Discontinued Powders?

[bruce moulds]

thanks 458.
i thought they were very close.
bruce.

 

[7x57Joe]

According the the CIP tables:
7x64 PTMax 4150 Bar
.280 PTMax 4050 Bar

 

[Earle]

Don't know if it's fact or not, but i read that the capacity's can change and even sometimes reverse, depending on the brand of brass and variances in brass thickness. Pretty close at any rate.

 

[bruce moulds]

well it looks like with sensible handloading to similar pressures, the cartridges are peas in a pod for performance.
i went for the good looking one, 280 rem, but then beauty is in the eye of the beholder.
i can remember when 280 rem was the biggest custom chambering for a long time.
these rifles don't seem to come on the market much, attesting to the usefulness of that set of ballistics.
bruce.

 

[fourfive8]

@bruce moulds. Yes, surprised me also. They are very close in volume, case design and geometric proportion. I imagine that other variables would be greater than that small difference of capacity. One thing that comes to mind is brass brand and thickness (as was posted by @Earle) and how deep the bullet impinges into the case volume and the design of the bullet itself... like flat base vs boat tail. The other variable which may affect pressures in a general way would be how the throat lengths and dimensions vary rifle to rifle. All these variables would tend to affect potential pressures more than that tiny difference of case capacity- I would think.

If I owned a normal, strong bolt gun in 7x64, I would be tempted to just start using 280 Remington data- pay attention to seating depth/bullet jump, start 10% below max and work up while using a chronograph.

 

[Longwalker]

The idea that the 7x64 has to be loaded with lighter charges of powder than the .280 Rem. is a myth in my experience. I have had a couple of Brno 21 H rifles in 7x64, and still shoot a current production Sako 85 and a 1968 Mannlicher-Schoenauer. All can safely take slightly heavier loads than max. loads listed in my manuals for the .280 Remington. I would work up loads carefully using published .280 data if that's all that is available, but would certainly not feel obliged to quit at 5% below "maximum". Throat length of all my 7x64 rifles is very long, and typical 160 grain bullets almost leave the case before engaging the rifling. I believe this is according to CIP standards, and is in no way unusual.

 

[bruce moulds]

some cartridge chamber specs have around 1/2 degree leade angle, and some 1 1/2 degree.
this can make a huge difference to pressures, and can give the illusion of long freebore in the lower angle.
i could look this up for these two rounds, but don't have time.
in general, the 280 loaded to specs are lower than say the 270 win, so one would expect starting loads for it in 7x64 to be ok.
BUT, erring on the side of caution never hurts when reloading.
anyone who has worked up loads for the 280 knows that handloading is usually beneficial.
bruce.

 

[Earle]

Some really good advice and info posted. Thanks to all. Still haven't 100% decided on the powder i will use first. Rifle in question has an extremely long throat, so have to do some experimenting. May have to for-go the 140g bullets and start with 160s.

 

[bruce moulds]

earle,
don't panic about the long throat.
try 140s if you want.
often bullets will shoot well in long throats and a lot of jump.
if it is a cip or saami std throat most rifles in that calibre will have it and they work.
bruce.

 

[Earle]

That's good to know. Seated at a listed max of 3.307" the 140s are a loooong way from the lands.

 

[bruce moulds]

earle, the good thing about that is that you can forget coal, other than to fit the magazine.
just load them long enough to have enough clearance in the mag so that everything is functional.
bruce.

 

[shootist~]

A good place to start is seating the base of the bullet to the bottom of the neck. (The Ogive part not the bottom of a boat-tail.) If that ends up being over book Max COL, no big deal, so long as you have room in the magazine and are not jammed into the lands.

 

[Earle]

It amazes me how a couple 2 or 3 sentence posts can impart knowledge that i can't find in 5 different loading manuals. Many thanks to all.

 

[fourfive8]

Yes, a lot is made about minimal bullet jump to lands but that is best left in the realm of target shooting where tiny group sizes outweigh most everything else. For practical purposes, IMO, a 100 yd group size differential of .1" is usually not much of a consideration for hunting. Magazine length clearance and feeding reliability and adequate neck tension are far more important than .1" differences in group sizes.

It would be reasonable to assume most of the older 7mm chamber designs would have a fairly long throat, one long enough for the older, common 173-5 gr roundnose bullet. If your rifle has a long throat, I would consider it a positive thing for a hunting rifle... for versatility affording a max number of options. Even more so considering today's loooong monolithic designs. I would be tempted, as Bruce suggested, to let the magazine length and function/feeding help dictate max OAL. I like to seat the bullet to at least one caliber (.284") depth in a 7mm or to the full neck length if possible where the bullet's base is at the junction of the neck and the shoulder- as @shootist~ suggests. Looking at the 7x64 drawing, it appears to have nearly an ideal neck length of .340".

 

[7x57Joe]

Contrary to common wisdom about bullet jump, my CZ-550 FS shoots my handloaded 140 grain bullets into nice little clusters as my notes show 12 groups averaging 1.10" loaded to function through the magazine. Furthermore, I was simply amazed at the accuracy of factory PPU 140 loads through it.
175 grain handloaded bullets shoots very well also!

 

[CoElkHunter]

Good point, but unless that AA powder was stored in bad conditions like extreme heat, it should be fine. AA powders of that era aren’t that old relatively speaking. If it smells like ether it’s fine. If it smells like old vinegar and has reddish dust, it is starting to deteriorate. Unlike nitro glycerine settling out of sawdust in a stick of dynamite, it doesn’t get more dangerous- if anything, the chemical energy simply decreases. Plus it doesn’t have any nitro glycerine in it anyway- being a single base powder. Simple nitro cellulose

I’ll take a pic of the 7x64 data page(s) in one of the AA booklets and post it today.

fourfive8,
Not to diminish this thread topic, but would you happen to know what modern smokeless powders stored properly in their original containers in a cool basement for a number of years, might be dangerous to use? I have a quantity of W748 that’s 7-9 yrs. old. I’ve shot some 20+ year old reloaded cardboard hulled shotgun shells with no adverse effects?
Thanks!
CEH

 

[fourfive8]

Not that I have ever heard of. What commonly happens with chemical deterioration of a smokeless powder is a decrease of energy potential.

One of the more recent powder recall notices was, IIRC, 4007 SSC. Bulk quantities of the stuff in storage could heat up and catch fire- but that recall had little to do with pressure issues of loaded ammo.

The only documented instance of a loaded powder showing an increase in energy potential (more precisely- rate of burn and higher peak pressure), I’m aware of, was some double base, coated spherical powder in a quantity of military ammo. Investigation indicated that long term, continuous vibration during transportation had abraded the burn rate control coating off the surface of the powder kernels, increasing the rate of burn and peak pressures to dangerous levels.

I guess the safest course, if in doubt, would be to spread around plants as a nitrate fertilizer But usually a chemically deteriorated powder is easily identifiable.

 

[Longwalker]

Here is an example of what deteriorated powder looks like. I have had powder that deteriorated after perhaps twenty years of storage ( someone else stored it, so no idea of conditions), and some that was more that 40 years old and still OK. If it looks and smells normal, it is good to use.