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Old March 20, 2007, 09:30 PM   #1
piercfh
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.308 reduced load

I don't know if I titled this correctly, and I don't know if this may be looked down on or not. Does anyone know of a subsonic .308 load, or have any recommendations for a reduced load for the .308. I have read about reduced loads with ok accuracy with a .270, but was thinking of trying it with a .308.
Might not even be possible but I thought I would ask.

Ideas on where to start powder wise would be great as well.

Thanks
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Old March 20, 2007, 10:04 PM   #2
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Played with reduced (squib) loads before I knew better ... i.e., before I saw a 30-06 detonate at the range one day. Some minor injury but all around were lucky. Having said that, yes, you can load reduced power loads. To subsonic, in a 30 calibre. I am not sure ... nor am I sure why and will not ask. BE VERY CAREFUL.
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Old March 20, 2007, 11:00 PM   #3
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Reduced loads are fun and easy on the shoulder. For the 308, try using Dupont IMR4759. It is real bulky and loading densities of 75%+ are possible. I generally load the same loading in both 30-06 and 308. I use 19.0 grs of IMR 4759 with a 147 gr FMJ. Primers don't seem to matter. Loading density is near 80%. All of my old 03 Springfields will shoot this load in a hole at 100 yds. Sights adjusted to 400 yds on the peep will put it on the money at 100 yds. It is a hoot to shoot especially if you have kids that would like to shoot a BIG gun. Even a 5 year old can handle this loading as there is little to no recoil- about like a 22 mag. For folks shooting the overbore pistols, take a look at IMR4759 in cases like the 30-30 pistol. The down side- it will not go thru a powder measure at all. It's a large stick powder and bridges constantly in a measure.
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Old March 21, 2007, 07:08 AM   #4
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I have read something online about "the load" which is a reduced 30-06 load. I couldn't find it this morning but I did find this:


http://www.reloadingroom.com/page46.html

I've never tried it but it does sound interesting. I sometimes have a need for sub-sonic loads in .30-06 so I'll be watching this thread with interest.
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Old March 21, 2007, 09:20 AM   #5
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Rocky's load is good, but I have seen even lighter loads work well, too. To go sub-sonic, you can use Trail Boss powder at around 6 grains and up, and will have plenty of bulk to avoid detonation. The lightest bullets may not be subsonic with that much powder, but heavier ones will. It is an ideal situation for cast bullets.
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Old March 21, 2007, 10:13 AM   #6
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Reduced 30-06 loads.................

I use 20.0 grains of IMR4227 and a Sierra flat base 150 grain bullet in my 03A3. We're talking 1 inch groups @ 100 yds. I have a ball shootin' it.
I might add there's a huge difference in group sizes just going up or down in one grain increments. So, working up loads in 1/2 grain steps is well worth it.
That's also using CCI200 primers.
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Old March 21, 2007, 07:44 PM   #7
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I have seen cases that have a 308 profile on the outside and a straight inside wall. So the neck is normal and below the shoulder is is supper thick.

That seemed to do the trick, but you'll have to do some load development and get a neck-sizer.



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Old March 21, 2007, 10:34 PM   #8
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WOW! Thanks for the info guys. Im going to keep researching for a while before I make anything final. Im sort of on a budget, and the ammo is for a friend of mine. Def dont want anything blowing up in our faces though.

Subsonic is the goal. I use 168 bthp for my rifle so I figured I would try them to use for the experiment.

Possibly the trail boss powder around 7 grains with the 168s is what Im guessing at right now.
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Old March 22, 2007, 11:06 AM   #9
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Piercfh,

You'll also find, if you look around, that a lot of boattail bullets are fired backwards in sub-sonic loads. This is because some rifles have too slow a twist rate for good frontward-pointing stability at lower velocities. A backward boattail is an inherently stable shape, with the center of mass ahead of the center of pressure, like a bottle rocket has. It just has a lousy ballistic coefficient. However, subsonics are not usually expected to go very far, so it works fine to 100 yards or so, anyway. Something to try if you find your loads are inaccurate or are keyholing on paper when you load them the usual way. The backward bullet seating will have little effect on peak pressure in a light load with all that extra case space available for the bullet ogive to occupy.


tINY,

I thought of that idea: a case to make a .30 carbine out of the .308 directly, rather than machining a .30 carbine adapter. I dismissed it, figuring it would be too expensive. Do you recall where you saw it or what it cost?
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Old March 22, 2007, 03:20 PM   #10
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My gun pimp (who is a class III mfg) had some - I'll ask.



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Old March 22, 2007, 03:37 PM   #11
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I loaded a bunch of 150-gr. lead flat nose bullets dropped from a Lee die and propelled by 12 grains of Red Dot out of my 722 Remington in .300 Savage back when I worked for NRA.

TURBO accurate. I'm talking easily 1 small hole at 50 yards, and well under an inch at 100.

The only problem was that it was INCREDIBLY dirty.
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Old March 22, 2007, 05:58 PM   #12
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Yuh! Red Dot. Smut in a can, but not the kind people will pay for. 12 grains of Hodgdon Clays will do almost the same thing; same pressure, same barrel time, but a little less muzzle velocity. So, will 13.2 grains of Hodgdon Universal Clays, but resulting in a little more muzzle velocity. Both way, way cleaner.
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Old March 22, 2007, 08:18 PM   #13
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Clays was, I believe, still a few years in the future when I was loading my lead bullets.
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Old March 23, 2007, 06:39 PM   #14
tINY
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A customer of his got them from a post on Sturmgewehr a long time back.

