Is there something wrong with compressed loads?

[Red_Beard]

Hello all, I was reading up on some new ideas for loading my 7mm RM and am really intrigued by the lower pressure, high velocity Retumbo/180 class bullet combo, but it seems like many people go to H1000 to avoid shooting a "compressed" load.

I will be shooting out of a 28" barrel, so the speed should be where I want it with either combo. Is there a downside to shooting a compressed load?

Another consideration is that these will be fed from AICS 300WM magazines. Will I be able to seat the 180's deep enough with the heavy powder charge to still fit and feed properly?

As always, thanks for the input!

-Red

 

[turbo54]

Many people have found compressed loads are often the most accurate.

No, there is nothing "wrong" with them, but there are some things to watch out for...

For starters, you must work up to be sure it isn't overpressure. Secondly, if you try to squeeze too much powder in there, sometimes the powder will squeeze the bullet back out. You'll have to experiment with it to see what you can get away with.

A drop tube is helpful when working with compressed charges.

 

[trailrider121]

Make sure to have enough neck tension as well. As Turbo said it will push the bullet out with compressed load.

 

[milo 2.0]

If I could have my choice, all my loads would be compressed, just doesn't happen that way though.

 

[Creature]

Nothing wrong with compressed loads but you should work up and always pay attention to the level of pressure you're getting. I think there's more even of a burn with the powder being compressed as there isn't any dead space in the case. With a non-compressed load the powder isn't evenly filled out in the case and I've always felt that that wouldn't be conducive to and "even" burn.

You probably shouldn't try and compress it too much as that might crush some of the granules and cause an increased burn rate/overpressure.

 

[wilecoyote]

confirming all the inputs above, I can only add that your drop tube can be obtained from a Bic biro pen,the cheaper,clear plastic type, removing the inner ink refill, of course...

 

[Twoboxer]

Only other con to compressed loads that I can think of is the Redding Competition bullet seater is not to be used with compressed loads. They say the increased pressure on the seater results and can lead to early demise of this expensive device.

 

[PharmShooter]

Only other con to compressed loads that I can think of is the Redding Competition bullet seater is not to be used with compressed loads. They say the increased pressure on the seater results and can lead to early demise of this expensive device.

I hadn't heard this...can anyone else confirm this? If so, wouldn't the warranty cover this? Any other thougthts???

 

[milo 2.0]

Yes it can ruin your seater stem, they will fix it you pay. About 13 bucks last time. Also not chamfering your cases can mess things up also.

 

[DocB]

Red,

A compressed load can also cause runout problems, at least in my experience.

HTH,
DocB

 

[DocB]

Red,

A compressed load can also cause runout problems, at least in my experience.

HTH,
DocB

 

[cjherrman]

Just don't overdue it, obviously work your load up but when you start trying to take it too far is when you run into catastrophic problems.

 

[AberdeenReb]

I seem to get the most accuracy just below a compressed load, say about 98-99% filled. To the OP, I have been here with the 7mm RM before. You will get better velocity with the retumbo, but I had trouble with extreme spread. I switched to h1000 and gave up a little velocity, but it shoots better.

 

[Twoboxer]

I hadn't heard this...can anyone else confirm this? If so, wouldn't the warranty cover this? Any other thougthts???

I learned it from the instructions that came with my 223 die.

>$100 for the die, one would *think* . . . oh, well

 

[1lnbrdg]

I hadn't heard this...can anyone else confirm this? If so, wouldn't the warranty cover this? Any other thougthts???

Redding doesn't harden the stem, Forster dies have a hardened stem. Guess where I spend my money? And yes, compressed loads will eventually swell the stem in a Redding die and they will replace it with another soft stem for a little bit of $.

 

[Red_Beard]

Thanks for the help and information everyone, this eases my mind a lot regarding the move to Retumbo

 

[Glockin' Bob]

I try to avoid compressed loads. In addition to sometimes causing runout issues and additional die wear, the bullet crushes the powder which affects burn rate due to the flame-deterrent coating getting fractured. I try to find a powder which gives me a high load density, preferably about to the point where a seated bullet just about touches the powder.

 

[PharmShooter]

I try to avoid compressed loads. In addition to sometimes causing runout issues and additional die wear, the bullet crushes the powder which affects burn rate due to the flame-deterrent coating getting fractured. I try to find a powder which gives me a high load density, preferably about to the point where a seated bullet just about touches the powder.

