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  #1  
Old 02-10-2010, 05:17 PM
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IMR 3031 Minimum Loads


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I have choosen to load some mild 130 and 150 gr .308 loads using IMR 3031. There is considerable data available normal and max charges. I can't however, seem to find much on mild and reduced loads. I have a 20" barrel, 1-12" bolt gun. There is IMR 3031 data available for .30-30 and .300 Savage. I am near certain these charges would be safe for a .308 Win, but I thought it prudent to ask some experts. Is going down to .30-30 levels with IMR 3031 an issue for a .308?
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  #2  
Old 02-10-2010, 05:39 PM
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300 savage would be a good place to start as the savage round is loaded to about 45,000 cup... you could probably go as low as the max loads for the 30/30 or maybe split the difference between the 30/30 max and 300 savage max and start from there.
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Old 02-10-2010, 06:22 PM
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Of course you should call the seller which I now think is Hogdon with your question.

I have used a lot of 3031 with light loads with great success. However I can't give you specifics.

IMR 4759 is best for very light loads as its made for that and high bulk to reduce the chances of a double charge.

Good luck.
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  #4  
Old 02-10-2010, 06:29 PM
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Bird Dog,

For reduced loads, you may want to look at a slightly faster powder, such as 4198 or 4227. Accurate 1680 might be a good choice, as well. You will not have the ideal load density with those, but you'll be able to create less pressure while still having consistent ignition and lower velocity spreads. Also, lower powder charge weights will create less recoil, overall.
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  #5  
Old 02-10-2010, 06:31 PM
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I reduced a 7mm Rem. Mag. 2 gr. under a starting load with a different powder to test for bullet expansion so I wouldn't have to shoot full power loads at 300 yd. and I got the click---bang deal. I quit that, being afraid of detonation.There was a little bit of powder in a lot of case! I don't know if detonation is possible but I'm not going to find out. Don't know if this helps but think about it. Call Hodgden.
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  #6  
Old 02-10-2010, 07:19 PM
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May I ask, why did you choose IMR 3031? If you're open to using a different powder:

On Hodgdon's website they have a document for reduced loads for youth or other light shooting. They recommend only H 4895 because "H4895 is the slowest burning propellant that ignites uniformly in reduced charges."

Basically they recommend that for any load with published data for H 4895, you can reduce it to 60% of the maximum load, and move up from there.

Basically for the .308 its 38.0 grs H4895 with a 125 gr NBT for 2592 fps, 37.0 grs H4895 for 130 gr bullets for 2542 fps, and 36.5 gr H 4895 and 135 gr bullet for 2494 fps.
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  #7  
Old 02-11-2010, 03:21 AM
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Quote:
Originally Posted by Jakeway View Post
May I ask, why did you choose IMR 3031? If you're open to using a different powder:

On Hodgdon's website they have a document for reduced loads for youth or other light shooting. They recommend only H 4895 because "H4895 is the slowest burning propellant that ignites uniformly in reduced charges."

Basically they recommend that for any load with published data for H 4895, you can reduce it to 60% of the maximum load, and move up from there.

Basically for the .308 its 38.0 grs H4895 with a 125 gr NBT for 2592 fps, 37.0 grs H4895 for 130 gr bullets for 2542 fps, and 36.5 gr H 4895 and 135 gr bullet for 2494 fps.
Well we went through this on a previous post. See "308 youth load needed". With a 20" barrel, some were of the opininon that a faster burning power was advantageous. 3031 is faster than H4895. 4227 was suggested also, but that leaves more space (a filler was suggested). I don't want either of those options. I am not talking about huge reductions. I would just like to go to mid to lower .300 Savage charges. Something in the 35 grain range of IMR 3031
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Old 02-11-2010, 03:49 AM
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Quote:
Originally Posted by Bird Dog II View Post
Well we went through this on a previous post. See "308 youth load needed". With a 20" barrel, some were of the opininon that a faster burning power was advantageous. 3031 is faster than H4895. 4227 was suggested also, but that leaves more space (a filler was suggested). I don't want either of those options. I am not talking about huge reductions. I would just like to go to mid to lower .300 Savage charges. Something in the 35 grain range of IMR 3031
If you use mid to lower .300 Savage loads of a faster powder, then your velocity will be lower. You'll need to use .30-30 Win. 150 grain bullets as the spitzer types might not stabolize in your 1-in-12" twist. I had an old Remington Model 788 in .30-30 and it's rate-of-twist was 1-in-10" and it shot fine with spitzers especially when using 34.0 grs. of WW-748 powder & 125 grain spitzer.
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Old 02-11-2010, 04:43 AM
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You'll be fine, Bird Dog. IMR3031 can't be reduced quite as far as 4895 can be, but cutting the load to about 75% of the normal maximum will be safe.

