None of the classic style Hi Powers has cast frames. None of the Mk II 9mm’s has cast frames. Early 9mm Mk III pistols didn’t have them either. All had forged frames. With the advent of the .40 Hi Power, FN went to cast frames and a different heat treatment that resulted in “harder” frames. This kept the slide rails from warping or breaking after as few as 2500 shots. I have never seen a 40-caliber Hi Power that didn’t have a cast frame. Current Hi Powers, be they 9mm or .40, have cast frames.
Here’s the easiest way to tell.
Look at the bottom of the pistol frame at the magazine well. If the surface appears smooth (left), the frame is probably forged. (Some early cast frames did not have the ripples. This IS apparently the case with an “NX” (’93) Mk III I have seen pictures of It does not have the grooves shown above.) If it has the longitudinal grooves or “ripples” (right), it is cast. Note also how much thinner the outer front edges of the frame around the magazine well are on the forged frame Hi Power on the left.
Here you can see the casting mark. I have read that it might be used to indicate the mould used for the casting or provide a method of determining when the frame, itself, was actually made. This information below was copied and pasted from an old Hi Power site no longer in existence. I tend to believe it. (Thanks to Mr. Robert T. Romanelli for permission to use this photograph.)
“This information was recently emailed to me, and I am very grateful for the time it took in assembling it and passing it on to all of us. Many, many thanks. The information posted herein does not originate with me. It has been collected from various magazine articles as well as from conversations with several gunsmiths.
When Browning started to develop the .40 S&W version of the Hi-Power in the middle 1990s, they quickly discovered that significant changes had to be made on that version in order to stand up to the beating of the .40 S&W cartridge. These included a thicker (stronger and heavier) slide, additional slide/barrel locking lug, and other items. Also, the strength of some of the materials was improved. The improved steels are now used on both the 9mm and .40 guns. Thus, any .40 Hi-Power should have the stronger steels, and the newer 9mm guns will also have them. Specifically, the receiver (frame) was changed from forged to cast steel. Although we tend to think of forged parts as being stronger, machining of the part becomes difficult when really strong steel is used. Practically speaking, cast parts are sometimes stronger than forged ones because really good steel can be used in the casting, with only minor machining required. The cast receivers have the minor disadvantage, sometimes found in cast parts, of being slightly porous in certain areas. This is most common at the bottom of the grip frame, and I am told that the ridges now found around the magazine well opening exist to disguise any slight porosity blemishes in that area. These ridges are the quickest way of identifying a cast receiver, but are not foolproof. I have seen a few forged receivers with the ridges, apparently produced during the changeover period. Another clue that a receiver is cast is the existence of a casting-facility ID mark on the inside of the magazine well. I have seen an emblem on the inside-right of the magazine well near the top (requires removing the slide to see), or just below the magazine catch inside the well, in the relieved area (requires removing a grip panel to see). A cast receiver may have a slight texture inside the magazine well, instead of showing machining marks. Also, the thin spots at the front corners of the magazine well are not quite as thin on the cast receivers. The newer receivers look like they have a small piece missing from the right-rear slide rail, when compared to old receivers. I was told that on the .40 guns this piece would break off after a while, no matter how hard the receiver. But since it didn’t affect functioning, the factory simply machines it off during manufacture of all the receivers now! The slide on the Hi-Power got some minor dimensional changes in the early 1990s to improve durability (compare ejection port shapes). During a phone call to the FN factory in 1994, I was told that an improved heat-treatment of the slide was introduced during the summer or fall of 1993. The manufacture year of a slide made during the 1990s is indicated by a hexagon with a single digit inside, stamped on the center rail underneath the slide (where the top cartridge in the magazine rubs), near the rear. The hexagon is always missing at least one side- the number of missing sides indicates the quarter of the year that the slide was made. After the first quarter, the hexagon is stamped along the edge of the sear-lever cutout in the slide, to create more “missing” sides. Thus, a hexagon stamped in the fourth quarter may be pretty hard to find because most of it is over the edge of the sear-lever cutout, in order to give the effect of 4 “missing” sides on the hexagon.”
It is not on my “NV” (’95) or “NP” (‘98”) Mk III’s so I it does not appear to have been continued but I have no idea exactly how long it was in use.
I removed the magazine release to show this casting mark inside the frame on my cast frame 1995 Mk III. Whether it has anything to do with the date the frame was manufactured, I do not know.
Purists will opt for the forged frame every time…and in my view, there’s nothing wrong with that.
If my intention was to shoot thousands of hot-loaded 9mm rounds, I’d personally go with the cast frame. I do believe that they handle the warmish ammunition a little better in the long run. With standard pressure, it doesn’t make me any difference.
Best.