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Old April 21, 2012, 01:31 PM   #26
animal
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Cool hhunter ! I was a EE major at MS State years ago(early ‘80s). Had to quit to take care of my family so I never finished.

Best wishes for you completing your degree.
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Old April 21, 2012, 01:57 PM   #27
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Thanks for that, Animal.

I'm in my junior year so I have about another year or maybe year and a half to go. After graduating I don't plan to stray far from the firearm and ammunition industry. It's an exciting adventure to say the least.

Well, I'm off to the State vs. Tennessee baseball game then the Maroon and White spring football game. Take it easy and shoot straight.

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Old April 21, 2012, 02:15 PM   #28
jason41987
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animal, my idea for the .223 case was to chop it off behind the shoulder, neck it down to .308 with an overall cartridge length of about 40mm.. thats my idea for the cartridge, you can find more .308 bullets than anything else it seems, so having that variety should help fine-tune a suitable load for it... meanwhile that 40mm overall length is still short enough to be used in a handgun... to use it in a handgun though someone would have to stretch the 1911 design about 6mm, and i believe 36,000 PSI would be your limit... but im focusing on a rifle right now.. perhaps a converted .30 carbine to fire this
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Old April 21, 2012, 02:20 PM   #29
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hunter, for my firearms experience, ive been around firearms since i was about 3... shot my first gun when i was so young, all i can remember from the experience was being thrown backwards (it was a 12 gauge).... but my love for firearms, and love for engineering go hand-in-hand pretty closely, and the interest in the various mechanical mechanisms inside them lead me to begin collecting them many years ago (im 27 now)...

when you see most machines they serve a specific purpose well, and there arent too many restraints on them, but when you look at firearms they have to be reliable, durable, accurate, all while fitting into a package thats comfortable to hold, and atleast survivable to shoot... its a tall order that leads me to great admiration for the early designers of the modern firearm world, like john browning for example
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Old April 21, 2012, 02:26 PM   #30
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Nicely stated. I concur with everything as you put it in the previous post. I was just stating that I don't say much about being a college student when posting on the forum.. There aren't alot, but there are the Nay-Sayers that will jump up and call you out stating that you don't have the experience to give a good opinion. As far as those people go, I don't let them worry me.
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Old April 21, 2012, 02:47 PM   #31
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Sorry, I was confused on the cartridge. Now it’s sounding like a reduced-powered 7.62 x 39. Why not just use it ?

Not sure that there would be enough neck with a 7.62 bullet in a .223 case. There is (or was) the 7mm TCU that might fit your idea.
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Old April 21, 2012, 03:06 PM   #32
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another cartridge for a suitable conversion is the 10mm, neck that down to 30 cal and you might have something... shorter case, but wider base diameter... the 224 boz for example (10mm necked down to .223) has around 900ft/lbs of energy at the muzzle... with the right powder, and a longer barrel you could possibly see 1200ft/lbs plus
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Old April 21, 2012, 03:07 PM   #33
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I’ll be damned … there is such thing as a .30 TCU and the little sucker is bad to the bone !

http://www.hornady.com/store/30-TC-1...superformance/


Sorry, the link above is to .30 TC ... made from shortening a .308 Win case
Couldn't find .30 TCU ...assuming the cartridge was never actually produced. Maybe someone more knowledgeable can enlighten us here.
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Last edited by animal; April 21, 2012 at 03:32 PM.
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Old April 22, 2012, 03:57 AM   #34
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hmm, more powerful than a .308, and a decent amount shorter too, sounds like a nice little cartridge to get behind in a new rifle design... but its still an odd ball cartridge, and doesnt seem like it would be worth replacing a .308 with due to availability of the .308... but hey, if you could chop .30-06 cartridges and make it then your ammo is as available as 30-06

id like to find out what the absolute best performance you can get out of an M1 carbine sized rifle though
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Old April 22, 2012, 04:05 AM   #35
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oh.. if anyone reloads for .308, im curious to know the overall projectile length for grain sizes under 140 grains if anyone can measure
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Old April 22, 2012, 12:03 PM   #36
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I’m a 30-06/.308 nut. Dunno if any of the following is useful to you or not, but here goes. …

A .308 Winchester is basically a shortened 30-06.
In metric, They could be called 7.62x51mm and 7.62x63mm respectively.

