burn rates

Perhaps you have looked at various "Burn Rate Charts" and wondered what good they are. Well, you have good reason to wonder. Burn rate charts seldom agree. There is no specific meaning for "burn rate," so it shouldn't surprise us that the numbers don't agree. They mean nothing by themselves.

What amateurs call burn rate is not used by professional ballisticians to develop loads. The actual term closest to burn rate used in interior ballistics is "Relative Quickness."

Relative quickness is defined by "closed bomb tests," which quantify pressure rise in a sealed container. However, professional ballisticians do not use relative quickness for load development, either. A closed bomb relative quickness value does not translate into any type of value outside of that 'closed bomb' test. Powder performance varies widely by actual application. Relative quickness is one of several preliminary considerations when assessing a powder's suitability for a particular application by ballistics, but nothing more than that.

Relative quickness does not tell use the physical shape of a powder, its composition, or the types of coatings. It cannot tell us whether a powder is single-based, double based, or triple based. It does not tell us the heat of explosion, the progressive / degressive gas creation values, the ignition characteristics, and so forth. There is no way to translate a double-based powder performance into a single-based powder performance level with any accuracy. Even further, relative quickness does not define the erosiveness of a powder, the residue left by a powder, its ability to meter properly; and on it goes.

Energy content of nitrocellulose varies by manufacturer. It varies by the amount of nitrogen in the nitrocellulose. The more nitrogen, the more gas a powder can make. Once you have a specific type of nitrocellulose the energy content is further controlled by the addition of nitroglycerin, which is basically what constitutes a double-based powder. Now you have further considerations, as nitrocellulose and nitroglycerin do not behave the same way as temperature changes. The amount of nitro percentage varies by powder to powder, and with it its performance in a specific application.

All this combines to make burn rate charts something to ignore, or to view with very little importance placed on them. Professional ballisticians do not use them at all, simply because they have no particular meaning. Ping-Pong balls are nitrocellulose, but not many of us would bother cutting them up and attempting to use them in a firearm.
 
The mathamatical formula is Relative Burn Rate is Muzzle Velocity X Powder sectional density grains divided by square inches.
Each manufacture does things a little different and the variables of coatings and amounts of nitrglycerin and nitrocellulose are all different, determining the single base double base and triple base powders. That is why every time you look at a Burn rate chart they are different and each company that put it out has their version.

If I would have put this first, you really would have thought I was being a smart [beeep].
 
By weight. That is why we measure weight for our reloading and don't count on volume. Although most times they are close enough that powder spoons can be used. (Lee spoons, and all mechanical powder measures ) not working close to maximum. Even then, volume translates to weight fairly accurately. I never run my powder measure to load without checking weight, and weight for consistency. Once volume is set for weight, I can load up. Makes,no difference single based to double based. It all works fine, ball powder to extruded.

Burn rate charts are most helpful, in that they give us a clue as to where that particular powder can be plugged in. If you are curious about Reloader 33 but have also heard of IMR-3031, with a burn chart, you can quickly decide which powder will fit your particular application. It's all relevant.
 
Well here's what I'm trying to do. My 204 is very accurate, shows no pressure signs, and ud like to find a powder, just a little quicker just to see what happens. Also my load in my 257 weatherby has a little room left and from everything i read they prefer to be full. So looming for a step or two slower.

Both are accurate. Just tinkering more than anything. But if the next step of powder is faster but takes up more volume per grain its a wash.
 
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Why don't you tell us a little about what you have used, and where you want to go. Guessing games are no fun. Lots of options and experiences out there. Be a bit more specific.
 
Specific efforts tried, or supplies that you have on hand, would help a bunch..

For my .204s, I've used Ramshot's X-Terminator, their TAC, and Winchester 748....The X-Terminator works really well with lighter weight bullets, the TAC with the heavier ones, and W-748 (right in the middle as far as burn rate charts) is a good all around powder, but it burns just slightly dirtier...I've found better accuracy in the .204 with Magnum level primers than with standards...

A lot of others have reported really good success with other powders and I don't dispute their preferences, the ones I listed above just happen to be the ones that were available when I started reloading for the .204...They also work well with my .223 loads and I've never found a valid reason to justify a change...I don't load for high velocities unless that's the only accuracy node that happens to be present...Most of my accurate powder charges will come in between .4gr and .7gr below most published maximum loads for the powders mentioned and produce .3"-.5" groups on a consistent basis...

