Thread: What happens when your case has lots of room left?

little spark.....funny story,years ago I had quite a few cases loaded that I pulled apart (might even have been the dud loads mentioned above) so I ended up with primed cases that needed to be resized.....how to deprime them in town???? oh I know ,place muzzle against my good polarfleece vest and simple fire off the cases one at a time,no noise no bother EXCEPT it burnt /melted round patches on my good vest!!!!flame had travelled some 21". plenty plurry flame there LOL.

Originally Posted by Micky Duck

Ive had loads of win 760 that were done for me by sports shop..110grn projectiles and I asked for about 3000fps....if I didnt tip rifle to sky before squeazing trigger they went BA...BOOM it was VERY off putting and did terrible things to accuracy and flinchyness.... Ive remade same loads with a little more powder in them and they are lazer beams without issue...either the powder he used was ???damp/old n stuffed....or the lack of powder was causing it....that they would work if muzzle pointed skywards first suggests the second...

Sounds like too much primer. I don't know about 760 my chart shows it on par with 2209 which is relatively slow. Manual also shows you should be cracking that speed quite easily with a full case of it.

My theory would be that the Primer was pushing the projectile out of the case and into the lands before the powder had sparked off
Take that for what it cost ya.

S.E.E has been observed in artillery size tubes, afaik never in small arms.

With the 6.5x55 in particular I was finding I could get marvelous accuracy with the 120/123 gr bullets and a healthy dose of 2209, but with a few grains less in the 140gr bullet size I just could not get the same sort of accuracy until I changed powders [in this case to VtVh N560] and filled the case back up.

Originally Posted by jakewire

With the 6.5x55 in particular I was finding I could get marvelous accuracy with the 120/123 gr bullets and a healthy dose of 2209, but with a few grains less in the 140gr bullet size I just could not get the same sort of accuracy until I changed powders [in this case to VtVh N560] and filled the case back up.

Possibly just fell out of the accuracy node rather than being related to case fullness?

Not to sure what you mean as, being a totally different bullet required a different work up, definitely wouldn't have run the 140 with the load I had in behind the 120 Nosler, I just just couldnt get it with 2209 , changed powder, fuller case again and away. May have been just coincidence.
Could have also been the rifle didn't particularly like the heavier bullet/ 2209 combo

Ah I see, my mistake, I read that as a couple of grains less powder and the accuracy fell off

Originally Posted by mimms

Cute picture. But no. The primer isn't a little spark at the end of the case, it will fill the entire case with flame.

And I'd be interested to see any evidence of the powder-location-vs-accuracy theory.

Lol.
If you want ultimate consistency then you want to minimize variables, and powder being able to slosh around in the case is just another variable. Im not talking about the powder failing to ignite, im talking about ensuring the powder column within the case is relatively consistent for maximum consistency. Its generally accepted that loads where the case is almost full with powder often perform better than those with more free space.
Is it due to the consistency of ignition and the way the powder burns? Is there the potential for powder sprinkled along the bottom of the case, or all packed up the front, only half filling it up to burn with less consistency than a case that is packed full?

Originally Posted by ChrisW

Lol.
If you want ultimate consistency then you want to minimize variables, and powder being able to slosh around in the case is just another variable. Im not talking about the powder failing to ignite, im talking about ensuring the powder column within the case is relatively consistent for maximum consistency. Its generally accepted that loads where the case is almost full with powder often perform better than those with more free space.
Is it due to the consistency of ignition and the way the powder burns? Is there the potential for powder sprinkled along the bottom of the case, or all packed up the front, only half filling it up to burn with less consistency than a case that is packed full?

Point of diminishing returns with all things "consistent". I'm not arguing that consistency isn't good. I'd like to see evidence.

Got any? "lol"

And I am all about the down-range, I don't want "ultimate consistency" i want "effective". I don't weigh cases, trim meplats, re-point projectiles, blah-blah-blah, not doing so will introduce inconsistency to my loads.
But I have a 99% chance of connecting the shots when i take em, so they're consistent enough

It is common knowledge that a cartridge which is full/almost full of powder will often perform with better consistency than a case with lots of free space within it. You can come up with your own conclusions as to why.
Generally loads with a 90+ % fill rate will be more accurate. Im not about to go and dredge the internet to back this up.

According to quickload the less powder in the case, the lower percentage gets burnt in a given barrel length (eg .308 with 35gr powder may only have burnt 80% of the powder in a 16” barrel whereas with 42gr you might have a 99% burn rate. If you are burning different amounts of powder every shot due to not all the powder being burnt, then that’s inconsistency

@mimms I ran some quickload data which should demonstrate this point fairly well.
First up we have a "normal" .308 load. Its a 165gr btsp in front of 45gr ar2208. Its got 104% case fill capacity, so will be a slightly compressed load. This should burn consistently. Note quick loads predicts a 98.55% powder burn out of a 24" barrel.


Next up we have a cartridge with "lots of room left in the case". Iv just halved the powder charge for demonstration sake. This load has everything the same as previous but only 22.5gr ar2208. Case fill capacity is only 52.2%. This one burns inconsistently with only a predicted 68.89% of the propellant being burnt in the same 24" barrel. This percentage could go up or down slightly depending on how the powder was clustered inside within case. Accuracy and/or consistency of FPS could (not will) suffer. Either way its an inefficient load.

The reason for the complete burn (in well packed cases), and the consistency that comes with that is that all the powder is packed neatly into a column, that cant move around much if at all, so more of it burns, and burns more consistently.

I have experienced this first hand developing a load for a 3855 using 4227. Starting at 15 gr and checking for unburnt powder. Plenty at 15, less at 16, none at 19. Case was still only about 70% full and nice tight groups.

Originally Posted by Sakoswarosorted

Possibly just fell out of the accuracy node rather than being related to case fullness?

Deffinately had the same thing with my swede. TBH that rifle only suffers from an inconsistent shooter (me). It has no nodes. The only thing a swede hates is a slightly loose projectile like a prvi partizan fmj rn. Other than that one projectile i could consistantly nail tight groups if i concentrate.

But i did notice it got distinctly easier switching to 2213sc and filling up the case more.