How to determine starting load?

[rodgervich]

I'm making a new 17 caliber wildcat, how do I figure out what load to start with?
I thought about finding a cartridge of the same caliber with a similar case capacity and start around there, lower of course. I have noticed that most cases get filled close to the shoulder but that seems like a pretty scary way to start guessing.

If the cases are similar capacity but different shapes how would that affect loads?

I can get an idea of the powder burn rate for similar cases but how much to put in?

How do you all do it? Thanks

[onesonek]

I have a old Powley slide calulator, of which I can figure starting loads. Or you can contact a powder mfg'r, and ask there recomendations.  Either way you'll need to know the case capacity (water), and bullet weight. If you do not already know, the best way to get the capacity, is to seat the desired bullet in a case to the depth you want (without a primer). Put a small piece of tape over the primer pocket. Then get a weight on this (tare weight). Then remove the tape and fill the case with water, using a sirynge(sp), cover with tape. Weigh again(gross), now subtract the tare from the gross. This will be the case capacity of water.  

[rodgervich]

Thanks for the reply, that is pretty close to what I ended up doing. I got a copy of "Sensational Seventeens" to start working with.  It has a table of cartridge case water capacity (full to top) so I measured my case the same way, got 11.1 gr H2O. This was 15% higher than 17CCM and 25% lower than 17 Hornet. I went to load data for these two cartridges and for a given bullet weight and powder type for each I added or subtracted the respective percentages to arrive at an approximation for mine. The two numbers did not match but gave a small range. For SAFETY, I'm not a fool :wink: , I started with 17CCM data @15% below approximate load and worked up by 0.1 gr at a time. So far I only have 20 cases formed so not much data yet. So far I have 20gr VMAX  at 2,900 ft/s and 15 gr Berger at 3,400 ft/s, no pressure signs at all and accuracy is acceptable for a first load attempt! These are approaching the LOWER of the 2 numbers derived from the standard cartridges. This is going to be a fun shooter!

[Toolpush]

Is there a sit on the net that has anything like the old Powley slide calulator?

[Toolpush]

Is there a site on the net that has something like old Powley slide calulator?

[onesonek]

I didn't get a chance to check it out. But did run a quick search  this morn'n before pheasant hunt'n (priorities you know). And found a down loadable  version, I think?  I just used powley load calculator in my search engine. You try that Toolpush. I might look at it alittle closer here in abit. Goina finish supper and clean birds first. Later

[rodgervich]

This is a zipped Excel spreadsheet and text file. I downloaded and tried it for my 17 cartridge. The spreadsheet will come out as "POWLEY.WK1" I had to rename it to "POWLEY.XLS" to open it. I have done a couple of test loads for my little cartridge and this sheet result is of no use for my application. I got the resulting powder suggestion "faster than IMR-4227", not much help there and actually pretty DANGEROUS. The powder charge and velocity are not far from what I actually got but this sheet is VERY LIMITED in application (only IMR powders are listed). Better than nothing but just barely, probably better off finding another one or just comparing other load data like I did originally.
I'm interested in a better one if someone finds one.
http://www.geocities.com/CapitolHill/Lobby/1221/powley.zip

[onesonek]

Ya, the powley is virtually obselete. And for IMR powders only. In the case of faster than 4227, (cause there are no suitable powders) Back off 10%, and use 4227. But here again, now days, I just call the mfg'r and give the the case capacity, and they figure starting loads. But I still use PSC for possibilites,or theoretical cases.