Assuming the pressures are fine, is there any upper limit to a compressed load in terms of %s? 110%?

The reason I ask is that I'm working up some loads for a 250 gr TTSX in a 375 H&H and I'm about 2 grains under listed max on Varget and 4 grains on RL-15. I have zero pressure signs at 100% loads with these powders at recommended Barnes COL (which gives me the best accuracy BTW). I'd be 2-6% range over 100%.

If the accuracy is good I see no reason to add more powder. you can use a drop tube and get more powder, or you can tap the case and pack the powder maybe get a couple more grains.
Dave

The problem with compressed loads is if when you seat the bullet,the powder grains are crushed and broken. This causes two problems. The burn area of the powder grain is increased due to the broken size and "edges. The other problem which really causes a very dangerous pressure spike is the powder grains deterrent coating is chipped off the surface of the powder grain. This causes the charge to burn much faster than designed.
You may read about a pressure wave moving through the powder charge. This is sometimes called a spike in pressure.
The tubular powder grains have the crushing problem. The ball powders have the pressure spike problem due to the tight packing of the charge when the bullet is deep seated. The pressure wave can easily move through the ball powder charge due to the lack of space between the grains.(balls) The speed at which this wave can move through the powder charge is amazing. Then it strikes the base of the bullet that does not want to move. Pressure and heat go through the roof. I have seen and felt the "double" impulse/recoil of a charge not burning properly.
Is there a cut-and-dry rule for how much compression is too much?...No. Too many factors come into play.
Some powders are more forgiving. IMR-3031 can tolerate more compression than most other powders.
H-335 does not like to be compressed at all.
As for compression and max loads,many loads are safe beyond 100% CDL. But the gain of 60 FPS may not be worth it in case life or accuracy.
You sound like you found your rifles accuracy load. You may want to stay with what works.
I seldom ever load to max loads.
I find in 90% of my rifles I shoot long distance,90-95% case density loads are the most accurate with today's powders.
Many of today's new powders require a lighter load and provide a faster MV.
The new Triple-Base powders are well worth trying.
I'm a big fan of the 8 Mag. 200-250 grain bullets moving well over 3,000 fps ( 6,500 feet ASL) are easy and safe to load. Low chamber pressure and stupid fast velocities. Case life is much better as well.

I never compress powder in any case (situation). If it won't fit with the bullet at most firmly resting on the top of it, I don't use it. Regardless of what is a "book" load. That doesn't mean it isn't safe with certain loads, but I don't like it. And what if it pushes your bullet back out; that is not good.
Now, I do compress black powder, but that is different.
Note that that "max load listed" thing is different with each book and each rifle.

OK - looks like I'll keep to my rule of not exceeding 100%.

quote:

looks like I'll keep to my rule of not exceeding 100%

What do you call 100%? Drop tube? No drop tube? Calculated?

After you seat a bullet....if the powder compression pushes it back out as it sits on the bench you might want to back up a bit

Reason I ask how 100% was determined. I have gone to using a drop tube and/or vibration to settle the powder in a couple of my cartridges.

Using IMR or sometimes RL powders a long drop tube or simply touching the case to a vibrator allows me to increase the powder charge WITHOUT forcing the bullet to compress the powder.

Comes in handy with my 380 & 400PDKs

Most other I can find loads that give me what I want with a 100% max.

crushing powder changes the burn rate - to me, 100% loading is the case minus the seating depth -- just let's say its 1.5 calibers - that's 100% --

the more you compress, the more you crush, the more you change the burn rate


and all of that said, you can't get another 100fps, and that last 100fps is VERY expensive in terms of pressure

jeffe

I sometimes put the cases in the loading block and touch it to the case polishing vibrator (running); that will settle the powder down quite a bit. I do this with black powder. That is one way of getting more in without compressing it. Except black powder which you do compress.

Slightly compressed loads have always yielded the most consistent velocities and usually the best accuracy in my hunting rounds. As Ted Thorn indicates, too much compression is when the powder charge pushes the bullet back out of the case after seating. Or, another measure is when the seating stem deforms or leaves a mark on the bullet. Either is a definite no-no, but compression below that point is not only just fine, it is somewhat desirable.

I have NEVER experienced any change in powder behavior due to compression (other than favorably in terms of velocity consistency). If a powder is compressed less than the amount that it tries to push the bullet back out, then it is a myth that such slight compression in some way "breaks it into smaller, faster burning particles" or "chips off deterrent coating". There is no empirical data to substantiate this claim.

