H4831sc and 6.5 Creedmoor

Intheshop

Well-Known Member
Question isn't "really" about the title in particular. A little backstory;

Was reading on the 6BR site about the 6.5 Cm,"Carolina" load. Which is 43.5g H4831sc behind a 140 class JB. The "Carolina" part is just some guy's,very quick... sounded good at the time nomenclature. Then,like fried chicken comes from a, barnyard buzzard it just is what it is and no reason to get pantys bunched up because you don't like the name?

Apparently,and this part,I get.... the 4350's are a natural in the 6.5's. Heck, I sure have used a bunch of it,albeit in other chamberings. But to suggest,and then go with 4831? And have it work? That is what sparked my curiosity.

But the above is all JB stuff. I shoot CB's.

>The question is,what are the pitfalls of using full cases( high loading density) of slower powders?

>Followed with,does load density trump some aspects of burn efficiency?

Understand about not reducing slow powders.... but I'm talking,full cases at reasonably HV for cast. An example of this would be going from Varget/4064 to IMR4350 in a 7-08 145g bullet. So,is 4831 even on the radar?
 

waco

Springfield, Oregon
In my HV 308 loads I had better luck with slower powders such as 4831, 4350, and H414. I was pushing a 165gr cast bullet at over 2600fps with good(2moa) accuracy.
4064 and Varget along with rx15 shot pretty good too. I was just able to get higher speed with an accuracy edge with the slower powders. A slightly more gentle push on the bullet.
Not sure how well this translates over to 7-08
 

Brad

Administrator
Staff member
7-08 can easily use 4831 with cast. Could even go slower like RE22.
The longer, slower pressure rise is easier on bullets as they enter the bore.
 

Brad

Administrator
Staff member
From a jacketed point of view maybe but not with cast. All depends on what you want to do.
 

Intheshop

Well-Known Member
4831 isn't listed on the Hodgdon data page for 145's in 7-08. Didn't check anything heavier.

I just always assumed it was for '06 and above case capacity.....and using heavy'er for cal bullets.

My cast goals are pretty simple,be "at" or durn near starting JB velocity,for a given bullet weight. And bughole groups with 200yds and under. Call it what you want,dumb luck....stupidity...whatever but,pressure has not been a problem. In fact,the only time it's seen any really issues so far was blowing a too thin,50/50 lube out of a jacked up 30-06,IMR4350 load. That was solved by going 70/30 or so(more BW),and using way less.

I'm not going out and buying any 4831.... mainly cause of having right much IMR4350. To me,this was as slow as needed.
 
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oscarflytyer

Well-Known Member
My 6.5x55 performed better with IMR 4831 than it did with 4350 in 120 grn bullets (JBs). was a bit surprised. Yet to load for the new to me 6.5 Creedmoor
 

Ian

Well-Known Member
Both of my scoped Military Swedes dote on 140 Sierra round-nose bullets and medium book load of H414, it's a magic combination that has held 3/4 MOA to 500 yards (and 200 and 300) on numerous occasions. One barrel is an armory "0" and the other is a "1".
 

oscarflytyer

Well-Known Member
Edit - One I am referRing tow/ 4831 is a Winchester Mdl 70 FW. Trying to get a 140 grn load it will shoot.... And, need to get my sporterized 96 (yeah, I know... what was I thinking? But, started the project 28 yrs ago! when they were $100) set up then find a good 140 load for it.
 

CZ93X62

Redlands, Kalifornistan
Both of my 6.5 x 55 Swedes favored IMR 4831 over IMR 4350 using 140 grain J-words. Both rifles liked 55.0 grains of WC-860 (full case) under 140s as well--superb accuracy and 1896 "spec" velocities (2450 FPS). Nice blasty double-based powder report, too.
 
