H4831sc and 6.5 Creedmoor
- Thread starter Intheshop
- Start date
This was written from behind the "bench" station inside the Houston warehouse.
Horizontal,once "loaded out".... still shows up because of wind(doh) and a pivotal NPA....natural point of aim. Especially,from field positions like,shooting sticks. Tubbs book helped me here because I'm learning/practicing "approach" to the X vs trying to hang onto a "hold". Extremely important varmint blasting.
Horizontal,once "loaded out".... still shows up because of wind(doh) and a pivotal NPA....natural point of aim. Especially,from field positions like,shooting sticks. Tubbs book helped me here because I'm learning/practicing "approach" to the X vs trying to hang onto a "hold". Extremely important varmint blasting.
I'm gonna say it's a pic from an IMR,sort of promotional,sort of not manual. Not mine,but I have one.... just a screenshot from unknown sources if there's any credibility issues. But dang,easy enough to cross reference which is common sense SOP.
Will say, I sure as heck didn't save it cause of 4831..... it would've been 4198
Will say, I sure as heck didn't save it cause of 4831..... it would've been 4198
fiver
Well-Known Member
it visually explains what I was saying earlier.
so now your looking at those 'other' powders and going hmm I'm trying to get to 2400 fps here, and,, well I ain't having a lot of success slamming everything forward like this.
then you re-look at some stuff and see hey that powder tops out at 2400 fps and the pressure is only xxxx.
I'm doing that same xxxx in my 44 mag with plain old WW's, why is this linotype letting me down at only 10-k more pressure, Richard lee says I can go to infinity with a BHN of blah blah.
hopefully things start to click as you question the why and where in your head.
why so hard,,,,, why where,,,, where does the lead from my lands go.
if the pressure curve is lowered and lengthened where is my bullet when the pressure flat lines.
so now your looking at those 'other' powders and going hmm I'm trying to get to 2400 fps here, and,, well I ain't having a lot of success slamming everything forward like this.
then you re-look at some stuff and see hey that powder tops out at 2400 fps and the pressure is only xxxx.
I'm doing that same xxxx in my 44 mag with plain old WW's, why is this linotype letting me down at only 10-k more pressure, Richard lee says I can go to infinity with a BHN of blah blah.
hopefully things start to click as you question the why and where in your head.
why so hard,,,,, why where,,,, where does the lead from my lands go.
if the pressure curve is lowered and lengthened where is my bullet when the pressure flat lines.
Ian
Notorious member
Yep, that data sheet explains pressure/velocity/charge weight/burn rate in a nut shell.
3031 is a unique powder, one of my favorites in medium/small cases. It has a very unique pressure curve in anything with a bottleneck, very slow to build pressure compared to other powders giving almost identical pressure/velocity curves. I'll go model a couple and show what I mean.
3031 is a unique powder, one of my favorites in medium/small cases. It has a very unique pressure curve in anything with a bottleneck, very slow to build pressure compared to other powders giving almost identical pressure/velocity curves. I'll go model a couple and show what I mean.
Ian
Notorious member
Here's the 4320 load, one of the supposed "slower" powders according to the burn rate charts, slightly compressed in the .223 case. I adjusted the load charge down to approximate the other models for load density and muzzle velocity close to the published data above.
Peak pressure occurred at 1.2 inches of bullet travel.
Peak pressure occurred at 1.2 inches of bullet travel.
Ian
Notorious member
Now let's jump up to 4064, several ticks "faster" on the burn charts. Again I adjusted charge weight to get the same compressed density as the other powders I'm modeling and the same muzzle velocity as the published data:
Notice the pressure and the peak point....1.5 inches of bullet travel. Why is this a longer push than the slower 4320? Should be the other way around shouldn't it? That's the thing the books don't explain very well, powders burn very differently in different cases.
Notice the pressure and the peak point....1.5 inches of bullet travel. Why is this a longer push than the slower 4320? Should be the other way around shouldn't it? That's the thing the books don't explain very well, powders burn very differently in different cases.
Ian
Notorious member
Now for my favorite, 3031. Notice how much I had to dial back the charge weight to get about the same load density as the other powders and how low the peak pressure is compared to published data for the same muzzle velocity. BTW, I've tested all three of these powders and more in the .223 and my data aligns with Quickload, always using less of it than published data and getting more velocity than other powders in the spectrum.
Faster than the other two powders, similar composition and grain structure, yet 3031 in this instance gives less pressure and a longer burn curve by far. The peak is at 1.7" of bullet travel, which is .400" farther up the bore and at several thousand PSI less than the 4320 which is quite a few lines down on the burn rate chart. In other words, it's totally backwards. If you wanted to push the bullet more gently than 3031 you might think about dropping to 4320....but that's not going to get you there, who knew?
These pressure curves can sort of be imagined from careful contemplation of published velocity/pressure data, but you don't always get the whole story such as actual loading density and you never get an indication of pressure RISE rate from the simple start/max published loads.
