I would like to see someone come out with a AR-15 in .300 Win Mag w/ gas piston.

It would be a SWAT usage rifle and hunting rifle. It would have a flat-top receiver for a scope and a fluted bull barrell with flip up iron sights for backup.

Not too much rail crap, that rail gets heavy and throws off the balance of the rifle.

A nice mount for a bi-pod though.

Someone I knew was getting multiple hits in 13 knot winds with no change in trajectory with that 300 round ( well under the standard 600 meters )  (not an AR)

This rifle would be for quick engagements of multiple targets.

i.e. Shoot it out quick and accurately in a hurry. (before they shoot you!)

that would be a hard hitter...however 300win mag was meant to be shot long distance of targets with large mass...the ar is not...also 300 win mag is not very good for quick shots on multiple targets, its more take one shot and rub your shoulder...if you want a quick takedown with a big punch at somewhat close urban range(swat usage) they already have 50 beowulf...6.8spc etc...300win mag is a wee bit over kill...but entertaining thought i would like to see and shoot such a creation

I do love the .300WM.  It is simply an awesome round...but "for quick engagements of multiple targets"?  Not this boy.

Give me a nice bolt action rifle, bipod and scope and I will shoot that sumbitch all day long.  I would not rapidfire a 20 round mag of it out of an AR, however.

How are you going to fit a 300 Win Mag in an Ar-15 platform? Perhaps an AR-10.

How about a 300 Rem SAUM, no gas piston though.

PANTHER™ LONG RANGE 300 REMINGTON SHORT ACTION ULTRA MAG
               (RFA2-300)
             
 Barrel:
• 20” Bull barrel, fluted
• 416 Stainless steel
• 6 groove, right-handed 1x10 twist, button rifled

Chamber:
•.300 Remington SAUM
   
MSRP:                   $1250

Check out Cobb. They make, or list that they will make, an AR style rifle (MCR)  in calibers up to 338 Lapua. At one point they had 300 Win Mag and others listed.

Quoted: Check out Cobb. They make, or list that they will make, an AR style rifle (MCR)  in calibers up to 338 Lapua. At one point they had 300 Win Mag and others listed.

+1
concept sound interesting, but as others have pointed out...you'll need the AR10 platform to do such a rifle.

Didn't I read on here that Olympic or somebody has a 30 caliber cartridge based on the WSSM family that could be used in an AR platform?

Quoted: Didn't I read on here that Olympic or somebody has a 30 caliber cartridge based on the WSSM family that could be used in an AR platform?

I believe TeppoJutsu was toying with some WSSM variants but was having problems getting components from Olympic. I don't know if they are still doing any of that. I believe MartyW is the member here from Teppo.

Quoted: Didn't I read on here that Olympic or somebody has a 30 caliber cartridge based on the WSSM family that could be used in an AR platform?

Take the K8 rifle and chamber it for the new Winchester® Super Short Magnum cartridges and you’ve got a K8-MAG.  This rifle is a flat top target grade rifle available in the .223, .243, and .25 WSSM chambering.  The K8-MAG launches a 55 grain .223 bullet at 3,950 FPS, and a 55 grain .243 bullet at 4,000 FPS.  Hardly the standard AR rifle, the K8-MAG is outfitted with proprietary high pressure bolts, barrel extensions, bolt carriers, and modified upper receivers.  While not standard, the upper receiver will still fit and function on any standard .223/5.56 caliber lower receiver without modification to the lower receiver.  Long time Olympic Arms customers spend hundreds less for the K8-MAG compared to other .308 rifles.  Or you can convert your .223 caliber AR into a MAGNUM by ordering just the upper receiver assembly.  

Base Retail Price: $1,074.00



Upper Receiver Base Retail Price: $672.00

Somehow rapid engagements and 300 Winchester Magnum do not go together well.

Actually as someone pointed out Cobb already makes such an animal in 338 Lapua and they did in fact make the same modular concept rifle in 300 WM I have seen it

I know RND makes a EDGE rifle in .300 mag.

Matt

Quoted: Actually as someone pointed out Cobb already makes such an animal in 338 Lapua and they did in fact make the same modular concept rifle in 300 WM I have seen it

I'm not talking about the technical feasability of the project.  I'm talking about field application.

I am personally a fan of the .300 Win Mag, but there are better alternatives to fill the gap between 7.62 and .50 BMG. For example, .408 Cheytac would be a better choice. This is an extremely capable cartridge that has the range comperable to the .50 BMG with some of the anti-material capability and a reduction of system weight. When compared to the .338 Lapua and .408 Cheytac the .300 Win Mag is antiquated. Current Remington 700 based sniper systems chambered in 7.62 NATO which are being used by the DoD have the capability to be converted to .300 Win Mag, but short of competition and limited combat use, the conversion has stalled. Since current 7.62

NATO systems have proven to be effective out to 1000 yards and with the .50 BMG and new 25mm for longer ranges, converting to .300 Win Mag isn't nescessary. A gas piston would be inappropriate for this type of weapon. The system isn't capable of the precision required for 1000 yard shots and precision weapons must receive special attention and this attention and care improves reliability. AR's capable of .300 Win Mag performance already exist. As mentioned, DPMS makes an AR in .300 RSAUM and others make AR in the various WSSM's, including .300.

Both the .300 Remington and Winchester "short magnums" generate .300 Win Mag performance without re-designing the platform. For all practical purposes, the 7.62 NATO fired from the Remington 700, M21/M25 or Mk11 has proven to be very effective, especially when supplemented with .50 BMG. Though the 7.62 NATO is extremely effective, there are better purpose built sniper cartridges which would offer increased lethality and anti-material performance without the weight penalty of current .50 BMG weapons. My vote is for a SASR chambered in .408 Cheytac.