Have you made some 'compressed' reloads?

[Ignition Override]

Having read a few months ago that it should be safe, I did so, but have Not yet used any of these forty rounds. To be clear, I'm a plinker, often hitting orange spots on concrete blocks.

Some once-used Prvi .303 cases were loaded with 45 (start) grains of H 4831, and it seems that the Lee chart giving loads for that powder in these cases should be reliable, as they must be well aware of how this powder leaves less space in the neck for the bullet.

The only thing which made me a little uncomfy was that when seating the 150 gr. bullets, a bit of resistance by the powder was felt using the press, compared to using IMR 4064, in order to keep the case length within the max. 3.075".

A friend sold me 4 lbs. of this powder along with mostly H4895 (saving this for the Garand).

 

[FrankenMauser]

I can't comment on the safety of your particular load, since I haven't looked it up; but I do shoot compressed loads.

As long as the powder is being compressed, and not crushed (breaking granules), you're fine.

 

[Ignition Override]

That Lee reloading chart which came with the .303 'British' dies has the H 4831 for a 150 gr. bullet, with the starting load of 45 grains. I weigh the granules on a mechanical scale, and it takes quite a while.

Before seating the bullets, the space visible in the .303 neck might have been half the depth of what is normally visible with the IMR 4064 powder.

 

[NWPilgrim]

There is nothing different about compressed loads versus non-compressed loads. It usually happens when you are loading a slower and bulky powder with a lighter bullet and it takes that much more powder to reach peak pressure. In fact, some powders seem to like being compressed, (Varget in .223 with 55-69 gr bullets, for instance).

As long as you are following the load data and working up from the start loads and not exceeding the max loads you should be fine. I don't know why guys get nervous about this but there is absolutely nothing different. You are not making the powder more powerful or faster burning by compressing it.

 

[Bart B.]

Compressed loads are the start of powder particle cracking and breaking. If enough of them get crunched into smaller pieces, the burn rate of the charge will change to faster as well as having a greater spread. And that's the first step to increased peak pressure and poor accuracy.

Therefore, I do not think compressed loads are a good thing to do. You decide your own safety margins and accuracy standards. Your're the one who deals with such things.

Use a drop tube to more compact the powder in a given space inside the case without changing its physical properties. This is the safe thing to do as long as peak pressure limits for the cartridge are not exceeded.

 

[Mike / Tx]

To answer your initial question, yes I have loaded a bunch of loads that were compressed. As mentioned some of the slower powders will fill the cases up and if using a longer or heavier for caliber bullet, you will squash some of it while seating.

Use a drop tube to more compact the powder in a given space inside the case without changing its physical properties. This is the safe thing to do as long as peak pressure limits for the cartridge are not exceeded.

As mentioned above here, a drop tube will go a long way in settling the powder in a more compact manner when poured into the cases. I have also found that while the cases are sitting in the loading block and charged, using one of the electric engravers and simply touching all 4 of the sides of the block, will usually settle it very good as well.

I have used both methods depending on just what powder or case I was working with.

One other thing, the data listed in the Lee manual wasn't actually tested by them. It is a compilation of other data they managed to get writes to reproduce in their manual. I usually check the loads in a couple of other manuals or sources to verify them before taking them as gospel.

Hope this helps.

 

[steve4102]

Yes , I have loaded compressed rounds. In fact most of my rifle ammo is compressed, some so heavily compressed I have to re-seat the bullet after a couple hours.

Compressing powder is perfectly safe as long as there is data to support the charge. If it were harmful/dangerous or altered the burn rate then the powder manufacturer's would post Warnings and not publish compressed data.

 

[Bart B.]

To all those "compressors" out there, pull the bullet from a heavily compressed charge of extruded powder, then inspect every kernel of it for uniform shape.

Better yet, do some valid muzzle velocity and accuracy comparisons.

Mike/TX, if you weigh powder and charge primed cases while an earthquake's at hand, powder compacting happens without human intervention.

 

[steve4102]

. Better yet, do some valid muzzle velocity and accuracy comparisons.

It's done with all my firearms and loads. Compressing powders delivers top velocities with outstanding accuracy. Plus, I love to hear that "crunch".

 

[243winxb]

The internal volume of different brands of brass may cause different rates of compression, using the same amount of powder. As said, to much compression changes the shape of the powder particle. On powders like IMR 4350, a stick powder, it may be possible to change burning rate IF over compressed. H4831 in the 303 is not the best powder for the job using a 150 gr. bullet, but should be safe. I can only find data for a 180gr. starting at 46.0 gr.

 

[flashhole]

I'm in Steve4102's camp. I go out of my way to make lightly compressed loads whenever I can. Excellent velocity and excellent accuracy. If you want to settle the powder in the case try using an electric toothbrush with the brush removed. I run the flat side of the vibrating rod up and down the side of the case. Powder settles really well.

Compressed loads in 7mm Rem Mag, 45-70, 25-06, 221 Fireball and 223 Remington. Also used compressed loads in 243 Win and 300 Win Mag before I sold them.

