Loading density/Loading ratio/Case filling %

[tfk]

I've been reloading for a few years and I have used mainly the slow burning powders which gave me 80%+ filling of the useable case capacity after seating the bullet. The main reason was my fear of possible double charge and its consequences. However, the fast burning powders are popular in combination with heavier bullets for their low felt recoil, I tried it and kind of liked it. I found many target loads for .45 ACP have case filling only about 50 % of its useable capacity. I am starting with reloading .40 SW and would like to make some target loads with PF between 130-155. With some powders it would be only about 45 % filling of the case. I would like to know your opinion of a safe minimal percentage of filling and also filling's effect on accuracy . How does half empty case and possible different position of powder affect accuracy compared to almost full case with relatively consistent ignition of powder? My most accurate 9mm reloads with 145 gr FP copper plated bullets have filling 90-95%. What's your experience? For example: Under 180 gr FP bullet for .40 minor with PF 151, would you choose 3.45 gr of N310 (61%), or rather 4.7 gr of N340 (73%), or 5.5 gr of N350 (78%), or 7.1 gr of 3N38 (90%), and why?

 

[troy fairweather]

There's more to worry about other the accuracy. Most powders don't like much air space, there can even be a double explosion,can't remember the proper name.

 

[Texas10mm]

2.7 gr Bullseye in a .38 Spl case doesn't take up a lot of case capacity, even with a 148 gr wadcutter loaded. It's a very accurate load.

IMHO you're obsessing about trivial things too much.

 

[entropy]

I've been reloading for a few years and I have used mainly the slow burning powders which gave me 80%+ filling of the useable case capacity after seating the bullet. The main reason was my fear of possible double charge and its consequences. However, the fast burning powders are popular in combination with heavier bullets for their low felt recoil, I tried it and kind of liked it. I found many target loads for .45 ACP have case filling only about 50 % of its useable capacity. I am starting with reloading .40 SW and would like to make some target loads with PF between 130-155. With some powders it would be only about 45 % filling of the case. I would like to know your opinion of a safe minimal percentage of filling and also filling's effect on accuracy . How does half empty case and possible different position of powder affect accuracy compared to almost full case with relatively consistent ignition of powder? My most accurate 9mm reloads with 145 gr FP copper plated bullets have filling 90-95%. What's your experience? For example: Under 180 gr FP bullet for .40 minor with PF 151, would you choose 3.45 gr of N310 (61%), or rather 4.7 gr of N340 (73%), or 5.5 gr of N350 (78%), or 7.1 gr of 3N38 (90%), and why?

If you develop and follow a safe regimen that defeats the possibility of a double charge, you can change your worries over to "Will I need to put fiberfill in to hold the powder down by the primer?"

 

[Rule3]

Just use the load data and don't worry be happy go shoot. Just make sure you are properly charging the case.

I don't use those powders but would not use a fast powder like N310 in 40 SW (just me)

https://www.vihtavuori.com/powders/n300-powders/

https://www.hodgdon.com/wp-content/uploads/2017/09/burn-rate-color.pdf

 

[mdi]

If you develop and follow a safe regimen that defeats the possibility of a double charge, you can change your worries over to "Will I need to put fiberfill in to hold the powder down by the primer?"

In 1970 I had a squib. Since that time I made a habit of looking in every case I have charged with powder (2.9 grains of Bullseye in a 38 Special case is just a dark spot in the bottom, but it is visible). Since that time I have seen some charges the just "didn't look right" for whatever reason so I just dumped it and recharged. I can use any powder/powder charge I feel safe (never a "detonation" either). I have reloaded more rounds than I would hazard a guess (reload for 12 guns) and have had no squibs nor any Kabooms...

 

[entropy]

I learned for one of my Dad's .38 wadcutter squibs.

 

[denton]

Some powders give very different results with the powder in the front of the case vs. the rear. TiteGroup, for example, is not position sensitive.

If your case is nearly full it's not a problem.

 

[ATLDave]

TiteGroup, for example, is not position sensitive.

That's the marketing claim, anyway. Actual testing doesn't always support it. Walkalong shares some of his position sensitivity data in this thread: https://www.thehighroad.org/index.php?threads/position-sensitive.436766/

 

[Paul Toms]

The best way I have found to reduce/eliminate squibs, is just stop the press when my Wife enters the room, usually with the ram at the top of the stroke.

 

[Blue68f100]

If your loading on a AP you can add a powder check die into the mix to detect double charges and no charges. I use WST for my 45acp and 357mag target loads. It's a low density fast powder so it fills the case better than BE or TG. It is reverse temp sensitive, meaning it gets slower as temp goes up.

 

[denton]

That's the marketing claim, anyway. Actual testing doesn't always support it. Walkalong shares some of his position sensitivity data in this thread: https://www.thehighroad.org/index.php?threads/position-sensitive.436766/

Did my own testing.

 

[Walkalong]

Tightroup was average as far as losing velocity when forward away from the primer. It still burned well and shot well, but as far as velocity loss from being forward away from the primer goes it was average at best there. YMMV of course, a different application than I tested in might have done fine, and lead always does much better than plated or jacketed when the powder is forward, which is what I tested.