Loose powder charge and accuracy.

[Bayourambler]

I've always read, and have noticed, that a good full case of the correct powder shoots better than a loose case of powder. However , in my 300wm, 70 ish grains grains of Reloader 22 is the sweetspot with a couple of bullets I use. Set at recomended load book OAL, this leaves a good bit of empty space in the case. These rounds shoot well and I've had no complaints until now. I like to check my hunting load from time to time during the season, and i have had a breakdown in a recent accuracy check. I checked my load at 400 yards the other day and had 2 very low impacts. Low enough to rob my confidence in this round. I pulled a couple of the bullets and rechecked the powder charge, they are perfect. When I did this, the powder was all stuck together , and I had to knock it many times to get it all out the case. My question is, can all this extra space in the case cause problems in this high humidity environment I live in?

 

[Llama Bob]

How much extra space are you talking? I have a hard time believing it's more than 5-10%. That should not be a big deal.

I firmly believe that step 2 of the reloading process (step 1 is finding a safe max charge) is to find a charge weight that is a velocity node (velocity doesn't change much when charge weight does) and that has a low extreme spread. Then step 3 is to achieve accuracy by manipulating seating depth.

I'm sort of thinking you must have skipped step 2 here.

 

[Bayourambler]

Well at 70.8 grains, there is more than 10% of air in there for sure. Pushing a 180 grain bullet at 3080 fps, I know that I'm up in pressure. As far as the accuracy node, I'm with you, and spend alot of time finding the powder weight range that is the most forgiving. I have tested this charge from 40 degrees to 90 degrees and feel like I'm in the sweet spot, staying away from pressure spikes. If I add or subtract 1 grain of powder, my velocity hardly changes.

 

[Englishmn]

It sounds as if you may have some moisture issues if powder is clumping in the case. I did that once by not waiting long enough for wet tumbled cases to dry.

 

[Bayourambler]

Moisture could be a problem. It is not when I load though. After cleaning my cases I always put them in a little convection oven to dry them. But here in Louisiana we regularly have days where the temp changes 30 plus degrees in 4 hours at 100% humidity. I'm guessing the brass could be sweating in the field when I'm out and about.

 

[Llama Bob]

Well at 70.8 grains, there is more than 10% of air in there for sure. Pushing a 180 grain bullet at 3080 fps, I know that I'm up in pressure. As far as the accuracy node, I'm with you, and spend alot of time finding the powder weight range that is the most forgiving. I have tested this charge from 40 degrees to 90 degrees and feel like I'm in the sweet spot, staying away from pressure spikes. If I add or subtract 1 grain of powder, my velocity hardly changes.

OK, that sounds good. But if your velocity is hardly changing, why did the rounds hit low?

Either there's a mechanical accuracy problem, or the velocity is changing but not when you're shooting over the chrono. Seems like the only two possibilities...

 

[Bfh_auto]

If you are loading ammo when the humidity in these room is high, the powder can be contaminated.

I think you have contaminated powder because it clumped.

 

[Blue68f100]

What is the age of the powder? The only time I've seen powder clump is when it's at the end of its life. May want to contact the mfg with the lot number and see what they have to say. Once a cartridge is loaded it should be fine. The interface fit joints normally seal off good enough for a submersion test.

My neighbor was using the RL-22 in his 7mm Mag. He ran into the same issue as you. But looking at the fps/°F change we decided it was the issue. If I recall without looking it up it's one of the worst powders on temp stability, near 2fps/°F. He developed the load in the 70-80°F and went to the mountains where the temp was in the 20-30°F in the morning. Then he had to make a 450 yrd shot which fail miserably. We were going to try to duplicate the conditions but he decided to break down all the ammo before we got to it. He did not report any problem with the powder when he broke them down.

I have found it I have a new bottle of powder that has an excessive solvent odor I tend to open the bottle and let some of that flash off. My reloading room/shop is climate controlled for temp and humidity. I run the humidity at 40%, outside the shop this time of year is 70-80%.

 

[Bayourambler]

My load room is is climate controlled and I store my powder in a mini fridge (not plugged in), and I've actually checked humidity in there, it is low. The powder is from a 5 lb jug I purchased last year. When I shot and got the low impact shots, i wasn't shooting over a crony. I checked the rifle with a known good load with 190 smk, and they shot great. I did a scope tracking test and it was on the money. I would even make a shot, bring it back to zero , knock the gun around, dial scope back and shoot again. It all grouped on a plumb line at 100 yds. , all less than an inch at the correct inch mark for the dial. One thing that does bother me is that I have had a few misfires out of this box of cci 250 primers. Could a bad primer cause this much of a low impact?

 

[Bfh_auto]

My load room is is climate controlled and I store my powder in a mini fridge (not plugged in), and I've actually checked humidity in there, it is low. The powder is from a 5 lb jug I purchased last year. When I shot and got the low impact shots, i wasn't shooting over a crony. I checked the rifle with a known good load with 190 smk, and they shot great. I did a scope tracking test and it was on the money. I would even make a shot, bring it back to zero , knock the gun around, dial scope back and shoot again. It all grouped on a plumb line at 100 yds. , all less than an inch at the correct inch mark for the dial. One thing that does bother me is that I have had a few misfires out of this box of cci 250 primers. Could a bad primer cause this much of a low impact?

Yes. It can cause uneven ignition.
I still think there was contamination somewhere. You have random misfires and clumped powder. It screams moisture.
I bet if you load some more and make sure you are still in your accuracy node, it will go back to normal.

 

[Bayourambler]

That's what I'm hoping for. I'm going to take my time and make 20 rounds today at the best of my abilities. This whole episode is aggravating being it hit in the middle of deer season!! Thanks

 

[Bfh_auto]

Been there. Just roll with it.

 

[splattergun]

Just a thought that hasn't been mentioned yet; humidity may or may not be the cause of the clumping. Other causes might be moisture in the brass left from a wet cleaning process like SS tumbling, or oil or wax from the sizing lube.