Wednesday - December 08, 2010
Just Dicking About
I spent a few hours this morning playing around with my collection of gun software. I’ve got pretty much all of it: exterior ballistics, interior ballistics, trajectory calculators, cartridge design programs, you name it. It’s fun stuff to play with, and I’ve learned a lot from it.
Every once in a while I approach the old Poodle Shooter problem, and attempt to find a solution. The what? The who? I could write pages and pages, but to try and be succinct as possible, I’ll say that, in the post WWII period, a gunmaker named Roy Weatherby pushed the idea that really high velocity equated to tremendous killing power. He was both right and wrong. Another gunmaker named Eugene Stoner took that idea, and sold the US Military on the idea of a small caliber high velocity rifle for our combat troops. Thus was born the M16 rifle, which fires the 5.56 NATO cartridge. I won’t repeat the story that you probably already know, but for whatever other great benefits that weapon has, it lacks close range stopping power and long range killing power.
If you don’t know that difference between stopping power and killing power, go read that post I did on the .600 Nitro Express pistol. Or look up “the caliber of any self defense pistol starts with at least a 4”. That’s stopping power. Delivering such a tremendous kinetic impact that it overcomes the target’s internal hydraulic flexibility and causes massive damage to the nervous system, physical support structure, and (as a secondary issue) massive damage to the major organs. In other words, it pretty much blows the target to shreds, at least internally. Bang. Drop. Dead. Generally you use the biggest bullets you can find to do this. Killing power is the ability of a cartridge to propel a bullet to and through it’s living target at some designated distance so that it leaves a hole at least half an inch across, with sufficient bullet mass and proper bullet and rifle design such that the bullet penetrates in a nearly straight line. Put a hole like that through any creature, and eventually it will die. Be a good hunter and make that hole in the vitals (heart, lung, upper spinal column) and “eventually” becomes “pretty quickly”. Controlled expansion bullets give you the best killing power. Too bad that such bullets are outlawed by the Geneva Conventions/Hague Accords.
Back to shooting poodles. I am not going to have the 6.8SPC vs 6.5 Grendel debate again. Both are great improvements over the 5.56 NATO at any range, and neither one is ever going to be adopted by the military. No, their decision is to go with that futuristic space gun micro-cannon thing that got mentioned here the other day, where computers and lasers in the weapon lob a small bomb out to the target and then set it off. It will cost billions, with the dual advantage that troops won’t need to learn to shoot all that well, and the military will never ever have to admit to the 47 year old mistake that is in our soldier’s hands right now.
Several tons of research by better folks than I have concluded that a mid-range assault rifle needs to accurately shoot a bullet with a sectional density of more than 0.2 and a ballistic coefficient greater than 0.35 at a velocity of 2500-2750fps. 1200 lb/ft of bullet energy at 300 yards/300 meters would be real nice. And to minimize shooter fatigue (ie recoil) this needs to be done with a caliber smaller than 30. But it also needs to be done with a caliber greater than .24.
I’ve designed a whole slew of cartridges on paper that can do the job, but it is just about impossible to do the task with the length and size constraints of the M16 rifle. The cartridge chambering area is simply too thin (in the bolt face) and too short (in the bolt length and cartridge well) unless the cartridge’s working pressure is cranked right up to the danger line. And really high pressures wear guns out really fast.
Hold a AA battery in your hand so that it lays across your fingers. The length of that battery is just 1/4” shorter than the 5.56 cartridge. The body of the cartridge is about the same diameter as the negative (-) terminal, that flat shiny disc on the bottom of the battery. See the little nipple on the positive (+) end of the battery? That’s the diameter of the bullet it fires. Pretty damn tiny, ain’t it? The .600 Nitro Express cartridge is about the diameter of a Churchill cigar, 3/4”, and nearly 4” long. [ or you could just click here and look at the picture. L-R: 7.62 NATO, 5.56 NATO, AA battery ]
Anyway, here’s today’s time waster. I call it the 6.5x39_25, since it’s based on the 7.62x39 Russian cartridge, blown out straighter and with a 25 degree shoulder, and necked down to 6.5mm.
Taking a good chunk of the body taper out of the 7.62x39 gives you more internal volume. More internal volume means more room to fit more gunpowder. It also means the cartridges will stack straighter in a magazine, which can mean easier feeding. The 25° shoulder angle gives more power room as well, without being “Ackley’d” out to a steep angle that makes for difficult feeding. Think of it as a stretched, softened, and necked up 6mm PPC. Taking the caliber down from euro-30 ( the 7.62x39 and the .303 British both use .311” diameter bullets, whereas the American designed .30-06 and the 7.62x51 NATO both use .308” diameter bullets ) to 6.5mm (.264") allows the same approximate weight bullet (120-125 grains) as the Red’s 7.62x39 to have a much greater sectional density and a much higher ballistic coefficient. And that’s nearly double the bullet weight of the 5.56, which will give you much better short range stopping power.
My calculations show that this cartridge can push a 120 grain FMJ bullet at over 2500fps, which would generate a very minor 8.15 lb/ft, 8.66fps worth of recoil in a light 7lb rifle.
The Norma 120gr FMJ has a sectional density of 0.246 and a ballistic coefficient of 0.428. That compares very well with the 7.62 NATO’s 0.226/0.411, the 5.56 SS109’s 0.179/0.397 and the commie 7.62x39’s 0.184/0.275. This means that this is a solid little bullet with great aerodynamic efficiency that should penetrate better than all of those others at similar velocity. It means that this one can be zeroed in at 255 yards and will stay +/- 4.5” out to over 300 yards, where it still carries more than 1000lbs/ft worth of energy. Which means point and shoot out past the point most folks are comfortable using regular sights. The standard 7.62 NATO ("way too much gun!!!") has 1400lb/ft of energy at that range, whereas the 5.56 NATO with it’s “heavy” 63gr SS109 bullet has only 690lb/ft of whack at that distance. So my design splits the difference right down the middle. Another advantage is that my round will burn up all of it’s powder in a 17” barrel, which makes for less muzzle flash and a quieter bang. It’s very close to being optimized for the really short barrels that the current M4 carbines use. In a full length M16 barrel this one would give you a bit more velocity, a bit flatter trajectory, and a bit more whack (1109lb/ft) at that same 300 yard distance.
