Hornady 338 ARC

[Konocti's Wigwam]

Any more updates on this powerhouse? I don't see too much traction on it yet, and I'm still pondering what it would solve for me over 300 blackout, but those Maker bullets do look pretty good. They look very similar in expansion to my eye with the Maker 110, a pretty good supersonic load. For me, subsonic is not important unless the Morse vs Raoul case in the 2nd District rules in favor of allowing suppressors at the state level.

The 300 blackout does well for me in subsonic, and I have it today. I saw Maker has an 85 grain, only $30/50ct, as does the price on the 110s, I shoot Hornady CXs and that looks like an XLNT alternative. Maybe it makes sense to have less twist in super, that I don't know. The rounds look odd to me, in regard to proportion. I would be the first to admit that 8.6 blackout could be novelty, but Grendel shoots good supersonics in a better proportioned round...just my $0.02, which doesn't mean much. I build for myself, not for anyone else, to date. I don't want anymore gas guns.

 

[LVLAaron]

Reloading Data Center – Hodgdon Reloading Data Center

hodgdonreloading.com

Load data now available

 

[boltfluter]

Got my updated ATF permission slip to cross state lines. (I live right on a state border, and my range is on the other side). Wind was 14 gusting 28 at the closest airport. I shot a box of subs - after getting it sighted, it was holding 3/4 inch groups at 50 yards. I'm pretty happy with that. It's a little snappier than I expected but fun of course!

Aaron,
Sweet looking AR15 buddy. We need details please. Gonna be working on your "mister twister " shortly. That .338 is a good looking round!
Paul

 

[LVLAaron]

Aaron,
Sweet looking AR15 buddy. We need details please. Gonna be working on your "mister twister " shortly. That .338 is a good looking round!
Paul

Aero Upper/Lower set from the days when Aero was good. Acog for the laughs. Midwest Industries rail that I sprayed. Odinworks barrel!

 

[LVLAaron]

Hornady load data

 

[Mexica55]

You've already got them on the website. Love the new site!

What website is this? Sorry for the dumb question.

 

[LVLAaron]

What website is this? Sorry for the dumb question.

Ray Gross is with Manson Reamers. I was complimenting the new web store / website

 

[LVLAaron]

Had to do some ramp tuning on my blaster. Rounds fed from the left side of the mag were always getting stuck...

 

[SKWERLZ]

I have a 1-3 and front half of a dead 1-8 338 barrel.
Plan on doing a bolt action and AR barrel this winter.

 

[LVLAaron]

I have a 1-3 and front half of a dead 1-8 338 barrel.
Plan on doing a bolt action and AR barrel this winter.

I'm very interested in a 1:3 ARC. I have a barrel blank... a reamer.... I wonder if the 307subx would hold together.

 

[Oso]

I'm very interested in a 1:3 ARC. I have a barrel blank... a reamer.... I wonder if the 307subx would hold together.

Seriously doubt it. Q stuck to 1:3 twist for 8.6BO, which meant that none of Hornady’s existing bullet line could be used. Hornady doesn’t offer a solid copper projectile.

I keep waiting for someone to confirm that SubX holds together in a 1:5 twist…

 

[LVLAaron]

I have an 8.6... I could test it I suppose.

 

[LVLAaron]

Seriously doubt it. Q stuck to 1:3 twist for 8.6BO, which meant that none of Hornady’s existing bullet line could be used. Hornady doesn’t offer a solid copper projectile.

I keep waiting for someone to confirm that SubX holds together in a 1:5 twist…

Subs generally don't need to be solids. the 300smk works great.

 

[SD guy]

I'm very interested in a 1:3 ARC. I have a barrel blank... a reamer.... I wonder if the 307subx would hold together.

