I need some help regarding the correct length of the barrel of the M107 gun.
I am trying to figure out the length of this part so as to turn a metal barrel for the Italeri kit on the lathe.
According to my estimates it should be 192 mm long in 1/35 scale. Can anyone help?
Looking it up online, the barrel length is 60 calibers, or 60 times the diameter. So 60 x 175mm is 10,500mm, or 10.5 m. That measurement is from the end of the chamber to the muzzle. (unless one of our Redlegs folks on here could correct that information for any mistake I may have made on caliber to bore definition) But you’d need a scale plan drawing of the full gun to measure that section of the barrel.
This does you little good, and someone will undoubtedly have the right answer for you before I find it, but I took measurements of the barrel and all of the segments all the way back to the breech on one of my many visits to Korea. I simply have to find them. The real problem was with the “cradle” assembly which was way off, and actually closer to correct if you turned it around, at least with the Italeri kit. For that rerason I wouldn’t suggest going off the kit barrel’s dimensions either. (which I have) I’ll see if I can dig up the measurements. I’ve got so many notebooks tucked away…
the barrel length is 32 feet long at 19,000 lb.
My math from online sources puts it at 34.44 feet.
The kit barrel (not that I advocate using a model as a reference) is 32.8125 scale feet from the front of the breech piece.
Thank you everyone for the feedback.
The whole ordeal started because I figured that the Italeri kit barrel is not the correct length.
I have this diagram with dimensions
from this TM
The Italeri kit barrel once assembled is 300mm which equals to 10.5m in reality, which is the supposed length in calibers too as Stikpusher indicated. If we remove the rear part of the barrel that cannot be turned to a lathe, which is 108mm in 1/35 scale the remaining length is 192mm. That is where I got that number in my first post.
My issue with that is that the barrel might be longer than that, since the caliber is measured from the muzzle, which is not a clear position on the model barrel. At least that is what I am thinking, I would be happy to be proven wrong and continue with the above measurements.
And here is the first attempt, a lathe copy of the kit barrel:
One thing to consider is whether the recoiling parts were the same for both weapons. It was long thought (but never checked, apparently) that the 155mm gun and 8-inch howitzer were identical except for the portion beyond the forward barrel band. AFV Club made their kits on this basis. In reality, the 155mm gun was different from breech to muzzle, being far more slender than the howitzer. (AFV Club has fixed this in their recent releases of these weapons.) Italeri may have done something similar on their kits.
Fair point. I had been trying to find out the differences are between each gun and here are some assumptions.
First of all, I do not own an AFV Club kit (I am not interested in spending 80 euros at the moment for a M110 kit, maybe in the future if I decide to do an Israeli vehicle).
Italeri kits of the M107, M110, M110A1 and M110A2 have only one change amongst them, parts 96/97 which are the front part of the barrel halves.
From my understanding of the available manuals and publications the cradle remains the same and the barrel and breech change. I will try to use the AFV Club instructions to demonstrate my assumption:
This is the lower/static part of the gun cradle:
This remains the same on all variants.
The sliding part of the cradle is what changes. This consists of a sliding plate and three retaining rings. AFV Club have molded the plate as a separate part (D3) and the retaining rings as part of the gun barrel (D2 and D1 halves). My assumption is that the three retaining rings definitely have to change in order to conform to the larger diameter of the 8 inch guns of the M110 series.
Another thing I cannot figure out is the breech mechanism details and whether they change. Judging by the photos parts E35 and E2 should be the same, whilst the other parts should have a different bore diameter (175mm for the M107, 8 inches for the M110). So parts E32, F48,F49, E3 are different.
This is what I think I have figured out thus far, as always I would be happy to be proven wrong. Any help is appreciated.
Been a very long time ago, but I think the breeches are similar. The chamber is huge on the 175 gun, where as the 8" chamber might be about two feet in length. The barrel is generally brought out in a very long box, and the breech is attached. Who actually attached the breech; I don’t know. On 155’s they do this in the rear depots. The actual barrel diameters back near the breech are the same on both types, and everything is pretty much the same except for the recoil system or the recuperator (one or the other). I’ve shot both guns, and I’d say they are the same (breech system).
