5.7 ammunition differences - URGENT -

[Ed Johnson 0]

This subject of different versions of 5.7mm ammunition is not a new subject, but recent marketing publicity suggests that I make a point of clarifying some things once again.

Several years ago, FN in Europe came out with a fairly expensive semi-auto pistol that was chambered in a new caliber, 5.7 mm by 28 mm. The round was reportedly developed circa the 1980's into the early 1990's and the military purpose was to develop a semi-auto hi-velocity handgun that fired high-velocity bullets that could penetrate conventional soft body armor.

As we know, my dad and John "Jack" Fitzgerald developed the M1-Carbine based system around our new cartridge, the MMJ 5.7 mm (.2235-..224) Spitfire, using M1 Carbine Brass necked down to a 5.7 mm 40 grain bullet with a total cartridge length of 1.65" (the same as .30 M1 Carbine). This produced the MV of 2800 - to 3000 fps from an 18" barrel, with an estimated energy of 720 Foot pounds capable of penetrating 1/4" steel plate. All of this took place during the early 1960's, well prior to the FN activity which came later.

Several years ago, I fired a friend's FN pistol and liked the low recoil. I did note that the FN round was noticeably shorter than our 5.7 Spitfire round. In my notes to new members of our 5.7 Spitfire Club, I have been making a point of advising that the two rounds are NOT the same.

Now, this month, both the AMERICAN RIFLEMAN and FIREARMS NEWS (formally Shotgun News) have feature articles on the new Ruger compact 5.7 mm x 28mm Carbine with 16" barrel, also featuring the FN various sources and models of the 5.7mm x 28mm ammunition. Bullet weights range from 40 grains down to 27 grains. The MV performance with commercial 40 grain is listed circa 2100 fps and with 27 grain 2900 fps. I would suggest reading both articles if you have a chance. Ruger is also continuing to make their 5.7mm x28mm pistol.

Note that both the Ruger 5.7mm x 28mm pistol and carbine use a modified blow-back system for this cartridge. A blow-back system would not work effectively for our 5.7 mm Johnson, which has a pressure range of 36,000 to 40,000 p.s.i......hence the need for gas assisted unlocking.

Also....please keep your eyes open for other shooters who might confuse the 2 calibers and try to use the wrong ones. Contact me if you have any questions.  ej