Faster than the other two powders, similar composition and grain structure, yet 3031 in this instance gives less pressure and a longer burn curve by far. The peak is at 1.7" of bullet travel, which is .400" farther up the bore and at several thousand PSI less than the 4320 which is quite a few lines down on the burn rate chart. In other words, it's totally backwards. If you wanted to push the bullet more gently than 3031 you might think about dropping to 4320....but that's not going to get you there, who knew?
These pressure curves can sort of be imagined from careful contemplation of published velocity/pressure data, but you don't always get the whole story such as actual loading density and you never get an indication of pressure RISE rate from the simple start/max published loads.
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Ian
Notorious member
In case you wanted to know what 4831 was doing with the published, compressed load, here ya go. You'd thing it would have a long pressure built and real gentle start but NOPE, it has the same peak point as a max load of 4064 at 1.5" of bullet travel and is only 3/4 burnt in 24" of barrel:
Ian
Notorious member
Now let's slow 3031 down to about the same pressure and velocity as a 107% charge of 4831 and see how far down the bore that peak occurs:
1.8" at the peak. Yep, 3031 is ultimately faster-burning OVERALL than 4831 in the .223 but marginally so, only 88% burnt for the same basic peak and muzzle velocity vs 76%. The 3031 pressure rise is, however, MUCH more slow and gentle, and that matters as far as the launch force the bullet sees.
1.8" at the peak. Yep, 3031 is ultimately faster-burning OVERALL than 4831 in the .223 but marginally so, only 88% burnt for the same basic peak and muzzle velocity vs 76%. The 3031 pressure rise is, however, MUCH more slow and gentle, and that matters as far as the launch force the bullet sees.
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Ian
Notorious member
One more. Ok, now this is interesting. 96% density, 4198 this time, pretty much maxed on pressure but quite maxed on load density, which qualifies as "just a touch too fast" for the system. If I told you, without these charts, that a max load of 4198 would peak the pressure at exactly the same distance (1.5") as a max load of 4064 would, you'd think I was nuts huh? You'd want to use a slower powder for your cast bullets in .223 to give them a "gentle launch", right? Well, in fact you'd be just as well off with 4198 as 4831 for that "gentle launch" that you ain't gonna get unless you use 3031. Model all these same powders in a .308 Winchester case with 170-grain bullets and the story is quite different at the extreme ends but very similar in the middle. "Relative" burn rates are indeed just that, relative to what you put them in and what you put in front of them, not to each other so much.
fiver
Well-Known Member
your still showing a different 'peak' and push before the roll on the red pressure curve.
the 3031 and 4831 are super similar though.
close-nuff you'd maybe not be able to tell either in recoil, bullet comparison from a trap, or in how an alloy would react.
but I'd bet the 4198 and 4320 would surely want a different alloy to work at it's best level of accuracy.
here is an odd one to mull over.
using the same batch of bullets, cases, primers, and powders.
I could take my IMR 4895 load and try the same exact amount in the 223 using H-4895 and blow the whole balance up.
let's see what happens in the 22-250.
more case volume should maybe,,, yeah uhh no same thing.
220 swift? nope, again things went over the hill, let's try the other 220 same-same.
why? what the hell.
I full well knew I was riding the edge with 22.5grs of IMR powder in the 223, but why did the bigger cases not allow [not only allow but why didn't they embrace] the slight powder change?
the 3031 and 4831 are super similar though.
close-nuff you'd maybe not be able to tell either in recoil, bullet comparison from a trap, or in how an alloy would react.
but I'd bet the 4198 and 4320 would surely want a different alloy to work at it's best level of accuracy.
here is an odd one to mull over.
using the same batch of bullets, cases, primers, and powders.
I could take my IMR 4895 load and try the same exact amount in the 223 using H-4895 and blow the whole balance up.
let's see what happens in the 22-250.
more case volume should maybe,,, yeah uhh no same thing.
220 swift? nope, again things went over the hill, let's try the other 220 same-same.
why? what the hell.
I full well knew I was riding the edge with 22.5grs of IMR powder in the 223, but why did the bigger cases not allow [not only allow but why didn't they embrace] the slight powder change?
Ian
Notorious member
If reducing the H-4895 charge a tick or two didn't fix it, the only thing I can say is crummy batch?
How come WW748 works so well for me and so poorly for you, and how WW760 works better than anything I ever tried with HV normal lubed cast bullets in .308 and XCB but Walter has better luck with other powders? One clue is I use hardened 50/50 for my loads and a more frictiony lube and he was using a much tougher, richer alloy, but other than that, hell if I know.
How come WW748 works so well for me and so poorly for you, and how WW760 works better than anything I ever tried with HV normal lubed cast bullets in .308 and XCB but Walter has better luck with other powders? One clue is I use hardened 50/50 for my loads and a more frictiony lube and he was using a much tougher, richer alloy, but other than that, hell if I know.
Spin,it is from an IMR manual. I had loaned it to one of the boys.... got it back last night.
