A question about a theoretical cartridge.

G

gsh341

New member
This is kind of a strange first post, but here it goes.

OK, here's the general idea and where it started coming from.

Some states only allow deer hunting with straight walled rounds and it's common for people to use a lever gun chambered in 44 Magnum.

That made me remember that you can make 44 Auto Mag cases by cutting down a 308 Win case to 1.298" and reaming out the case mouth an extra .018 or so to fit the 0.430" 44 caliber bullet.

But what if instead of reaming it out you loaded a 180 grain 41 caliber bullet (0.410) instead and left the case at 1.860"?

We already know that a 308 can safely fire a 180 grain bullet, so the weight shouldn't be an issue.

A full to the top case of Varget at that length is about 48.5 grains and leaving out some powder to get an uncompressed load would be about 42 grains.

According to the Hodgdon Reloading site the minimum load on a 308 Win with a 180 grain bullet is 41 grains and a max (compressed) load is 45 grains. So that puts us somewhere in the possible sweet spot for powder.

So you have a straight wall case firing a 180 grain bullet and the Ballistics By The Inch website says that the 180 grain 41 Rem Mag will have a 1,629 fps velocity from an 18" barrel.

Hodgdon says a 180 grain 308 with a 41 grain load from a 24" barrel should be about 2,500 fps. (I know, rifle powder and pistol powder aren't the same, but I'm just tossing out ideas, OK?)

Considering that it's straight walled and will lose some pressure, but will be shot from a 18" to 22" barrel, I'm thinking that it might have about 2,000 fps to 2,200 fps for a muzzle velocity. Let's split the difference and say it's theoretically 2,100 fps

Given the BC of .180, you only have a 100 yard range before you go below 1,000 ft-lbs of energy, but you start out just over 1,000 ft-lbs with a 44 Mag from a lever gun anyway.

With a 41 caliber, all copper bullet with a longer and better shape, that range could be extended out past 125 yards for 1,000 ft-lbs of energy.

Of course, not being rimmed it would have to headspace off the case mouth like a semi-auto pistol, but you could use a 308 rifle with a custom barrel on it.

Also, the total case length would only be about 2.150 which means it could theoretically be fired from an AR-15.

Anyone have any thoughts on it?

This is all just random thoughts and I was wondering what anyone else thought.
 
.415 and .445 Super Magnum come to mind.
Also .444 Marlin. (Developed from straight-walled, rimmed, and trimmed .30-06.)
And .357 Maximum.
And .416 JDJ.
 
The closest would be the 415 Super Magnum, but those are all rimmed cases using pistol powders.

The 444 Marlin uses 240 grain or larger bullets in a much longer case.

I was thinking of a 180 grain to no heavier than 200 grain bullet shaped more like the Barnes TSX 405 Winchester bullets, but shorter with a boat tail to lighten it up from 300 grains to 180 grains and give it a higher BC than a pistol bullet.

https://www.barnesbullets.com/product/tsx/

The big advantage though would be the amount of brass available for converting and the possibility of using an AR-15 or a re-barreled 308 or 30-06 rifle.
 
If it scratches your itch, try it.

Something i would consider is a rifle built around the 45 Win Mag.
Essentially a 45 ACP lengthened, with thicker walls able to go to 40,000 psi.
Buffalo Bore is showing a 230gr bullet at 1,600 fps from a revolver.
So a 185gr from a longer rifle barrel would be in the 2,000-2,100 fps range i'd imagine.
 
I have pistols in .44AMP and .45 Win Mag. One of them is a 14" .45 Win Mag barrel for my Contender. I haven't chronographed anything from that barrel, but I would expect a 230gr getting 18-1900fps or more entirely possible.

Not sure why you're interested in a 1,000ft/lb energy limit, doesn't take near that much to take deer or even larger animals.
 
While less than 1,000 ft-lbs can kill a deer, I believe that is the minimum a round should have to ensure a quick kill. That much power will give a through and through and smash any bones that get in the way.
 
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Even in a theoretical exercise it is important to define the parameters. Here is what we are working with in Indiana. Within the set parameters you would have a fair bit of flexability.

