Readers of the Scrapboard will know that I'm very interested in the Russian 9x39mm round that was created by opening out the 7.62x39mm M43 case. When Ed Sackett was discussing his ideas for a 7.62x51mm NATO bullpup rifle he also suggested a .45 bullet mounted in a 7.62mm NATO case. Ralph Zumbro has also suggested such a round, and pointed out to me that the .45 Springfield Magnum pistol round based on cut down .30-06 brass that I've suggested would also work in a rifle action, the 30-06 and 7.62mm NATO cases being effectively the same except in length.
Recent discussions in G2mil on large calibre rifles or Thumpers causes me to return to the idea of a .45 bullet in a 7.62mm NATO case. For the moment we'll call this the ".45x51", although the actual case length may differ in practice.
What advantages does the .45x51 offer over the various other proposed Thumpers?
Firstly, by basing the weapon on the .308 win/7.62mm NATO case the round can easily be adapted to a wide range of weapons, including but not limited to the FAL, G3, M14, AR-10B, SR-25 and various bolt actions. Secondly, the choice of .45 calibre offers a wide range of potential projectiles, ranging from pistol bullets for the .45ACP and .45 Colt to the heavy bullets designed for the .45-70. Shot, duplex and other specialty loads are also possible. With a shot loading the weapon can fill a similar role to the Saiga 410. The round is likely to be very similar to the .45-70 in power, but capable of being used in self-loading or selective-fire weapons fed by box magazines. As has been noted on another of my pages, a 45-70 can take any animal in North America, including angry Grizzlies
Ralph Zumbro: One of our local vets, (Grenada, Panama, Desert storm), tried an experiment on a level III vest that had been shot up. He aimed a 45-70 at an unused place and let go. The 405 grain alloy unjacketed slug at 1300 fps went all the way through, including the ballistic plate. Very interesting.
One of the most useful applications for the .45x51 is as a entry weapon for SWAT teams. Police units need not be restricted to military calibres, particularly if something better is available. The considerable stopping power of this round makes it particularly suited for this role. With the correct ammunition the rifle can be used to blast out door locks and hinges, a task that usually requires a shotgun. During the writing of this article I came across a release from a well known company that is offering a 11.5" barreled 5.56mm weapon as an entry weapon. This borders on the criminally irresponsible. It is well publicized that 5.56mm FMJ rounds have considerably reduced wounding power when fired from a barrel of under 14.5. Even though police are permitted the use of JHP and JSP rounds, these require a certain level of energy to work, and since 5.56mm rounds are lightweight this needs to be provided by the round's velocity.
Being based on a battle rifle the .45x51 entry weapon will been somewhat heavier than many of its Assault rifle or SMG based peers. Given that this weapon will usually be carried in a vehicle until needed this is not a major drawback and will probably aid accurate shooting and control. An idea of what such a weapon may look like may be gained from this image of a shortened 7.62mm FAL For Entry and CQB missions such a weapon is likely to be fitted with a Blast Suppressor. The final weapon may resemble the STG 44 in dimensions and weight.
Update This company has developed the .458 SOCOM round using a case with the same rim diameter as the 7.62x51mm (but not the same case). Interestingly the round feeds through normal M16 magazines.