Lowest pressure powder for .308?


December 1, 2013, 11:41 PM
So I have a 1902 Carl Gustaf small ring Mauser, 1896 receiver, that has been rebarreled by Kimber into a .308. I don't really feel comfortable loading to the top of the .308's pressure specs, but I'd still like to do some paper punching and hunting with the gun.
What powders should I look into that will give me decent velocity? say, 2750 fps with a 150 gr sp, +\- 50 fps or so, while staying below the pressure the rifle was originally chambered in, the 6.5x55, which was at 51k psi max chamber pressure vs 61k psi for the .308....just for safety and early metallurgy's sake.

Powders I have are:
Imr 4064
Imr 3031
Imr 4350
Imr 4831
Reloader 22.

The last two I don't think would be even useable, as I don't have any data for that slow of powder for .308

Of those, according to the data I can find, the 3031 and h380 look promising, but the 4064 and varget are too high pressure unless downloaded. I was having troubles developing a good load with either 3031 or h380 last I tried, but I think I was having scope issues as well. I am also having trouble translating, half the loads are listed in cup, half in psi.

I am tempted to find some win 748 to experiment with though.

Any thoughts? Lyman's 49th has been my guide so far

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December 1, 2013, 11:54 PM
If you are trying to limit pressure but still hit your target velocity, I think the best approach would be to find the powders that produce the highest velocities and then download them to reach your target velocity. They should have the corresponding lowest pressures to reach what you are trying to do. The only concern might be consistent ignition if they are too low.

Looking at Hodgdon's online load data, looks like both Varget and and IMR 4064 will be right around your target velocity with starting loads well below 50,000 PSI. As long as they get decent accuracy and reasonably consistent velocity, those will probably be easiest on your rifle pressure-wise for getting 2700 fps.


December 2, 2013, 12:01 AM
Interesting, I would have thought that finding the powders with the lowest pressures at max loads would be my best route, since what I have read seems to suggest that max loads should be more consistent. If I could find a good, consistent load with varget, I would be happy, since I have a lot of that particular powder for loading for my FAL....would be perfect if I could find a load that works in both guns. With the adjustable gas system of the FAL, it should be flexible enough to take a lighter load.

December 2, 2013, 12:04 AM
A case full of the slowest burning powder will give you the least locking lug shock, and probably the lowest chamber pressure too.

3031 is too fast!!

Probably all the 4831 you can stuff in a .308 case with any bullet will give low pressure, less locking lug shock, and eargasplitten muzzle blast!

But it will be safe!


December 2, 2013, 12:29 AM
Now that sounds interesting, I have 4831 to play with, and some reloader 22, for really slow burning powder....should I worry about a compressed charge? Or go with a magnum LRP?

December 2, 2013, 12:32 AM
Now that sounds interesting, I have 4831 to play with, and some reloader 22, for really slow burning powder....should I worry about a compressed charge? Or go with a magnum LRP?
Just don't go with too slow a powder or you won't build enough pressure to insure the bullet leaves the barrel.

December 2, 2013, 09:28 AM
Just don't go with too slow a powder or you won't build enough pressure to insure the bullet leaves the barrel.

+1. That eliminates IMR4831 and RL22. With a 150gr bullet, I would use IMR4064, which you will find load data for. Stay away from the very top end loads and you will have good velocity loads at low pressure.


December 2, 2013, 09:32 AM
~ 155gr bullet with a near starting charge of 4895 should give good accuracy and be well below max pressure of 50K psi. I don't know how the initial force would compare to a slow powder combo though.

December 2, 2013, 09:46 AM
I think you're looking at it wrong. You won't get a consistant burn at reduced pressures, they are made to operate best at normal pressures. Using a "too slow" powder won't allow you to attain that pressure. IF your goal is indeed to load to a reduced speed you'll still need to obtain a good burn for accuracy and consistant velocity. That will require a reduced charge of a "too fast" powder and load it in the normal pressure range but the velocity will indeed be reduced.

Don McDowell
December 2, 2013, 11:40 AM
You need to look a little closer at the data you have on hand. In the 48th manual most of the pressures for the 308 and 150 gr bullet is listed in cup and not psi.
The powders you have on hand most any of those will work , the slower the powder the less pressure when working with full cases, altho you can get some low pressure loads using the slower powders the velocity is likely to be low as well ( find an old IMR load guide they list just about every powder they made for each cartridge and bullet weight). The problem you can get into with the slow powders is pressure spikes from to small of a charge.
748 is my favored 308 powder followed by rl 15 (varget and 4064 are the same burn rate family).
Kimber is not going to turn out a rifle that will not stand saami spec loads, so while caution is always a good thing, sometimes it can be to much of a good thing.

December 2, 2013, 01:12 PM
Just for the heckuvit, I ran comparative QL loads between IMR3031 and IMR4831 for 150FMJ/2,750fps.

The time-to-peak-pressure was for all practical purposes the same. However 3031 was able to achieve the required velocity while "still in the 40's", while no practical amount of 4831 could be sufficiently stuffed into the case (I quit at 113% case fill) to reach even close.