In regards to cartridges

Rifles straight walled only.
PUBLIC AND PRIVATE LAND:
Bullet diameter: .357” minimum
Casing length: 1.16–1.8”

Handgun
Handguns\Barrel length: 4” minimum
Bullet diameter: .243” minimum
Cartridge length: 1.16” minimum, except for 10 mm
• 10mm also legal cartridges (i.e. 10mm Auto and .40 S&W)
• rifles with barrel less than 18” are NOT considered handguns
• .25/.20, .32/.20, .30 carbine, and .38 special ammunition is prohibited

In regards to handguns, as I understand it bottleneck rifle cartridges are permitted. Thus the smaller minimum bullet diameter, as well as no maximum case length specification.

In reference to muzzle energy.
Air rifles .40 caliber or larger that fire a bullet with a single discharge
of 400 ft. pounds of energy

Notes: I am not a fan of allowing 40S&W in a 4in barrel pistol (g23) for hunting. I have no idea where they got 400ft lb for air rifles, it is in the range of a 9mm but 9mm is no allowed.
 
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While less than 1,000 ft-lbs can kill a deer, I believe that is the minimum a round should have to ensure a quick kill.
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Thanks for the clarification that it is your personal opinion.

I disagree with you on this.
 
Regarding the idea of going to a smaller bullet to avoid neck reaming:

It might work fine. I don't know. I never tried it.

But there could be a problem. A thicker neck might not expand,or obturate as easily. An indication of that is sooty cases.
It may not be a problem. Good luck!
 
Similar to a .414 SuperMag. Encore barrels are available for it. My 10" SuperMag delivers some powerful deer medicine. I originally shot IMHSA with it, but it works for other stuff.

I'd be more likely to shoot a 10mm DI AR than the chamber a repeating rifle for .414 Superman, especially when 444 Marlin and .45-70 are out there in abundance.
 
A 357 Mag has less energy than that and can kill whitetails just fine. KE is no better than other measures of stopping power; they all work in some situations and fail in others. Enough KE to drive a .224 FMJ into a hog's brain will cause a varmint bullet to blow up in the subcutaneous fat layers of its shoulders and, if you are lucky, will kill the hog a week or two later from the wound going septic. It's always less about how much KE you have than it is about what you do with it. This is why bullet choice and shot placement are important.


gsh341,

Getting back to your first post starting the thread, what you are not considering is that the wider 0.410" bullet will have lower sectional density than the same-weight .308" bullet, and the wider bore will have a greater expansion ratio for the same barrel length. This will mean you need a faster powder than Varget to approximate Varget's interior ballistic efficiency with a .308" bullet.

The sectional density is proportional to how much bullet acceleration you get for a given number of pounds per square inch of pressure on its base. This is because the force pushing the bullet forward is equal to the cross-sectional area of the bore times the applied pressure. So, at, say 10,000 psi, the .308 bullet in a bore with 0.0736in² cross-sectional area will have a force of 736 pounds accelerating it, while a .410" bullet in a bore with 0.128in² cross-sectional area will have a force of 1280 pounds accelerating it. Thus, if the two bullets weigh the same 180 grains, the bigger diameter bullet will be accelerating 0.128/0.0736 or 1.74 times faster. This means, at a given pressure, the wider bullet is running away from the breech faster.

The bullet moving down the bore adds the volume of the case neck and free bore and barrel bore behind it to the volume inside the case to arrive at the volume the powder is burning in. This is called expansion. The bigger that expanded volume, the lower the pressure for a given amount of powder gas and the slower the powder burns in that lower pressure. Because the 41 caliber bore is bigger than the 30 caliber bore, the bullet doesn't have to move as far down the barrel to double that combustion volume. Now, add to this what we found in the last paragraph, and you will see that at lower pressures the bullet runs away from the powder faster and adds to the volume it is burning in faster than the 30 caliber version does. Both factors mean the powder has to burn faster to gain as much pressure in the same volume as the 308 load achieved. In effect, the powder has a harder time making gas fast enough to keep up with the wider bullet. Hence the need for a faster powder to equal the ballistic efficiency (the percent of the powder's potential energy converted to kinetic energy in the bullet) of the Varget in the 308 Winchester.
 
44 AMP said:
Thanks for the clarification that it is your personal opinion.



I disagree with you on this.
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While this is my opinion, it is a very common opinion in the hunting community that 1,000 ft-lbs is the minimum for an ethical and clean kill.

However, many of the common rifle cartridges happen to hit the 1,000 ft-lbs minimum about th same time the bullet drops below 1,900 fps, and which is th common manufacturer recommended minimum velocity for reliable expansion.

With that being the case, I determine my personal max effective deer hunting range for any rifle being 1,000 ft lbs of energy or 1,900 fps velocity, whichever comes first.