Running "Hot" loads will tend to shorten your brass life and while it's reasonably available now, if we fall back into a shortage situation, similar to a few years ago, brass life can be very important..The old adage of "Waste Not, Want Not" applies...I try to keep a minimum of 1000 rounds of virgin brass on hand in every caliber I have and very seldom have to scrap the 100-200 rounds that I currently have in use...
 
The 204 load is:
28.2 gr H4895 (all I can squeeze in with a few taps)
35 Berger HP
BR4 primers
3850 fps

100 yards

The 257 is:
74.2 gr RL19
85 gr Nosler BT
Fed 215s
3950 fps

370 yards(Im 100 percent sure the one high out of the group I pushed, the other 4 measure 2.1, but I didnt want to call it a "flier")

I'm really happy with both of these loads and not really wanting to go anywhere in particular. Just want to get to know these rounds better. See if I can find a sweeter spot. I won't spend a lot of time or a ton of money on it. I think i have the basics down now ready to learn a little more about how it works accept this powder was in the manual, its not over pressure, and its the one that I found shoots the best out of what I've tried.
 
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Have you looked into adjusting the COAL? This was something else that is vital to accuracy. You could check your COAL and if you have room to go closer to the lands then you could try that. Maybe start right at 0.005 off the lands and then move back Usually 0.005 - 0.015 should give you the best results in accuracy.
I am only quoting the last paragraph of your last post. NO money spent, don't have to change powders, and you may find the sweet spot.

I do understand wanting, and having, at least three powders that will work with each gun. So if this is what you are after, then you would be advised to ask about that specific. Many are glad to help.
 
Originally Posted By: mbaysinger89Well here's what I'm trying to do. My 204 is very accurate, shows no pressure signs, and ud like to find a powder, just a little quicker just to see what happens. Also my load in my 257 weatherby has a little room left and from everything i read they prefer to be full. So looming for a step or two slower.

Both are accurate. Just tinkering more than anything. But if the next step of powder is faster but takes up more volume per grain its a wash.



The 204 I had loved H-322 and would push the 32gr BK over 4000fps with great accuracy. 1/2 MOA with boring regularity.

On the 257, look for Rl-22 or if you can find it, the new Rl-26 is getting excellent reviews.
 
The 100 gr tsx load I use in the 257 is RL 22. I saw some 26 the other day but I'm thinking itd work bestwitg 115s which I'll never use. I could probably reach the lands in the 204 with 55 bergers but id have to single load them. I'll never reach lands in the 257 until iI have it set back.

What is RL 33?

Like i said while I'm looking for information, I'm really not looking for anything in particular with these loads. Maybe a backup powder. More than anything more understanding of burn rates, fill capacity, and who the two correlate.
 
Originally Posted By: mbaysinger89

The 257 is:
74.2 gr RL19
85 gr Nosler BT
Fed 215s
3950 fps







This load, according to a generic Quick Loads run, is 74,964psi CIP, and 3985fps with a 26" barrel. That is about 11,777 Psi over. CIP for the 257 Weatherby Max is 63187 psi. FYI

Also says that load is compressed 1.7%


But if I reduce the load to within CIP standards I get:

RL-19
70.6gr
3804fps
85gr Nosler BT

_______________

RL-22
73.3gr
3836fps
Nosler 85gr BT

_______________

RL-26
75.3gr
3876fps
Nosler 85gr BT


As you can see, the slower powders in RL-22 and 26 actually serve your 85gr bullet better than RL-19. That matches my experience also.

If I run the same generic plugins for the Barnes 100gr TSX it looks like this at max charge:

RL-22
69.1gr
3591fps
Barnes 100gr TSX

____________________

RL-26
70.8gr
3624fps
Barnes 100gr TSX

Once again the RL-26 is your friend for top speed.

RL-33 is a bit slow burn for the 257 Weatherby. You could find it useful with 120gr bullets, although most likely not the best choice.

 
I know for a fact it isn't a compressed load. It also doesnt show signs of being over pressure in my rifle. This load was worked up to from the starting load suggested in the nosler manual. I tried 22 and i couldn't get it to shoot well at all. RL 25 was sloooooow.

Thank you for the FYI, I will go back through my records and double check all the information. If I remember correctly I started getting flattened primers at 73.5
 
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