Compressed loads question

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new210/22

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So I hope I can ask this in a comprehensible way.
When reloading increasing powder charges in .3 grain increments as I do when developing a load I assume that you would increase pressures at a predictable rate. Once you get into the hotter end of the spectrum and loads start getting compressed, does that affect the pressure increase or would it increase at a faster rate due to being compressed?

Hope that makes sense.
 
new210/22 said:
So I hope I can ask this in a comprehensible way.
When reloading increasing powder charges in .3 grain increments as I do when developing a load I assume that you would increase pressures at a predictable rate. Once you get into the hotter end of the spectrum and loads start getting compressed, does that affect the pressure increase or would it increase at a faster rate due to being compressed?

Hope that makes sense.
Click to expand...

With most powders, mild to moderate compression makes absolutely no difference. Most sphericals are difficult to compress any significant amount.

There have been certain powders that did funny things when compressed [obsolete H205 (not N205) comes to mind] It became erratic with
any amount of compression at all.

OTOH, I have compressed some powders so hard that they wanted to push the bullet back out of the case without any adverse reactions.

Regards, Dave.
 
Several loads I do are compressed. I myself, don't really like the issue, but it has proven to be safe in those max loads. I would never compress any load that is not listed for a compressed max load.
 
I've loaded tons of ammo with compressed loads and didn't worry about it. That changed this spring when two rifles, both loaded with compressed charges of 7828 locked their bolts up with those same loads after they sat all winter. It wasn't any hotter in the spring than it was in the fall, but the first shot with both locked them up harder than a whore's heart. After 2 trips to the gunsmith I backed them off a smidge.

If you would have asked me years ago I'd have said no problem. Trouble is, you're asking now and I can only say I don't know, but don't bet the farm on it being all good after they sit.
 
Dogleg said:
I've loaded tons of ammo with compressed loads and didn't worry about it. That changed this spring when two rifles, both loaded with compressed charges of 7828 locked their bolts up with those same loads after they sat all winter. It wasn't any hotter in the spring than it was in the fall, but the first shot with both locked them up harder than a whore's heart. After 2 trips to the gunsmith I backed them off a smidge.

If you would have asked me years ago I'd have said no problem. Trouble is, you're asking now and I can only say I don't know, but don't bet the farm on it being all good after they sit.
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I'm curious as to why after sitting they become so hot.... I can't make sense of that. What am I missing?
 
Dogleg said:
That changed this spring when two rifles, both loaded with compressed charges of 7828 locked their bolts up with those same loads after they sat all winter. It wasn't any hotter in the spring than it was in the fall, but the first shot with both locked them up harder than a whore's heart. After 2 trips to the gunsmith I backed them off a smidge..
Click to expand...

I would first suspect the bullets were pushed out of the case enough to reduce any previous jump to the lands the rounds may have had.

I don't use many heavily compressed loads except for one that involves 62 grains of RL22 in a 30-06 case. That one load, even with good neck tension, will always "grow" if the bullet is not crimped in place,
 
Compression generally doesn't change much with rifle powders, but definitely does with some pistol powders.
Moreover though, don't assume that pressures increase in a linear fashion along with increases in powder. There are points where a 5% increase in powder can increase pressure much more than 5% for example. This is especially true of cartridges that are necked down dramatically, for instance 17 Fireball.
 
'Boo said:
I would first suspect the bullets were pushed out of the case enough to reduce any previous jump to the lands the rounds may have had.

I don't use many heavily compressed loads except for one that involves 62 grains of RL22 in a 30-06 case. That one load, even with good neck tension, will always "grow" if the bullet is not crimped in place,
Click to expand...

Both cartridges were Weatherbys, with 1/2 mile of free-bore. Both are loaded to mag length, so if there was a meaningful bullet bullet creep they wouldn't have fit. When I pulled all the ammo and weighed all the charges they checked out, but the powder was packed to the point where it was hard to get out of the case. I used a wood screw as an auger and a fair bit of banging.

In the interst of science I did a quick work up back to the same old level and it was once again safe but not mild or anything. Same as before. These test loads were assembled out of the same 8 pounder can of powder. I've got a ton of the stuff, all the same lot but these were even the same can. Life's too short for unplanned proof loads, so I backed the loads off and never had another issue. As a side note, the Weatherby rifles survived without a blink.

That's why I changed my opinion on the topic. I used to "know" something and realized that I really didn't.
 
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