This makes sense. I can only think of one of my loads that is just slightly compressed.

 

[Twoboxer]

Had one other thought . . . FWIW . . . compressed load means (to me) you're asking the powder to do something it wasn't exactly designed for.

May well be fine, may even be great. But . . . not inside design parameters.

 

[turbo54]

Had one other thought . . . FWIW . . . compressed load means (to me) you're asking the powder to do something it wasn't exactly designed for.

May well be fine, may even be great. But . . . not inside design parameters.

Disagree.

Most loading manuals include compressed charges... If Hodgdon didn't think compressing their powder was perfectly acceptable, they wouldn't include them in their manual.

 

[turbo54]

I try to avoid compressed loads. In addition to sometimes causing runout issues and additional die wear, the bullet crushes the powder which affects burn rate due to the flame-deterrent coating getting fractured. I try to find a powder which gives me a high load density, preferably about to the point where a seated bullet just about touches the powder.

I've run a lot of compressed loads with several different powders, though most were Hodgdon "extreme" powders.

I've also had to pull down plenty of these. I've never found a fractured kernel...which isn't to say there have never been any...but if there are, there are so few it has no appreciable affect on burn speed.

Again, if Hodgdon says its cool to crunch 45.5gr Varget under a 175smk loaded to 2.810" in Winchester brass, who are we to argue its bad juju on account of a fractured kernel?

 

[timjoebobbradley]

If most of the fractured kernals are right below the base of the bullet, I imagine they are part way down the bore before they ignite, so they don't have a significant difference on burn rate of the whole powder charge.

 

[Twoboxer]

Disagree.

Most loading manuals include compressed charges... If Hodgdon didn't think compressing their powder was perfectly acceptable, they wouldn't include them in their manual.

We have no disagreement . . . the loads are acceptable. "May even be great loads."

 

[Greg Langelius *]

I don't run away from compressed loads, and as a general rule, like my loads to be right around 100% load density for accuracy consideration. Some small degree of compression seems to help that, and as another general rule, if an accurate load density falls below 95%, that's a potential recommendation for me to try the next slower powder burn rate.

I often collet pull old loads. Compressed loads usually won't dump, the powder ends up being glommed together into a single clump. When you break those clumps apart, it can mess with the kernel coatings, often increasing burn rates. That's a very good reason to be careful about using salvaged propellants; especially if you're not the one doing the salvaging.

If I were a rocket scientist, I would call that charge a monolithic grain, and that's why and how model rocket engines employing black powder usually have their propellant 'grain' heavily compressed, to reduce the potential for catastrophic detonation. Seams and cracks in the grain increase burning surface area, significantly increasing the charge's burn rate, sometimes with catastrophic consequence.

Properly compressed/monolithic solid rocket propellant charges burn at a safer sustained rate and pressure, and I suspect there could be come carryover to metallic rifle cartridge propellant charges, as well.

That's a THEORY.

 

[turbo54]

Interesting thoughts, Greg.

I've also noticed that when I pull down a compressed load, the powder doesn't all pour out when I tip the case over to dump it. I usually get a small pour, and then I have to "thwack" the cashead down on my bench (with finger over the case mouth) to break up the powder stiction...then it all pours out nicely.

I routinely reuse my pull-down powder, and have never adjusted/reworked the load. I've not noticed any difference between the pull down loads and virgin loads - but sounds like an interesting thing to test.

 

[X-fan]

I don't run away from compressed loads, and as a general rule, like my loads to be right around 100% load density for accuracy consideration. Some small degree of compression seems to help that, and as another general rule, if an accurate load density falls below 95%, that's a potential recommendation for me to try the next slower powder burn rate.

I often collet pull old loads. Compressed loads usually won't dump, the powder ends up being glommed together into a single clump. When you break those clumps apart, it can mess with the kernel coatings, often increasing burn rates. That's a very good reason to be careful about using salvaged propellants; especially if you're not the one doing the salvaging.

If I were a rocket scientist, I would call that charge a monolithic grain, and that's why and how model rocket engines employing black powder usually have their propellant 'grain' heavily compressed, to reduce the potential for catastrophic detonation. Seams and cracks in the grain increase burning surface area, significantly increasing the charge's burn rate, sometimes with catastrophic consequence.