My initial guess was as long as you stay subsonic the 1 & 3 may work. Then I 2nd guess myself, in excess of 250,000 RPM may be a lot to ask, for a projectile that is meant / designed to perform at subsonic velocities & less than 1/2 the RPM you are looking at. Rifling finish and configuration will be a factor as well, given you are approaching that ragged edge. Monolithic may be required with that barrel twist. Keep us posted how she works out for you!

 

[Oso]

I have an 8.6... I could test it I suppose.

I was hoping you might say this!

 

[LVLAaron]

excess of 250,000 RPM

490,000 at 1050fps

 

[LVLAaron]

Bullet Spin Rate Calculator - Calculator Academy

Enter the muzzle velocity (fps) and the barrel twist rate into the Calculator. The calculator will evaluate the Bullet Spin Rate.

calculator.academy

 

[SD guy]

Long hand & w on-line calculators my results repeat w 252000 rpm. Your App & my apple device do not work w one another.

Bullet Spin Rate Calculator - Savvy Calculator

Learn how to calculate the spin rate of bullets with our Bullet Spin Rate Calculator. Input muzzle velocity and barrel twist rate, and instantly get the Bullet Spin Rate in RPM.

savvycalculator.com

 

[SD guy]

chat got seems to concur w the 252,00 rpm.

What rpm will the bullet be spinning when fired through a barrel rifled at 1 in 3 twist & a velocity of 1050fps?

ChatGPT said:​

To find bullet spin in RPM, use:

RPM=Velocity (ft/s)Twist (ft/rev)×60RPM=Twist (ft/rev)Velocity (ft/s)×60
Given:

• Velocity = 1050 ft/s
• Twist = 1 turn in 3 inches
  → 3 inches = 0.25 ft per revolution

Step 1: Revolutions per second

RPS=10500.25=4200 rev/sRPS=0.251050=4200 rev/s
Step 2: Convert to RPM

RPM=4200×60=252,000RPM=4200×60=252,000

= 252,000 rpm​

If you'd like, I can also calculate centrifugal force, stability factor (SG), or compare to other twist rates.

 

[SD guy]

Seems Grok made the same error coming up w 420,000 rpm initially. When I asked grok to double check the following was the answer I received & feel is correct.

The standard formula for bullet RPM is:

RPM=Muzzle Velocity (fps)×720Twist Rate (inches per turn)RPM=Twist Rate (inches per turn)Muzzle Velocity (fps)×720

• Muzzle velocity = 1,050 fps
• Twist rate = 3 inches (for a 1:3 twist)

RPM=1,050×7203=756,0003=252,000RPM=31,050×720=3756,000=252,000

Step-by-Step Derivation of the Formula​

1. The bullet travels forward at 1,050 feet per second.
2. Convert to inches per second: 1,050×12=12,6001,050×12=12,600 inches per second.
3. For a 1:3 twist, the barrel imparts 1 full rotation every 3 inches of travel.
4. Revolutions (turns) per second = distance per second / twist inches = 12,600/3=4,20012,600/3=4,200 turns per second.
5. Convert to revolutions per minute: 4,200×60=252,0004,200×60=252,000 RPM.

(Equivalently, the "720" in the formula comes from 12×60=72012×60=720, combining the unit conversions in one step.)

Notes on Jacket Integrity for the Hornady .338 Sub-X​

• At 252,000 RPM, you're right at the upper edge of typical safe limits for jacketed lead-core bullets like the Sub-X (generally 250,000–300,000 RPM max before centrifugal force risks jacket separation).
• For subsonic loads, a 1:3 twist is unusually fast (most .338 setups use 1:8 to 1:10), but it could stabilize heavy bullets like the 307 gr Sub-X at low velocities without immediate failure. However, real-world testing (e.g., via chronograph and high-speed video) is essential, as the Sub-X's design isn't optimized for spins this high—potential for in-flight instability or early fragmentation if pushed.
• If this is for a custom build, consider monolithic bullets for higher RPM tolerance.

My earlier mention of 420,000 was a calculation error (I forgot the full conversion to RPM); apologies for the mix-up.