Your plan of using 300 Savage loads is great. The 30-30 ones ought to be acceptable, as well. Work down to them, though.
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  #10  
Old 02-11-2010, 06:29 AM
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Birddog
I have some questions why are you trying to find reduced load data for the 308?
Is because of the recoil form the 150 grainers from the 20 inch barrel?
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  #11  
Old 02-11-2010, 08:56 AM
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It's recoil. These are for some kids and my GF. I am thinking 35grains of 3031 and the 130s will be a nice load. I am not needing a very light load, just lighter than full power 150-165 loads.
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  #12  
Old 02-11-2010, 09:20 AM
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Part of the issue is not just powder burning rate, but powder bulk density and its ignition characteristics. With any powder you have to worry about a form of flashover. This happens to powder filling less than about 60% of the space in the case under the bullet. This flashover happens when the powder lies level in the case and the primer flame spreads over and ignites the whole exposed top surface of the powder, lighting more than would normally be started at ignition. That increases peak pressure by burning the powder too soon. Some powders are already producing inadequate pressure for consistent burning before you even down to 60% so you have to eliminate them based on that. The faster powders tend to do better there is all.

I have some graphs in an old 1965 pressure study of .30-06 loads showing the effect of charge reduction. One shows IMR 3031 under a 220 grain Remington Core Lokt bullet, and as that load is reduced, the peak pressure reduces until about 30 grains of charge. Below that, pressure starts to go up again irregularly due to flashover. With that heavy bullet, 30 grains is just about 60% of the volume available under the bullet. The big bullet's mass also provides a lot of inertia for the powder to build pressure against to help it burn, so the peak pressure still gets to about 21,000 psi.

Here are some IMR burn rates from QuickLOAD:

IMR 4895 0.5200
IMR 4064 0.5890
IMR 3031 0.5772
IMR 4198 0.8912
IMR 4227 1.0140

Note that the the order of 3031 and 4064 is reversed from most burn rate charts. This is because actual samples were measured in a lab for the QuickLOAD database, and in the particular lot tested, that's just what it turned out to be. The important thing to note is the first three powders are all in the same general burn rate ballpark. It isn't until you get to 4198 that burn rate starts to increase substantially. So, choosing 3031 over the other two just didn't really move your burn rate much.

Another issue is bulk. Following the 60% rule, because IMR 4895 is a little more dense, 60% gives you almost two more grains of it. As a result a 60% load of 4895 actually produces more pressure and velocity than a 60% fill of 3031 does. Both powders in QuickLOAD are running below 15,000 psi at that load density under a 150 grain bullet, and under 14,000 psi with a 130 grain bullet. They both burn very inefficiently at those pressure levels, with ballistic efficiency at under 20%.

I find, just as an observation from loading for .45-70, that burning the IMR smokeless rifle powders below about 25,000 psi increases fouling and irregularity of the burn, and so it would be good to get at least 25% BE at a pressure at or above 25,000 psi and at a case fill of not under 60% to avoid having to add polyester wadding.

So, with that information in hand, I reexamined your lowest possible loads in QuickLOAD. The results were interesting:

With the light 130 grain bullet, at the lowest case fill, 60%, the only IMR powder that will meet all the criteria is IMR 4227. With the bullet seated one caliber into a typical .308 case (57 grains water capacity), 60% fill produces just a shade over 25,000 psi and gets 27% ballistic efficiency in QuickLOAD. Velocity predicted is not quite 2200 fps, which is a good light load with that bullet weight.
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  #13  
Old 02-11-2010, 12:00 PM
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Tell me this Nick, what % (on the 60% rule) is 35 grains of 3031 in a .308 case? My IMR table tell me that 46.7C is a max load for 130gr bullets. Since that load is compressed, I assume that is 100%. Am I tracking? So 60% would be 28.02 grains. I am only wanting to take it down to 35 grains (which should be a good solid .300 Savage level load). So at 35 grains of 3031 in a .308, do I have any issues with flash-over or detonation etc? I don't think I do, and your post seems to confirm that. It seems if I would go all the way down to .30-30 loads, then yes, I might approach that 60% threshold. But 35 grains is 75%. It sure seems like that is a completely reasonable and safe load. Yes, no? Comments?
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Old 02-11-2010, 01:20 PM
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According to my calculations, you're at 74.9% with that load of your max listing.
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  #15  
Old 02-11-2010, 02:13 PM
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Quote:
Originally Posted by Bird Dog II View Post
Tell me this Nick, what % (on the 60% rule) is 35 grains of 3031 in a .308 case? My IMR table tell me that 46.7C is a max load for 130gr bullets. Since that load is compressed, I assume that is 100%. Am I tracking? So 60% would be 28.02 grains. I am only wanting to take it down to 35 grains (which should be a good solid .300 Savage level load). So at 35 grains of 3031 in a .308, do I have any issues with flash-over or detonation etc? I don't think I do, and your post seems to confirm that. It seems if I would go all the way down to .30-30 loads, then yes, I might approach that 60% threshold. But 35 grains is 75%. It sure seems like that is a completely reasonable and safe load. Yes, no? Comments?
Depending on bullet length and seating depth, 35gr of IMR-3031 is going to use 75-80% of available case capacity and generate ~2450fps and ~25,000psi of pressure. Meanwhile, 32-34gr of IMR-4227 is going to use the same 75-80% of case capacity, but generate ~2700-2850fps and 42,000-48,000psi. Due to the lower charge weight and 300 Savage-like velocity, felt recoil of the 4227 loads will probably be what you're looking for, in a reduced load. The load density/burn rate of 4227 will give much more consistent pressures, which will translate to better accuracy. You might even go as low as 30gr of 4227, if 2700fps is still more than you're looking for, but any less than that and I think you start running into the same problems 3031 presents.

