How much compression

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Hey guys how much compression on the powder is too much compression? I know its a tricky one but any advice is appreciated.
I am using vihtavuori N150 with Lapua Brass, max load is 46.8g, at 46g I get some serious compression (I think).
 
Avoid heavily compressed loads. Try long drop tubes. Is the cartridge 308? If powder is level with case mouth I would consider that heavily compressed. If powder is just into the case neck that would be fine. Prefer full to slight compression.
 
If you would have asked me a year ago I'd have said that as long as you could get the bullet seated everything would be OK. I've got loads that will push the bullets back out if they sit long enough.

This spring I was forced to re-examine that position. I had developed a couple of loads on two different Weatherby cartridges with old 7828 in late summer/early autumn. Pressures were right up there, and charges were maximum in some books and over others. In short, I'd pushed it about as far as an aggressive but not insane reloader would. Loads were compressed, but not overly so. Primer pockets held tight.

Fast forward to this spring. I took the same rifles (at different times) and the same ammo that had sat over the winter. First shot out of the gate with one rifle was a locked bolt and blown primer. Tearing down all the ammo showed that the hand weighed charges of the remainder were all bang on. It was a pain to get the powder out the case with some banging, scraping and scratching and staring inside with a light. Eventually I just assumed that there must have been something, somehow wrong with that one cartridge. I backed the charge off and reworked the loads and settled on 2 grains less than before. I had them up to the same level as before without trouble, but life is too short. When you're pouring powder into cases 80 some grains at a time 2 less isn't going to make them bounce off a deer hide.

Somewhat later I had the same problem with another rifle. First shot, locked bolt. No damage. After another trip to the same gunsmith I tore down that ammo too. Once again the powder had compacted. All the other cartridges checked out for weight. At this point it was a little harder to write it off as some unexplainable fluke. The rounds in both calibers had been loaded with the same powder, and if not out of the same keg at least out of the same lot. The only thing that had changed is that the ammo had sat over the winter. I reworked that load as well, and once again managed to reach the same powder weight. I backed off that charge 2 grains as well. In both instances 2 grains was the difference between hearing the powder shake and not. That's not a ton of compression.

How does that apply to your situation? I don't know. There are an infinite amount of powder type/ caliber combinations and it might not matter on most of them. I believe that if you work up to your charge you'll be OK with compressed loads in anything, that day. Shoot them fresh and there won't be any trouble. What will happen after the winter, or after a year or 5 years with all compressed combinations I don't know. Neither does anyone else. Maybe it'll be good, maybe it won't. Maybe is poor comfort when your bolt handle is stuck down. Actually a stuck bolt is one of the better outcomes.

Something to think about anyway.
 
Here is something I have heard said..........NO confirmation..........NO reference.......Just rumor maybe.

The reason powder comes in differant shapes and sizes is related to it's coating, if any, and also to the
surface area available for ignition.
In other words, the rumor says that if a powder is made in very small granuals, it should provide extended
surface area during burning.
If the powder is made in larger granuals, the burning should take longer (subjective).

Some powders have a coating to slow down/speed up ignition.
Some powders have a coating to prevent fowling and/or carbon.

What the rumor DOES not explain is how compression will affect the above.
Just something to add to the discussion.

Anyone know anything about this? Confirm it? Call BS?
 
Put your finger over the mouth of the case and tap it on a wood block (etc) to compress the powder before you seat the bullet (Just be careful where you tap it, you don't want anything pointy under the bottom of the case that could set off the primer). This will actually buy you a fair bit of room in the case as the power packs/compresses down.
 
Over the years, I have observed that some powders are quite tolerant of compression, while others get erratic when heavily compressed..

My thought on the matter is that a very light compression is fine with most powders available to us.

However, as Dogleg mentioned, strange things can happen with heavier compression and certain powders.

I recollect, many years ago, Hodgdon marketed a slow burning powder called H205 [Not Norma 205] This powder really did crazy things when compressed any amount at all.

Most sphericals cannot be compressed much, due to their finer physical nature, and most do not take well to compression anyway.

I am not particularly fond of heavy compression, but some compression with certain cases/powders is a way of life to the handloader.

Regards, Dave.
 
I will go along with dogleg and eagleye. IMHO If you are compressing the powder, you are using the wrong powder. Of course that is my opinion. Many people think powder compression is just fine.
 
Dogleg said:
If you would have asked me a year ago I'd have said that as long as you could get the bullet seated everything would be OK. I've got loads that will push the bullets back out if they sit long enough.

This spring I was forced to re-examine that position. I had developed a couple of loads on two different Weatherby cartridges with old 7828 in late summer/early autumn. Pressures were right up there, and charges were maximum in some books and over others. In short, I'd pushed it about as far as an aggressive but not insane reloader would. Loads were compressed, but not overly so. Primer pockets held tight.

Fast forward to this spring. I took the same rifles (at different times) and the same ammo that had sat over the winter. First shot out of the gate with one rifle was a locked bolt and blown primer. Tearing down all the ammo showed that the hand weighed charges of the remainder were all bang on. It was a pain to get the powder out the case with some banging, scraping and scratching and staring inside with a light. Eventually I just assumed that there must have been something, somehow wrong with that one cartridge. I backed the charge off and reworked the loads and settled on 2 grains less than before. I had them up to the same level as before without trouble, but life is too short. When you're pouring powder into cases 80 some grains at a time 2 less isn't going to make them bounce off a deer hide.

