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Sturgeon's House

Designing A Rifle From Scratch(ish)


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8 hours ago, Collimatrix said:

 

 

That's what I figured.

 

The hinge hole consists not only of the end plate that's welded on to the front of the magwell, but also of an extension of the receiver itself.  The hinge hole is twice as thick as any other point on the rifle's receiver.  If the hinge point is a specific weakpoint, then you might as well throw up your hands and say that the entire damn rifle is flimsy.

 

But I would expect the stock hinge, last round hold open, handguard, or the really dodgy welds at the back of the upper receiver to go first.

 

That was sarcasm lol

 

This picture of a Sterling illustrates it best:

 

AR180_2.jpg

 

Notice three spot welds holding the hinge point on. Not like spot welds are notorious for breaking under stress or anything.

 

This thing *is* just a reinforcement of the lower, but if it were to come off the gun would still be inoperable (probably) due to the hammer striking off-axis.

 

klh5Z14.jpg

 

AR-180 on right

 

You can also see how thin the sheet is, even doubled up. Not hard to imagine that it could get twisted, bent, or misaligned by an overzealous cleaning from Chongo the Marine. Yes, it's the thickest part of the rifle, but it's also the place where Chongo has the most leverage (using the upper receiver).

 

 

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Glued on a SCAR-H-compatible lower file I found online: 

 

czeMlQw.png

 

This informs me of a couple of things I need to do to make my upper work with whatever lower I end up designing. First, either I will need to pick a different takedown method (I was originally going to have it come apart like a SCAR), or make my front bulkhead longer. Of the two, I will probably make my front bulkhead longer but I definitely will investigate the former. Also, there will be an interesting problem to solve when it comes to fire control, as there may be some excess distance between the hammer and the bolt carrier. It also looks like further reducing the height of the feed tower on the magazine isn't a good idea, or at least it doesn't look like it right now (you can see how shallow the magazine well has to be already to accommodate the current magazine). All of this to me says that now is the time to take another look at all the components and then move beyond the layout stage to the initial assembly stage once all the parts are properly re-dimensioned and modified.

 

Also, I noticed a new design feature of the AK while looking at this: The bolt protrudes out of the back of the carrier to bring the striking face of the firing pin back far enough for the hammer, but when unlocked the rear of the bolt is flush with the carrier. This saves roughly a half inch of space, allowing for more overtravel for the same length of receiver. I will probably incorporate something similar.

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19 minutes ago, Sturgeon said:

Glued on a SCAR-H-compatible lower file I found online: 

 

czeMlQw.png

 

This informs me of a couple of things I need to do to make my upper work with whatever lower I end up designing. First, either I will need to pick a different takedown method (I was originally going to have it come apart like a SCAR), or make my front bulkhead longer. Of the two, I will probably make my front bulkhead longer but I definitely will investigate the former. Also, there will be an interesting problem to solve when it comes to fire control, as there may be some excess distance between the hammer and the bolt carrier. It also looks like further reducing the height of the feed tower on the magazine isn't a good idea, or at least it doesn't look like it right now (you can see how shallow the magazine well has to be already to accommodate the current magazine). All of this to me says that now is the time to take another look at all the components and then move beyond the layout stage to the initial assembly stage once all the parts are properly re-dimensioned and modified.

 

Also, I noticed a new design feature of the AK while looking at this: The bolt protrudes out of the back of the carrier to bring the striking face of the firing pin back far enough for the hammer, but when unlocked the rear of the bolt is flush with the carrier. This saves roughly a half inch of space, allowing for more overtravel for the same length of receiver. I will probably incorporate something similar.

Considered bullpup design? 

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8 hours ago, Sturgeon said:

 

That was sarcasm lol

 

This picture of a Sterling illustrates it best:

 

AR180_2.jpg

 

Notice three spot welds holding the hinge point on. Not like spot welds are notorious for breaking under stress or anything.

 

 

 

 

 

That's one of the better looking Sterlings I've seen.

 

Many are simply terrible.  Sloppy welds, (the ones along the upper that hold the bolt's cam track are often not straight or lack full penetration) sloppy stamping and painted finishes that look like they were applied with a floor mop.

 

No kidding, they were considered "parts guns" (As in you bought one to keep your Howa or Costa Mesa gun running) for quite a while.

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9 hours ago, Xoon said:

Considered bullpup design? 

 

Bullpups have to be designed from the start as such.  Ideally, a bullpup would have almost the entire mass and bulk of the moving parts group in front of the breech.  E.G. an Oerlikon 20mm cannon.  The majority of bullpup rifles start with very orthodox breech mechanism designs, and end up mediocre to bad as a result.

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17 minutes ago, Collimatrix said:

 

Bullpups have to be designed from the start as such.  Ideally, a bullpup would have almost the entire mass and bulk of the moving parts group in front of the breech.  E.G. an Oerlikon 20mm cannon.  The majority of bullpup rifles start with very orthodox breech mechanism designs, and end up mediocre to bad as a result.

