Need help in deriving a load from two different given weights and charges

[Dannix]

Is it possible to estimate how much charge I'd want of Unique from two given 30-30 loads, to push 110 grainers at a given speed? (Assuming here constant case capacity, and assuming no fps difference due to boolit and bearing surface area)

Given loads:

Projectile Weight Unique Charge FPS
in grains in grains
45.2 5.4 1159
150 10 1394

source 1 (http://www.castbullet.com/shooting/rb30.htm), source 2 (http://www.rifleshootermag.com/ammunition/size_061305/)


Desired deduction from above given loads:

Projectile Weight Unique Charge FPS
in grains in grains
110 ? 2000

Sure, I could just slowly work up to the fps I want with a chrony, but I'd like to know out how to solve this sort of math problem if any of you guys here have any insight. I have access to a Ti89, Excel, and OpenOffice, so I'm sure I got the tools, I just don't know how I would approach a problem like this, if it's even doable.

[MT Gianni]

Within any given table you can interpolate but not extrapolate. In laymens terms you can go with number of gr of Unique = 100 and 1/2 number of grains =50 therefore 3/4 number of grains =75 and be safe and close. You are trying to go from a halfway point in weight between two values to a velocity exceeded by any data [velocity] that you have. Short answer is no safe way to go with the data given.

[rhead]

There is a formula for estimating this in Richard Lees manual. It involves the ratios of the fourth root of the velocities divided by the charge. The times I have checked this it has proven to be at least reasonably accurate. My son has my manual at the present so I hesitate to give more precise data.

I would suspect that 2000 fps with unique will be very close to if not exceed max pressures in a 30 30. double check all findings before trying and work up slowly.

[jecjec13]

I ran this on my Quickload program. The amount of unique it would take to reach 2000 fps would put you start pressure way over the limit. cant be done safely. you need to use a much slower powder.

[Dannix]

You are trying to go from a halfway point in weight
between two values to a velocity exceeded by any data [velocity] that you
have.
How would you approach it if the target fps for the 110grn load was a similar velocity, say 1250fps?


There is a formula for estimating this in Richard Lees
manual. It involves the ratios of the fourth root of the velocities divided by
the charge.
I dug around and couldn't find it. I thought roots would get involved. In my attempts to come derive my own formula I had only tried as far as square roots (I was messing with GoalSeek in Excel/OpenOfficeCalc). Please let me know if you find out where Lee's formula is in the manual. I'll keep digging around.


I ran this on my Quickload program. The amount of unique it would take to reach 2000 fps would put you start pressure way over the limit. cant be done safely. you need to use a much slower powder.
Bummer. Oh well. I'll use the 1lb of Unique I got for kiddy/grandma loads then. What fps does Quickload give for 10grn of Unique behind a 110grn j-word? 1500fps?


While I was digging in the Lee manual for the formula rhead referred to, I came across a reduced pressures load section (starts at page 140 in the 2nd edition). H335 and H4198 appear to be good choices for ~2000fps. I grabbed Unique in part because it happened to be a shop I visited to day. I should have looked into Unique more, as the Universal I already had appears to be able to do anything Unique does, but I guess this is what I get for an impulse buy. Looks like I'm going to have to pay up online to achieve the end goal. [/shakes fist in HAZMAT fee's general direction] I do have some 748 I could try though (appears to be faster than H335, slower than H4198).

p.s. Any rhyme or reason on the 4xxx numbers? I can never keep them straight, which is a real pain when glancing over the few powders in stock at a local shop. I wish H/IMR adopted a more human-friendly naming scheme, like Alliant.

[geargnasher]

748 will work, but you might find that you fill the case all the way up before you overpressure it with those lighter boolits, and 30 grains might get you where you want to be velocity-wise. Try it. If it burns clean enough, you're home free. Otherwise, try the 4198 or even 2400. Lyman Cast#3 lists a 115 grain GC boolit with 2400 starting at 13.5 gr./1553fps/15,700CUP and max of 21.2 gr./2282fps/34,300CUP, so you should be in the upper 2/3 of the pressure range to get 2k fps which should give a good, clean burn and still not be near the top end on the pressure.