You have to anneal the necks every time you reload because they are soft brass. He's gonna look at the markings and see what he can find.



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Old March 23, 2007, 11:43 PM   #15
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"You have to anneal the necks every time you reload because they are soft brass."

Uhm... that doesn't make any sense.

The purpose of annealing is to soften something that is too hard.

If the brass is already soft, it doesn't need to be annealed.
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Old March 24, 2007, 03:24 AM   #16
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Pardon my ignorance, but why would a lighter charge cause an explosion? Or did I just read that wrong. I always wondered about light loads but was always afraid to load them.
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Old March 24, 2007, 08:04 PM   #17
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You read correctly. There have been a number of reports of guns bursting when firing very small loads with lots of air space. I originally heard of it with small quantities (like a couple grains) of slow rifle powder (surplus 4831) in a big bottleneck case. Later I found a web page of Finnish gunwriters who have pictures of a .308 blown apart by about 3 grains of Vihtavuori N320, a pistol powder about like Bullseye in burning rate. Nobody seems to be able to replicate it with regularity, so it isn't understood well, nor are the conditions it really requires.

The idea is that the small quantity of powder accumulates at one place in the case, then detonates (combusts supersonically, by shock wave) rather than deflagrates (burns subsonically, by flame front). In the former case the energy is released faster than the gases can get clear of the exploding mass, momentarily concentrating the pressure. I calculated this pressure would be about 175,000 PSI for one particular powder, but it was long ago, and I don't recall which one? Anyway, that shatters the steel adjacent to the powder lump doing the detonating, which starts cracks, like a "bullet" stone chip in a windshield, and that the small quantitiy of gas from the powder is enough to spread them and break the gun the rest of the way.

There have been a lot of theories about the detonation being initiated by colliding reflected pressure waves, but none of that is confirmable. The same idea had passed around for years to explain detonation of air and gasoline mix in engine cylinders (knocking), but it turned out not to be true. It is just heat that initiates it.

One gunwriter poo-pooed the whole idea of detonation in guns, but he studied only "Bullseye suprise" in .38 Special cases, so he didn't have the large empty space condition. He wound up putting the apparent phenomenon off to double-charging, which would explain popping a .38 Special, but doesn't explain blowing up a .308. Double charge of 6 grains instead of 3 in a .308? So what? Even that fast N320 won't get a .308 to peak pressure until you multiple charge six times over. Not a probable loading error.
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Old March 24, 2007, 11:34 PM   #18
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So the question is, is lighter loading safe and if so, how do you develop a lighter load? What precautions should be taken to reduce/eliminate the risk of rifle explosion?

Didn't mean to jack your thread piercfh.

Last edited by Mr Beta; March 24, 2007 at 11:36 PM. Reason: Apology
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Old March 25, 2007, 03:18 PM   #19
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Lighter loads are safe down to a point. The problem is that nobody can tell you exactly where that point is because nobody can replicate detonation consistently. 3 grains of powder in a .308 is clearly too little. I know a lot of people using 5 or 6 grains and up in .308 and .30-06. None have had a problem yet. Your best bet to avoid trouble is to get rid of the empty space by using a bulky powder. Most rifle powders have bulk density in the range of 0.9 or so. A good bulky light load powder is IMR Trail Boss, which has a density of only about 0.32. I now use it for all very light reduced loads in rifle cases. For middle range reduced loads, IMR 4759, mentioned earlier, is another bulky powder commonly used for the purpose, though not as bulky as Trail Boss. Find the powder that fills the case best for the performance you are after.
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Old March 25, 2007, 06:20 PM   #20
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Detonation seems to occur with light loads of IMR-type powders. Using shotgun or pistol powders shouldn't cause any problems.

E.g., for years I've loaded plinkers with around 20 grains of 2400. You can use almost any weight of bullet in most any 30-cal cartridge, although that's max in a .30-30. Not sub-sonic, though.

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Old March 26, 2007, 11:56 AM   #21
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I know, that sounded weird to me too....

It might just be the alloy that hardens quickly, or I might have missed the "not" part of his statement. It sounded like it was machined, so a harder brass would make sense.....



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Old March 26, 2007, 01:45 PM   #22
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Art,

I think it was first noticed in the IMR types in this country, but after looking at the damage three grains of shotgun powder did to the rifle on the Finnish site (next to last answer on .308 reduced load questions on this page) (and the author claims to know of three such cases), I'm not clear that it is limited to any particular powder necessarily. The reports of "Bullseye Surprise" being another example. I think until it can be established for sure what the mechanism is, about the only safe assumption is that any powder could do it. An interesting thing the Finnish site reports as part of its own theoretical explanation of the phenomenon, is that jacketed bullets have a higher safe lower charge limit than lead bullets. If true, it suggests that delayed bullet start due to low pressure is part of the mechanism.


Finnish site picture.
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Old March 28, 2007, 10:04 PM   #23
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Small powder charges lay loose in the case. When the primer fires it all 'explodes' rather than a controled burn. The 06 I saw cracked a bolt lug, jammed bolt and action and buldged the bbl like you'd expect from a plugged bbl. Gun had been used immeidatly prior to that last shot and bbl was ok. Nothing remained in bbl ... so detonation was the conclusion.
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Old March 29, 2007, 12:55 AM   #24
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So is there a unanimous best powder for these types of loads?
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Old March 29, 2007, 01:23 AM   #25
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What I would do is look to find some published data, someone mentioned 2400 and I would think that should work in a 308 case and Trail Boss being bulky, would also be worth researching. See what data you can find in print, that is always a good idea.
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