In-Box Review
M21 81mm Mortar Motor Carriage
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by: Stefan Halter [ DANGEROO ]


I must admit that I wasn’t very enthusiastic about Dragon’s latest installment of the U.S. halftrack, the M21 MMC. The M21 was neither a very important version, nor was it produced in large numbers. But it is a logical step in two ways: for one it is the vehicle that logically follows the previously released M4 MMC. For the other it “replaces” the old Tamiya kit of the same vehicle, and with that all three Tamiya halftracks are now also produced by Dragon.

The M21 was developed as a follow up to the M4 / M4A1 81mm Mortar Motor Carriage. The M4 was conceived only as a carrier for the mortar and it was only to be fired from the vehicle in an emergency. The M4A1 rectified that problem but the mortar could only be fired out the back side. Combat experience showed that this was not very practical and the mortar should be able to fire out the front. The 2nd Armored Division solved this problem by modifying their M4s to fire out front. The Armored Forces Board had its own solution based on the M3 halftrack, the result being the M21. It was produced only in small numbers (110) from January to March 1944. 54 of these were provided to the Free French Army and the others stayed with the U.S. Army. Only few pictures exist of the M21 apart from those of the trials vehicle.

The M21 has a crew of 6. Its main armament consists of an M1 81mm mortar with 97 rounds. Secondary armament consists of a .50 cal. M2HB on pedestal mount with 400 rounds. It also carries mine racks along the sides (with 12 mines issued) and has provisions for a 2.36 inch rocket launcher (bazooka) and an M3 SMG.

The Model

The kit comes in the standard sturdy Dragon box with the smaller sprues, decal sheet and PE on a cardboard backing. There is usually more than one sprue packed into one bag, which in my example led to several parts breaking off the sprue. The model is built up in the way that can be expected, with Dragon drawing mostly on sprues already existing from the other halftrack kits. For more details on these I refer you to the reviews of the:
M2 halftrack

M3 halftrack

in detail

Instructions are the standard outline drawings and are as clear as they get.

Sprue A is by now well known from the original M2 release and all the others since and contains chassis, front suspension and engine parts.

Sprue B is also well known from the M2 and contains the front body parts with rivets instead of screws. The “rivet for screws”-issue was solved on some recent kits by providing correct fighting compartment armor panels and a new sprue (from the M3 75mm GMC) with the correct front body parts. This is not the case with this kit, and Dragon have unfortunately made a step back in this respect. The new fighting compartment panels have rivets as well. This is good for those who don’t bother, as both parts will be the same in this respect. It is bad news however for those who want to correct this issue as it means more work.

Sprue C, another M2 sprue, provides parts for the front bumper and the mine racks with 12 mines each molded in one piece. This would make 24 mines for the vehicle which is double what was issued but this problem can be solved with sprue J (see below). Of course it could have been possible that the crew scrounged together more than the issued number of mines. About half of the parts of sprue C are not needed for this kit.

Sprue D (x2; from the M2) provides the track assembly and bogies as well as the front wheels (NDNS tread on combat rim) with bulge. The wheels are the correct pattern for this late version of the halftrack. This is also true for the tracks which are well tensioned and don’t have any sag. Sag was only present on some early production vehicles but not apparent after the track tensioner was added on later production vehicles.

Sprue E is the standard clear sprue from the M2 with the front windows and headlights.

Sprue H is also well known from all the previous releases and includes the two versions of the front grill with open or closed armor.

There are two types of J sprues, which are provided twice each. The first one was present in all DML’s halftrack kits so far and contains the machine guns and tools. It is not clear to me why this is provided twice, as the only parts used are those for the M2 machine gun. The rest goes into the spares box. The other J sprue comes from the M3 halftrack kit and has a new side rack and separate mines. These are to be completed with two PE parts each. This leaves the modeler the choice to either use the rack with mines in one from the M2 or this one with separate mines.

Sprue K provides parts for a driver figure and is also well known from other kits.

Sprue R is the only new sprue for the M21. First of these parts to be used are those for the radio assembly. According to Hunnicutt, the M21 was equipped with either an SCR-509 or an SCR-510. According to my information this was basically the same radio, but the 509 was for manpack and the 510 for vehicular mounting. Dragon provides a detailed radio set made up of 4 parts plus the rack it sits on.

Next is the fighting compartment floor. While the basic details are correct here, the M21 had a distinct treadplate pattern which is not present on the kit part, the surface being smooth.
Gas tanks, seats and ammunition storage are added to the floor part. Unfortunately the racks and ammunition are molded in one piece and with full ammunition storage. This makes depicting the vehicle in action with some shells already spent quite difficult. The RHS ammunition storage also has a noticeable electrical box in its corner which is not present in the kit.
The lower floor is added to the floor next. This was the floor that had the mortar socket plate assembly attached to. This then protruded through the fighting compartment floor, leaving considerable gaps, especially in the front of the mount. Unfortunately Dragon mounts the mortar socket plate assembly directly to the fighting compartment floor leaving no gaps at all.

The back fighting compartment armor plate has the correct details with the door and mortar base plate added. To the sides of the doors are the storage racks, finely molded (so fine in fact, that one truss has broken in my example, probably also due to the packaging). Some may nevertheless wish to replace this with PE (for example this set by Voyager). It is unclear if this configuration was ever used in combat as some later photos of the trials vehicle show the racks removed and the mortar base plate strapped in place of the right side rack. Additional stowage was strapped to the other side.