But, you do what you feel is best.
 
Unclenick said:
gsh341,

Getting back to your first post starting the thread, what you are not considering is that the wider 0.410" bullet will have lower sectional density than the same-weight .308" bullet, and the wider bore will have a greater expansion ratio for the same barrel length. This will mean you need a faster powder than Varget to approximate Varget's interior ballistic efficiency with a .308" bullet.

The sectional density is proportional to how much bullet acceleration you get for a given number of pounds per square inch of pressure on its base. This is because the force pushing the bullet forward is equal to the cross-sectional area of the bore times the applied pressure. So, at, say 10,000 psi, the .308 bullet in a bore with 0.0736in² cross-sectional area will have a force of 736 pounds accelerating it, while a .410" bullet in a bore with 0.128in² cross-sectional area will have a force of 1280 pounds accelerating it. Thus, if the two bullets weigh the same 180 grains, the bigger diameter bullet will be accelerating 0.128/0.0736 or 1.74 times faster. This means, at a given pressure, the wider bullet is running away from the breech faster.

The bullet moving down the bore adds the volume of the case neck and free bore and barrel bore behind it to the volume inside the case to arrive at the volume the powder is burning in. This is called expansion. The bigger that expanded volume, the lower the pressure for a given amount of powder gas and the slower the powder burns in that lower pressure. Because the 41 caliber bore is bigger than the 30 caliber bore, the bullet doesn't have to move as far down the barrel to double that combustion volume. Now, add to this what we found in the last paragraph, and you will see that at lower pressures the bullet runs away from the powder faster and adds to the volume it is burning in faster than the 30 caliber version does. Both factors mean the powder has to burn faster to gain as much pressure in the same volume as the 308 load achieved. In effect, the powder has a harder time making gas fast enough to keep up with the wider bullet. Hence the need for a faster powder to equal the ballistic efficiency (the percent of the powder's potential energy converted to kinetic energy in the bullet) of the Varget in the 308 Winchester.
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This is the sort of discussion I was hoping for.

As I said, I was just tossing the idea around in my head and since I had Varget available I used it as a baseline for the capacity measurements. Maybe a faster powder would be better. I'm not sure.

But this is more of a thought experiment than anything else.
 
Over 1000lb./ft. of muzzle energy can be attained with a 210gr. XTP by loading it to over 1500fps in a .41mag. While that’s a pretty warm round, I’d id feel comfortable shooting it out of my Henry. My heavy load that I like right now is around 1450fps and definitely thumps and shoots more than accurate enough out to 100yds. I’ve pushed it beyond this but found the best accuracy in my rifle at this level.
 
It's not 1,000 ft-lbs of energy at the muzzle that's what I want. It's 1,000 f-lbs of energy at impact.

That means a 180 gr, 41 caliber round with a BC of 0.185 would need to be going 2,000 fps at the muzzle (which results in 1,600 ft/lbs. at the muzzle) to have 1,000 ft/lbs of energy at 100 yards.

If you used a 180gr 405 Winchester round it might have a BC of .250 (just a guess) and that would allow the velocity to carry an extra 25 yards.

Your 41 mag has about 688 ft-lbs at 100 yards and the round I'm suggesting would have that much energy at just under 200 yards. That's a considerable difference for a straight walled 41 caliber bullet.
 
gsh341 said:
It's not 1,000 ft-lbs of energy at the muzzle that's what I want. It's 1,000 f-lbs of energy at impact.

That means a 180 gr, 41 caliber round with a BC of 0.185 would need to be going 2,000 fps at the muzzle (which results in 1,600 ft/lbs. at the muzzle) to have 1,000 ft/lbs of energy at 100 yards.

If you used a 180gr 405 Winchester round it might have a BC of .250 (just a guess) and that would allow the velocity to carry an extra 25 yards.

Your 41 mag has about 688 ft-lbs at 100 yards and the round I'm suggesting would have that much energy at just under 200 yards. That's a considerable difference for a straight walled 41 caliber bullet.
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One thing you will have to take into account is the bullet itself. Bullets pushed past their intended velocities can perform poorly. For example in 44 magnum my 240g XTP's state they are intended to work between 700fps and 1500fps. If pushed too hard they could over expand, under penetrate, or fragment.