 

Yes if you want a truly decent bullpup, then you need to really engineer the thing for that at the start. I do have some ideas as to how best to do that, so maybe I will do that project someday.

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On 9/22/2018 at 1:51 PM, Sturgeon said:

 

 The early M16 was also too fragile. There could be a very interesting discussion of what "underbuilt" really means with regards to rifles that would almost exclusively cover AR-15 variants. They run the gamut. The first 17 AR-15s were so light and fragile that a whole host of changes were proposed during testing in the 1950s which caused them to gain three quarters of a pound by the time they hit production as the Colt 601. Being underbuilt by that much is perhaps one of the most extreme and clear examples I can find. The 601, though, was still too light and by the time development of the M16A1 was done it would weigh 0.69lbs more than that, almost a pound and a half heavier than the first 17 prototypes when they came out of Armalite's shop. Not all of that weight was to improve durability or reliability, but almost all of it was. And even then, the 1970s era M16A1 still had shortcomings in durability, which led to the M16A2 growing by another half-pound. So the total difference between the M16A2 (which was fully ruggedized) and the first 17 AR-15s was nearly two pounds - that's more than even the weight growth of the Dutch AR-10, which grew by about 1 2/3s pounds over its development! The AR-15 is a smaller caliber rifle, too to so when we compare these in terms of percents the degree to which the initial AR-15 was underbuilt becomes very clear:

Dutch AR-10: Grew by 1.66 lbs (23% of initial weight)

 

AR-15: Grew by 1.92 lbs (34% of initial weight) (!!!)

 

 

What would you say was the minimum necessary amount of additional weight to soldier-proof the M16A1? Is it mostly the furniture, or were additional steps such as the new lower receiver and the accursed barrel truly needed?

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50 minutes ago, OnlySlightlyCrazy said:

What would you say was the minimum necessary amount of additional weight to soldier-proof the M16A1? Is it mostly the furniture, or were additional steps such as the new lower receiver and the accursed barrel truly needed?

 

M16A2 is basically the minimum, although in my personal opinion the longer stock and thicker barrel were unnecessary. If they were to make an "A1E3" with S-S-A FCG, A1-length A2 stock, and A1 profile 1/7 barrel in the 1970s/1980s, it would have been roughly the same weight as a 1970s-era M16A1, possibly 3 ounces or so more. I base that on data here and here. There were rifles during the M16A2's development which conformed to this, and those still exist at IMT, but I didn't get a chance to weigh them.

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23 hours ago, Sturgeon said:

 

No.

ok.

 

22 hours ago, Belesarius said:

Bullpups are haram.

I am deeply sorry for offending  you, your highness. 

 

20 hours ago, Sturgeon said:

Lower receiver is roughed out. Until all the dimensions are done I am not adding any fillets.

 

HucPKIZ.png

 

It also occurred to me while doing this that my magazine currently has no provision for a hold open activator,  so it may get a slight redesign.

I have a curious question. How is trigger guards manufactured? 
Bending a square rod?
Bending a wire/rod?
Stamped?
Milled? 

 

Molded plastic guard?

 

14 hours ago, Collimatrix said:

 

Bullpups have to be designed from the start as such.  Ideally, a bullpup would have almost the entire mass and bulk of the moving parts group in front of the breech.  E.G. an Oerlikon 20mm cannon.  The majority of bullpup rifles start with very orthodox breech mechanism designs, and end up mediocre to bad as a result.

 

13 hours ago, Sturgeon said:

 

Yes if you want a truly decent bullpup, then you need to really engineer the thing for that at the start. I do have some ideas as to how best to do that, so maybe I will do that project someday.

Thank you for telling me, I did not know this. 

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I made significant progress on the lower today:

 

E7fjugf.png

 

It uses a trigger pack arrangement where the packs can be assembled using AR-15 trigger components. That way you get drop-in trigger changes, but you can also use AR triggers. You just need the box.

The magazine and bolt catches have not yet been added, nor has their mounting hardware been modeled in the lower yet. More work to do!

 

1OZ8OwV.png

 

Current estimated weight is 6.67 lbs unloaded, almost as light as an M4A1.

 

 

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23 minutes ago, Sturgeon said:

 

It's long enough for it

You make it, I WILL buy it. As I know if it's in 6.5 Swede, I can make it in 7.5 X54.. And have a cest magnifique  rifle.

 

(which now that I think about it, I have a source of 24/29 mags.  That would be badass.

A wood stocked, semi/ MAS 44/FAL using 24/29 mags ..

Maybe.  If I could keep it from slamfiring.

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6 minutes ago, Belesarius said:

How hard to take it from Solidworks to a working prototype?

And what kind of cost?

 

 

Probably an order of magnitude harder than designing it in the first place. Definitely more expensive.

 

I am not even that comfortable saying I "designed" it, as this is more of a design study than an actual design you could produce - at least not without a lot of hard work figuring out tolerances and such.

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