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fiver

Well-Known Member
lets go into the why a bit so we can help BW figure this out.
Walter already touched on the longer slower push part, so I will expand from there.

think about moving the projectile from the case to the muzzle.
the whole way from starting to the muzzle exit.
pressure plays a role in both places and can have no effect or a big impact.

the first part of using the too slow powder is in starting out you don't have all of the powder burning just yet but the bullet is moving forward.
point A. unburned powder is protecting the base of the bullet.
point B. you don't have 50-K of pressure pushing the bullet forward.
point C. your allowing the bullet time to find the barrel [we hopefully have our poop together and already aimed it there] without bending it or mashing the base up to try and fill it.

another part is you went past the 100% case fill, 100% pressure, 100% velocity for that case and have started sliding down the backside of the hill.
100% case fill... check.
100% pressure... ain't gonna happen the bullet is moving away from the gas volume faster than it is being generated.
100% velocity... see above.
how is this useful?
well you are kind of limited in how far down the hill you can go before it turns to blah and your back to going 1800 fps again only with a mess of unburned powder to deal with.
so you start helping the primer out by extending the effective range and initial pressure spike to get that powder burning more efficiently again.
[right I'm talking about a duplex load]
first step [say 4grs of red-dot] gets your pressure back up to about 35-K and picks your speed up to around 1950 fps or so.
second gets more, and more again when you have to change kicker powders and up the game a little bit.[other wise your just kicking your initial pressure spike to 40-K and not gaining anything except pressure, your actually burning red-dot as the propellant and not using it as a priming/ignition aid anymore]
[now you have switched and your using 10-12grs of 4227 and the BMG-50 powder is packed in the case to 105%]
your starting to climb the mountain again and ticking off those 100% boxes above.
your once again using the powder as a priming aid, and starting to burn the powder more and more efficiently.
but how? right.
speed and time,,, your not just foofing the second kicker powder until you start getting into it's 100%,100%,100% box too and it then starts becoming the main charge and the second powder becomes part of the ejecta weight even though it too is burning. [it's just too late after the pressure rise of the first powder]

so what happens is this makes every powder available to you useable if you understand the concept.
and you can then start really looking at jacketed bullet powders as indicators and steps.
your gonna look at powders for cast bullets that are starting at the slowest [compressed limited velocity jacketed loads] and moving back 2 steps slower than the slow ones for jacketed bullets to help you gain velocity [above the middle speed powders] without the snappy pressure rise with your cast bullets.
you can set a baseline easy enough by looking in the books and predict pressure loss too.
not perfectly but enough to feel comfortable, and your working down hill, so there really is no risk.

hope this helped.
 

fiver

Well-Known Member
one more thing.
if I had a 7-08 I would be using 4831 or RL-19 as my jacketed bullet powder with 140gr bullets.
same as I use in my 7x57's now.
it wouldn't hurt my feelings even a little to be stepping back to rl-25, or reducing some rl-22 and using 1 grain of Dacron instead of trying to work the kicker route.
you have options, it's just whether you want to burn 10-50 or 25grs of powder.
 

Intheshop

Well-Known Member
Just read an article in the,new to me... Art of Bullet Casting book, about expansion pressure. Moving peak pressure closer to muzzle.....

And like so many articles,some of the material raised more questions,and that is in a positive,or desirable direction. One raised by this is how air pressure is fighting against the powders pressure.... and it's possible? effect on the bullet itself. Wasn't thrown down as any sort of "firm" statement... more of another question. Decent article.

One aspect of the OP,which wasn't an initial part of my concern,but came to me later; the "Carolina" load is one of those loads that so many find,right durn close to optimum that it's more than coincidental. I've seen it with Unique loads,Bluedot,4198,4350..... just interesting.

Am going to retract not buying any 4831sc haha.... gonna find some.
 

Intheshop

Well-Known Member
Interesting too on this book.....

Articles are from 1961-'81,or some such. There are right many on HV,which I think is interesting. Read a few. Most(all) are pushing Loverin designs and running LOTS of lube.
 

Intheshop

Well-Known Member
Can "almost" say this for sure but? always subject to change. And I really don't give a sheet about JB's anymore from a shooting standpoint,yeah they work... yeah they're good for hunting.

The faster rifle powders do a pretty linear job,going up with charge rates until,it just falls off accuracy wise all of a sudden. That's not to say it isn't a good load,just that it may explain why accuracy isn't consistent on a day to day(weather) basis. When other load aspects get the "blame"?
 
