Teresa, you may want to try the shell holder #32 you can get them here at buds,
https://a.co/d/0gQlfYk7
Here is a link for one from Amazon, free shipping if you have prime.
Happy Shooting

Hi Teresa, .338 ARC uses shell holder #32, as seen here >>> https://rcbs.com/reference-table/
budsgunshop.com/product_info.php/products_id/752011433/rc+shell+holder+32 ,
Stay safe & have a great day!

Hi Teresa and welcome. The 338 ARC uses shell holder #32 (RCBS), Hornady: #6 and Lee: #12. The 338 ARC parent case is the 6.5 Grendel who's parent case is the 220 Russian. #32. Cheers, stay safe and enjoy! precisionreloading.com/cart.php#!l=RC&i=09232 --------------------------------------------------- academy.com/p/hornady-6-shell-holder ----------------------------------------------------------------- ebay.com/p/665880677

The .338 ARC uses a 6.5 Grendel / 6mm ARC shell holder (commonly an RCBS #32 or Hornady #6) due to its shared case head diameter, according to user reports and reloading references. It is designed for AR-15 platforms using a 6.5 Grendel-type bolt face.
eBay
eBay
+4
Shell Holder Options:
RCBS: #32
Hornady: #6
Lee Precision: #R2A
These shell holders are used on single-stage, turret, and standard reloading presses.

Good evening to you!! The 338 ARC used shell holder #32 (RCBS). The 338 ARC parent case is the 6.5 Grendel who's parent case is the 220 Russian. #32 can also be used on the 45 LC and 454 Casull. Hope this helps. Have a good rest of your day.
🇺🇸🇺🇸 'Merica' 🇺🇸🇺🇸

For the .338 ARC (Advanced Rifle Cartridge), the shell holder matches the same case head as the 6.5 Grendel / 7.62×39 family.
✔️ Correct shell holder:
RCBS: #32
Hornady: #6
Lee: #12
This is because the .338 ARC shares the same bolt face / rim dimensions as those cartridges (same family as 6mm ARC and 6.5 Grendel)