Hello:
I have a turned aluminum barrel for a 1/35 35.5 cm Haubitze M1 German Howitzer. The problem is that the barrel has no rifling. I went to all the lathe workshops in my town and all of them said that can´t do it.
Can someone give advise how can I make the rifling without turned it? (I also search for a photoetched piece, but nothing).
Your feedback will be very appreciate.
Best regards.
If no PE exists not all is lost. Stick a piece of paper in the barrel and trim it until the edges meet - making a liner for the barrel. That’s your template. Remove it, and cut an identically sized piece of brass shim - available at Hobby Lobby. Cut with kitchen shears - it cuts easily. Remember which edges are the front and back edges. Scribe slightly canted, parallel lines down it’s length. The angle isn’t as important as uniformity. Use the back edge of an old no. 11 X-Acto blade for best results.
Maybe ask a gun smith to do it? It is a 10mm barrel…
Armor Research did a PE rifling kit. They have been out of business for many years. But someone bought all of their remaining stock and has been selling it at the IPMS/USA Nationals. I had a couple in the stash and bought 5 more at the last Nats. These work really well and are the only solution that I know of.
How deep would this rifling be? Chances are that in 1:35 scale it would only be 0.1 mm deep or so, in which case machining it into the barrel would probably make it overly deep (and probably wide, too). Scribing it into a piece of brass, as recommended above, is more likely to give you a scale depth, IMHO.
But then the question is: would you even see rifling at scale depth?
Well, that’s certainly a thought, but most gun smith aren’t even set up for something like that. It’s an expensive set up, and would take an inordinate amount of time. Most “hand made” guns are built from barrel blanks, which are pre-grooved to precise standards.
How physically realistic you need this? You can paint imitation in a non-metalic metal style.
As a real world example the rules of thumb for artillery design are:
Number of grooves = 8x Bore diameter (inches), rounded up to an integer value.
The ratio of groove width to land width is 3:2, that is, the groves are wider than the lands.
Groove depth = 0.01 x Bore diameter; deeper for small bores and shallower for large bores.
So, a 355mm bore is 14 inches, hence 112 grooves would be plausible with a depth of 0.14 inches.
If you go with a scribed strip in the 1/35 bore it will be 0.400 inches long with a 0.0035 inch (the diameter of a human hair) spacing and 0.004 deep grooves. Together, that’s going to be virtually unrecognizable on a model. As long as your model bore isn’t mirror smooth, I think it will pass it you don’t do anything beyond painting the basic bore.
However, an older gun may have used much different parameters. I would look for 12-, 14-, 15-, and 16-inch naval gun information. If those numbers are similar, I would look at playing with a piece of metal tubing with a similar bore to see what you can do and what you want to do.
EDIT:
British 14-inch naval guns had 72 lands and grooves, US 14-inch coast artillery guns had 136 lands and grooves.
KL
No. That will give you 1/1 10mm rifling (normally 6 grooves), not 1/35 355mm rifling with at least ten times more grooves.
KL
Barrel wear on guns of this sort was enormous. The 28 cm gun started out with with grooves at a depth of 10 mm, but was eventually reduced to 7 mm. And we’re talking about a much larger gun with much heavier projectiles. It would seem likely it’s not going to be in the 3 mm range for a 35.5 cm barrel.
Also, the 21 and 28 cm guns had 64 lands and grooves, as a reference.
Either way, having visited several big guns in the past few years, they are indeed visible at scale.
Humm… Maybe take a stiff metal bore brush and pull it through, scratching the aluminum barrel with parallel lines. Maybe twist the brush as you pull it through for twisted scratches. Probably only one pass should be needed.
That may be because your math ain’t mathin’.
You wrote .0035 spacing in 1/35 scale - so what’s the spacing it 1:1 scale? .0035 x 35?
I get .1225. So the real world spacing of .1225 inches sounds just a tad off to me. If it were indeed the case, yeah, that might be a little tough to see. But it isn’t.
Let’s get the circumference of the tube: 35.5 cm x pi. I’m just going to say a bit over 111.5 cm. We’ll use your 112 grooves. I don’t know where you got that, but let’s assume you’re correct.