Properly compressed/monolithic solid rocket propellant charges burn at a safer sustained rate and pressure, and I suspect there could be come carryover to metallic rifle cartridge propellant charges, as well.

That's a THEORY.

If you ever hunt Africa you will get a lot of suggestions not to assemble highly compressed loads as it creates ignition problems.
The theory is that heavily compacted powder melts into a lump in the African heat. There is significant evidence that this situation can lead to to massive pressure spikes.
The original 458 Win factory loaded 510 grain loads were well known for this. The load would often fail to fire or when it did fire it would occasionally stick a bolt shut.
Not really relevant to precision shooting, but an interesting data point.

 

[Greg Langelius *]

I totally agree with the Africa anecdotes, but when I speak of mild load compression, I'm speaking about my loads, which get shot at a range, and get handled with heat exposure as something that needs to be avoided. I really should have given that aspect more emphasis.

Rockets work because the ignition starts at the casing's point of exit. That's the complete opposite of the cartridge casing.

 

[rodnocker1`]

Nothing wrong with compressed loads but you should work up and always pay attention to the level of pressure you're getting. I think there's more even of a burn with the powder being compressed as there isn't any dead space in the case. With a non-compressed load the powder isn't evenly filled out in the case and I've always felt that that wouldn't be conducive to and "even" burn.

You probably shouldn't try and compress it too much as that might crush some of the granules and cause an increased burn rate/overpressure.

Not to highjack the thread but more to go along with it.

I've never done it but I've heard others say that they have used filler to take up the dead space when the powder doesn't fill up the case. Is this a good idea and if so, could you add a little more filler to make a compressed load or would that be detrimental?

 

[milo 2.0]

Not to highjack the thread but more to go along with it.

I've never done it but I've heard others say that they have used filler to take up the dead space when the powder doesn't fill up the case. Is this a good idea and if so, could you add a little more filler to make a compressed load or would that be detrimental?

I don't know what would be safe to use, but have friend that used corn meal. He no longer has a right eye, and has an extractor stuck in the back of his skull.

Use this info as you may.

 

[rodnocker1`]

I don't know what would be safe to use, but have friend that used corn meal. He no longer has a right eye, and has an extractor stuck in the back of his skull.

Use this info as you may.

I hadn't heard of anything like that happening before but that was sorta what I thought might could happen. I never bothered to ask them if they mixed the filler in with the powder, placed it on top of the charge, or....?

My thought at the time was why not just use a bulkier powder.....

 

[ksthomas]

The NRA has recommended against using fillers for many, many years now. Lot'sa problems down that particular road, and they're not readily reproducible in the lab. That's not to say it's safe, just that it doesn't happen often. Or, as Dirty Harry once said, "So you gotta ask yourself, do you feel lucky?"

 

[sandwarrior]

As mentioned above, many pro's to compressed loads. Consistency, stability of powder in the case (yes, powder 'form' during ignition does cause it's own vibration/harmonic). Also, as mentioned, one of the big cons to it is 'over compression' can cause damage to and even change the physical properties of the powder. Use some common sense when building up to a compressed load and I think you'll find you will be very happy with the loads.
Something you mentioned is to get a lower pressure, longer burn. That is probably the biggest barrel saver right there. If you can get consistency from your compressed load, it goes without saying, you're going to have longer accuracy with that barrel.
One other factor/issue to work out is using a compressed load with the bullet way down in the case. I know the 7mm Rem mag is a fave, but where this really works and saves is choosing a case with a long neck.

So, in summary, I suggest never going over 103% of case capacity with a compressed load. I gauge it by actual capacity of the case, then the "feel" of the powder as you bring the ram up to load the bullet. I never have more than 1/8th of the stroke where I can feel powder crushing.
Keep the bullet as far above the shoulder/body junction as you can (for accuracy).
Retumbo may work for you but look into some of the double-based powders such as H869. Double based .50 cal powders work quite well in this role.

 

[Greg Langelius *]

This is in direct parallel with my own philosophy of getting the velocity from greater barrel length and more reasonable charges, you rifle's throat and bore will thank you.

Greg

 

[CTone03]

As someone else posted, BIC pen tubes are your friend:

As a powder trickler



As a drop tube



I do compressed loads occasionally as long as they're mildly compressed. Unless of course it's RL17, then I break out the cheater-bar to get those bullets down in there