If you're dead-set on using 3031, it will work...it's just not the best option for reduced loads, in that cartridge. (If you were shooting a 300RUM, 70gr of IMR-3031 would make a nice reduced load. I threw that in just for Tang! )
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Old 02-11-2010, 04:36 PM
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OK, Nick, Broom, since you have the tools (all I have is load charts) what pressure and velocity is 37.5 grains of IMR3031 with 130 grain bullet going to get me?
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Old 02-11-2010, 05:29 PM
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Unfortunately they don't say how much compressed. 102%, 105%? That would be the volume of the uncompressed powder as a portion of the empty space available under the bullet.

I don't know whose case you are using? The ones I've measured range from about 55.5 (IMI) to 59.0 (three year old Winchester) grains of water capacity, as measured by filling a 2.005" long case level with the mouth with water, but no meniscus, and weighing it before and after filling it to find the difference.

But, to find some sort of useful starting point, I can run some QuickLOAD numbers with a typical case. Remington, Lapua, and Federal are usually in the neighborhood of 57 grains of water capacity. so I'll use that. The bullet will be a 130 grain Hornady Spire Point #3020, seated to 2.690" COL (Hornady manual COL for that bullet). I can then look for the smallest load that both fills the case at least 60% and reaches at least 25,000 psi so that both objectives are met. If the powder is fast enough, 60% will exceed 25,000 psi, and if it is slow enough it will take more than 60% to reach 25,000 psi. The recoil is for a 7.5 lb rifle (scope included) with 20" barrel for velocity. When I do this exercise I get:

IMR 4227, 26.5 gr., 60.0% fill, 26,190 psi, 2,156 fps, 6.5 ft-lbs recoil
IMR 4198, 28.8 gr., 66.6% fill, 25,023 psi, 2,182 fps, 7.0 ft-lbs recoil
IMR 3031, 35.7 gr., 79.2% fill, 24,974 psi, 2,288 fps, 8.6 ft-lbs recoil

What you can see is that to meet both limiting parameters, you can get the fastest powder to give you the lightest load. Mind that the velocities assume tight minimum chamber and a standardized 4 groove rifling with 0.0736 in² bore cross sectional area.

If I next level the playing field by producing the same velocity as the minimum 3031 load with all, I get:

IMR 4227, 28.4 gr., 64.3% fill, 30,237 psi, 2,288 fps, 7.4 ft-lbs recoil
IMR 4198, 30.4 gr., 70.3% fill, 28,094 psi, 2,288 fps, 7.7 ft-lbs recoil
IMR 3031, 35.7 gr., 79.2% fill, 24,974 psi, 2,288 fps, 8.6 ft-lbs recoil

So you can see the faster powder is most economical in that velocity range, and produces 14% less recoil than the 3031. That's because less powder mass is being propelled forward and lower muzzle pressure is contributing to rocket effect. Now, as to which is most accurate? That you'd have to try, but the better case fill with the 3031 might get the nod there. You'd just have to try. With all that empty space, magnum primers will probably give you better velocity consistency.

37.5 grains of 3031 with the same case and bullet and COL assumptions is 83.2% fill, 28,237 psi, 2,403 fps, and 9.4 ft-lbs of recoil.
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Last edited by unclenick; 02-12-2010 at 06:16 AM.
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Old 02-11-2010, 05:44 PM
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Um, yeah...what he said.

9.4lbs of recoil is pretty typical of a full-throttle .243 load. If you're comfortable with 9lbs of recoil, you can get better pressure/velocity from 4227 than you can from 3031, and probably better accuracy, as a result.
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Old 02-12-2010, 09:30 PM
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Full throttle .243 recoil will be just fine. I am going to start with 37.5 grains of 3031, 83.2% fill, 28,237 psi, 2,403 fps, and 9.4 ft-lbs of recoil, and go up from there if necessary. Only holes in paper can prove accuracy.
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