I have no idea what various methods might be used to calculate "100%" density, so can't comment on just what percentage above "100%" it is advisable to compress a powder charge. My practice with charges which fill more of the case than there is room after bullet seating is to first drop through a drop tube in order to get the most efficient settling, then seat the bullet no deeper than a reasonable amount "into" the powder charge -- that amount being dependent on the total volume of the case and the diameter of the bullet relative to the body of the case. I have no formula for this -- common sense should rule. I like to stop when I hear the first "crunch" of powder inside the case, but everyone's hearing varies (as does the "audio" of compression of various powders!)

One note: Ball or spherical powders have somewhat less "give" than stick powders, so stick powders will tolerate more compression.

Of note: The "extra velocity" or "light magnum" loads available from various ammunition manufacturers don't use some magic, high energy powder unavailable to handloaders. They do use powder compression techniques which allow them to use more than a typical amount of a slower burning powder. The energy contained in a unit of most powders is roughly the same, so if you can put more powder into the case without exceeding chamber pressure limits you can get more velocity out of it. My understanding is that these factory "compressed" loads use an unrevealed powder compression technique that avoids breaking the granules or "caking" the powder. The technique probably involves compressing the powder prior to bullet seating so that the act of seating the bullet doesn't require so much pressure on the seating stem.

quote:

I have NEVER experienced any change in powder behavior due to compression (other than favorably in terms of velocity consistency).

Just did a quick test using my 400PDK. Simply using a 4" tube vs none I increased the powder to the base of the bullet by a touch over 6% using IMR4895. So which is 100%

The most of my most consistent loads are compressed. In 375 H&H and 8x57 IS (RL-17), 460 Rowland (VV N105, 800-X), .500 S&W (VV N110) . . . Some powders are easy to compress (like flake IMR 800-X), there should be maybe 120 % no problem, but I will be very careful with ball/spherical propellants.

Jiri

no offense to anyone - let's talk about this

Let's see - part of the burn rate is the coatings and the size -- crush grains, OF ANYTHING, it burns faster -- in fact, BP is a great example, ffffG burns faster than fG, right? identical chemical compound

if you take coatings into account, you reduce the burn rate retardation of the coatings

quote:

Let's see - part of the burn rate is the coatings and the size -- crush grains, OF ANYTHING, it burns faster

Wonder if it simply could be that when you compress you crush just a small amount so minimum impact?? I would think that you only crush the top layers. Can't see how you damage the bottom majority.

A small amount of damage sure doesn't compare to fg and fffg I wouldn't think

sure Paul -- f and ffff are hufe difference, and meant to be an example that everyone could get on identical chemical composure - you don't just crush the top, you put pressure on the entire stack, and unless you are swinging the ram really fast, the bottom takes a pretty good load, too ... all else being equal.

but it's not just about crushing the same thing, its about changing the surface flame retardant -- a 5% crush is pretty huge

H4831 vs H 4831SC

I get no velocity difference using these with two of my .270's

quote:

you put pressure on the entire stack, and unless you are swinging the ram really fast, the bottom takes a pretty good load, too ... all else being equal.

Jeff,
seems to me in my earlier days I had to do an experiment in a class that said otherwise. But that was at least 45 yrs ago and I have slept since then. Maybe a younger mind can speak up.

This is all way over my old head. If I can't get a drop tube long enough or vibration cant give me enough room I'll stick with my own rules and look to faster powders.

I'll let the smarter guys figure it out.

From my own experience, some loads can be very heavily compressed and not only work fine but work much better than less (or not) compressed loads. I had a Remington 270 with a somewhat oversize chamber and using H-4831 filled it right to the case mouth and seated the bullet. I never had a bullet back out of the case and the load performed superbly. Reliable, fast, and consistent. That's the most I've ever compressed a load, but I've used lots of other compressed loads with excellent results.

quote:

Originally posted by ted thorn:
H4831 vs H 4831SC

I get no velocity difference using these with two of my .270's

Perfect Ted -- and a related fact to the position that surface coatings matter - the SC is smaller, and with the coatings on all surfaces ...


just saying, guys, if you break kernels, you are going to change effective burn rate -- and a 110% load crushed under pressure --- well, powder is more solid than sponge, right? something has to give, and its not just "squishing" around in the case

quote:

Originally posted by jeffeosso:

quote:

Originally posted by ted thorn:
H4831 vs H 4831SC

I get no velocity difference using these with two of my .270's

Perfect Ted -- and a related fact to the position that surface coatings matter - the SC is smaller, and with the coatings on all surfaces ...


just saying, guys, if you break kernels, you are going to change effective burn rate -- and a 110% load crushed under pressure --- well, powder is more solid than sponge, right? something has to give, and its not just "squishing" around in the case

