slow burning verses faster burning powders

[longguner]

Hi again,
I read in the past that slow burning powders are used for heavier bullets and the faster burning powders are used for lighter bullets.

But when you look at data it seems to be that it's a mix. I always like to research what powders are best suited for a particular caliber. A hodgdon rep. told me that slower burners generate more pressure.

Such as BLC2 was designated for the .308 winchester..... guess it's just depends on the gun it shot out of.

I used it with 180 Nosler PT with BLC2, which are harder than other bullets, and had excess pressure out of my Remington 760.

Any input or advice what to powder works best with .308 winchester?

What contributes most to excess pressure. It seems there's a way to experiment without wasting components.

 

[Guy Miner]

Too much of almost any powder can generate excess pressure.

I've used BLC2, happily, in the .308 Win. The more popular powders for it are usually Varget and RL-15, although good old IMR 4064 continues to shine as well.

Excess pressure can also be created by brass that hasn't been appropriately trimmed. Or bullets seated into the lands.

Pressure in itself isn't a bad thing. It's needed to kick the bullet out of the case and send it through the barrel, accelerating. Excess pressure though - that's a problem. Start low with the recommended powders and work up. Take a look at the powders Nosler & Sierra recommend as their accuracy or hunting loads. Ask here. Many sources of info.

Regards, Guy

 

[longguner]

Yeah IMR 4064 was recommended by Hodgdons.

I had an experience with bullets jammed into the lands... tight group, but the pockets opened up and the head swelled, to the point of chucking the brass.

I guess if the primer pockets don't open up but I have flattened primers, it should be good to go,and the case head doesn't swell past specs I should be good.

 

[.300winmag]

I used IMR 4064 for 180 grain SGK's and they shot extremely well, for 168's and 175 grain bullets, VARGET has always done extremely well for me as has IMR 4895.

 

[DrMike]

Your assessment is a general rule, and general rules are, well, general. As a rule, slow powders are more appropriate for heavier bullets, and fast powders are more suited for lighter bullets. There are many other factors that must be considered before giving a hard and fast rule, however. Burn rate changes with charge weight, case volume, bullet weight and even with primer brisance. Consequently, there are numerous instances where a faster powder proves a better choice with a heavier bullet than a slower powder, and vice versa. The powder that works best with your .308 is determined by trial and error. In general, however, you would be well advised to consult a good reloading manual and consider the recommendation of the ballisticians who provide the information therein. For instance, the Nosler Guide will list the most accurate powder, which means the powder that gave the lowest standard deviation for that particular bullet under the conditions specified; it is a very good place to begin looking.

 

[longguner]

Got em all... reloading manuals...LOL with the exception of a few.

The powders listed from 300winmag kinda narrow it down I think....

Dr. Mike thanks for your insight.... but I WAS HOPING YOU WOULDN'T SAY "Trial and error" LOL :wink:

I really though BLC2 was the key according to some sources. It looks like IMR 4895, 4064, and Varget are the ticket.

I just wish Partitions would come in 100's instead of fifties..... and the test increment spreads would be shorter... some are, like IMR 4895.

 

[Polaris]

Learn from the mistakes and successes of others. You are in the right place here.

The variables affecting performance of a given powder/bullet/case/caliber/rifle combination are legion. Not all are understood or quantifiable by science. Lyman has IMHO one of the best sections for the beginning reloader delving into this subject.

I don't have much experience loading 308 with heavier bullets. My loading of this round has been limited to 150 and 165 grain bullets. I've had excellent results with Bl-C2 and IMR 4320. Based on this and experience with heavier bullets in calibers of similar geometry, I'd think IMR 4320 would be about perfect, IMR 4064 or Varget will give you a bit more versatility.

You mentioned bullets touching the lands. This generally causes a spike in pressure and should only be attempted by experienced loaders and worked up to very carefully. Changing a single component or seating depth can cause NON-LINEAR changes in velocity and or pressure.

Do some homework, ask around... there is no such thing as a dumb question... and happy shooting.

 

[Horsethief]

I have used H-4895, Varget, and W-748 in the 42 - 44gn range with 165gn Sierra and Hornady bullets and had sub-inch shot groups from my Savage rifle with a fairly loose 308 Win chamber. You can also tweek the seating depth, and making the COL a bit longer can be one of the things your particular rifle chamber likes. Also, when you're working on the accuracy, take on one thing at a time. If you choose to seat the bullets out farther in the case, do it the same length for all the powders, not just one. That invites two variables when you only want to look at one at a time.
The reloading manuals usually use 24" barrels, which are almost certainly going to reach a faster velocity than a 22" barrel. Don't feel like you're failing if your velocities aren't what the books have. Accuracy is more important than velocity, in my opinion, but I think we all want to be the fastest and the most accurate we can.

 

[JD338]

The mid range burn rate powders work well in the 308 Win. IMR 4895, IMR 4064, RL 15 and Varget are all excellent choices.

JD338

 

[Mountain Goat]

I'm surprised nobody mentioned RL-15. After all, it is the powder used in the military's 168gr sniper round. I have only loaded for a few 308 Winchesters but RL15 has sure been nice in my 300 Savage with 180gr Speer Mag-Tips.

I had a Savage 12BVSS in 308 that shot 150gr Ballistic Tips over RL-15 into rather small holes. That rifle never went anywhere but to the range, so I sold it for something that I thought was more usefull.

 

[gerry]

RL 15 and Varget is the ones I would look at both are capable of great accuracy and good velocity. I bet that Big Game would work very well too.

 

[.300winmag]

With the 180gr. SGK I 43.5grs, IMR 4064 and am getting .5 MOA out to 500 yards, I'm not sure what you're getting but that would be my starting point. I am shooing them out of a custom .308 winchester with a boots-obermyer chamber , so I am touching then rifling to 0.005" off on all of my loads. Velocity out of a 24" barrel at 4750 is 2,771fps.

 

[SJB358]

300WM, that sounds like a great load right there. 2700 with a 180 in the 308 is scootin. Might have to look into that one some more.

 

[RiverRider]

Here's a bit of info that can provide a little insight: grain for grain, smokeless powders contain roughly the same amount of energy and generate the same volume of gas. The burn rate determines how quickly it's released.

 

[shoots_5]

Don't forget that barrel length plays a role in powder selection as well. A 18" barrel and a real slow powder is going to be a poor combination compared to a 26" barrel that will take advantage of burning all of that powder before the bullet exits. There are many many factors that make certain powders stand out over others but I would listen to the advice you've gotten already from these fine folks as they are pretty spot on!

 

[HTDUCK]

My go to powder for 308 Win is H380.
It's about the same burn rate as RL15 but being a ball powder it meters beautifully.
I've used BLC2 and Varget but with the 150-165 gr bullets H380 gives me better accuracy.

 

[longguner]

looks like the old standard IMR 4895 4064.... also got the Varget.

Thanks guys!!!

 

[longguner]

something I read from an old IMR load manual.....

Load the start load and shoot several rounds to see if your can raise the charge... if you have pressure signs use another powder.

Something I would have thought although I never ran into flattened primers until I loaded Noslers PT, they were flattened from the start.