Being as you want to make your own barrel, I’ve seen three slightly different 175 gun profiles. The one used by the IDF differs the most. Yet the barrel slides will be the same no matter which. The recoil cylinder looks the same, but also may differ internally. I never did the caliber change over like some folks, but have been told more than one the recuporators are unique to each barrel.
This is some very useful information.
If the breech is the same (I just realized that the breech does not have to be the same as the barrel diameter, it can be bigger) and its length is not counted in for the barrel length I need to add some length to my barrel, about 2 scale feet or 17,4 mm.
I noticed the differences in the profiles, for examle the IDF guns have a much more noticeable flare att he muzzle. Could these differences be owed to production batch alterations/improvements?
There’s another problem, this time with the Italeri gun tube rear part: On the prototype, the three “rings” around the tube are fixed to it by small cutouts in the rings into which “strips” fit that are welded to rings and tube. These are at the rear sides of the rings, while Italeri molded them to the front, see the kit instructions above and compare Italeri’s to AFV Club’s. Adding insult to injury, Italeri also flattened the rings on their sides (because otherwise, they wouldn’t have passed through the top of the cradle?), see illustration from the instructions:
I “corrected” that on my M107 by puttying up the flat areas, turning the assembly around and transferring the breech ring locators to the new rear - ignoring that now the different length of the rings isn’t quite correct, but I find that less obvious than the cutouts in the wrong places.
Sorry if this means even more work - but after all, it’s your model, you can ignore all this.
Reviews by the “experts”: never seem to catch that fact.
That’s the biggest reason I measured those rings in the first place. My intent was to make one really good master and then cast as many as needed, but then I saw something else shiny…
To start with the breech housing is roughly 18" long (give or take an inch or two). Honestly two feet in length seems excessive. The breech on the 175 gun is very over built, but still had issues. Never saw one fail, but they did! The 175 gun was rather dangerous to shoot, but they also never told young kids about this.
Barrels; oh my! The first thing I noticed about the IDF barrels was the change in taper forward of the six or seven foot mark. Never really noticed the flared muzzle. 175 barrels were well known for catastrophic failures (like a banana peel), and the normal barrel life for the barrel was 80 shots of zone three powder charges. The never x-rayed the barrel, but simply changed it! This is why we see the IDF changing the barrel profile (I think). They were also prone to shooting the breech backwards a hundred feet or so. None of these issues existed with the eight inch howitzer. They were fun to shoot if you were still in the learning curve. Keep in mind I only shot them at Ft. Sill, and never saw combat on one (long story). The real solution was to shorten the barrel to about 15 feet, and shorten the chamber a foot or so with a smaller powder charge. You’d loose about three miles of range with a major increase in accuracy and barrel life
One thing the Italeri guys really missed on was the hydraulic tubing that runs along the sides of the trunion. They are stainless steel with Swedgelock fittings. Paint won’t stay on them very well, and also due to expansion and contraction. They have some seriously high pressures inside the (19,000 lb. per square inch)
More really useful information. Many thanks.
I found this presentation about barrel life
And this photo, that shows a barrel change and what I guess to be an 8 inch barrel replacing the 175mm one
I think that my best option to figure out the barrel length is to build the hull and use the measurements of the transportability guidance to approximate the total length of the barrel with the breech.
interesting! Every barrel I saw was changed with with two ten ton wreckers. They’d have them facing each other and about six feet apart. Once the barrel is free; they simply drove out from under it. Takes about three hours after you’ve done it a few times.
Ideally, you want to change the barrel in the rear areas. Getting two cranes together can be a problem. The next issue is shooting five or six rounds thru the new barrel!!! They use a very long lanyard, and everybody gets as far from the gun as they can. Those first few shots are known to be dangerous. That’s usually when the breech flies off the barrel, but have heard of the barrels splitting wide open. We always heard they dumped the old barrels in the ocean.
I checked the 1972 parts manual and it explicitly states that the 8-inch and 175mm breech ring assemblies (including the breech block) were identical.