping list because you will need a Big Boy Can for any of these large projectiles!

 

[SD guy]

For what it is worth on the 338ARC vs 8.6BO contemplation… if “bolt rifle” then 8.6BO makes more sense than 338ARC. The 8.6BO cartridge should (1) more reliably/smoothly feed from internal magazine or AICs mag and (2) increased case capacity should provide greater velocity for supersonic loads.

As to other larger caliber cartridges then you can have some fun going down rabbit hole watching loads of ballistic gel comparisons on YouTube

Don’t forget the 375 Raptor as well. The only other consideration is no use shooting subsonic without having a quality suppressor…. Add this to your shopping list because you will need a Big Boy Can for any of these large projectiles!

Regarding the suppressor, this is a strength of the 338 ARC. A more moderate pistol suppressor would suffice for that task. I am just seriously kicking this around & appreciate the discussion. My goal was 1000 ft lbs at the muzzle. If I were able to back off on this criteria this becomes a lot less involved IMHO, Give up on the sub sonic & things