A very productive session today with a lot of pics to go with it so I'll just dive right in.
Step 10 begins the work on the main gun and is actually organized in three sub-steps to complete the full step. The first sub-step assembles the breech end of the gun along with the recoil guards. This assembly goes together fairly easily although you do have to give some thought as to the order of things. I started with the front halves E3/E2 and slowly worked my way backwards. The two part breech has a solid fit but there is a slight seam that results that has to be carefully sanded to create the unified block look.
The next sub-assembly deals with the external portion of the gun and the mantlet. The instructions would have you glue the barrel into the mantlet at this point but this could cause problems if you aren't careful since the base of the barrel has a D-shaped tab that is supposed to fit into the neck of the breech half of the gun and you don't join these together until Step 14 when it's time to install the gun and mantlet into the casemate, so I left them separate for now as a precaution.
The third sub-assembly is the creation of the gunner's side of the gun mount. This adds 7 parts to the gun mount and then the step is completed by joining the two halves of the mount together. If you follow the instructions and don't apply any glue to the trunnion pins, the gun will remain able to elevate and has enough friction in the fit to hold its position without glue. I also added parts E18 and E19 to complete the base at this point even though those aren't show as installed until Step 14, it makes sense to add them now in preparation for painting. Step 10 also calls for the assembly of the holder for the two "C" towing hooks but I put that off until later since they aren't actually installed for some time in the instructions.
Step 11 deals with the inserts for the interior sides of the casemate structure and the first order of business is to modify them to conform to the StuG IV vs. the StuG III G hull. This requires that the lower portion be removed, I did this using sprue cutters and then trimmed/sanded the area smooth as needed. In the pic below you can see one modified and one still in its original state to get an idea of how much needs to be removed.
Once that's taken care of, the radio gear that goes in the side sponsons is assembled and added. To save on plastic, DML designed these as multi-part assemblies that are hollow on the inside and the faces of the radios have some very nice raised detail as a result. Since I will only be displaying the loader's hatches open, I drilled out holes with a #72 finger drill in that side's radios for a little wiring to be added later on. This step also calls for the construction of the spare wheel box and installation of the wheels but I will leave that for later after I get the casemate installed and prior to paint.
Step 12 is a big step, it deals with the casemate itself and since I'm adding the zim, required a lot of attention in that department as well. I started by removing the two bolts on either side that aren't indicated until Step 15 that need to be removed to allow the schurzen rails to mount properly. It's much easier removing them now vs. with the casemate installed as directed in the instructions. I then added the zim panels starting with the commander's side and working my way around, again using the same combo of Gator Grip glue and liquid glue as needed. The zim panels did not include cut outs for the lifting eyes on the casemate sides so those had to be glued directly to the panel using CA gel. I used Squadron white putty to fill the gaps between the panels where needed.
The radio inserts were also added and the driver's hood assembled and installed as directed. The zim panel for the left side needed to have a cut-out created to take the lifting eye on that side, easily done with a #11 blade. I also removed the small molded on pistol port to allow the panel to fit properly and replaced the right side bolted-on armor plate with the resin piece provided in the Atak set. I also had to do some hunting for the small triangular pieces that install into the gun opening. The instructions label these as parts K39/40 but no such parts are present on the K sprue. They are in fact on the G sprue and are parts G23/24. I also opted for the PE version of the C-hook holder and installed that in front of the casemate vs. on the right side fender...this piece of gear moved around on different vehicles so the choice is up to you on where to place it although that choice isn't indicated until Step 14.
For the panel on the left side of the casemate, a little bit more work was needed. Since this side receives the 2 3-link spare track holders, I had to create cut-outs for the bases of those holders in the panel. This required some very careful cutting and measuring to get it just right since the cuts had to go almost to the base of the panel but not quite.
Last but not least, I added the rear panel. It's important to install this first before adding the exhaust fan cover or the antenna mounts due to the size of the cutouts provided. The Atak set does include a small circular piece just for the armored cover so it too was zimmed and then installed with CA gel to the panel. I cut off the small antenna stubs molded into the antenna bases and drilled out mount holes with a #72 finger drill to allow for installation of RB Models 2m brass antennas later on to complete the step.
On a side note, this step also presents the option of installing an angled rain guard, part K5, but this isn't an accurate feature for the time-frame that the other features of the kit represents so I left it off. This, along with other parts marked as not for use, are appropriate for a later StuG IV so the hint is there that DML will likely issue a "mid" or "late" production variant some time in the future.
