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Old August 13, 2010, 09:36 PM   #1
sserdlihc
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Compressed loads anyone?

Does anyone on TFL have any experience loading compressed loads?

Primarily I am looking for anyone who has reloaded 30-06 and used or is currently loading compressed loads. Please tell me what you have ran into with these type loads, pressure signs...etc. I see alot of compressed loads in Nosler's 6 manual. Just wondering how safe they are.
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Old August 13, 2010, 09:47 PM   #2
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Some loads (4350 in 30-06) max out with compressed powder charges, haven't made them work for me yet. Maybe someday. Black powder requires a certain amount of compression but compressing smokeless makes me nervous.
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Old August 13, 2010, 09:58 PM   #3
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The only thing compressing does that is different from increasing % powder fill in a case that still has room left over is that it reduces the volume the powder starts burning in more rapidly per additional grain. This is because it consumes not only the room the additional powder needs, but subtracts it from space between the grains of the total charge at the same time. The result is that pressure grows more rapidly with charge increases above 100% fill.

That has a limit, since you could theoretically squeeze all the space between the grains out, making a solid with no way for the flame front to move through it. But for most rifle powders that solid state is somewhere between 160% to 180% filled, which is well beyond how much you can compress without the case bulging or the neck buckling anyway.

Use a normal work up until you get to the compressed point, then go in small increments, like .3 grains or so, while watching for pressure signs, and you will be perfectly safe.

High percent compressing lets you use somewhat slower or bulkier powder than you might normally choose for a bullet.
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Old August 13, 2010, 10:01 PM   #4
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I use a compressed load for my .221 rem fireball. In fact the load I use came from the Nosler manual. The starting load using AA2015 is a compressed load. I have not had any problems with it. I have not any pressure sighns at all. I loaded test loads for start medium, and then a few at maximum. The differance in the groups was marginal at best so I stick with the starting load.
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Old August 13, 2010, 10:01 PM   #5
sserdlihc
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Quote:
but compressing smokeless makes me nervous.
I agree.

Noslers' manual states that the most accurate load for a 150 gr bt was 61.5 gr of RL19, which is a compressed load. Load density volume is 107% I just wonder how safe this practice is?
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Old August 13, 2010, 10:05 PM   #6
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Thanks Unclenick, great explanation.
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Old August 13, 2010, 10:21 PM   #7
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I load 58.0 gr of IMR7828 behind a 150 gr SGK in .270 WIN.... it's a compressed load..... no troubles for me. Very consistant.

IIRC, one of my manuals (Nosler fifth ed., IIRC) said higher load density= more consistency..... something about the powder always being on the same position within the case.....
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Old August 13, 2010, 10:22 PM   #8
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+1 on Unclenick's explanation. For me it seems the pressure curve gets a whole lot steeper in a big hurry once you pass 100%. It doesn't take many percentage points to get me out of my comfort zone.
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Old August 13, 2010, 10:49 PM   #9
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As a rule, I'm not a huge fan of compressed loads, and won't load them except with extruded powders. I'm just a bit concerned that compressing ball or flake powder may change the burning rate too drastically.
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Old August 14, 2010, 03:10 AM   #10
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I try and load all my rifle cartridges with compressed loads. Compressed loads are perfectly safe as long as there is load data to support the charge and you work up. In my experience compressed loads are more accurate than non-compressed loads, luv-em.
Take the 7.62x39 for example, out of 11 powders listed in the Speer manual, 8 of them are compressed and of those 8, three are ball powders.

BTW, Nosler has changed the way they determine load density. IMO their new method is incorrect.
For Example.

Nosler #4
30-06
180gr bullet
IMR 4350 55gr
Load Density 94%

Nosler #6
30-06
180gr Bullet
IMR 4350 55gr
LD 100%.

Nosler #6 also lists 58gr of Hunter to be 105%. Well, I've loaded Hunter in my 06 and I can tell you that that load is no where near compressed let alone 105%.

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Old August 14, 2010, 03:33 AM   #11
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I am fine with what I would call a "tamped" load.Fill a fired case(loose neck) up with powder and thumb press a bullet into it.There is a springy feel,then it gets hard.
Match grade bullets and varmint bullets have thin jackets and soft coresUnless a bullet says it is bonded or hot cored,.If your seating punch leaves a witness mark,and that bullet isnt quite as good as when you bought it.
I suggest,go easy on compression.
Experiment with a drop tube.Get some hobby shop brass telescope tube and modify a powder funnel to fit.Flare the other end to cover over the neck.I tapped a regular drift punch,the tapered part into the tube to flare it.Try it and weight the change .
You may well find what was a serious compressed load is now just lightly tamped.
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Old August 14, 2010, 10:36 AM   #12
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Agree with HiBC on the drop tubes. They can create a surprising amount of additional space if you need it. If you don't need it, though, you may find more consistent ignition without. Federal's original 168 grain Sierra GM Match .308 load of 4064 was just slightly compressed and was very good. I haven't pulled one of their current RL15 loads to see if they are compressed? I don't know Federal's powder drop, either. Probably more than most hand loaders use.

Sinclair has drop tubes for different powder measure brands if you want a plug-in. Midway used to have (and probably still does) a funnel set with a drop tube. There are others.


Steve4102,

There is no exact formula. If you look at Accurate's web site (they are the only brand I know that provides this data) and click on one of their powders, you'll see a bulk density number come up. For Accurate 2520 it is +/- 3.6%. For Accurate 4064 it is +/- 3%. For Accurate 4350 it is +/- 2.2%. So, even if you stick to the same brand of case, the fill could swing 7.2%, 6%, or 4.4% extreme spread, respectively, depending what powder lot number you bought a pound of and how much it was tossed around in transport.

Then, of course, you have brand to brand case variation. A Winchester .30-06 has about 2.5% more usable powder space under a 168 grain SMK bullet, for example, than a 12 grain heavier Remington case does. Since SAAMI only regulates the exterior dimensions of cases, the manufacturers are free to design as much space in as they please, just as long as it still holds up under SAAMI proof pressures.
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