Burn rates

[PawPaw]

Looking at powder choices and wondering about burn rates.

We all know that two of the most traditional powders for the .30-06 Springfield are IMR 4895 and IMR 4064. Going to the Hodgdon burn rate chart, we find them listed at 89 and 93, respectively. Loading the -06 with those powders is a long respected choice and I've got a couple of loads that I've used for years with those powders.

So, if we step down to the -06 derivative, the .308, we find that two of the commonly used powders are Reloder 15, and H-Varget, listed on the chart at 97 and 99 respectively. Slower than the traditional powders for the -06. We can go to Hogdon's website and find Varget data for the -06 and we can go to Alliants despicable site and find RL15 data for that cartridge as well.

However, if we go to the Nosler Manual (#5) and look at their data, it tells us that with 150 grain bullets, Reloder 19 (at 120 on the chart) is the most accurate powder tested.

I know generally that when we get to overbore cartridges, the slow burners work better. I'm a big fan of IMR4831 (#121) in the 7mm Rem Mag and I'm a big fan or Reloder 22 (#129) in the .243 Winchester. I get that concept, but how do we decide which powder speed is best for the cartridges that are not overbore? It looks to me like a wide range of powders is useful in the .30-06 and I'm a great fan of great choices, but how does this whole question of bore size and powder burn rate work into our calculations? It seems like a paradox.

Thoughts?

[Clark]

I have never got the accuracy I wanted with 308 nor 30-06, and I am sure it is all my fault.

But I have been getting accuracy and shot 3 animals in 2010 and 2 animals in 2011 with the 7mmRemMag.

I used to use Re22 in the 7mmRemMag, but I have switched to H4350. In long range hunting, I want the temperature stability.

[hooligan1]

I've had tremendous luck using IMR 4350 in the 06, and I like the IMR 4831 with 140 grn Accubonds in my 7mm rem mag. But I have found that with a 24 inch, 1 in 9.825 twist, our mauser .243 loves the Winchester supreme 780. I also use, IMR 7828 in my 7mm, with 160 grn Accubonds, and IMR 4350 with 150 Partitions,.
Back to the 30-06, My son's 700, shoots less than 1/2 moa, at 100 yds, 150 grn B-Tip, 58 grns of IMR 4350, and my Savage 111 loves a 57.5 grn loading, heck it shoots tighter than the 700 at 100 yds,,, try IMR 4350 in your 06.

[PawPaw]

Thanks guys, but I'm not looking for loads, simply wondering what difference the burn rate makes in what we consider an appropriate propellant?

Originally Posted by hooligan1

I also use, IMR 7828 in my 7mm, with 160 grn Accubonds, and IMR 4350 with 150 Partitions

But, that illustrates my question. We find that both IMR 7828 (listed at #132) and IMR 4350 (at #113) both work great in the 7mm. Two different burn rates that both give good results in the same caliber. Why is that? Does burn rate have any play in what makes a good propellant?

[Scorch]

how do we decide which powder speed is best

Step 1- Select a metallic currency disc unit.
Step 2-Placing said unit on the distal phalanx of the pollicis, impart a rotational impulse to said disc, while accelerating it vertically.
Step 3- Capture the disc while in motion, position it on the doral surface of the opposite appendage, and observe the characters thus displayed.

[amamnn]

A lot of what powder and burn rate you use is personal choice within certain parameters, which are mutable to a certain extent. The best rule of thumb might be that we don't use pistol/shotgun powders in rifles and vice versa, though even that can be incorrect in certain circumstances. This is why people buy reloading manuals and look at reloading suggestions at powder maker's websites.


BTW, the best burn rate chart I have seen is at the Lapua/VhitaVuori website in the reloading section. Instead of just a list of powders, you can see at a glance how all the powders listed relate to each other...


http://www.lapua.com/en/home.html

[PawPaw]

Originally Posted by Scorch

Step 1- Select a metallic currency disc unit.
Step 2-Placing said unit on the distal phalanx of the pollicis, impart a rotational impulse to said disc, while accelerating it vertically.
Step 3- Capture the disc while in motion, position it on the doral surface of the opposite appendage, and observe the characters thus displayed.

Yeah, I got'cha.

[hooligan1]

My 7mm likes three different powders, not including a commercial loading from Hornady, that I neglected to mention. So it likes at least four different powders and it shoots them to 1/2 moa.

[Unclenick]

Paw Paw,

The burn rate charts are not a very reliable means of choosing a powder. Online I have seen a number of burn rate charts, and have found at least one each that says Bullseye is #1,#3,#8, and even #15. The problem is that the makers pay a lot of money for burn rate testing and don't publish the numbers for the competition, so those charts include a lot of SWAG. Also, the burn rate is tested under one standard set of conditions. In actual guns at your actual pressures, the numbers can change order because the burn rate response to pressure differs with the pressure profile curves for the different powders. I agree that the Vihtavuori type is more useful, but again, you need to check several to be sure where it all lands. GS custom has another like that you can use.

4064 used to be what Federal Gold Medal Match 168 grain SMK loads were charged with before they changed to RL15. 4064 works fine in .308. .30-06 is only limited to medium speed powders like 4895 and 4064 in the M1 Garand action. When you get to bolt rifles, that big case is better filled by powders in the 4350 range. For .308, most shoot them in bolt guns or in the M14 action for self-loading, and the M14's gas system is less vulnerable to pressure differences than the Garand's, so you can use slower powders in it. Unless you are shooting a .308 modified Garand, you don't have to be stuck with 4895-ish burn rates.

Choosing a powder takes a strategy. Basically you want powders whose maximum loads fill the case pretty well. For stick powders, the 85% rule works pretty well. The bulk density of many stick powders are in the range of about .84 to .90 times that of water. You just pick a fired case you have not yet resized and make sure a bullet of the kind you want to use will slip into it. (Sometimes they won't because the case mouth curls over a little and doesn't expand to fill the chamber completely. You can remedy that by running a cast bullet type expander into it to flare the mouth a little.) You then weigh the case dry and write that result down. Fill it with water and push the bullet in to your normal COL—this squirts water out, so you have been warned—and then remove it. Wipe any droplets off the outside of the case and weigh it again. Write down that weight and subtract the first weight from it so you have the weight of the water that was in the case. Then multiply that water weight by 0.85, and write down the result as a charge weight.

Now you go through load manuals looking for the stick powders that give your bullet or others of the same weight and construction the highest velocities with that charge weight. You may have to interpolate between some loads to get your velocities. That works pretty well because velocity and charge weight tend to have a linear relationship if the loads are not compressed. The powders you select this way will tend to be good powders to work with in developing a load with your bullet unless you have a Garand, in which case you have to limit yourself to medium speed powders.

I change the rule to 95% for spherical propellants. That means I multiply by 0.95 for spherical powders, because they are typically higher in bulk density.

Remember, these are just suggestions, but they usually pan out pretty well.

[a7mmnut]

I'll echo the accolades for 4350 as a generalist powder, even in the .243. I try for case density above 90% volume if I'm guessing at new powders for an accuracy load. The trick is trying to burn it all at exactly the same rate each shot. (shot-to-shot velocity deviation)

-7-

[uncyboo]

Step 1- Select a metallic currency disc unit.
Step 2-Placing said unit on the distal phalanx of the pollicis, impart a rotational impulse to said disc, while accelerating it vertically.
Step 3- Capture the disc while in motion, position it on the doral surface of the opposite appendage, and observe the characters thus displayed.

Now THAT"S darn funny........