With that step out of the way, I could now paint and detail the interior in anticipation of installing all the different elements into the lower hull. I applied a coat of Testors Model Master enamel Panzer Interior Buff by airbrush to the gun and various interior portions of the fighting compartment that would be visible through the loader's hatch. I detailed the breech with non-buffing Metalizer Gunmetal, dry brushed some Steel, and used enamel Silver for the chromed breech block surfaces. I applied a wash of Raw Umber and then dry brushed more of the Panzer Interior Buff over that to create a weathered appearance.
I also added a spent shell basket courtesy of a spare part left over from a DML Pz III N build. After playing around with it, I can see why DML didn't include a shell catcher basket in this kit...the dimensions on the interior don't allow for one to be properly attached to the extended holder arms provided and still allow the gun to elevate properly...which is a big issue due to the way you have to install the gun in order for everything to fit properly...more on that in a little bit. I just wanted the basket there to occupy the blank space and the way I have it installed it would interfere with the gun recoil but is a compromise vs. not having anything present at all. As I mentioned, it's not possible to do this accurately so it's the best possible solution under the circumstances. I didn't bother with painting/detailing the gunner's side since after a test fit with the roof and the gun in place nothing from that side is visible anyhow.
For the rest of the interior, I painted the floor with my own custom mix of Red Oxide primer by hand and weathered it by dry brushing enamel Steel, stippling on more Red Oxide, then stippling some Raw Sienna for a slightly muddy/dirty appearance....even though most of it won't be seen once the roof is on, it's there if you look! I also detailed the radios and added some wiring in the form of 0.5mm diameter solder installed with CA gel and painted with Flat Black. One key detail that the kit doesn't provide that is very prominent/visible on the real vehicle is the MP40 mounted on the rear wall so I added that using a left-over gun out of the spares bin and rigged up a simple square bracket from a spare Eduard PE fret. The part was about twice the size I needed it to be so I cut it down and re-glued the necessary folding parts to reduce the size, then glued it to the wall with CA gel and voila! MP40 and holder. There should be a 2nd smaller holder for the barrel to achieve 100% accuracy but I couldn't really make that one work out after a couple of attempts so abandoned it in favor of just using the one.
Step 13 deals with the exterior components of the roof including the commander's cupola, so I skipped that for the moment and proceeded directly to Step 14. This is an incredibly tricky step as it installs the gun into the fighting compartment, installs the casemate to the hull, and installs the exterior gun barrel and mantlet to the gun...and also adds the roof (which I haven't finished yet). What makes this tricky is that there's a very specific order that you have to do all these things in or it will not work properly...and there's only ONE way it will all work...so I studied this very carefully and did lots of dry-fitting before committing to glue. So, here goes...this is the order you have to do it in:
1) You must install the mantle to the breech portion of the gun
2) You must then elevate the gun to it's highest possible elevation which in turn depresses the recoil guard at the base to it's lowest point
3) You must then slip the elevated gun, from the bottom, up over the bottom lip of the opening in the casemate. This is a tough thing to do and you have to be patient because the tolerances around the mantlet are tight but if you carefully work at it, you can get it all to fit. Don't force it though and make absolutely sure the mantlet glue has set up properly to avoid an accidental separation of the mantlet from the breech.
4) You must then place the casemate and the gun together onto the lower hull, which means you have to simultaneously glue the base of the gun into the mount plate and glue the casemate to its mount points on the fender. Test the gun elevation carefully as pressure on the mantlet front end can cause the base to lift up from the mount plate which can cause major problems if it comes all the way undone.
5) After you have this all glued in place, you then add part C12 to the top of the casemate gun opening and that essentially secures the gun in place permanently.
If you pull all that off successfully, you get a very nice solid installation of the gun and casemate sans the roof. I did encounter one small fit problem with the front where the extension plate meets the glacis and I'm not sure if this is the result of the replacement using the Atak plate or not, but the gap that resulted was substantial enough that I had to use some styrene rod to fill it vs. putty. I placed a length of rod, applied liquid glue, and used a squared off toothpick end to gently prod and push it down into the gap and resolve the issue.
Last but not least, I did have a small issue with the front mud flaps wanting to flare out at a slight angle so I used some CA gel to glue the bottom corners securely to the hull side just over the final drive housings to solve that little irritation.
I told you it was a productive day! Next up will be the completion of the roof and cupola, installation of some of the details on the fenders and other miscellaneous items and then it will be time for paint!