Additionally, the .308 has the same outer dimensions and neck thickness as the 7.62x51mm NATO. Case thickness is different in the head and part of the wall, so the NATO version has less case capacity. Pressure ratings are also different: the NATO version having less pressure than the upper limits of those allowable in the commercial .308 Win. From the outside, they are the same and are (for the most part) interchangeable. Usually the difference is not a problem unless you’re reloading or wanting to use heavier bullets in military semi-autos(that weren’t designed to handle the higher pressures of some commercial loads).
Some commercial loadings in 30-06 more pressure (or the wrong pressure curve) than the military loadings of 30-06.

Basically, you can’t feed a Garand a diet of heavy bullets without tearing it up and the same goes for military semi autos "chambered in .308". There are similar differences between the .223 Remmington and its military sister, the 5.56x45mm NATO. What matters here is not only the peak pressure, but the pressure at the time the bullet reaches the gas ports.

The .30 TC is another step in decreasing the case size in the family of cartridges based upon the 30-06 case.
What’s happened over the years is that improvements in propellant technology have allowed the case to be smaller.

The .30 TCU is different, and based on the .223 family of cases. I had never heard of it or the .30 TC until this discussion.

To measure case capacities, I pour known volumes of sand (or powder) into the case. The "measure, mark, measure" method for deciding where to cut one.
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Old April 22, 2012, 01:37 PM   #37
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the .30TC is less than 1/10th shorter than a .308 with the same base diameter, or so this article im reading says... is it worth the pain in the rear of finding rifles to fire this, finding ammo for it, for less than 1/10th of an inch shorter case?...nothing went into the .30TC that cant just as easily be used in a .308 and give the .308 even more power still simply by using a different powder
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Old April 22, 2012, 01:54 PM   #38
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Well, yes and no.
Part of the reason for a "new case" is to prevent people from ruining their rifles. Theoretically, you could use a new powder to soup up the .308 beyond the 30-06. Prbably be fine in most bolt guns, but any of those loadings would tear the hell out of a M1-A and many other semi-autos out there … not just the heavy bullet loads.
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Old April 22, 2012, 01:55 PM   #39
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Standard Military loading for .30 M-1 Carbine yielded 110gr bullet @1975 fps, ME= 955.. In an old notes, I found 100gr @ 2170 (using 2400 powder), ME would be 1050.

I seem to remember that the military had stability problems with bullets over 110gr when developing this round, but dunno for sure.

Since it headspaces on the case mouth, it might cause problems if you tried to soup it up, especially in a semi-auto.

Never liked this round or gun personally. It seemed like one that was kinda between uses… What it was powerful enough for, it wasn’t accurate enough … and vice-versa. … Works good on feral dogs /coyote sized stuff, but I never trusted it beyond 100 - 150 yds.
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Last edited by animal; April 22, 2012 at 07:30 PM.
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Old April 22, 2012, 02:22 PM   #40
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hmm.. 10mm has a significantly larger case capacity than 30 carbine and shorter overall length, and as much power from a pistol as the carbine produces out of the barrel... with the right powder that 10mm would absolutely dominate a .30 carbine
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Old April 22, 2012, 02:32 PM   #41
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You might want to look at the previously mentioned .338 Spectre and other wildcats based on the 10mm case. There's a good chance that what you want, might already be made.
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Old April 22, 2012, 03:08 PM   #42
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the overall length of that .338 round is the same as a .223 with less power... so would rather take a .223 over that.. i wish the 6.8 SPC had gained more popularity, thats a nice round, as is the version of it necked up to .30 cal... but, i think the .300 AAC blackout would be a nice selection for a new rifle
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Old April 22, 2012, 04:58 PM   #43
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I would design a mechanism that allows the operator to choose between open- and closed-bolt operation, that way you can decide between a open-bolt for lower chance of overheating, or closed bolt for harsh enviroments where clogging is a problem. Short-stroke gas piston system similar to the M6A2 PSD
Either 6.8mm or 7.62mm NATO Caliber, If a 6.8 it would feed from a 30 round box or 100 round Beta C-mag, if in 7.62mm NATO, it would feed from a 20 round box or 80 round drum.
The gun would probably be a IAR(Ifantry Automatic Rifle) With one of those foregrips that doubles as a bipod. M-16 pistol grip with Magpul stock and Quad-rail handguard. 1.5x Red Dot sight and a two-position gas valve regulator, choice between 600 rpm or 900 rpm.
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Old April 22, 2012, 05:05 PM   #44
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Jason, your design parameters seem to be fluctuating?
Sorry, I just can’t seem to nail down the idea of what you’re looking for, at least not enough to be of any help. I thought it was .30 or above bullet dia. in a small diameter case and of intermediate power. Oh well, I guess I'm still confused?

