Burn rate and load

[bsekf]

If 2 powders are next to each other on the burn chart, can they be safely interchanged? And, would we be talking volume or weight? I have always followed the reloading manuals, but with powder getting scarce I am looking for alternatives. I always start low and work up watching for pressure signs. For instance, Varget and Win 748.

 

[MikeT124]

You are asking (no Really begging) for trouble. If you can't find a reliable source for that particular powder in the caliber/bullet your looking for with all of the sources available to you in manual form and on the internet my advise is to forget it. I know it's a major pain to have a powder in your stock that is near burn rate in a manual suggested powder, but if it isn't tested and recommended, don't use it.

Mike

 

[Murray Brook]

I believe the short answer in no. If you check several charts you will find that they vary as to where several powders are on the burn rate. Sometimes to as much as several rungs on the rate ladder. But as you stated starting low and working up would be safe after checking a reliable source. JMO

 

[Doom]

Prove it to yourself. Look at IMR 4166 and IMR4064 on Hodgdon's reloading data in 308 with 168 SMK. Two powders side by side on the Hodgdon Burn Rate Chart. Powder composition including additives and geometry of the powder affect the heat input per grain of powder and burn rate.

 

[barefooter56]

Short answer... NO !!!

 

[Mulligan]

Interchanged-NO

But,
Powder companies do not test everything.
Bullet manufactures do not test every powder with their bullets. Some try hard (Sierra) others (Nosler) try a few.
If benchresters only used the powders listed in a manual with a PPC, What would everyone be shooting.... 2800 FPS with imr 3031????

Alliant just came out with 15.5..... not much load data anywhere for it. Yet, the NBRSA nationals were won this year by a fella shooting 15.5 in a BRA with heavy bullets.

Use common sense, start low and work up........ or better yet buy a copy of Quick Load and model it the best you can.

Good luck
CW

 

[markm87]

For instance, Varget and Win 748.

Those are two wildly different powders. Yeah, you can probably shoot the same bullet with both, but as advised, work the new load up. FYI Win 748 is fairly temp sensitive. I used to down load it 100 fps in .223 to allow for hot days.

 

[RegionRat]

@bsekf , The Burn Rate Charts should come with some words to the effect of don't try to assume load data from this chart alone.

Sometimes, powders next to each other on the chart follow each other very well, but too many times they don't.

As a novice, what you should look for is your alternate powder in several load manuals. You may or may not find the one you want, but do not assume the burn rate chart alone will be grounds for a substitution.

Now, the reasons for this are a long discussion. It takes a strong background in chemistry and thermodynamics of combustion to learn about smokeless powders and internal ballistics. It isn't necessary to study these things unless you find yourself in the design business for that industry. There are good books on the subject for folks who just want to know about load development.

You can learn to model these pressures and internal ballistics well enough with a couple of days invested to learn one of the consumer programs like Quick Load or Gordon's Reloading Tool. There you will see that powders are not described by one parameter like the burn rate chart, but several parameters including dependency on the specifics of the other parts like the cartridge, bullet, and gun. This is why you should look for load manual recipes and more than one. YMMV

 

[shoot4fun]

If 2 powders are next to each other on the burn chart, can they be safely interchanged? And, would we be talking volume or weight? I have always followed the reloading manuals, but with powder getting scarce I am looking for alternatives. I always start low and work up watching for pressure signs. For instance, Varget and Win 748.

As already mentioned above, Varget and WW748 are worlds apart.
I used WW748 as a go-to rifle powder for many years, Why? it worked in my 30-06, 7MM08, 308 and a couple others and it flowed well thru my Uniflow powder measure. Then came a little 788 rifle in 243. I searched everywhere possible for data but found none. This puzzled me because if it worked in the 7MM08 and the 308 it should be fine in a 243. After all, it is the same basic case design. Finally, I called (Speer IIRC) to ask if they could supply data. The guy said that he was sure they had it and would be happy to. The answer astounded us both. They had indeed tried WW748 in 243 using the exact components I had on hand but found there was less than 1 grain between not enough powder in the case to well over pressure.
I've been at the reloading game very near 50 years now and, to my thinking, there are no more dangerous words than assume, extrapolate and burn rate.