If you talking 2000fps at the muzzle you will have to be careful with your bullet selection.
 
gsh341 said:
It's not 1,000 ft-lbs of energy at the muzzle that's what I want. It's 1,000 f-lbs of energy at impact.

That means a 180 gr, 41 caliber round with a BC of 0.185 would need to be going 2,000 fps at the muzzle (which results in 1,600 ft/lbs. at the muzzle) to have 1,000 ft/lbs of energy at 100 yards.

If you used a 180gr 405 Winchester round it might have a BC of .250 (just a guess) and that would allow the velocity to carry an extra 25 yards.

Your 41 mag has about 688 ft-lbs at 100 yards and the round I'm suggesting would have that much energy at just under 200 yards. That's a considerable difference for a straight walled 41 caliber bullet.
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Ah, upon rereading your post I realized my interpretation was in error.
 
CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

I built the 41-308 in QuickLOAD. With a 24" barrel, 47 grains of Varget behind a Barnes 180-Grain XPB, it achieves a projected pressure of about 20,250 psi, and the bullet is going about 2041 fps for a muzzle energy of 1655 ft-lbs. Ballistic efficiency is terrible for a straight-wall cartridge at 18.3% because 38.69% of the powder is blown out of the muzzle as yet unburned. The G1 ballistic coefficient of that bullet is 0.126, so it needs about 2200 fps at the muzzle to carry 1000 ft-lbs at 100 yards. So, as expected, Varget is far too slow in this application, wastes powder and can't get you where you want to go.

The theoretical cartridge is closer to its peak performance with 46 grains of Lil'Gun, peaking at 52,522 psi, producing a muzzle velocity of 2935 fps, and a muzzle energy of 3443 ft-lbs. Ballistic efficiency is 38.3% and all of the powder burns up inside the barrel. 47.5 grains of H110/296 revolver powder gives close to the same results. However, both increase pressure rather rapidly with little additional powder at these pressures, so I would not work up the load that high. Also, if the load is to be downloaded to about 2200 fps MV, the case fill is too low for either of these powders to do well. At that point, a load of about to about 2500 fps and stop. The best option for that looks like about 38.5 grains of VV N120. The case fill is then almost 87%. Not great, but not terrible. About 11% gets out of the muzzle unburned, but that's a more reasonable sacrifice than something slower will stick you with.
 
Unclenick said:
CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

I built the 41-308 in QuickLOAD. With a 24" barrel, 47 grains of Varget behind a Barnes 180-Grain XPB, it achieves a projected pressure of about 20,250 psi, and the bullet is going about 2041 fps for a muzzle energy of 1655 ft-lbs. Ballistic efficiency is terrible for a straight-wall cartridge at 18.3% because 38.69% of the powder is blown out of the muzzle as yet unburned. The G1 ballistic coefficient of that bullet is 0.126, so it needs about 2200 fps at the muzzle to carry 1000 ft-lbs at 100 yards. So, as expected, Varget is far too slow in this application, wastes powder and can't get you where you want to go.

The theoretical cartridge is closer to its peak performance with 46 grains of Lil'Gun, peaking at 52,522 psi, producing a muzzle velocity of 2935 fps, and a muzzle energy of 3443 ft-lbs. Ballistic efficiency is 38.3% and all of the powder burns up inside the barrel. 47.5 grains of H110/296 revolver powder gives close to the same results. However, both increase pressure rather rapidly with little additional powder at these pressures, so I would not work up the load that high. Also, if the load is to be downloaded to about 2200 fps MV, the case fill is too low for either of these powders to do well. At that point, a load of about to about 2500 fps and stop. The best option for that looks like about 38.5 grains of VV N120. The case fill is then almost 87%. Not great, but not terrible. About 11% gets out of the muzzle unburned, but that's a more reasonable sacrifice than something slower will stick you with.
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Thanks, Unclenick!

I was curious about the best powder but I was seriously impressed by the theoretical limits of the loads.

Using that bullet and the Lil' Gun load at 2,500 fps, the round would have 2,498 at the muzzle and wouldn't get down to 1,000 fps until around 160 yards at which point it's still cruising along at 1,500 fps or so. If you figured a minimum velocity of 1,100 fps, it wouldn't hit that until 275 yards where it would have 485 ft-lbs of energy.

That's a lot better than I thought.

What do you think would happen if you loaded it with the 300 grain 405 from Hornady and used a 20" barrel?

https://www.hornady.com/bullets/rifle/405-cal-411-300-gr-interlock-sp#!/
 
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