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fiver

Well-Known Member
that and heavy air.
if you change the conditions of the air resistance you will at minimum move the POI of the projectile.

well.
I'm trying to keep it all C/B but the comparisons have to be made between to two just for powder rate comparisons.
everybody knows 3031 is faster than 4064 and I-4895 is slower than H-4895.
but is the H closer to IMR 3031 or I-4895.
yeah not a thing but a switch to H from I will blow groups into patterns your that close to the edge at times without a weather problem too.
moving back away to the 4831 and RL-19 area gives you I-H-4831sc & RL-19 plus superformance, AA-3100, H-450 and a few others all piled on top of each other.
you could use them all and see minor variances or see such a change you'd swear you used the wrong powder measure.
a primer change [or a 1gr powder drop] could fix the issue, as could a bit of case filler and a 2gr drop in powder.
your right back to the same problems the faster powders give you your just in a different zipp code for speed and pressure.
 

Intheshop

Well-Known Member
Oh,I'm all for studying JB's..... the more info the better. Just ain't into shooting them.

Went to get cases yesterday but the gunstore is closed on Monday. And drove right past a walmart to go there. Which I've been doing now for quite awhile. It's a nice,good ole fashioned gunstore. Going tomorrow.
 

Ian

Well-Known Member
I know we're discussing powders but also consider how the physics of the powder burn affect the bullet at various points within the rifle as well. Pressure in front of the bullet is probably negligible, I don't really know but haven't seen any evidence of it causing a problem. However, I have seen beaucoup problems from too much pressure on the bullet's base at launch.

Ever wonder why copper jax foul the first six inches of the barrel so much worse than any other part? It's mostly because the bullet didn't cork the bore up as it was getting engraved and some of the jacket got washed off. It takes pressure to move the bullet and a lot more to engrave it, but the bullet's resistance to being engraved (together with its mass resisting acceleration) can be less, or more, depending on its design and the way the burning charge is pushing it. The factors of pressure rise and bullet resistance within the first half inch of the barrel are intertwined and make or break you in a variety of ways. If you "jump" the bullet you will have some blowby. If the powder is burning slowly, the pressure will be low and the blowby less, also less if you have a long column of powder and almost nil if you have a buffer to seal up all the gas behind the bullet. If the powder is burning on the faster end of the spectrum (making gas pressure faster due to less deterrent), then the bullet pops out quickly and corks the bore quickly. If the bullet has to "jump" to the ball seat, it has an inertial running start and engraves with relatively less needed pressure, also leading the expanding powder and creating more space....which puts more X and less Y into the burn curve...which does less damage to the bullet base as it transitions into the barrel.

Now consider if the bullet DOESN'T jump and is parked firmly into the ball seat with all matching fit etc.: The powder pressure must start the bullet from a standstill, against a load. Think air compressor unloaders and air conditioning system time delays for compressor re-start which keep the compressor from having to start up against heavy head pressure. When you start the bullet against a load with a fast powder, the bullet base will rivet if the force required to get it started squeezing through the throat is more than the bullet's base can withstand without permanent deformation. Also think about engraving force (with or without jump, and with or without a positive ball-seat shape match) and how that can be reduced through strategic placement of crush zones, alloy manipulation, and jacket material properties. My goal has always been to get the bullet (any kind of bullet) going up the middle of the pipe and the base to the end of the ball seat BEFORE the pressure needed to get it there exceeds the bullet's ultimate compressive strength. Hard to do when all this happens in microseconds and the peak pressureswe're working with are easily quadruple that of the alloy's strength, or in the case of most copper jacketed bullet cores, more than five times the bullet's strength. Peak pressure in a typical bottlenecked rifle load at 100% of the velocity/pressure rating of the system typically occurs about two inches up the barrel, so you might think you're easily safe not compressing the bullet during the engraving portion of the trip, but you may not be. If the bullet has excessive resistance to moving (remember, force vs. TIME here) then its strength can easily be compromised before it even gets out of the neck, and even worse, if some of the gas has somewhere to go other than up the barrel (it always does as the neck expands and gas flows to fill the tiny space around the bullet driving bands and any extra room in front of the case mouth and throat) just as the nose slams into the ball seat and goes "OOOMPH!", that short burst of gas flow will wash out the base band of the bullet. So, how your pressure rise, powder column, and engraving force curve interact with each other in the first half inch of bullet travel are critical, and you can't just look at one part and hope to see the big picture.

