After a few months of waiting, I finally got my paws on a custom 375 Raptor barrel from the fine folks at X-Caliber to complete my hog hunting rifle. In my quest for the biggest and baddest round for the AR-10/LR-308, I was in intrigued by the ballistics of this new cartridge and its ability to shoot flat out to 200 yards with enough energy to bring home the bacon.

I present to you the 375 Raptor.







I have already started working up some loads (as the 375 is a wildcat cartridge) and I just can't stop thinking that this looks like the big brother to the 300 BLK. Below you can see the similarity in how cartridges are necked up to take some fat bullets, but performance between the two is another story. With the 22" barrel, I'm hoping to get up to 3500 lbs./ft. at the muzzle using 350gr. bullets and stay within SAAMI pressure specs for the 308 parent case.



Range report coming soon!

interested to see results.



what are the weights of projectiles/FPS?


and how does it compare to just a basic Ar-10 in 308?

Wow, looks bad ass. Post muzzle velocities when you can plus plenty of pics.

I'm waiting on dies for this cartidge.  Planning to convert one of my 358 Winchester ARs over to this.

You can find the performance and load data at 375raptor.com. I'm gonna start with the GameKing 250gr bullets and switch out to Barnes TTSX, as the places I hunt are lead free. Since I'm not running a muzzle brake I imagine this will kick a bit more than my LR-308 upper (in .308). Weight of the bare rifle is 8.5 lbs.

Luckily I was able to order a set of dies directly from Arne Brennan, himself (very nice fellow with tons of knowledge to share). I'm looking forward to more widespread adoption of this new cartridge, but we'll have to see how things go. I wouldn't expect to see dies from Hornady or RCBS any time soon.

That's awesome, the 375 variants have always interested me.

SiCO Hybrid suppressor

Is there a factory TTSX load?

Yeah, I'm curious what kind of speed you can get out of the 235 grain Barnes TSX bullets.  I would think that would be a fast and powerful combination.

Based on my experience with the .45 Raptor, yes!

Only recently learned about this round...I'm hoping it truly does compare to being the 300BLK of the LR308/SR25 platform. The biggest question I've been wondering is with the larger bullets (350gr SMK) loaded to subsonic velocity reliably cycle the action? Going even further, if the answer found is yes, can it do it with a simple Adj. gas block, so that you could still shoot supers?

I was pretty impressed with the numbers out of their 10.5" test SBR....If this cartridge could cycle subs and supers, in a 12.5" barrel suppressed and still retain a full 20 rounds in the mag...that would be one heck of a build.

Excited to see more of this!

I think I might jump on this vs the 45 raptor at the moment considering someone actually produces ammo for it.  I have a reloading setup, but I dont want to get all invested in it before I decide if I want to keep it.  I have an ar10 upper and handguard waiting for a barrel and gas block.  Might as well go for this and having something different!

I'm building one. Very impressive.