Would the true 7mm please stand up!!!

[mikenc]

Is there really a true 7mm. I've done some looking this afternoon and I have found at least 18 calibers that are or are based on the 7mm.

Everything from:
.280
.284
7mm-08
7mm TCU
7mm IHMSA
7mm stw
7mm Rem. Mag.
7mm Weath. Mag.
7mm x 47
7mm x 61

The list is numerous.


Mike Alford

 

[700xcr]

guys i have had great luck reloading my brothers kimber 270 wsm and it likes 7828ssc give it a try we have had great luck with it.

Thank for the info. What primer and bullet weight are you using?

 

[J E Custom]

Mikenc

I only found a few rounds that were not .284 .

6.8x57 chinese .277 dia (the only other one except the winchester
and 4or 5 wildcats).
280 british .283 dia
276 pederson .285 dia
7.35 mm carcano .298 dia. (The right designation but the wrong Dia).

As far as I can tell there are no true 7mm (.275.5) cartriges.

Very Interesting
J E CUSTOM

 

[mikenc]

Mikenc

I only found a few rounds that were not .284 .

6.8x57 chinese .277 dia (the only other one except the winchester
and 4or 5 wildcats).
280 british .283 dia
276 pederson .285 dia
7.35 mm carcano .298 dia. (The right designation but the wrong Dia).

As far as I can tell there are no true 7mm (.275.5) cartriges.

Very Interesting
J E CUSTOM

I agree, there does not seem to be a true 7mm. The calibers and chambering I am currently looking at are in the R W Hart calalog. You as a custom builder probably are very aware of Bob Hart. To start with the .280 remington and carrying on to the 7mm-300 with at least 16 choices between. It seems there are many many variations of the 7mm.

I suppose it's like everything else, personal choice/preference.


Mike Alford

 

[ncpreacherboy1]

why does remington call their 270 cartridge a 6.8?

 

[dave42]

.270win is the real 6.8mm?

For those that don't know.
The bore diameter of a 7mm/.284cal is .277 hence the 7mm designation.
James

I agree with James.

Example: 308win has a bullet diameter of .308 but the bore diameter is .300 which converts to 7.62mm as everyone knows.

So when it comes to the 270win sure the bullet diameter is .277 = roughly 7mm but the bore diameter is still only .270 so that means that the .270win is not the real 7mm but it is the real 6.8mm if that helps.

So next time someone has an argument about this ask if there talking about the bullet diameter or the bore diameter.

I don't really care one way or another but I'm glad I read this thread anyway because finding out that berger has a .277 150gr VLD kicks ***!!!!!

Dave

 

[Dave Schenck]

sectional density

If the bore diameter is .270 and the bullets are .277 then it stands to reason that the bullets are "squeezed" down the barrell as they bite into the rifling. Does that then mean that the SD of the bullet changes as it is forced down a slightly narrower tube on its way to the target? If we measured the bullet diameter after it was shot, what would it be?
You have got me thinking!

 

[Pdvdh]

If the bore diameter is .270 and the bullets are .277 then it stands to reason that the bullets are "squeezed" down the barrell as they bite into the rifling. Does that then mean that the SD of the bullet changes as it is forced down a slightly narrower tube on its way to the target? If we measured the bullet diameter after it was shot, what would it be?
You have got me thinking!

I believe they are talking about the rifling land versus groove diameters of the bore. For example, the groove diameter of a 300 Win Magnum is the same as the bullet diameter (.308 inches). However the rifling lands in the bore are at a diameter of .300 inches. So no, the bullets aren't swaged down by 0.008 inches in diameter, but the rifling does imprint into the jacket of the bullets. Make sense?

 

[Dave Schenck]

yes - makes good sense
thanks