Ammunition

I vaguely recall from my early days of reloading for my '06 that "0.3085" was significant. Would this have been the "ideal" bullet diameter for a good seal in a bore of 0.3080? Or what? My Phil Sharpe's "Guide..." is packed away in the Great Somewhere. :)
 
Art, that's the diameter of the arsenal 172-gr. match bullet used in M72 .30-06 and M118 7.62 NATO match ammo. It shot much more accurate in NM barrels than the smaller diameter ball, trace and AP ammo bullets at .3080" and smaller. NM barrels' groove diameters were .3082" to .3083 on average. The broach rifler when new, made them about .3085" but many barrels later it had worn down and groove diameter was down in the .3075" range. In comparison the broach used rifling the 7.62 NATO Garand barrels for the USN and USAF were air gauged and those in the .3075" to .3079" range were set aside for match conditioned Garands.

Most barrels need bullets at least .0003" larger than groove diameter for best accuracy. And even .0015" larger will do just fine. I and others have shot .3092" bullets from .3075" groove diameters with excellent results.
 
Last edited:
I see Palma barrels at .307" groove mentioned.
Is this for the 155 gr bullets now used in international Palma or is it a throwback to the days when Palma was shot with hardball?
 
Don't forget the US gov. also had 3 number designators for the .45-70's such as .45-70-405 one of the early standard rifle rounds .458 bullet 70 grains of powder behind a 405 grain bullet, sometime around 1879 (I think anyway) this round was changed to .45-70-500. Now the carbines had their own loads that were different from the rifle loads in bullet and powder weights. I will have to dig out some info on these, Can not seem to recall what they were right now but am thinking .45-50 (maybe 55)-330 was one.
 
Last edited:
The 1873 carbine load was .45-55-405 versus the rifle load of .45-70-405.

The later .45-70-500 was an outgrowth of the Sandy Hook extreme long range tests. They really liked the .45-80-500's ballistics but did not want to change over to its longer case and chamber.

Modern BPCR shooters tend towards even heavier bullets, 520 to 540 gr .45s are common. I am shooting a 404 gr .40 cal and will be going up to 420 when my supply of Snovers is gone.
 
Jim, those .307" groove diameter barrels were first made for arsenal 3075" diameter 7.62 NATO bullets. Probably in Great Britian or one of its Commomwealth countries. They aren't allowed to use handloads and every one has to use the same lot of ammo. Their arsenal ammo bullets are sometimes .3070" diameter so they use .3065" groove diameter barrels to shoot them accurately. They often to all that very well.

In 1991, when Sierra first made their Palma bullets, they were .3084" diameter. They shot 1/2 MOA at 600 in .3065" to .3080" groove diameter barrels. All their previous HPMK 30 caliber ones were kept at their same size of .3082". I have no idea why that diameter was used.
 
Last edited:
Add to the confusion that some wildcats are described in their early days by simply naming the bullet size and case. Such as the .30/5.56 - the slash designating the combination of the two components.

If it has any chance of success then the inventor will rename it, buy using the bullet diameter number that will embrace a distinction, then, adding their name. If then introduced by a major Brand, they get "naming rights" and add their own.

And often as not, the inventor decides to embellish even further with an obscure reference to mythology. Or, dissimulate any connection at all, to cover it's origins.

The result is the 6.8SPC Remington, or the 6.5 Grendel. Now, if another maker decides to copy it and contest the market by challenging shooters to adopt a name by popularity, we get the .264LBC. And AAC renames the .300 Whisper and it becomes .300 Blackout.

Improve the chamber and make ammo that will only shoot in those guns safely (which is arguable,) and you get the 6.8 SPC II, or all the "Ackley Improved" versions.

Add some trying to embellish the round with their aspirations of it becoming official - and therefore being able to buy cheap surplus - and you get 6.8x43 NATO. There are barrels so marked on the market.

So, you wind up with a cartridge loaded with a .277 bullet, in the .30 Remington (Rimless) case, and yet to be issued by any NATO signatory.

The real purpose of a cartridge name is either to officially designate it in the inventory of a military establishment, or to market it to the general public. And there are few rules that ensure any dimensional accuracy other than to be specific about what it constitutes. The naming is more based on it being the least likely to be confused with it's nearest in size, and sometimes the system doesn't work. 9MM Kurz isn't 9mm Luger isn't 9mm Parabellum, but you have to know it for sure rather than guess. On the other hand, the various .22's, from cap to Long Rifle, are nearly interchangeable in some guns, although the results are dramatically different.

Goes to some shooting enthusiasts who collect cartridges, and the trade in exotics or rare ones amounts to a significant portion of our hobby.
 
Add to the confusion that some wildcats are described in their early days by simply naming the bullet size and case. Such as the .30/5.56 - the slash designating the combination of the two components.
Click to expand...

Yeah, and often retain the name when made "official" by an ammunition maker.

Example. .25-06.
 
You must log in or register to reply here.
Back
Top