To the side armor panels are added the mine racks and the rod storage racks (often identified as ladders, even by Dragon themselves on the box). Unlike with Tamiya’s ancient M3A2 kit, these are molded separately and care should be taken when removing them from the sprue.
Photos of the trials vehicle show several poles added to the upper rim of the fighting compartment. These were either not present on later vehicles or Dragon missed this item. Also, most pictures show the hood frames in either stowed or deployed mode. These are not provided by Dragon.

Sprue T is the 81mm mortar sprue from the M4 MMC and provides everything for the mortar including the base plate for use outside of the vehicle. Not on this sprue is the mortar tube which is provided as two separate turned aluminum parts, the same as in the M4 MMC. Detail on the mortar is great and hopefully Dragon will someday release this separately with an appropriate crew.

The PE fret is marked “M21” but doesn’t supply any parts that would be specific for the M21 (all the parts are also to be found on the PE fret for the M3/M3A1 halftrack). More than half of the fret is taken up by parts or the mines. The rest are the well known parts from previous halftracks such as front grill armor, back mud guards, direct vision slot armor and windshield wipers.

Also contained in the small bags on the carton backing are the well known idlers and drive sprockets for the track and a piece of chain and string each for the winch.

There are two decal sheets provided. The first one is well known by now and contains generic numbers and letters for the unit markings. This approach leaves a lot of options for the modeler and is a great approach. The second sheet contains mainly several different sizes of white stars with or without circle (even though the marking options only have stars without circles, another great touch from Dragon), as well as the individual markings for the two marking options in the kit:

Option one is from the 2nd U.S. Armored Division, Ardennes 1945. Its distinguishing feature is the large yellow 1-15 on the sides but there are no bumper codes (the MMC were allocated to the HQ & HQ Companies of the armored infantry battalions and tank battalions so it would probably be safe to have bumper markings accordingly).

The second option is for an unidentified unit, Western Front 1945 with the only distinguishing feature being the white number 93 on the front bumper. Most pictures in Hunnicutt’s book (see references below) are from this trials vehicle, identified as the M21 serial number 25 at the Engineering Standards Vehicle Laboratory (presumably in the U.S.) on 28 April 1944. Either this vehicle went to the western front unchanged marking-wise (which is highly unlikely) or Dragon has not done their homework on this one. Unfortunately no Free French Markings are provided even though they were issued half of the production run.


A quick comparison to the Tamiya M21 shows the Dragon kit to be several generations ahead in all respects, which of course is no surprise considering the Tamiya kit was released in 1976. Leaving out the obvious parts common to all Tamiya halftracks (for example the tracks), Tamiya’s rendition of the M21 has the correct treadplate pattern on the fighting compartment floor even though other details of the floor are not correct.

Tamiya attached the mortar in the same way that Dragon did (directly on the fighting compartment floor). Tamiya also has the ammunition molded directly into the racks, but not with a full compliment. And of course Tamiya has the correct screws on the outside and not the rivets. Tamiya has no storage racks (neither on the sides or the back) and mounts the mortar plate for firing outside of the vehicle on the right side of the back door. Tamiya offers lots of stowage and also includes the hood frames.


Dragon provides a basically fine kit of the M21 bit with several issues. Some are new, like the false mounting of the mortar and the missing treadplate pattern detail on the fighting compartment floor, others have been taken over from earlier halftrack kits, most noticeably the rivets-for-screws and some might also consider the bulged tires in this category. It is also too bad that the ammunition is molded in one piece with the racks, but this is something that we’ve seen on other halftrack kits before, so is no surprise. The misidentification of one of the marking options leaves some doubts as to whether Dragon have really done their homework on the research. On the other hand, the kit has some great details, in particular the mortar and the more or less generic decal sheets. With a little scratch work a highly detailed and accurate M21 will result.


- Half Track– A History of American Semi-tracked Vehicles, by R. P. Hunnicutt
- M3 infantry Half-Track 1940-73, by Steven J. Zaloga (Osprey Publishing, New Vanguard)
Highs: Generic markings, mortar detail, storage racks.
Lows: Floor detail, mortar mounting, rivets instead of screws, ammo racks and ammo molded in one piece.
Verdict: Recommended; with a little scratch work a highly detailed and accurate M21 will result.
Percentage Rating
  Scale: 1:35
  Mfg. ID: 6362
  Suggested Retail: 53 US$
  PUBLISHED: Jun 13, 2010
  NATIONALITY: United States

Our Thanks to Dragon USA!
This item was provided by them for the purpose of having it reviewed on this KitMaker Network site. If you would like your kit, book, or product reviewed, please contact us.

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About Stefan Halter (Dangeroo)

I'll build just about anything military related that gets my interest, though most of it is 1/35 scale WWII Allied.

Copyright ©2021 text by Stefan Halter [ DANGEROO ]. All rights reserved.


Wow! That must have been the fastest publication I've ever seen! Sent in and published the same day! Thanks and cheers! Stefan
JUN 13, 2010 - 07:52 PM
A very nice and detailed review, Stefan! I've been contemplating getting one of these and your review was very helpful. Thanks for sharing! Rob
JUN 14, 2010 - 06:38 AM
Thank you Rob, glad I could help. Cheers! Stefan
JUN 17, 2010 - 07:35 PM

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