ME, while extremely important, isn’t the be all and end all of performance. Bullet diameter, shape, and weight also play a huge part in determining how well a particular job is done by the bullet. Design concept is always done in reverse; whether you are attempting to copy an existing piece of technology, or figuring out how to achieve a specific goal. Decide upon a goal(what the bullet needs to do). Reverse time in your mind, using your goal as the anchoring point, rather than trying to build something from scratch using the beginning of the prototype as your anchor. The thought process of creation, involves reversing the thermodynamic arrow of time, imo... from end all the way to the beginning. Creation is the beginning and end. All else is engineering in reverse (done in your mind), and engineering foreward (done by hand).

Without the military adopting the 6.8 SPC, it was doomed to failure in the civilian market. Aside from a very narrow niche. (and other, already established, civilian rounds are in production that fill the niche quite nicely), anything it can do, either the .308 or .223 can do better. I suspect that the military came to pretty much the same conclusion due to practical concerns.
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Old April 23, 2012, 04:02 AM   #45
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animal, i was just discussing multiple ideas.. it seems the best youd get with a 357 mag or .30 carbine would be whatevers possible with leverevolution bullets

gunnut17s idea of a mag-fed LMG is pretty good, and designing something that could operate from a closed or open bolt doesnt seem too difficult either
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Old April 23, 2012, 04:09 AM   #46
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Quote:
gunnut17s idea of a mag-fed LMG is pretty good, and designing something that could operate from a closed or open bolt doesnt seem too difficult either
Actually, Mag- fed light machine guns(I assume that's what you meant by LMG) are actually quite common: The BAR, Bren light machine gun, HK M27 IAR, and LWRC M6A4 are all magazine-fed.
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Old April 23, 2012, 05:11 AM   #47
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you forgot MG36, russian RPKs, and so forth... thats not uncommon, just the open/closed bolt is, and wouldnt be particularly hard to do either
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Old April 23, 2012, 08:53 AM   #48
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My father designed a lot of guns.
There is a calculator in one hand and a telephone with a US representative or US senator in the other.

You walk into Rock Island Arsenal with the greatest gun design ever, and you will be greeted with, "So, what else is new?"

The way it works is, you receive an RFQ [request for quotation].

What does is all mean?
You can't sell your own idea of a gun.
You must design per what some mediocre bureaucrat defines.
And to win the proposal, it matters in which state you reside.
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Old April 23, 2012, 08:57 AM   #49
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There have been several designs of autorifle/LMG built to fire closed bolt semi, open bolt full. The Johnson LMG did. I gather that it was concluded that the feature was not worth the mechanical complication because there was seldom a use for slow semiauto fire from a LMG. Kind of like the magazine disconnector on a 1903 Springfield, built to an obsolete doctrine of preventing dumb soldiers from "wasting ammunition."
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Old April 23, 2012, 09:53 AM   #50
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oops. Man am I embarrassed ! ... brought a design hat to a brainstorm ... sorry about that, chief !

here’s my weirdest idea so you guys can laugh ...
sabot encased projectiles are scooped up and aligned with the barrel by a cam (no cartridge). The firing chamber behind the cam has electronically controlled injectors to meter a liquid solution of hydrazine and other, more nasty stuff. Firing is by a high voltage spark. This was from musings in 1980 or so. . . for a deck mounted machine gun.
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