I saw this on their FB page.  The top receiver is going to be for .300 Win Mag length cartridges.



SI Defense FB Page

Best,
JBR

Seen the concept in the market place before, but not for under $9k. It's nice to see other manf jump on this to drop the prices down.

Nemo Arms

RND did this back in the late 90s early 2000s.   Still doing it all the way up to 338 Lapua if I recall correctly.   RND was source for old JP Enterprises Grade 3 based guns.  CNC built receivers almost 15 years before it was common place.

Nemo .300 Win Mags run about $4500 to $5500.
They are in stock in some local stores here in Montana.

Seen one, surprisingly, in my LGS a few months ago for $2900. Good to see someone else jumping in to the market. This is relevant to my interests.

Whats a built out 300WM AR weigh?

Answer: 10.6 lbs per the nemo link.

I would be hard pressed to pass one up for $2900.

maybe it was $3900. Dont recall. Someone must have bought it because I havent seen it there lately.

Any updates on this?

.300 win mag has nothing much over the .300wsm and .300saum.
Armalite was building 10T uppers in .300saum ten years ago....

Look at the loading manuals and compare. Nothing really to be gained


Now a .338win mag is a different story!  shorter case so you can load the 285/300gr VLD bullets with better seating options.


Have done a 6mm/22-250AI upper in my AR-10.  Been wondering about the .338/284 and even a .358/284.  Just so many more bullets for .338 bores.

Probably pretty damn easy to open up an AR-10 bolt from .475 to .538 or whatever the nominal boltface measures. Yet, with the .284 case you got a rebated .473 case head, and the the case is .500 with a bit of taper and has the 35deg shoulder in orig format.  Then there is Lapua brass....


Why spend the extra thousands to chase a bit of velocity?  Look to Ballistic Coefficiency and less is more!

Personally I'm not that intrigued to exceed my .308 AR10, but one advantage of the 300 Win Mag over the calibers you suggested is ammo availability and price.  While good ol' Rem Core Lokt is about the same price as say the Winchester Short Mag, most all other suppliers are noticeably cheaper and more readily available in 300 Win Mag.  It sounds like you reload...so do I.  Many/most don't so off-the-shelf price and availability might give the nod to Win Mag.  I'm in a hunting/sportsman rich area, even some of them with a lot of dollars.  Quite a few of them have a 300 Win Mag...or two.  I don't know anyone locally who has a short mag, the .338, or .358 you mention.  And please...not arguing the performance or benefits in some of the calibers you mention...just not more mainstream for ammo and awareness for most shooters.  The 300 Win Mag has quite a following, and that alone will probably drive the market for AR development.  I read American Sniper a few months ago...didn't Chris Kyle comment that the 300 Win Mag was his best all-around choice?...or something along those lines?  I may have gotten that wrong over this much time.  Heck, I didn't even know the military used any 300 Win Mag rifles for sniper work.  Look, I know we're not talking about Seal sniping stuff here, but you know stuff like that is going to drive the market.  It's a popular caliber.

I thought Nemo bought SI several years back?

I have a Rem700p in 300WinMag and love that rifle with 190-210grn match bullets.   Was just really easy to load for despite the whole belted mag nonsense.

First load out of the gate with a 190 seated to just off the lands was more accurate than Fed Gold Medal.

My only issue with a semiauto would be with having to seat to mag length.   I had jumped my 190s and 200s almost .250 out from Fed Gold Medal (yeah long throat) to tighten up groups.

If they can fit a 300wm in there, then they should be able to stuff a 375 ruger in there.  Now that would be a lot of hitting power.

Wonder what mags they'll be using?

Looks proprietary.

Photos from their FB page.









Best,
JBR

Holy crap.  Is that a girl holding up that rifle?  Check out her bicep!

Edited...VA-gunnut




I really like this idea. 300Win Mag is a fantastic round. What i don't like, is SI-Denfense's horrible execution of the forward assist. Being so close to the ejection port makes it look extremely ugly and just wrong. This 300 shouldn't even have it, same with their 308 receivers, it's just flat out ugly.





And for the money they ask for the receivers, you'd think they would realize how bad it makes their rifles look. Maybe it's just me, but its hideous. And i usually like the look of a forward assist. But not their design.





They need to remove the forward assist, or move it back. Ruins the look.
 

I'd bet good money they are the same mags used by the NEMO Omen rifles.

They only lasted a couple of months before they split and called it quits and went their separate ways.

This kind of excites me as it will operate the same as a regular AR, just bigger.

cool. wanted something like this since Cobb went under/was consumed by Bushmaster

Any news on this?

Q2 this year... which means in six to eighteen weeks

That video of firing the 300WM doesn't really surprise me as far as recoil goes.  I was amazed at the lack of recoil in my .308 AR10.  When the BCG, buffer system, and gas system are tuned and matched properly to the caliber and barrel length, the AR design is really impressive in soaking up recoil.  The heft of these rifles tend to help too.  I'm curious how this model of 300WM compares to that Nemo model.