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That's what I meant - since each of the parts would need to be designed from scratch I don't know what the sizes of those custom parts would be (or specifically which parts need to be altered in relation to the caliber, as opposed to in relation to the difference in shape/size of the gun itself). I've been trying to find that information but haven't had much luck.

You won't find that information, because you need to figure that out yourself. Nobody has built a functional bolter yet Do you want to make a Bolter for space marines or for humans?
Bolters do not just come in .75 cal size. Forgeworld for example has a .6 cal Bolter in one of the pre heresy books, and i find it only makes sense if you look at this artwork for SOB for example.
http://static.comicvine.com/uploads/original/12/123441/2652728-sisters_of_battle_gear_3rd.jpg
I really like this artwork, because the bolter looks like it can work without too much suspension of disbelief. It's obvious that those bullets in the mag can't be .75cal. A smaller caliber allows you to carry more ammo, and for humans its easier to handle. Also remember, the magazine should have 20 to 30 rounds in it - so you are limited in caliber by the form factor. .75cal for a bolter for human sized hands won't allow you to put 30 rounds in it, at least not without a very long and thick magazine (which wouldn't match the Artwork) All that for a gun that is essentially with the form factor of a submachinegun / a pretty short assault rifle. Truth be told, it looks more like conventional ammo in the artwork...
Smaller (standard)caliber for humans also explains why astartes bolters are supposedly stronger.

If we are talking about a real weapon with present day propellants and explosives though... i don't think it makes much sense. It makes more sense to have a unpropelled projectile with more explosive. Because the more propellant you put into the projectile the less explosive it can take. The more propellant you put into the bolt however, the less initial charge you need, reducing recoil, which you need for automatic/semi-automatic firing. First you need to mock up the gun to figure out how large the projectile would be/could be, how long the barrel approximately is, how much it weighs approx. Then you need to figure out how much recoil would be acceptable, then come up with a good ratio for powder to rocketpropellant to explosive to "dead" projectile mass. Then you design the real ammo, then the real rifle. And calculate again what you have and readjust again. It's an iterative process and if you are not into real engineering... don't waste your time. It's not as easy as putting some rough measures together.

Here is my current state for a human held bolter after the SOB Godwyn Deaz Style in .6cal. The left side is a mag with 30 rounds and the right how a 20round mag would approximately be - closer to the artwork (though it would be slightly longer because it needs a strong spring). Bullet/Shell sizes based not based on any calculation whatsoever.

You could totally fit 30 rounds in a bolter magazine. .75 cal is not that big. It would be fairly large as far as weapon mags go, but its well'within possibility.

How do Orks work? They're essentially Fungi... Why do they need blood?

If the casing was the same width as the projectile, that means 22.5 inches of bullets.

 Co'tor Shas wrote:
If the casing was the same width as the projectile, that means 22.5 inches of bullets.

Except they're not all in a line. Real magazines have the bullets side by side not stacked in a line.

You'll really have three rows of ten bullets each off set, not one row of 30.

So a clip 3" X 8"? That's still pretty damn big.

Yeah, but its not absurdly huge. There are banana mags which are longer and drum mags which would be heavier.

Still big enough to beat someone to death with.
Although, I didn't know three in a row mags would work. I thought they could only do that with 2 in s row.

Its completely doable. Its just mostly been unnecessary with our smaller calibers.

Hey, you learn something new every day!

3 in a row mags would be more prone to jamming, but the larger bullets would make it easier to fix the jam, and its consistent with the fluff.

 Grey Templar wrote:
You could totally fit 30 rounds in a bolter magazine. .75 cal is not that big. It would be fairly large as far as weapon mags go, but its well'within possibility.

-.-" of course you can fit ammo with .75cal projectile into a 30 round mag, its just too large to a) handle b) carry alot of them c) fit the artwork for humans! It's not like i haven't tried, but .75 cal for a human bolter with 30 round mag is too big (therefore heavy) to be feasible as a weapon for non-Marine-sized Characters.

3 in a row mags would be more prone to jamming, but the larger bullets would make it easier to fix the jam, and its consistent with the fluff.

Then please make some scale images to prove that its feasible for the artwork we are dealing with...

 Keep wrote:

 Grey Templar wrote:
You could totally fit 30 rounds in a bolter magazine. .75 cal is not that big. It would be fairly large as far as weapon mags go, but its well'within possibility.

-.-" of course you can fit ammo with .75cal projectile into a 30 round mag, its just too large to a) handle b) carry alot of them c) fit the artwork for humans! It's not like i haven't tried, but .75 cal for a human bolter with 30 round mag is too big (therefore heavy) to be feasible as a weapon for non-Marine-sized Men.

I think you are seriously overestimating the size of .75 cal rounds.

i'm not estimating! i'm modelling it in 3D and CAD if you haven't noticed...

