[Snagman]

Yes, the 338 ARC is based on the 6.5 Grendel case. According to the very little info I can find on the web, the original 338 Grendel was based on the 338 Lapua Magnum. Not sure that really makes any sense though. You may be right, Carry on.

All I can say is my shooting buddy has a 338 Grendel, also known as the 338 Spectre, and it is now called the 338 ARC. They use the same brass and bullets.

 

[Snagman]

Not sure why you keep saying that. They are not the same cartridge. Similar but not the same. One is based on the 338 Lapua case, the other on the 6.5 Grendel. Pretty good bit of difference in the parent cases.

You may want to look closer. The 338 ARC is based on the 6.5 Grendel case, just like all the other ARC calibers. A buddy of mine actually built a 338 Grendel years and years ago. He was disappointed with it and tried to sell it but no one wanted it. He pulled it out of the back of his safe and 338 ARC ammo runs just fine through it. The only difference is Hornady created bullets with a longer olive which dramatically changed how it shoots. Bad thing about 338 ARC is the bullets rarely expand. They will penetrate but not much happens as it goes through. Of course I don't want to get hit with that thing, but I really wouldn't recommend it for ethical kills on hunting game. I know people will claim it drops everything from cats to elephants, but it's not anything I'd recommend.

 

[Snagman]

I have been thinking about building another hard hitting AR-15. Originally I was thinking about either the 458 socom or 375 socom. Looking at the supersonic ballistics of the 338 ARC it kind of intrigues me. I would be primarily be using it supersonic. Would it be worth building or should I stick with one of the socoms?

The 338 Grendel has been around for a long time. No one wanted it until a bit of smart marketing called it ARC. If you plan to go supersonic and hunt, then the 458 Socom is the better choice.