If you could design a cartridge from scratch

[Darryle]

If I wanted a SNIPER Cartridge I would look for something like the Cartridge used in the movie "The Gunman" with Sean Penn when he used a Sniper Rifle to assassinate the Head of Ministry for the Country on Natural Resources.
The movie only showed the Cartridge in the magazine for a few seconds. It was very FAT and short. Looked to be a 50 cal case shortened and necked to something

Got curious, IMFDB says it was a 50 BMG

 

[sable tireur]

I have played with wild cats for a long time. Longer necks give less throat erosion as PO Ackley mentioned. I made a 6 XC with a .400 length neck, formed brass from Lapua 308 Palma brass, and the lack of throat erosion at 900 rounds was only .007, which is nothing short of amazing! 105-107g bullets at 3150 out of a 31" 8T barrel.

I had noticed previously having shot out a multitude of 243 Win barrels and 6 Rem barrels that the 6 Rem had less throat wear.

I would love to play with longer necks from some other cartridges.

The 6mm Crusader which originated at GAP, is the 6mm Rem. using a 32 degree shoulder and a slight case improvement. Great design for throat preservation and higher performance with those heavier 6mm bullets available now.

It has been supplanted by those much smaller 6mm cartridges used in PRS competitions. I still have and use my barrel because of the performance.

6BR, 6.5x47, 243, 6mm Rem, 6mm Crusader and 6.5x284

 

[Coyote Shadow Tracker]

Got curious, IMFDB says it was a 50 BMG

View attachment 470667View attachment 470668

OK
I thought that it looked shorter than a 50BMG

This is a picture of Lake City 50BMG 660gr
The cartridge in the movie sure looks different. Look at the necks and shoulders.

Thanks!!!

 

[sable tireur]

I have moved towards the 6.5x284 but with a longer neck. Yes, you lose a little capacity but not as much as you might think.

 

[scpaul]

I'm getting the pieces to assemble a 6mm Rem instead of a 243 mainly because of the longer neck. I assembled with some help a slightly modified 7mm Valkyrie ( 7/300wm, 7mm practical) I didn't do many changes. I blew the case out for min. taper and flattened the shoulder about 3 or 4 degrees. It had already been flattened prior. The little that I've shot it I haven't experienced any case growth and this is premature or neck thickening.
Ultimately I'm thinking about something similar on the 6mm Rem. I haven't checked but I don't think that I'm the first. If I like what I get to begin with then I'll research it and see what someone smarter than me learned. I'm always wondering about prior efforts that didn't have our bullet and powder technology.

 

[FrogFire7]

220 SWIFTER Exact same everything just a different head stamp. Spend more on internet fantasy claims and some hunt influencer on exaggerated and select info on what it can kill and do. Boom capitalize on ignorance and internet intelligence and you have the newest and best selling cartridge.

But with faster twist barrel. Lol. Then it would be like the .223/5.56thing where there could be hundreds of pages on the internet explaining how you can chamber either ammo in either rifle but only one should be used out of one or both, etc. Really create mass confusion for the uneducated.

 

[MagnumManiac]

I designed 2 wildcats based off of the 416 Rigby case, blown out with .005" per inch taper, 338 and 375 cals with 45° and 40° shoulders respectively. Necks are .050" longer than calibre and the idea was to gain maximum velocity without excessive pressure and to keep the flame front as close to the shoulder as possible. This has worked, as throat growth was way less than what I predicted in both cals.
Funny thing is, the Norma, Lapua and others came out after my design and the David Tubb line of XC cartridges are very similar.
Had drawn up a reamer for a 30 cal variant but it never came to fruition due to circumstances changing.
Running 9" twists in both 33 and 37 cal gave me more flexibility, as I was also designing CNC turned brass solids with VLD features. They end up very long and require HBN coating to keep pressure down and velocity up.

Cheers.

 

[scpaul]

I do have the ability to moly coat. I've never had any problems with it. I only shot it in barrels that were well broken in and smooth. In some cases the vvelosity went up substantially and I saw a reduction in what the beginning of pressure signs. I also used it on the early X-,-,Bullets with some success.

 

[del2les]

I have played with wild cats for a long time. Longer necks give less throat erosion as PO Ackley mentioned. I made a 6 XC with a .400 length neck, formed brass from Lapua 308 Palma brass, and the lack of throat erosion at 900 rounds was only .007, which is nothing short of amazing! 105-107g bullets at 3150 out of a 31" 8T barrel.

I had noticed previously having shot out a multitude of 243 Win barrels and 6 Rem barrels that the 6 Rem had less throat wear.

I would love to play with longer necks from some other cartridges.

Simply changing the 243 to AI 40 degree gave me about 50-75% better throat life, and my 6RemAI's have better throat life than my standard 6Rem's. It changes the turbulence point to remain more in the case neck instead of the throat.

 

[scpaul]

I agree I think. Atleast that appears what is happening on my 7mmValkyrie. The thickening of the neck since the case isn't growing, do you think that it's a possibility within a reasonable life of the brass in general. No specific brand?

 

[Bghunter338]

Just you wait!

With these new high bc .25 cal bullets there is opportunity! So many on here hate anything creedmoor…but what if…I wonder…do you think we could use the .22-250 Remington case instead and still be cool? Just imagine? A 250-22-250. Why hasn't someone done this yet???

It's kind of like my wildcat idea based on the 7mm stw necked up to 8mm

I like where your going with that. Lol. Maybe a 7stw necked up to 338

 

[scpaul]

When I go to the range I very seldom fire over 3 rounds of my magnums. I may increase that in the future with this less intense round.
I built a 12v barrel cooler with a computer fan, plastic 50 round ammo box, switch and a length of hose that fits into the area just prior to the Chamber. In 100* heat (shade) I can cool a 26" bull barrel to ambient temp.
in about 15 minute. I used one of the small emergency exit sign batteries and it all fits in the ammo carrier. Originally for 300 RUM.

 

[Calvin45]

Revisit the concept of frontal ignition via a tube inside the case terminating near the mouth so that the primer spark touches off the front the of the powder column and it burns back toward the case head instead of back to front while half the powder is already down the dang barrel. Seems like a lot of fiddling around…I love it!!!

Should affect efficiency and throat erosion youd think.

 

[coop2564]

Really nothing new under the sun. I think the 270 wsm is one of the best cartridge designs ever. Just needs guns built with the right twist rate to make it great.