From the peak pressure point to the muzzle is a zone with a completely different challenge. Say you got the alloy, bullet design, seating depth, and propellant all worked up and sorted for a HV launch. Great. But right before you get where you want, the bullets start scattering all over the place. Why? Well, either you actually DON'T have your launch sorted anymore at that point and the bullet is getting damaged before it even gets fully into the bore, or something else is happening farther up the bore. Some of us have dug up the old formulas and done calculations on land stress during acceleration and compared that to alloy strength. The initial finding is that in most cases the alloy should be strong enough not to smear and wash out. However, it does. WHY? Heat and unsuitable alloy is why. Lead alloy at 150 degrees is half the strength of 70 degrees. The land/engrave interface generates enough surface heat to weaken the bullet so much that it begins to lose metal, leak gas on the trailing edge, and when it reaches the crown, uneven gas pressure slings the bullet out yawing willy-nilly. You see this at shots 3,4 and 5 or near the end of a ten-shot string as barrel heat increases. So is that "walking" tendency the barrel corkscrewing or is it just getting hot and losing the bullet? Many possible misconceptions here, particularly with cast bullets. By the way, PAPER jackets have demonstrated to me a virtual immunity to the heat fade, similar to copper but better. Powder coat is in between copper and plain, and not as far down toward plain as might be thought from its physical properties. Going back to powder for a minute, if the powder is burning hard through the whole barrel, muzzle pressure, heat, and muzzle velocity will be high. If the pressure peaks early and peters out quickly, the "heat" is off and the drive splines of the bullet can handle a lot more heat (longer, faster shot strings) before breaking down. Hot, long-burning powders give a nice gentle launch, but can fry your bacon closer to the muzzle. There are limits to everything and finding success is all about understanding how all this stuff works together as a complete system, so try to throw all of it in the blender when ruminating over the stuff you put in the case and how it will affect launch.
 
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Intheshop

Well-Known Member
Yeah but...... fluted barrels fixes a lot of that. That's a joke,well maybe?

No, I hear you. There are combinations... cause I seen it,and can reproduce it where due to case shape,burn rate,jam,and to a slightly lessor degree,..... loaded neck clearance/anneal. That pimples or little dots get blown? back and deposit on the outside of case neck. Can't say that about really slow powders cause,4350 is the slowest I have.

Torque,reaction.

Now this is a feel thing so,is hard to assign numbers to and further,most reasonably thinking shooters opt for heavier rigs when chasing groups. I happen to "like" cheap tupperware stocks and skinny barrels. But hanging onto them,shooting cast just feels like there's a whole lot more bullet "traction",yanking the rifle over than JB's. It's probably a time thing? Am looking fwd to 4831 behind this,real tight nosed,RCBS 145SIL to do SxS with my jacked up 130 Lee/Varget HV load(7-08).

3 vs 5 vs 10 shot groups,and how using slow powders effects them from a shooters standpoint.
 

Intheshop

Well-Known Member
Slight tangent.... jump vs jam and the bullet's ability to withstand the jolt.

Is "one" way to explain or express? bumped noses during sizing. Slow,long tapered die entrance,and greased (4831)..... the bullet nose is less likely to "upset" during sizing. Conversely, minimal leade in taper....hardly any lube,an open top punch,and a quick snap down on the luber handle and produce a bulge or bump in the nose dimensions. Which is easily reproduced.....

The resultant shape is,and Googled it yesterday.... then got bored N quit.... like a wasp waisted airplane or missle shape. Hope y'all know what I mean. Anyway,I'd seen it a good while back when first dinking with the Lee 130 7mm. Turned it from a round nose to a flat point with the bulge. You can tell the upset consistency by casual glance at the resultant meplat. Then chambering and see the land tracks.... or,catch it in the right light/shadow and visibly,see the bump. This happened to the 145SIL mould too. Can't say for sure but,it's like pre compression..... basically acknowledging the bullet shape is gonna get wanged/upset.... so,let's get this show started before the launch. It's a little more complex then that but is one way to view it.
 
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