Gear

[Dannix]

Lyman lists a 748 min load for 110grainers at 2280fps, so I'll just try that. I think if I go too far beyond that I may be getting into the >20% slow powder reduction, but I'll have to check that.

If I end up having to buy something, I'm currently leaning towards H4198 and looking into SR4759. I'll look into 2400, but a quick glance at the burn rate chart would lead me to believe it may be too fast for 2000fps and reduced pressure. I've also seen Reloader7 around, and may look into this as well.

I'm probably going to scratch off H335 from the list, as 2000fps would be only around 20k psi (Lee 2ndEd, p.140) and H335 apparently isn't the best choice for such loads:

Hodgdon lists loads for it at all three pressure levels. They don't show any real low velocity mouse fart loads for a reason. The lighter the load and the lighter the bullet, the less consistent the powder is. It does not like being down loaded as well as other powders. It prefers higher pressures and heavier resistance to burn properly. Other powders do a much better job at light loads. If you stay at the low end start loads, you might try magnum primers. No they aren't going to run up pressures much; less that 2,000psi on light loads. It helps a little but is just a bandaid. It's just the wrong powder for really light loads.
source (http://www.marlinowners.com/forums/index.php/topic,18998.msg192774.html#msg192774), context: 45-70

I only got data for H4198 for 110grain boolits in 30-30, but no SR4759 or 2400 data. Now I got to look into just how much H4198 likes lower pressures, and how hot it burns (this is a plinker round, so the goal is something I can shoot a lot, and not be too worried about barrel heat).

[jecjec13]

as per quickload, 10 gr. unique = 1813fps 21653 psi chamber pressure. Thats in a 24 inch barrel. looks to be a fair load for playing, may kill a can or two.

[pmeisel]

Dannix, years ago when I was trying to develop new loads and experiment with different powders, I made some notes on the back of business cards and put them in my wallet so I could keep all the powder numbers straight.

Now, if I try one new powder every couple of years that's a lot....

[geargnasher]

Lyman lists a 748 min load for 110grainers at 2280fps, so I'll just try that. I think if I go too far beyond that I may be getting into the >20% slow powder reduction, but I'll have to check that.

If I end up having to buy something, I'm currently leaning towards H4198 and looking into SR4759. I'll look into 2400, but a quick glance at the burn rate chart would lead me to believe it may be too fast for 2000fps and reduced pressure. I've also seen Reloader7 around, and may look into this as well.

I'm probably going to scratch off H335 from the list, as 2000fps would be only around 20k psi (Lee 2ndEd, p.140) and H335 apparently isn't the best choice for such loads:

source (http://www.marlinowners.com/forums/index.php/topic,18998.msg192774.html#msg192774), context: 45-70

I only got data for H4198 for 110grain boolits in 30-30, but no SR4759 or 2400 data. Now I got to look into just how much H4198 likes lower pressures, and how hot it burns (this is a plinker round, so the goal is something I can shoot a lot, and not be too worried about barrel heat).


You have the data for 2400 above. If you're set on 2k fps for plinking it's the one you want IMO.

Gear

[woody1]

2400, 4759 or 4227 would be (are) my choice for what you're trying to do. I hope you're planning on using gas checks. Regards, Woody

[Dannix]

jecjec13, thanks for looking that up for me!
pmeisel, you saying I should just despair now? ;) I've found a whiteboard works best for me, though I'm only reloading one caliber right now.
geargnasher, woody1, I'll keep my eyes open for 2400, 4759, 4227, 4198, and 5774 when I go primer hunting at another local shop. Said to say, I'm not GCing as this is a j-word. I'm looking for ~2000fps because it has some nice terminal performance (http://ammo.ar15.com/project/Self_Defense_Ammo_FAQ/index.htm#.30%20carbine) at that speed, so my plinker load can be my defense load as well. Don't worry, I've got this slated for conversion to boolits.


Back to the math, has anyone figure out the formula, even for one only valid with a similar fps?

Projectile Weight Unique Charge FPS
in grains in grains
45.2 5.4 1159
150 10 1394
110 ? ~1250