December 2, 2013, 01:41 PM
I don't shoot 150's in my match rifles, but I have shot thousands of 168's with 39. grains IMR 4895 or AA2495, and have no issue using H4895, standing and sitting rapid fire at 200 yards.

This load is very accurate, moves about 2450 fps and I would assume a 150 grain bullet with the same charge would be going over 2500 fps. For your rifle, I think any 308 load that is in the middle to low 40 Kpsia range, from manuals, would be fine. It is when you start pushing loads to 50, 60 Kpsia that I would be uncomfortable using in these old actions.

This was shot in a 100 yard reduced course match, 20 shots prone, iron sights, with a sling.

http://img.photobucket.com/albums/v479/SlamFire/Targets/M70Win200-14X168Nosler39.jpg (http://smg.photobucket.com/user/SlamFire/media/Targets/M70Win200-14X168Nosler39.jpg.html)

I am unconvinced that fast versus slow rifle powders really mean anything to the bolt lugs or receiver seats. The load is an impact load, so the distance the case has to travel before encountering the bolt face probably imparts more shock impact than any differences between rifle powders, and of course, the pressure.

Low pressures are always easier on the rifle than high pressures, but I have never been able to get decent velocities with the IMR 4350 series of powders. As can be seen in this series of tests with 155's and IMR 4350

Pre-64 M70
24 " Krieger Barrel 1:10 twist

150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR OAL 2.785"

29 May 2010 T = 83 F

Ave Vel = 2785
Std Dev = 23
ES = 75
High = 2820
Low = 2745
N = 14

155 Nosler 46.0 grs IMR 4350 wtd, Lot 6164 (60's) mixed cases CCI 200 OAL 2.780"

29 May 2010 T = 82 F

Ave Vel = 2418
Std Dev = 17
ES = 60
High = 2441
Low = 2381
N = 10

155 Nosler 47.0 grs IMR 4350 wtd, Lot 6164 (60's) mixed cases CCI 200 OAL 2.790"

29 May 2010 T = 82 F

Ave Vel = 2490
Std Dev = 17
ES = 59
High = 2515
Low = 2456
N = 10

best IMR 4350 group

155 Nosler 42.0 grs IMR 4895 thrown, Lot L7926 TZ cases CCI#34 OAL 2.750"

29 May 2010 T = 83 F

Ave Vel = 2677
Std Dev = 27
ES = 76
High = 2727
Low = 2651
N = 8

Best Clustering , better than IMR 4350 groups

Maybe someone with quickload can give an opinion of what pressures 42.0 grains IMR 4985 produces with a 150. It shot very well in my rifle and seemed to be a medium pressure load.

December 2, 2013, 03:13 PM

Arkansas Paul
December 2, 2013, 04:25 PM
My dad has a small ring Mauser that was converted by the Spanish to shoot 7.62mm and we don't feel comfortable shooting full throttle .308s through it either. I just load the Hodgdon youth load data with H4895. It is basically a .30-30 that shoots spitzer bullets, but I don't want to subject it to that much wear and tear.

December 2, 2013, 09:20 PM
I wouldn't worry too much about having too little pressure for a starting load to burn reliably. The starting load pressures are right around the max SAAMI pressures for 6.5 Swede. If the powder burns just fine at max Swede pressures, I don't think it would somehow not burn alright in a .308 starting load at nearly the same pressure. You've also got a margin built in. The 51,000PSI is just a (over?) cautious limit from SAAMI. The European standard is 55 kpsi. You see similar situations with 7x57 and 8x57 Mauser.

As I said before, I'd look at Varget and IMR-4064 starting loads. If for some reason the velocity is erratic, you could go to a slightly faster powder that has to work a little harder pressure-wise to get to 2700 fps and subsequently might have more regular ignition.

December 3, 2013, 09:55 AM
I too have a 1916 Spanish mauser in .308.
I use either IMR-4895 or IMR-4064 and keep the loads at the Minimum.
But to save wear, I shoot mostly Cast Bullet loads out of that rifle using 2400 or Unique.
The Spanish Mausers are more prone to Set back in the Receiver than were the Swedish Small ring Mausers.

December 3, 2013, 01:35 PM
well, since I have plenty of varget, I'll try that...
I just have to decide where I want to start. Hornady and Lyman have significantly different starting and ending ranges, with Lyman starting just a little under where Hornady gives as max load, then going significantly higher.

December 4, 2013, 12:43 PM
I don't think I'd like full house loads in a Spanish small ring either.
But you gotta wonder why Norma, CG, and others just screw on a 308 barrel onto a 96 action and call it a CG 63. Does anyone mention any problems with CG 63's in 308(7.62Nato). Load for accuracy and safety. Stay away from magnum range and you should be fine.Best

December 6, 2013, 12:28 PM
I found this useful for loading up some reduced rifle rounds.


December 6, 2013, 12:29 PM
H4895 youth loads.

December 6, 2013, 05:40 PM
Yep, loaded 30-30 for my youngest son to try out the model 94.

December 7, 2013, 10:07 AM
Try LeverE powder. works in my 308.

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