|Ramo M600||Ramo M650|
|Caliber(s)||.50 BMG (12.7×99), 12.7×108 Russian, 14.5×115 Russian|
|Operation||manual rotating bolt action, single shot||manual rotating bolt action|
|Barrel length||813 mm||762 mm|
|Overall length||1384 mm||1448 mm|
|Weight, empty||10.4 kg with scope||13.5 kg|
|Magazine||none||7-shot detachable box magazine|
The .50 caliber Model 500 rifle was originally designed by the team, lead by the D. Haskins, then working at Research Armaments Prototypes (RAP), a small company then located in Jacksonville, Arkansas, USA. Developed at the request ofUS Armed forces during 1981-82, along with smaller Model300 rifle, Model 500 was purchased by US military circa 1983 in small numbers – about 125 rifles were initially delivered, and went to Beirut,Grenada, Panama, Iraq and probably several other places. The Model 500 paved the way into military service for numerous other .50 caliber anti-materiel rifles, such as various Barrett models. But it had a very controversial life of its own. During 1980s the design was bought from RAI by the Daisy Weapons Systems, then it went for Iver Johnson Arms. Iver Johnson sold the Model 500 as AMAC-1500, but when it went bankrupt, the parts and machinery were sold on auction. The AMAC-1500 rifles are still offered in USA by the Ultimate Accuracy Arms.During late 1980s the Daisy slightly modified the design, so it became convertible to three major "big bore" calibers, .50BMG (12.7×99),12.7×108 Russian, and 14.7×115 Russian. The model 600 was initially offered by Daisy, then by Redick Arms Development. In 1999 Redick Arms was purchased by Aurora tactical LLC ,which offered the Model 600, as well as improved, magazine fed version, Model650. For some time, M600 and M650 rifles were also distributed by RAMO Defence, before it went out of business.
The RAP Model 500, Iver Johnson AMAC-1500 and M600 are all similar in basic design, being different mostly in the shape of the barrel, muzzlebrake, and bipod. All these rifles featured a removable "shell holder"rotating bolt with three lugs. For each shot bolt was rotated and removed from the receiver, then cartridge was inserted into bolt face, and then bolt with cartridge were inserted back into receiver and locked. Fully adjustable trigger and adjustable buttstock allowed for some "personalization" of the rifle. Neither rifle was intended to be fired offhand, and thus had no forearm.Instead, each rifle was issued with folding bipod. For carry, rifle was easily disassembled into several major parts. Neither rifle also featured open sights -only telescope sights were used. According to some sources, the now famous Leupold Series M scopes were originally developed especially for Model 500rifle. On all variations, barrels were fitted with large and effective muzzlebrakes of slightly different contours.
Model 650 rifles differed from those described above by having a 7-shot detachable box magazine, and anon-removable, manually operated rotating bolt action. Because of larger and longer receiver, M650 rifles are significantly heavier, than m500 and m600 rifles.