The M3 GMC was a stop-gap US tank destroyer mounting an M1897A4 75mm gun (the French “soixante-quinze
”) on a standard M3 halftrack with a simple box gun shield. DML released this interesting vehicle in plastic a few years ago as kit no. 6467. A review of said kit can be found here:
M3 75mm Gun Motor Carriage
The kit barrel, made up of 4 parts has been of some concern with a straight alignment being the major issue here. RB Models
of Poland come to the rescue with a turned aluminium barrel.
The kit is packaged in a simple plastic bag and contains a one piece replacement barrel and a small etched fret with 8 parts. Unfortunately, it contains no instructions and these would certainly be helpful here as it is not just a simple one piece replacement. It is however not a big problem with careful study of the parts. Hopefully the attached pictures will be of help as well.
The PE parts are the sledge to which the barrel is mounted for the recoil. They are rather simple to fold and two parts each make the four attachment points. Then you add the kit breach (DML part S18) and you are ready to go. Be sure to align the PE parts correctly and the fit to the kit parts will be no problem.
The replacement barrel has some discrepancies compared to the kit part. Generally, the DML part is slightly larger in diameter overall and slightly shorter. The sledge attachment points on the RB Model barrel are located slightly farther forward than on the DML parts. This is especially true for the one closest to the breach. Comparing to photos of the original vehicle I would tend to say the DML part is more accurate. Overall though, I consider these discrepancies minor and they won’t be noticed on the final model.
On the other hand, the RB Model barrel has nice rifling in the muzzle, and the muzzle is centered, unlike the DML part on my example where the muzzle is misaligned slightly but noticeably.
While this is certainly not just a simple replacement and involves a bit more work to build, it nevertheless attaches to the DML kit without any problems and solves a possible problem nicely. The possible inaccuracies mentioned will not be noticed on the final model and are, in my opinion, well within tolerances. Highly recommended!