 

[10 Spot Terminator]

I too dont mind abit of compression as long as everyone understands we are talking about extruded or ""stick" type powders here as they are called . Ixnay on ball or flake powders . Insofar as breaking a few kernals having an adverse effect on burn rates I would state my tests over a chrony have not borne that out and when testing both H4831 and IMR7828 in their long and short cut offerings I got no differences. If you actually take some long cut kernals and check them under a strong magnifying glass you will find minor variations in the kernels as came from the factory . I do however as many others here attempt to settle the powder charge inside the rifle cases with vibration . I prefer to use an engraving pen lightly touching the case as I slow pour the powder into the case as it seems to settle deeper than filling the case first and then trying to work the entire charge down . A remark was made here that the compression would alter the burn rate in different cases to which I comment that all brands of brass and even different lots of brass by the same maker have slighly different internal capacities which will have slightly different pressure values when all fed the same exact powder charge . For this reason it is a good reason to seperate your brass by lot, manufacturer and times fired from initial load workup through its useable life to keep your loads uniform . This I have found to be a controlling factor proven by the chrony as well as the noteable change in bullet grouping but not compression of the powder . Weaker primers may play into this somewhat but I burried that problem years ago when I switched to Fedral Match primers .

10 Spot

 

[FrankenMauser]

I too dont mind abit of compression as long as everyone understands we are talking about extruded or ""stick" type powders here as they are called . Ixnay on ball or flake powders[.]

I take it, by that statement, that you haven't dealt with shotgun reloading or powders like Blue Dot, very much.

Some shotgun loads, for example, have so much (required) compression, that the powder will come out in one solid mass, if you pull the load down or cut the shell apart. Under those conditions, it behaves as it should. But, if you don't compress it far enough, you can get nasty, undesirable pressure spikes.

 

[NWPilgrim]

I have pulled bullets from compressed loads of Varget and there is virtually no breakage of the kernels or sticks.

For one thing, most "compressed" loads are under 8% of case volume, mostly under 5%. A very few may get to 10% - 12%. There is a lot of air in a case of extruded powder. Seating the bullet merely compacts the column of powder; there is a lot of give in the whole column.

Secondly, IF any sticks are broken then it is a very few and a very insignificant percentage of the total, like 10 out of 300 or something? And that breakage apparently has little increase in burn rate, certainly not 100% or greater increase for those sticks. Overall, IF there are a few broken sticks you are talking about a fraction of 1% change. That is less than the accuracy of my Uniflow powder measure.

As stated above, every manual states whether a tested load is compressed. I have never seen a manual that warns to ONLY load compressed charges with a drop tube. Never. In fact my Varget compressed loads aren't even max! The manual suggests it could be safe to load higher (SAAMI pressure, not 5.56). For those I would need a drop tube just to get all the powder in the case. As it is, I get good accuracy at less than max weight and can fit it in without a drop tube.

Edited for typos and clarification.

 

[math teacher]

One side effect of compressed loads is that you sometimes get a compression ring around the bullet. I haven't noticed where it affects performance.

 

[243winxb]

The Manufacture of Smokeless Powders and their Forensic Analysis: A Brief Review

Shape and size have a profound effect on the burning rate and power generation of a powder (Meyer 1987).

http://firearmsid.com/Feature%20Articles/McCord_gunpowder/index.htm I am guilty of not doing my own testing. If the reloading manual lists the load as compressed, it should be safe.

 

[TimSr]

I have to admit that when I first started loading rifle cartridges, that I was little uncomfortable with the idea of crunching down the powder with the bullet, but common sense eventually told me that if the tell you in the load data that it is compressed, and if the amount of compression was critical to safety, that it would NOT be an unpublished secret. I have never seen load data warning about over compression.

Vacant case space seesm to affect consistency on certain powders much more than the amount of compression. Stick powders aren't the only ones that may perform better compressed than with some vacant space. Blue Dot and 296/110 are sometimes compressed as well, and neither likes vacant space.

I was working on some .308 loads, and the "compressed" charge in the book would not even fit in the case to be compressed! I Poured the weighed charge into teh funnel, and when I lifted the funnel, the powder cascaded over the sides of the case onto the bench. I think it was with IMR4350, but don't remember for sure which powder it was.

Needless to say. I don't get excited over compressed loads any more.

 

[madmo44mag]

I have never loaded any rifle ammo with a compressed load but many pistol ammo's.
Some well above max pressures.
I only want to caution here.
Be careful even if the load is listed.
Brass that has been work hardened will tend to split.
Always work up the load and use extreme caution even if it is a load you have loaded before.
The integrity of the brass is always compromised to some degree in a compressed load IMO and experience.

 

[jimbob86]

Consider the application ......

Better yet, do some valid muzzle velocity and accuracy comparisons.

....

I use a compressed load of 7828 in my .270WIN ...... it is more accurate than the start load .... smaller SD ....... smaller group. It is my understanding that most really slow powders work best near or at max pressure ...... and this has been proven true in my (limited) experience.

While there may be a slightly more accurate load for my gun, spending any time or money in search of it would be a PII* error ....... something I keep in mind when reading Bart's posts ....... such things are important in the benchrest game ..... which I do not play....



*"PII"= "Preoccupation (with) Inconsequential Increments" - Spending much time and energy debating such topics as "How Many Angels May Dance Upon The Head Of A Pin", when it is enough to know that there are indeed Angels, or one load will give you a .1" better group than another, when the shooter can't hold to .1" without a machine rest anyhow .......

 

[4runnerman]

As stated earlier. My 223 load. 25.5 Varget. This is a compressed load. Very accurate and very safe. No pressure signs at all