How large are your rounds then? BTW: CAD is still just estimating, its just putting a visual onto the estimation.

Well, TBF, I have a .50 round, and the casing it'self is probebly around .75-1.0 inches. If you scaled that up it would make the rounds be 1.125-2 inches thick. That could mean a 6"/10" mag.

Its probably a .50 cal armor piercing round with the casing being much wider than the bullet, right? Bolters would have normal casings roughly the same width as the bullet.

 Grey Templar wrote:
How large are your rounds then? BTW: CAD is still just estimating, its just putting a visual onto the estimation.

I'm an engineer, you dont need to explain to me what CAD is or isn't. Entering exact measurements isn't estimating...
The round i have in that image is 15.25mm in caliber and 71mm long (base to tip). The projectile itself is 51.4mm long.
The reason why the casing is not thicker is so that more bullets fit into the magazine... if the casing would be much thicker (like for regular small arms bullets), even fewer rounds would fit into the magazine.

The 30rd magazine would be 282mm heigth, 36mm width, 157mm length... thats very large. The 20rd mag would be 200mm in heigth

I'll admit I'm not an engineer, but I'd certainly be willing to learn or perhaps if I could find someone with that kind of experience to work with me and try to make it happen that would be a super cool project to undertake in my opinion.

What type of weapon is the Emperor's sword, anyway? Some depictions seem to indicate it's similar to a Loi-pattern power weapon, while 6E's Codex: Space Marines has a picture that makes it look like a force weapon.

Some comparison images and other data about large-calibre rounds:




.75 cal rounds are not at all outside the realm of feasibility. The magazines to bolt-weapons *are* big and chunky, and hold 24 rounds (boltgun) or 8 rounds (boltpistol), which is within the depictions of the artwork.

Plasma weapons work in a feasible way.
A pellet heavy with fusion reactants is launched and has intense heat imparted onto it by a sort of action mechanism right before leaving the barrel causing it to almost immediately turn into a dense ball of incredibly hot gas.

 ThePrimordial wrote:
Plasma weapons work in a feasible way.
A pellet heavy with fusion reactants is launched and has intense heat imparted onto it by a sort of action mechanism right before leaving the barrel causing it to almost immediately turn into a dense ball of incredibly hot gas.

Yup, such a weapon is theoretically possible if you manage to build a containment system for it that is also small enough to be practical as a weapon. Plasma can also be manipulated using magnetic fields, so a projected magnetic tunnel could deliver a "bolt" of plasma to a target(instead of it immediately dissipating if it had no containment, likely injuring the wielder and/or making it more akin to a flame thrower)

 RaptorusRex wrote:
What type of weapon is the Emperor's sword, anyway? Some depictions seem to indicate it's similar to a Loi-pattern power weapon, while 6E's Codex: Space Marines has a picture that makes it look like a force weapon.

Well, assuming its the actual Burning Blade, imIIRC it was forged by the Emperor himself and probably imbued with his own power. So a magic sword.

It's a SPACE magic sword.

 RaptorusRex wrote:
What type of weapon is the Emperor's sword, anyway? Some depictions seem to indicate it's similar to a Loi-pattern power weapon, while 6E's Codex: Space Marines has a picture that makes it look like a force weapon.

Definitely a force weapon. No way the most powerful psyker in history doesn't have a force weapon.

Plus I've seen artwork where it's covered in flames/lightning, stuff power swords don't do.

So, what exactly are the differences between the Godwyn pattern and similar-looking weapons, like the Baal or the Ultima patterns?

 RaptorusRex wrote:
So, what exactly are the differences between the Godwyn pattern and similar-looking weapons, like the Baal or the Ultima patterns?

Likely just cosmetics or minor changes to suit the individual chapter, like making it lighter to hold in one hand or something. The only pattern that seems significantly different is the Hesh pattern, which is shorter, almost the same size as a bolt pistol but with the power and range of a Bolter.

 RaptorusRex wrote:
So, what exactly are the differences between the Godwyn pattern and similar-looking weapons, like the Baal or the Ultima patterns?

Aside from cosmetics, there are likely smaller subsystems in each bolter that are different.

We know bolters contain targeting, stabilization, ammo counter, and multiple other misc systems. Different bolter patterns will have different systems integrated into them.

There is no functional difference on the table top, but in the RPG and fluff there will be differences in the bolter patterns.

So, what exactly are the differences between the Godwyn pattern and similar-looking weapons, like the Baal or the Ultima patterns?

Imo the they should look different as well... because what they did in the codices is just pointless. Putting a different name on an gun that just has a different color.
I think the ones responsible just didnt have any guts whatsoever to try and change the artwork/design.

The only pattern that seems significantly different

Look at forgeworlds bolter patterns. They did a vastly better job there then GW - not a surprise.