That hardly even needs a calculator - almost exactly one whole centimeter between grooves. That sounds like a much more plausible figure.
One centimeter? 
Yeah, about the width of my pinky. I can definitely see the width of a pinky on a 1/35 scale figure.
Since German 14 naval guns had 88 lands and grooves, I’d be more inclined to go with that figure, or something close to it. It sounds reasonable - the Missouri’s sixteen inch guns only had 96 lands and grooves, and they’re quite visible.
FWIW, British 14-inch naval guns had a 3mm +/- groove depth depending on the model.
KL
I recognize that gun tube , it’s the one on display in the USS NJ parking lot.
My numbers were from the Army Materiel Command Engineering Design Handbook on Gun Tubes.
But as I said, that’s just a rule of thumb (RoT). Absent the actual data on the M1, I mentioned it as a reasonable value for making something on a model. The Handbook also has this graph derived from historical data, no doubt American practice.
One can see in that in bores larger than 8 inches (~200mm) actual practice increasingly falls below the RoT value. That being said, the US M1920 series of US 14-inch guns went well above the RoT line with 136 grooves. Note also that deepest grooves shown by precedent are only 0.16 inches deep (~4mm), far shallower than the 7-10mm mentioned earlier. There are practical limits to how deep the grooves can be; 7-10mm sounds like something used with pre-engraved projectiles. I doubt the M1 is a “hypervelocity weapon” like in the EDH text.
FWIW #1, there’s also this useful table:
Could be. It’s almost five years since I’ve done any real engineering. Skills fade.
For example, calculating a circumference requires pi in there somewhere, and clearly I didn’t include it. So, 355mm x pi = 1115mm, at 1/35 scale it’s 31.86mm or 1.25 inches, not 0.400 inches. So, taking 112 grooves from the RoT we get a rifling pitch of 1115/112 = 9.96mm, or let’s say 10mm (*). Following the other RoT about the groove:land width ratio = 3:2, we’d have grooves 6mm wide and lands 4mm, or in 1/35, 0.17mm/ 0.007 inch grooves and 0.11mm/ 0.004 inch grooves. Remember though, this isn’t “correct” for an M1, it’s just a plausible number for a real weapon of that size.
(*) The pitch isn’t the “distance between grooves”, it’s the distance from one point on the profile to the same point on the adjacent profile. The distance between grooves in the example is only 4mm.
FWIW #2, Surprisingly, Naval Nuclear plants use scribe lines for many things. Their practices held that the smallest discernible line scribed in metal was 0.010 wide.
I was going to say that since the OP wrote that he turned an aluminum barrel he apparently has a lathe. In that case he should put the barrel back in his chuck or collet; mount a 96T change gear on the back end to use as an indexer; grind up a small scribing bit; cut his own grooves. He could even include twist if he sets things up right.
KL
Wow. All that effort to show that the method, with a photo no less. won’t work. Brilliant.
Like I said in another thread recently, the effort some of you guys put in. you should all have PhD in something. Not sure what.
Wow. All that effort to show that the method, with a photo no less. won’t work. Brilliant.
Like I said in another thread recently, the effort some of you guys put in. you should all have PhD in something. Not sure what.
Have you heard of something called Mechanical Engineering?
We all enjoy the hobby in our own way. Some of us enjoy spending part of our time showing why things are the way they are. We also hate seeing people waste their precious hobby time going down a blind alley so we try to point them in directions that might turn out better, if they want to pursue them.
Other folks get enjoyment from mocking the people who don’t do the hobby as they do.
“It takes all kinds”, they say.
KL
Ithink your only chance is to use a old reamer more time like an internal knurling
Although there may not be a quick or easy way to simulate rifling, there is this; you will need some paper thin brass (K&S brass have a selection), or aluminum - not too thin or it will just tear. Measure the circumference of the inside of the barrel - that’s how long the metal strip should be; width doesn’t have to be more than 1" - 1 1/2". Scribe a series of angled parallel grooves - if you’re totally anal you’ll have to count them and correctly space them. Cut the metal strip and neatly curl it - since the brass is naturally springy it should conform to the inside curvature of the gun barrel. Glue in place with CA, seal around the outer end, and when cured, sand the end smooth.
