Help with working out loads

[Wicky]

Hi Guys - I have just spent 2 hours trawling through some search resuts trying to find out if there is a 'formula' for working out a starting load for a cartridge to no avail. Found heaps of other good stuff though:)
My problem is this - up until just recently all my loading Cast and J word boolits has been for cartridges that data is available for. I had built last year a 404 Aussie Stalker (the makers name not mine) It is a 300 win shot mag case necked up to 423 (404 jeffery boolits) It works fine with my max charge of 68gns 760 (not chronied yet) and gives just over inch groups at 100 metres - and kicks!!!:roll:

Finally my problem - I have bought a 400gn mould and cast 40 odd boolits but am in a bit of a quandry on what to load these with.

I have found a couple of posts that say the existing J word boolits load can be used and can be reduced by up to 15%.

Any inf you guys can throw my way in relation to this would be greatly appreciated.:veryconfu

[cbrick]

hhmmm . . . 68 gr. of 760 and one inch groups at 100 meters, that's good but with what weight bullet? A SWAG on velocity?

400 gr. cast boolits. Gas check? Alloy and or BHN?

I often use jacketed load data for my cast boolits within reasonable velocity but your post didn't contain enough info to be able to tell you much.

Best I can offer is; yes, sometimes its very possible to use jacketed load data with cast but . . .

Rick

[Wicky]

Thats me not enough info as usual. the jacketed stuff is 400gn Woodleigh - those loads are fine, supposed to be around the 2000 - 2100fps, feels like it but I'll know for sure when I chrony the round..

The cast boolit is a PB lyman #2 approximately - 8lbs WW and 2lbs 50/50 solder.

I thought that maybe using 325 win short mag data might be closer but even then I am not sure about where to start. I get a little wary of having a potential bomb next to my face. Seen too many blown guns to want one myself.

[Bass Ackward]

The cast boolit is a PB lyman #2 approximately - 8lbs WW and 2lbs 50/50 solder.


Wicky,

What do you want from the load? Cause at 15 BHN of Lyman #2, you are only going to be able to push about 30,000 psi before your accuracy is going to go squirrely.

You can start with your lowest jacketed bullet load and work down one grain at a time. Your biggest worry is leading at the high end and erratic ignition if you go too low. So I would heat treat my bullets in the oven or mold some more and drop them in water. (But if you HT them in an oven, you can probably shoot 55-60 grains of 760 and do well)

I assume that you have a chronograph. When you start to see erratic velocity, then you are getting erratic ignition and you must go to a hotter primer, start using a filler, or change to another powder that burns better to continue on down. I would say H-4895 would work better here for a base powder to do this with as it would be mid range.

What you are doing is not trying to build a cast load here. You are building a powder chart and confidence without leading. Then as you work down you can periodically substitute the 15 BHN bullets for the hard stuff and see what happens. Once you get low enough that your rounds don't go squirrelly on a target, then you know you are in a working range for that pressure with that hardness in that gun.

This should work for any powder that you can find jacketed data on. But you can then extrapolate data too. Say you stay with 760 that is close to 4350. IF you go up in burn rate to Varget or 4064, then that is two IMR burn rate steps up. At about 3 grains per powder step, Varget or 4064 should be about 6 grains less powder than what you found with the 760 to produce the same pressure range. Should be in that general area with any powder in that burn rate area like 748 or Ball C. Go up to 3031 and you go up another two IMR burn rate classes so you will need to cut another 6 grains now to approximate the same pressure range. This ought to get you ball park to get you data with some powders.

If you are wanting cheap squib stuff, then this ain't gonna help ya much other than for guestimation. But as you become more familiar with the recoil of the rifle and what you see on the target, you will be able to gauge pressure better and of coarse the target will tell the tale. If you start with the 4895, then as you go down in burn rate you add grains, up you would subtract grains. IF your chrono says everything is good and you get a delayed click bang, STOP, you have gone too far with that powder. Some of the older technology balls are terrible reduced. Sticks tend to be better burners. Click bang is dangerous ignition. But hard bullets can probably be shot close to full power and save a lot of this charting also.

As you build the chart, you may find a better corolation factor too. It runs two grains with a 30-06 size case. So my 3 grain figure is only a guess. It might turn out to be 2.5 or 3.5. Once you see what this variable is, recompute using the same pattern logic.

This is how I would do it if I didn't have Quickload or load data.

Did I tell you to keep good records.

[Leftoverdj]

I'd agree wholehearted with Bass were you shooting a GC bullet. You're shooting a PB bullet and I have never had a bit of success with those at anything close to full power loads. My approach would be to assume that your greater case capacity and smaller bore cancel each other out and use .45-70 trapdoor level loads for the 400 grain bullet.

You're not going to get in any trouble with the faster powders because you have a huge safety margin. Accuracy is going to be your limitation, not pressure. I'd start with 28 grains of 5744 or 30 grains of either of the 4198s.

[cbrick]

Good stuff from Bass, I'll stess some of his points to help save you some time, frustrstion and possibly help keep you safe, plain base bullets, soft alloy and ball powder.

I have never gotten satisfactory results with reduced charges of any ball powder, ball powder is at its best burning rate/consistency in the higher end of its pressure curve. Also there is the possibility of SEE with a reduced charge of a powder as hard to ignite as a ball powder and as slow as 760.

I have never tried driving a plain base boolit to 2,000+ fps. That's not to say it can't be done but with soft plain base bullets your in all probability going to have to reduce the pressure/velocity significantly. Life would be simpler if your boolit wore a gas check, is another mould a possibility? 2,000 fps with cast is very do-able.

Stick powders such as and with a burn rate in the range of SR 4759 could be a good place to start. This powder is also bulky and will aid in filling the case and is much easier to ignite than the ball powders. Other stick powders such as 4198, V-N135, 4895 etc could be good choices.

Heat treating your wheel weight alloy could help also but if you do keep in mind that if your reducing the load you probably won't need the absolute hardest that's possible, reduced enough you may not need to HT at all. Here's an article on HT that may help: Heat Treating Lead/Antimony/Arsenic Alloys (http://www.lasc.us/HeatTreat.htm)

See if you can find data for a another cartridge that has a very similiar case capacity and bullet weight, could help get you a decent starting point.

I hope there is some help for you with this. Keep us informed of how things go, curious minds want to know.

Rick

[Wicky]

Gentlemen many thanks for this info. My initial reason for going to the cast PB was for a bit of "plinking' fun and maybe smaller game hunting. That and a reduction in recoil! I was looking at probably around the 1200fps as a top velocity esspecially with #2 in a PB boolit.
Some of the IMR powders are very difficult to find over here but I can extrapolate for our locally made ADI stuff.
Once again many thanks you have given me a good start in sorting this one out. I shall post results as I test. Now I need to get out there and do it!