Fast burning powder for 7mm mag in 24" barrel?

[Snakum]

I've been researching barrel length for 7mm rem mag rifles and its affect on velocity. I've seen that most factory ammo ballistic charts are developed thru 24" barrels, which shouldn't allow all the powder to burn, as I understand it. So I'm wondering if there is a faster-burning powder for 7mm mag handloads that will "get all the work done" in a 24" barrel?

 

[R.W.Dale]

Not the "faster powder for shorter bbl" MYTH.............again


Powder burnrate is specific to the CARTRIDGE not the bbl length. Bullets are not rockets where propellant must be burning to provide thrust. Rather a rifle is a air gun in a way in that propellant burns rather quickly (in the first few inches of bullet travel) and is converted to a large volume of gas at very high pressure. This pressure us what drives the bullet not burning thrust like a bottle rocket

 

[Snakum]

I had two gunsmith's tell me that I should be using a "faster burning powder" when handloading for a 7mm mag with a 24" barrel. But when I asked specifically what kind/brand they suggested they went off into technical handloading info that was way over my head since I'm not a handloader yet. I will have someone do it for me, and that person was also curious about what "faster burning powder" they are suggesting.

So, you're saying this is really an old wive's tale and that faster or slower for shorter or longer magnum barrels makes no diff and shouldn't be a consideration?

 

[R.W.Dale]

Don't misunderstand me a longer barrel will provide more velocity as the aformentioned high pressure gas will have longer to push on the base of the bullet.


However using a faster than optimum powder will not provide more velocity in a shorter bbl but will in fact provide less velocity in ANY barrel length. Within reason

 

[Snakum]

Thanks for the info.

 

[ants]

You need the powder and charge that give you the best accuracy for the bullet you choose in your barrel. Anything else you do is a waste of time if it does not improve accuracy. Higher velocity is useless if it sacrifices accuracy.

 

[JimKirk]

The IDEAL solution is to find a powder that will give you BOTH accuracy and velocity.

Why lug around a 7x57 or 7-08 in a heavy framed gun if that is all you get,You bought a 7mm Magnum. Realize that accuracy depends on lots of factors, which include the powder, but also includes the bullet and the barrel and the rest of the gun too.

That "figuring out" is the beauty of reloading, as we have the chance to experiment with different combinations of bullets, powder, primer, various COAL and all the other "part" that make a accurate rifle.

There are plenty of powders which are suited for the 7mm Remington magnum! My findings are that the slower powders give the most velocity and some will give great accuracy too! The trick is to find the combo that works in your rifle! Reloder 19, IMR 4831, IMR 7828 all give both good velocity and accuracy in my Rem 700 7mm mag. All my loads were at book MAX or over.

Jimmy K

 

[counterclockwise]

Hodgdon's data is based on 24" non-vented test barrels. Their data probably translates directly to 24" bolt gun barrels.

Go there {www.hodgdon.com} and find your optimum powders suitable in the 7mm rem mag range for the bullet wt. & design of your chosing. When you find the combo that works best for the 24" bbl, it will be the best for shorter and longer barrels as well, because of what Krochus said.

 

[Kernel]

However using a faster than optimum powder will not provide more velocity in a shorter bbl but will in fact provide less velocity in ANY barrel length. Within reason

The same thing can be said for using a SLOWER than optimum powder.

you're saying this is really an old wives’ tale and that faster or slower for shorter or longer magnum barrels makes no diff and shouldn't be a consideration?

Yep. Smokeless powder combusts almost instantaneously. So fast there’s only time for the bullet to travel a few inches. Trace amounts of powder DO burn in the barrel. But that powder adds practically NOTHING to bullet velocity. It’s due to the pressure/volume/bullet/barrel relationship. Longer barrels do increase velocity. But that’s not due to powder combustion.

That’s how a good old wives' tale gets started. It’s logically to think one plus one equals two (longer barrel + more powder combustion = higher velocity). But in this case it doesn’t equal two. Because it’s not one plus one. It’s one plus zero.

 

[rcmodel]

Quite frankly, your two gunsmiths don't know what they are talking about.

We have the same discussion going on concerning the .44 Mag short barrel revolver.
See this about that:
http://www.thehighroad.org/showpost.php?p=6193051&postcount=2

The same exact rules apply to rifles.

Whatever powder gives the highest velocity in a long barrel will also give the highest velocity in a short barrel.

The only good application for a faster powder in a 7mm Mag rifle would be to decrease muzzle blast, or for reduced recoil "youth" loads.
But at a reduction in velocity over what is possible with a slower powder better suited to the 7mm Mag..

rc

 

[R.W.Dale]

The same thing can be said for using a SLOWER than optimum powder.

100% correct

my quote

Too slow a powder and full chamber pressure cannot be reached because the bullet outruns the powders ability to change to gas. So after a point you need more powder than can psychically fit in the case

too fast a powder and the bullet cannot get out of the way fast enough and chamber pressure spikes. At which point you must use less powder. less powder = a lower volume of gas and therefore lower pressure pushing on the base of the bullet resulting in lower muzzle velocities in ANY barrel length

This is why you always want to use the slowest powder that the cartridge can actually make use of. This would be a propellant that can reach max chamber pressure AND have the highest load densities (IE a case full)

 

[Snakum]

Thanks for the info. The rifle is a new/old stock USRAC Model 70 Black Shadow that I picked up along with a NOS .300 Win Mag Black Shadow for a song, and I'm trying different things to see what might make it more consistent across factory loads. The 300 was nowhere near as accurate and carried too much punch for a lot of range work, so I sold it and am trying things on the 7mm and watching the results.

With trigger work and free-floating the barrel I've gotten 100 yard groups down to 1" with a couple inexpensive factory loads and less than an inch with a friend's handloads (160gr ballistic tips). I'm having 2" taken off the barrel (make it a 24") and a recessed target crown done to see what effect that has. As near as I can tell, the two inches will cost me between 30 and 60 fps in velocity, but will make it easier to lug in the woods when hog'n and increase the stiffness of the sporter barrel, which may contribute to accuracy.

Eventually I will use the action to build a heavy barrelled, long range thumper and will throw the rest away. So I can experiment and learn and have fun doing it.

 

[Jefferson Herb]

Having a 7mm rem mag[not ultra] since the 80's,and having fired few factory rds.
I love the sierrs 175gk w 63 gr H4831,It is accurate and case life is good for a mag.
I also broke ranks and use 78 gr H870 w a 140 ballistic tip.I'm going to try H1000 next time I have to load,but not for a while.
I have never tried to use a reduced load,7mm mag likes to be near the top,[I have a 338 that is the same way] I have used the ww std/mag primer but prefer the Fed mag/mag match. Your Friend has a good load,swap bt for accubond and try.