/r/GunDesign

Photograph via snooOG

Please limit posts to information on gun design, gun theory, ballistics, gun modifications, metallurgy, gun tools, gunsmithing, gun-related machining or CNC work, gun-related 3D design, how-to/DIY, or other advanced gun topics.

*Please limit posts to advanced gun topics. For the love of Xenu, don't post any pictures of stock Glocks.

*No discussion of any illegal modifications.

*Question posts & discussions are allowed if they are related to advanced gun topics. No questions along the lines of "first-time gun owner here, what sort of lube should I use". There are many other subs for that sort of content.

*Have fun and be nice. This is a fun sub, meant to be a positive and educational place. If you want to be mean, there are plenty of other gun subs for that too.

*Make sure your content is interesting and educational. We are here to nerd out on interesting advanced gun topics, so please keep that in mind while posting.

*Posts that don't follow the "essence" of the advanced educational nature of this sub may be removed to keep content information-rich.

/r/GunDesign

3,902 Subscribers

2

[Forgotten Weapons] So You Want to Design Guns? You Need This Book. ("Firearm Anatomy Book III: The Remington Double Derringer" by David S. Findlay)

0 Comments
2024/06/10
07:47 UTC

1

Reasonable safety margins in action designs?

0 Comments
2024/05/08
01:16 UTC

2

What's the best way to design a adjustable gas piston system?

2 Comments
2024/03/22
22:47 UTC

5

can you comment on this?

6 Comments
2024/03/15
03:19 UTC

1

Cock on open or close for striker fired semi auto rifles?

0 Comments
2024/01/30
23:10 UTC

2

Garand pattern extractor or dual M16's for a Quad lug bolt design?

1 Comment
2024/01/30
22:07 UTC

6

[Forgotten Weapons]The Gun Science Says Can't Work: Madsen LMG Mechanics

0 Comments
2023/11/26
14:30 UTC

2

What would actually be cheaper? A question on charging handles

The M3A1 grease gun is generally considered a very cheap and easy to manufacture weapon, and a small part of that seems to rely on its utter lack of a charging handle. To charge the weapon you have to grab the bolt directly and pull it back. However every other SMG, even the cheapest of the cheap like the Sten, had a charging handle.

This got me thinking, would the grease gun's lack of a charging handle actually be any cheaper? You still have to make the cut in the bolt, but now you have to do it at an angle that can be readily grasped by a finger. Comparatively a charging handle would've just required a bit more depth, but in theory any random bolt or screw or pin could have worked to fill the role (texture it if you can, if not it's not a big loss). Seems like the M3's method would have required a bit more machining (and/or an additional bit size), if only fractionally.

Mind you I'm not considering other features of the guns, such as "safety cuts" or dust covers or so on, and I get how these could affect production costs beyond here. However just in this one area, the M3 seems to be "complexly simple" - simplified in a manner that requires greater complexity in the manufacturing process.

6 Comments
2023/11/02
06:08 UTC

4

[Forgotten Weapons] Gas Delayed Blowback Pistols: A Tour of the System

0 Comments
2023/10/27
12:33 UTC

5

Which type of short stroke piston is the most reliable? A momentum system or Pressure system?

2 Comments
2023/09/13
21:15 UTC

4

Greasy Trapezoidal/ACME threads and static coefficient of friction values?

Hi I'm trying to figure out which static coefficient of friction value(s) to use when determining which Trapezoid or ACME threads to use for my projects? As I can't find a consistent value (a) for hardened steel against steel when greasy. As I have to assume user ignorance and less than ideal circumstances.

Ideally, the threads would be kept dry but considering that rifle bolts are often have a lubricant of some kind, usually light grade machine oil or something similar. Thought there could alternatives and that's one problem as source (a), which gives several different static and kinetic coefficients of friction depending on the lubricant being used. As depending of the the static coefficient of friction used can eliminate specific thread pitches (b),(c)&(d) from consideration due to the possibility backdrive.

Backdrive, is when a load that is perpendicular to the threads causes the screw to unscrew itself. Which can't happen, as bolt thrusts and max average pressures vary from 4.41 KN at 170 MPa (1000 lb at 25 Ksi) for .22 LR to 50.8 KN at 450 MPa ( 5.71 Tons at 65 Ksi) for most magnums.

In order for backdrive to not happen the back drive efficiency (f) (which is used in calcuatinting several different things (e))must be <0 with the variables being, angle of the pitch, flank angle, and the coefficient of static friction. Which depending on the lubricant, coating and other things can vary and I'm not sure where too look or which values to use.

Any information would be greatly appreciated, sincerely the OP

a. https://engineeringlibrary.org/reference/coefficient-of-friction

b. https://www.engineersedge.com/hardware/iso-metric-trapezoidal-threads1.htm

c. https://www.engineersedge.com/hardware/external_acme_thread_13360.htm

d. https://www.engineersedge.com/hardware/internal_acme_thread_13361.htm

e. https://www.roton.com/screw-university/formula-calculators/

f. https://www.roton.com/screw-university/formula-calculators/efficiency-power-screws-backdrive/

2 Comments
2023/08/06
23:57 UTC

2

Is 2mm (~0.079") enough distance for primary extraction?

0 Comments
2023/08/02
19:04 UTC

2

Is my design original? (and can I get some feedback on it?)

4 Comments
2023/07/26
23:23 UTC

1

What's the best manufacturing philosophy for service rifles?

1 Comment
2023/07/20
15:30 UTC

4

Polymer vs Aluminum for recivers

Hi, I'm wondering which material is better for a rifle receiver? Using the following assumptions: that the barrel is using a barrel extension that the lugs lock into, and carrier tilt is accounted for (with steel inserts for the aluminum and stamped steel with a steel skeleton for the polymer) as I'm thinking of going with Siminov style short stroke piston system which will introduce carrier tilt for the first few millimeters of bolt group travel.

5 Comments
2023/07/19
23:14 UTC

5

Turbines in gas operated semiauto rifles

Out of curiosity, are there any show stoppers for having a rotary bolt semiauto rifle use a turbine to open and cycle instead of pistons?

3 Comments
2023/07/09
19:35 UTC

6

Cock on Closing Strikers vs Rotary Hammers

3 Comments
2023/04/15
20:17 UTC

9

Calculating the strength of roller lock actions

0 Comments
2023/04/11
21:24 UTC

9

Improving the AR-15's bolt and barrel extension strength

2 Comments
2023/04/04
21:40 UTC

4

Does anyone have any experience with extension springs?

Hi, I'm Wondering if anyone has any experience with extension springs?

0 Comments
2023/03/28
23:40 UTC

4

Is this firing pin and spring design achievable?

0 Comments
2023/03/22
22:08 UTC

3

Selecting steels and heat treatments

0 Comments
2023/03/22
03:18 UTC

7

Steepness of camning surfaces

Hi I'm trying to figure out how steep is too steep for dual camning surfaces, like those found on AR-15's but on both sides of the bolt group to increase leverage. So what do you think is too steep an angle?

0 Comments
2023/03/18
22:25 UTC

3

SI Units vs American Units

1 Comment
2023/03/13
17:47 UTC

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