Jeff,
Normally, I would agree with most you say, you are a knowledgable handloader, but, in this instance, I disagree with you.
Having pulled and dumped many heavily compressed loads, and using them regularly, the amount of kernels damaged by compression is the same as the amount of kernels cut in a powder measure. It is so few, that the affects on the burn rate is moot.
I have dismantled 375 Weatherby rounds with 760 powder, so tightly packed that I had to use a sharp pencil to poke the powder to get it out.
No powder was damaged, the coatings were intact and the pressure on my pressure trace tracked just as it did with loads that weren't packed quite as tightly.
When I'm running compressed loads, I swirl the charge into the case with a funnel, this gives the same results as a long drop tube, allowing more room for the bullet. This also lowers ES and SD in tuned loads that normally would be erratic without attention.
I have never seen crushed or broken kernels in a compressed load yet.
Any load that runs in excess of 90% capacity will be slightly compressed when a bullet is seated anyway.
The ammo companies use less than 80% in their loads, BUT, they crimp most loads to boost start pressure and get good ES and SD numbers in numerous rifles.
I also agree that heavily compressed loads that force the bullet back out, are not a good idea, as the backing out may go unnoticed.

Cheers.

The most heavily comprised charge I have ever used was from the Barnes Manual with the old 130 gr "blue" bullet in the 270 Winchester with 65 gr RL25. The load gave a very uniform 3200 fps from a 22" barrel of a M70 Classic without a hint of a problem.

The load was so heavily compressed it gave me pause,even though I have been shooting H4831 in the 270 for decades and seems that has always been compressed....but nothing like that Barnes load of RL25.

I too have heard that compressed charges break up some powder and heard this is not good, but have never encountered any studies indicating this actually leads to excessive pressures. At least for me it never has.

thanks guys -- it's okay to disagree, and I am all ears for other's POV -- appreciate yall

In theory I agree with Jeff. Breaking grains would lead to change in Burn rate due to differences in exposed surfaces without deterrent coating. Only way to prove that would be to count, photograph, document an group of powder kernels that when put into a case and compressed would "crunched" and then take that same powder back out, document the change in the physical grains, find a way to put that into a metric, then fire the loads for Pressure testing. Nope, we are not going to do that! I personally have crunched lot's of 4831 and don't have any issues to report. I have also heavily compressed some H 414 and indeed, had some 5+ year old loads give me problems with going bang. (I think I had 64.5 grains, 5 gains too much, under a Barnes 165 X bullet in a 30-06. The old gun it was in handled the loads fine and shot great.) Upon disassembly, the Powder was a solid. To be fair, this ammo probably did not have a Temp controlled life. Probably had been hot in the summer and cold in the winter.

One of the more famous ones was Winchester when the .458 came out.
They had lied on the specs and needed to compress powder heavily to get near the claimed. That powder caked and several African hunters got nasty suprises as critters got mad/vounded instead of dead because of cigarette burns and sad pops.

A lot of my 375 H&H loads are heavily compressed it doesn't bother me at all.

My limit is when seating the bullet takes more force on the press handle than full length sizing of the cartridge cases.

In 1963 I stared shooting my McGowen made 22 Varminter ( later to become the .22-250 ). The cases were made from .250-3000 cases.
The cases were filled to the top with 4831 or IMR (Dupont)4350 and compressed with a Barnes 70 gr. bullet. Never had a problem and the rifle and I shot 1/2 MOA all the time.This rifle accounted for many mule deer with the Barnes bullet but badly wounded a small nunber with cup and core bullets.

My .358X41 uses nearly a full case of 4198 that is compressed with a 300gr. gas checked bullet. Gets an energy level equivalent to a 30-06 and no prblems.

FYI!! I learned that when you are greatly compressing ball powders you can unseat the primers.
roger

Most loading books go with around 105%, Ive used about 102% to 103% on many occasions. In many cases powders like 4831, RL-22,25 and 19 will take a lot of compressing and get you top accuracy and pressure isn't an issue in come cases depending on caliber..Some of the books show you the pressure and percentage of compactness...They are a good place to start, then its up to you to find the max load for your rifle..I wouldn't worry about compaction except from the standpoint of misfires..I like a little compacion, but not much.

I have seen instances when 60 to 62 grs. of old 4831 would push bullets out a bit over night, but pressures were low with that old stuff..Jack O'Connor liked that 62 gr. load with a 130 gr. bullet in both his 06 and 270..Its surely an accurate load and velocity is right around 3200 FPS..depends on the chamber and the resized case with that big dose of old 4831..I know a gent who had that 270 62 gr. load pressure tested with that O'Connor load and the PSI was 52,000 PSI, surprisingly mild..Damn that was good powder, I still have a good deal of it, but I hate loading those cutting grains..I pretty much have been using RL powders.