Somewhat later I had the same problem with another rifle. First shot, locked bolt. No damage. After another trip to the same gunsmith I tore down that ammo too. Once again the powder had compacted. All the other cartridges checked out for weight. At this point it was a little harder to write it off as some unexplainable fluke. The rounds in both calibers had been loaded with the same powder, and if not out of the same keg at least out of the same lot. The only thing that had changed is that the ammo had sat over the winter. I reworked that load as well, and once again managed to reach the same powder weight. I backed off that charge 2 grains as well. In both instances 2 grains was the difference between hearing the powder shake and not. That's not a ton of compression.

How does that apply to your situation? I don't know. There are an infinite amount of powder type/ caliber combinations and it might not matter on most of them. I believe that if you work up to your charge you'll be OK with compressed loads in anything, that day. Shoot them fresh and there won't be any trouble. What will happen after the winter, or after a year or 5 years with all compressed combinations I don't know. Neither does anyone else. Maybe it'll be good, maybe it won't. Maybe is poor comfort when your bolt handle is stuck down. Actually a stuck bolt is one of the better outcomes.

Something to think about anyway.
Click to expand...

Not to take away from the OP, but thanks for sharing this info
 
I've experimented with compression to the point that the seating die stem deforms the bullet ogive, bullets creep back out of the neck overnight, and case bodies swollen to the point that the round will no longer even chamber.

For what?.

Nowadays, with stick powder the charge will not be more than 1/8'th up the neck, after falling through a 18" drop tube.
Ball powder will not come above the shoulder/neck junction.

All is good if there are no crunchy sounds or noticable increase in ram handle pressure when seating.
 
I noticed when I was loading some hot 223 rounds, I can hear varget and 4895 "crunch" when I seat it the last few MM, is this to much? im only over max by .3 of a grain with no pressure signs...
 
triple tap said:
I noticed when I was loading some hot 223 rounds, I can hear varget and 4895 "crunch" when I seat it the last few MM, is this to much? im only over max by .3 of a grain with no pressure signs...
Click to expand...

If seating depths don't creep longer over time, if pressure signs are totally absent with never an ejector mark on the case head, if primer pockets stay tight for reload after reload ... then were it me, I'd carry on with a good load that "crunches" just a wee bit.
A wee bit mind you .. not a wee lot ..
 
My VHT N150 load in 308 would fill the neck sized case almost to the mouth. I bought a drop tube funnel and tacked it to the lip of my bench. Now I take the powder from the ChargeMaster and drop it through the tube. Powder sits just above the shoulder, for a light compression.

I don't like heavily compressed loads. Never had any bad experience with them, except some deformed bullets/cases.
 
Work up gradually and slowly.
Test and check for pressure and accuracy.
Most of my rifles achieve better accuracy below max load and increasing powder charge any further just makes their grouping spread.
 
I know a reloaders that when dealing with powder, well up into the neck, holds them up against a vibrator tumbler to settle the powder....I don't load any loads where powder is well into the neck.
 
vviking said:
I've experimented with compression to the point that the seating die stem deforms the bullet ogive, bullets creep back out of the neck overnight, and case bodies swollen to the point that the round will no longer even chamber.

For what?.

Nowadays, with stick powder the charge will not be more than 1/8'th up the neck, after falling through a 18" drop tube.
Ball powder will not come above the shoulder/neck junction.

All is good if there are no crunchy sounds or noticable increase in ram handle pressure when seating.
Click to expand...

Yup. That's exactly what I've found.

Another observation is that best accuracy is often found at just that point - with a case full enough that there's no room to shake, but just before compression.
 
Starting about 108-110% of load ratio, depending on powders, you start see things like bullets slowly coming out of the case after being seated.
 
Maybe it's just me, but I find all the rifles (with one exception) I have loaded for to date achieve their best accuracy at or near starting loads. If a book provides a load that is compressed (and I find that often loads that are starting to compress are not indicated as such) I will switch to a different (faster) powder. It's the .308 family that are the most challenging to find the best powder for the best accuracy at or near 100% load density, especially in bullets over 150 grains in mass. I know it's not rational, but the notion of compressed loads troubles me.
 
Interesting woodlot ^.
It's gotta be just the luck of the draw, or maybe just the way each of us handloaders tends to approach the same thing somewhat differently, but I have yet to load for a rifle that shows at it's best when downloaded to "mild" pressures.
The upper acceptable safe pressure accuracy node most often proving to shoot the best with well suited powder choices to that projectile weight.
Over 40 years and a pile of rifles, I cannot recall even one, of any cal., that has shot it's absolute best for me below 85% load density.

.308 with Varget for example:
With 155gr through 180gr projectiles, a close to max upper node load will in many rifles be 95% to 105% load density. IE, no powder sounds when shaken, on up through mild compression depending on ones seating depth. Some guns want a wee bit more powder, some less.
My point is, show me a .308 that won't shoot at or close to it's best with Varget, at or near to 100% load density.

Other cals. are different, 6.5/06 needing super slow numbers like Retumbo to even approach compressed powder charges. In my rifle, Retumbo was very steamy at 100% LD, but the rifle grouped much better with RL22 at 90% LD to the upper vel. node.

Personally, bullet base touching powder with little or no compression is what I strive for based on experience.

~ And the exception will no doubt prove the rule~ lol!.
:cheers:
 
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