Compressed Loads

Brian in Montana

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I haven't worked much with compressed loads and it kind of makes me nervous.

This weekend, I loaded some 165gn Fed TBT's for the .308 using Big Game. The max load in the published data is 51grns (which sure seems like a lot for .308). I was loading a 13 round ladder test with my highest charge being 51gn. I didn't measure each round, just got the seating stem where I wanted it for a COL of 2.8 and went ahead. After loading all 13, I measured some of them and the higher charges were longer. Well... That won't do for a ladder test or really anything. So, I thought about it for a while. Ultimately I just pulled the bullets and started over.

This time, instead of using an arbitrary COL from the manual, I used the magazine from the rifle to determine how long I could load the bullets. My first round, I put on the press and ran it into the die, took it out and tried to put it in the magazine. When it "barely" fit. I measured the round from the ogive with a comparator and got 2.223 (not sure what the COL from the tip of the bullet was, around 2.84 or so). Then I loaded the rest of the batch increasing each rung by .2 grains. I measured every round the same as the first and adjusted the seating stem ever so slightly as needed on the higher charges to get them all the same length: 2.223 from the olive. Seemed to work pretty well, I measured them all again once I was done and they were all within .001 of each other, not bad for an amateur with a crappy single-stage Lee press.

Any thoughts or opinions on this from you guys with more handloading experience? I'd rather not blow up my rifle, or my face for that matter.
 
I’ve had some compressed loads before, but none that wouldn’t allow me to seat my bullet to my desired depth.
 
I'm not sure what to make of that either. I loaded some 7-08 afterward (not compressed) and it did fine. Maybe there's just a little play in the ram or in the die. I did need to adjust it a couple times on the higher charges, although just barely.
 
So I'm going to spitball an idea...it's probably wrong but it has to be similar to compacting soil...Big Game is a relatively fine ball powder (small pore spaces of air between the kernels) so it takes more energy and time to compress compared to an extruded powder with big kernels and lots of pore space. Compressing the load in a slow, methodical fashion may also help reduce the "rebound effect" of the compression. My theory is you could also implement a drop tube (like blackpowder shooters do in their loads) or you can vibrate settle the powder by tapping on the case. I'm sure there is something to do with neck tension also.
 
I am no expert, but drop tubes have significant impact on powder loading density in my personal experience. I would definitely try that.
 
I've run a number of loads that are "compressed." As Mthunter mentioned a drop tube, it helps. I usually have to is to adjust the die so I can get the proper seating depth depending on the powder/compression. Its been my experience that highly compressed loads don't shoot very well, and tend to have big swings in velocity between shots. I suspect because some of the powder is burning as it exits the barrel?

I have no experience with Big Game. The nosler manual has it listed at 52.5gr with a 165 at 114% compressed load. Personally I've had the best luck with powders that results in a 100% load+/- 5% for virtually all rifles I load for. My 308 likes RL15, Varget and 4064.
 
This doesn’t relate to your question but you don’t always just go by what the book does for an overall length do you?
 
Gotta vibrate them a bit

Yep, I just tap them on the bench a few times with my finger over the neck opening. Seat the bullet slowly. If you’re highly compressed it’s probably time to load for a different powder.
 
Today I shot the previously mentioned ladder test. I won't be using this bullet/rifle/powder combo again. Even with 51grn the highest MV I got was 2650fps. Also, the data was crazy. Velocity would climb as expected for 2 or 3 rounds then drop. It made me very nervous. The only reason I finiahed the ladder was there were never any of the classic signs of pressure on the primer or casing. And extractions were smooth. My theory is that I was just having unignited powder blowing out the muzzle. Whatever the case, it was not good, moving on. I have some much better loads in that rifle with Varget and H4895.

That said, I also did some follow up with the 7mm-08 using Big Game and 140grn Accubonds. 46.8grns put 5 shots in less than .8 inches. I need to chrono that load again, but I believe it's moving around 2815fps. Not too shabby.
 
That said, I also did some follow up with the 7mm-08 using Big Game and 140grn Accubonds. 46.8grns put 5 shots in less than .8 inches. I need to chrono that load again, but I believe it's moving around 2815fps. Not too shabby.

If you have a load that shoots .8”, I would load every piece of brass I owned with that load and call it a day. We all like to tinker and I know you’re trying to get the most out of your rifle as you can, but I would go work on my shooting skills at this point
 
If you have a load that shoots .8”, I would load every piece of brass I owned with that load and call it a day. We all like to tinker and I know you’re trying to get the most out of your rifle as you can, but I would go work on my shooting skills at this point
I agree. 0.80 MOA or better is my goal for hunting rounds. 0.35 MOA for target.
 
And I really hope that didn’t come across as a negative comment. That point I’m trying to make is, we as hunters are never going to shoot an animal from a bench. It’s important to have accurate ammo but that doesn’t matter if you can’t build a stable shooting platform. We need to get off the benches and shoot as we would in the field to figure out what works and what doesn’t. I’ve spent countless hours tinkering with different loads trying to sqeeze another .25” out of my hunting rifles but I don’t do that anymore. Being able to shoot comfortably from alternate positions will make up that difference and then some
 

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