I'll throw in another theoretical consideration. I noticed that with surplus WC860 powder, originally for US .50 BMG and close in burning rate to old H870, that in my .300 Weatherby Magnum with 180 grain Hornady Interlock bullets increasing charges past the point of compression produced little change in velocity and no signs of high pressure. I had previously studied loading manuals for H870 and AA8700 loads and noticed they were limited by case capacity with compressed loads around 93-96 grains from 150-220 grain bullets, all with less than maximum pressures for the cartridge and none giving top velocities achieved with other powders. So I cautiously tried going up in small increments till I got 100 grains in neck sized cases with vibration and firm compression. Quickly applying a Lee Factory Crimp prevented bullet extrusion, but I quit when I actually had some cases bulge at the shoulder when I worked the press ram too quickly! As I said, velocity increases were negligible and none of the usual signs of high pressure appeared on firing them. The 100 grain loads made it to 3050 FPS from my 24" barrel, which is about what 95 grains gives. Here is what I think happened: As the spheroidal powder grains are forced together, they deform plastically rather than fracturing. I was applying sufficient pressure to deform them significantly, but nowhere near "dead pressing" the powder into a solid mass with no air space. As the spheroidal press against each other and deform, they flatten against each other forming facets that are occluded from the air space between grains. When the primer fires and the bullet has not yet moved, the hot gases flow through the interstices between grains igniting the exposed surfaces, but cannot touch and ignite the facets pressed together. That significantly reduces the initial burning surface area, much more so as the powder is compressed a little more. When the bullet starts to move, initially the rate of volume expansion is proportionally very rapid. As the powder grains start to pull apart the facets are exposed, still coated with full thickness deterrent that has largely burned away from the already exposed surfaces and would have more uniformly burned off in a non compressed charge. So a large part of the powder has a significant ignition delay as the bullet has already started moving. Yes, fractured propellant grains make fast burning fragments. But that wasn't happening much with this ball powder. So apparently it becomes slower burning as it's compressed more.

If you would have asked me a couple years ago I would have said that as long as the powder didn't push the bullet out again you were good to go. I've had reason to reverse that position.

I had a couple stiff but reasonable loads that just happened to be for the .257 and .300 Weatherby and both with 7828 out of the same keg. Both were compressed a rather lot. Velocities were about as expected. All was well in the fall and come spring I started dragging rifles out and shooting them again. The first one of the two to get fired was the 300. The very first shot locked it up solid. Take to gunsmith and debate pulling the barrel solid. Blown primer and seriously desecrated casehead solid. The rifle survived without issue.

I pulled down the ammo and weighed each charge. Had to scrape them out with a nail. Each charge was right where it was supposed to be within a tenth. That doesn't prove that the fired one was perfect, but there is no real way to assess that. I then worked up the load again and ended up at the same place. Still, life is short and vision precious so I backed off 2 full grains and left it at that. Wrote it off as "shit happens" and that when you are riding on the edge you might go over.

A short time later the .257 come up in the rotation. Again it had the same ammo that had been loaded in the fall and stored for the winter. All weighed, safe maximum loads of 7828 from the same jug as the .300. First shot out of the gate and same thing. Locked bolt with no damage to the rifle. Pull the ammo down and weigh each charge. No problems there, although the powder had to be pried out of the cases. Backed off the charge two grains as well. Neither has missed a beat since.

The only things those two loads had in common was the same powder and both were heavily compressed. Neither gave a bit of trouble til they sat for 5-6 months. Here's the thing; I have no way of knowing what a compressed charge of any particular powder will act like in six months or six years. I doubt that anyone else does either, for every possible combination. Never saw a footnote in a reloading with a *** passed 7 year compressed storage test notation either. Lifes too short. I don't mind tagging the powder but I'm not going to squeeze to one hard ever again. That also lead in part to rechambering my 458 Win to Lott. I was on the fence about that, but this pushed me over to the safe side.

We have hunted with very compressed charges - we use a 2 foot drop tube, and the powder was almost falling out of the case neck!!

And the bullet was seated, and crimped in.

Worked just fine.

quote:

Originally posted by Saeed:
We have hunted with very compressed charges - we use a 2 foot drop tube, and the powder was almost falling out of the case neck!!

And the bullet was seated, and crimped in.

Worked just fine.

I think you could write an AC/DC song about that load of the sound of it!

I've read that Jack Lott has some experience with compressed loads in the 458 Win Mag.

How do you compress ball powder ?

Alf,
Apparantly you can put it in a quart jar with 4 teaspoons of honey and let it roast for 30 minutes at 450 degress, they use it for glass bedding compound or filling a case with it and letting it set up overnight...shoot it with a heavy glove on and around the corner..velocity is right up there. Never mind!!