Is this the magic cure all? No. It’s a little down in terms of energy at distance compared to the 6.5 Grendel, but it eclipses the 6.8SPC. And it would require opening up the M16’s bolt face diameter by 0.069”, which is doable. Don’t forget that my numbers are all calculated; actually building one and testing it would result in real-world differences (ie lower performance). Too low? Try one and find out.
So I’ve built a solution in search of a problem no one official will admit exists. It would make a very mild 250 yard deer rifle though.
Ok, fun time is over. Let’s go see what Onitwit is up to today. I hear the far-left is PO’d at him now over the tax cut thing. Guy sure knows how to make himself popular, don’t he? 
Posted by Drew458
on 12/08/2010 at 01:06 PM
Filed Under: • Miscellaneous •
• Comments (4)
•
Trackbacks(0)
Permalink • Five Most Recent Trackbacks:
Once Again, The One And Only Post
(4 total trackbacks)
Tracked at iHaan.org
Thｅ advantage to having a guide with you is thɑt an expert will haѵe very first hand experience dealing and navigating the river with гegional wildlife. Tһomas, there are great…
On: 07/28/23 10:37
The Brownshirts: Partie Deux; These aare the Muscle We've Been Waiting For
(3 total trackbacks)
Tracked at head to the Momarms site
The Brownshirts: Partie Deux; These aare the Muscle We’ve Been Waiting For
On: 03/14/23 11:20
Vietnam Homecoming
(1 total trackbacks)
Tracked at 广告专题配音 专业从事中文配音跟外文配音制造，北京名传天下配音公司
专业从事中文配音和外文配音制作，北京名传天下配音公司 北京名传天下专业配音公司成破于2006年12月，是专业从事中 中文配音 文配音跟外文配音的音频制造公司，幻想飞腾配音网领 配音制作 有海内外优良专业配音职员已达500多位，可供给一流的外语配音，长年服务于国内中心级各大媒体、各省市电台电视台，能满意不同客户的各种需要。电话：010-83265555 北京名传天下专业配音公司…
On: 03/20/21 07:00
meaningless marching orders for a thousand travellers ... strife ahead ..
(1 total trackbacks)
Tracked at Casual Blog
[...] RTS. IF ANYTHING ON THIS WEBSITE IS CONSTRUED AS BEING CONTRARY TO THE LAWS APPL [...]
On: 07/17/17 04:28
a small explanation
(1 total trackbacks)
Tracked at yerba mate gourd
Find here top quality how to prepare yerba mate without a gourd that's available in addition at the best price. Get it now!
On: 07/09/17 03:07
DISCLAIMER
THE SERVICES AND MATERIALS ON THIS WEBSITE ARE PROVIDED "AS IS" AND THE HOSTS OF THIS SITE EXPRESSLY DISCLAIMS ANY AND ALL WARRANTIES, EXPRESS OR IMPLIED, TO THE EXTENT PERMITTED BY LAW INCLUDING BUT NOT LIMITED TO WARRANTIES OF SATISFACTORY QUALITY, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, WITH RESPECT TO THE SERVICE OR ANY MATERIALS.
Not that very many people ever read this far down, but this blog was the creation of Allan Kelly and his friend Vilmar. Vilmar moved on to his own blog some time ago, and Allan ran this place alone until his sudden and unexpected death partway through 2006. We all miss him. A lot. Even though he is gone this site will always still be more than a little bit his. We who are left to carry on the BMEWS tradition owe him a great debt of gratitude, and we hope to be able to pay that back by following his last advice to us all:
It's been a long strange trip without you Skipper, but thanks for pointing us in the right direction and giving us a swift kick in the behind to get us going. Keep lookin' down on us, will ya? Thanks.
- Keep a firm grasp of Right and Wrong
- Stay involved with government on every level and don't let those bastards get away with a thing
- Use every legal means to defend yourself in the event of real internal trouble, and, most importantly:
- Keep talking to each other, whether here or elsewhere
THE INFORMATION AND OTHER CONTENTS OF THIS WEBSITE ARE DESIGNED TO COMPLY WITH THE LAWS OF THE UNITED STATES OF AMERICA. THIS WEBSITE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE UNITED STATES OF AMERICA AND ALL PARTIES IRREVOCABLY SUBMIT TO THE JURISDICTION OF THE AMERICAN COURTS. IF ANYTHING ON THIS WEBSITE IS CONSTRUED AS BEING CONTRARY TO THE LAWS APPLICABLE IN ANY OTHER COUNTRY, THEN THIS WEBSITE IS NOT INTENDED TO BE ACCESSED BY PERSONS FROM THAT COUNTRY AND ANY PERSONS WHO ARE SUBJECT TO SUCH LAWS SHALL NOT BE ENTITLED TO USE OUR SERVICES UNLESS THEY CAN SATISFY US THAT SUCH USE WOULD BE LAWFUL.
Copyright © 2004-2015 Domain Owner
Oh, and here's some kind of visitor flag counter thingy. Hey, all the cool blogs have one, so I should too. The Visitors Online thingy up at the top doesn't count anything, but it looks neat. It had better, since I paid actual money for it.
RSS 2.0 
Atom 
