Llewelyn Moss (Josh Brolin) uses a 12 gauge Winchester Model 1897 sawn off pump for a large part of the film, and uses it to wound Anton. Winchester no longer makes this model, and those still in circulation are considered collector's items. The actual firearm used in the film was a clone of the Winchester 1897 made by Norinco.
Colt M1911A1
Llewelyn takes a nickel plated M1911A1 off a dead drug dealer, a .45, according to the book.
Heckler & Koch SP89
A Heckler & Koch SP89 is picked up by Llewelyn Moss at the scene of a drug exchange gone wrong. If this film takes place in 1980, then the SP89 is anachronistic, since the gun was not manufactured until 1989.
Colt Series 70 Combat Government Model
Sherrif Ed Tom Bell (Tommy Lee Jones) carries a Colt Series 70 Combat Government Model. This was the only model in that time frame that would have had black grips with the gold medallions, and combat style hammer. The Series 70 Combat Government Model was the forerunner to the Combat Elite.
Intratec TEC-9
Anton Chigurh (Javier Bardem) uses a suppressed Intratec TEC-9 pistol when he is chasing Lleweyn Moss in Eagle Pass.
(This is anachronistic because the TEC-9 was not manufactured until 1985 and the film takes place in 1980)
Intra-Tec made Tec-9's in the 1980's, that's correct....but the before that the same basic gun was made by Interdynamics and sold as the KG-9 (open bolt) and the KG-99 (closed bolt)..so, it's not entirely a timeline problem
Norinco Type 56
Several Norinco Type 56 copies of the AK-47 assault rifle (both the fixed stock Type 56 and folding stock Type 56-1) can be seen on the ground next to dead drug dealers at the site of the failed exchange.
MAC-10
A MAC-10 can be seen next to the dead drug dealer on the left.
Cobray M11/9
In the motel a drug dealer is seen using a Cobray M11/9. As with other guns depicted (e.g. the SP89 and 11-87), the M11/9 is an anachronism for the film's date of 1980, as it was first manufactured in 1983.
Anton Chigurh (Javier Bardem) uses a sound-suppressed Remington 11-87 Semi-Auto shotgun with a sawed off barrel in four shooting scenes in the movie.
(As with the TEC-9, this is also anachronistic because the Remington 11-87 was not designed until 1987 and the film takes place in 1980.)
Remington 700
Llewelyn Moss (Josh Brolin) uses a Remington 700 when hunting a Pronghorn.
According to the novel [1], the rifle Llewelyn uses to hunt Pronghorn is a "heavy barreled .270 on a '98 Mauser action with a laminated stock of maple and walnut. It carried a Unertl telescopic sight of the same power as the binoculars [10x]". This description closely matches the Parker Hale 1200 series rifles [2], although the movie prop is most likely a Remington 700 variant, based on the appearance of the action and the placement of the safety.
The stock appears to be that of a 700VLS and the rifle is most likely chambered for .243 or 308. The 700VLS is anachronistic, as it was first produced 1995.
SIG-Sauer P226
When Llewelyn first finds the trucks, he opens the door to a red truck, and beside the driver you can see a SIG-Sauer P226.
Glock pistol
When Anton Chigurh first goes to the trucks with the "mind riding bitch" guy, he executes both him and his partner with what appears to be a glock pistol. A Glock would also be an anachronism as they were not produced until 1983.
Uzi
When Sheriff Ed Tom Bell and Deputy Wendell are checking out the drug deal gone bad. An Uzi is seen lying next to a drug dealer. (It may just be me, but I think it looks more like a Polish PM-63 RAK.
Captive Bolt Pistol
Chigurh seems to prefer to use a Captive Bolt Pistol on his victims when he can. He also uses it to blow out door locks. The Captive Bolt Pistol is a pneumatic gun that fires a bolt into the brains of cattle to stun them before slaughter. Like the name suggests the bolt never entirely leaves the gun, it is shot out by air (or a blank) and then retracts back into the gun by return springs. Though not a "firearm" it is a gun and does play a big role in several scenes.