I see from the topic heading, that a big bore is 375+ bore dia. Is there a "power" factor that defines a big bore? I see from earlier posts, that the 45/70, and the 444 Marlin, while qualifying in the bore size catagory, are looked down upon by big bore shooters. Just curious, and wondering what the definition is.
krag35

I don't know if this is right but I class the .375 H&H as a medium and from .458 win mag on up a large bore. The .416's are neally large bores but spleit the diff between the .375 & the .458 whatevers. The 45/70 for what its worth is not a true large bore. I tend to go on the power that various calibers produce.

It depends on who is doing the defining, and what caliber rifle he has.



Most folks consider anything over .40 caliber with a 400 grain bullet traveling over 2000 fps to be a large bore "cartridge."

(this should start a lot of arguments)



The British don't consider anything under .45 to be a large bore.



Most folks would agree that the .375 is a medium bore.

.

oh fiddle..

hell, boys, the 577, at one time, was considered a MEDIUM (in the black powder days) and anything less than an 8, well, that wasn't sporting.

IMHO, one should take bullet SD, velocity, AND BORE to define a big bore...

so, I'll put "my" formula up again (it aint anything I developed, it's just what I use)

1: bullet weight about or over 300 grains
2: SD of over .300
3: velocity of at least 2050, idealized at 2400fps at muzzle
4: bore of at least .366

rationales
1: big bullets stay together and SMASH things,
2: high SD means long bullets for caliber/diameter. long bullets are going to be LESS likely to fail

3: because that's at least what the Nitro express version of whatever caliber you would want to compare your round too and large research taht demonstrates higher velocities make bullets fail.

4:legal for most DG in most countries, that's why

muzzle "energy" is unimportant, as a direct factor. It is a function of the above. Of course smaller bores will have higher velocities, in my opinion because it's FAR less recoil to take a 286gr 9.3 to 2400fps then a 500gr 458.


reaching ALL the way down to the 9.3x64, if one loaded to 2300 fps with a 286, that's about 3400 ft/lbs.. more or less 338 win mag country. In fact, i BELIEVE the 338, with premium bullets, would be an EXCELLENT round, but laws prepend this.

I myself, don't consider the 45/70 to be in the english sense, a big bore... if you took an outrageous load, say a woodleigh 480gr (SD, remember) and took it to CRAZY pressure, 45K psi, you would wind up with less than 1800FPS (failing vel) and the "same" energy as the 9.3 above, just shy of 3400 ft/lbs.

Since I did my own experiment on .458 bullets at low speeds, not penetrating nearly as far as higher speeds. (i spill a box of rem 405 sp's on my reloading bence, they fell off more or less one by one, and by golly, not ONE of them even penetrated my plywood floor. I had expected them to still be on their way to china, if one believe garrett's claims). I will conclude the the 45/70 is an awesome slayer, I just wouldn't point it at something that fights lions for a living.

All of the above was more academic, as I shoot, well, all the way to 500 jeffe-ry, and will carry the largest that I am comfortable shooting... and yeah, my deer/hog/varmit rifle is a .375 (376 steyr)... I don't consider that to be a big bore, but it does meet all the requirements.

jeffe

Alf,
I didn't read the article, but shouldn't it have said

Intermediate bore: 33 cal to 375
large bore: 400 to 45 caliber
Superbore: 468 and larger.

At least in american english, intermdiate is generelly interchangable with middle or medium, and has a minor negative connotation.
j

Armchair definitions keeps some folks entertained while other folks are culling cape buffalo with their 45-70s. What a wonderful world we live in!

Perhaps the modern Ford mustang is not considered a true performance car by the armchair experts, but the V8 powered affordable buggy will do 160mph. Sure, its not a Ferrai. Sure it doesn't have the proper European lineage. But everybody can own one and it will do 160mph whether the armchair experts will believe it or not.

So it is with the lowly 45-70. More and more people are drilling 1/2" holes completely through buffs with their lowly 45-70. The buffs are dying needlessly I'm sure. If only someone would tell the buffs that they're not being hit with a true big bore, you could put an end to this silliness. Imagine all the elephants that would've lived if they had understood that Bell was braining them with cartridge equivalent to the lowly American 30-30!

I watched another lion charge video thanks to the wonderful internet. A rather large male kitty took a mediocre hit from a .378 Weatherby (gobs of ft/lbs of energy). Then the kitty took a hit in the right front paw from a .460. There was much shooting, bullets kicking up dust and I'm sure that muzzle blast was hearing damaging - all quite impressive, but that kitty had the bad form to ignore this display of "true big bores" and charge the hunter. I'm sure it must be the snotty attitude of the west that has been bred into modern lions causing them to display such attitudes when facing "true big bores".

It must be truly galling to some to realize that "big bore" now must accept the achievements of a $500 American levergun chambered for an antiquated cartridge.

Did anyone else read the new Rifle mag on 45-70 in Afrika part II. It seems he killed 2 buff's with one shot as the bullet penetrated the big Bull and then took out a cow on the off side that wasn't seen. The bullet ended up on the far side of the cow under the skin.

A big bore is 0.458" and up.

Medium bores are from 0.308" to 0.440" (commercially made bores anyway).

Small bores are everything below 0.308".

Scott

Lar45,

No I did not, but that is why it is important that you KNOW what is behind your intended target!

Scott

I see PMC have put out a 2025fps 350grn 45/70.
Goto new products top right.

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