I have been casting my own .590" bullets for the T-Rex, but how much XMP 5744 should I use to attain 1500fps?

There is a lot of data on jacketed & heavy cast bullets, but nothing on the lighter bullets. I use a generous portion of Lee Liquid ALOX in the grooves for lube and was thinking 45gr of 5744 would be about right to start, but that's just a guess. Any better 'guesses'?

XMP5744 is very easy to develop loads for. Just use the case volume ratio. For example, find the case volume of a 470NE which uses 35 grs of Xmp5744 with a 500 gr bullet and use that as your basis. Multiply 35 times the case volume ratio of the T-Rex over the volume of the 470NE and you should be just fine. I have used up to 55 grs with a 650 gr bullet in the 500 A2 and it develoed only moderate pressure.
I hope your sizing these bullets down to .586. .590 will be too large for the .585 bore and may cause excessive pressure problems. I never shoot cast bullets more than .002 over the groove diameter. Make sure you slug the bore and know exactly what the groove diameter is. Best accuracy usually comes at .001 over with cast bullets.-Rob

[This message has been edited by Robgunbuilder (edited 05-23-2002).]

Thanks Rob. I use these .590" HB bullets in my 130yr old Snider and they work well. The Hollow Base reaches .5" up into the bullet which is 1.04" long. Also, the nose rounds down to where the HB begins.

With XMP 5744, which is nice because there is no need for a case filler because of it's high nitrocellulos content & low pressures, there shouldn't be a problem. Also, with a HB design, the bullet is allowed to obtrucate (sp?) in or out easily as needed.
Thank you for your info & warnings.

I think the case capacity of the T-Rex is about 200 because the case capacity of a Nyati is about 184-185 or so. With the formula I'll do the conversion. I am also only looking to drive them at 1500fps.

Thanks

Ok, I found the case capacity of a 45-70 case and it's 79-80gr. Fron the Accurate powder web page it shows 530gr lead RN bullet data. With 28.5gr of 5744 it pushes the bullet at 1280fps with 18,400psi.

Sooo...
28.5/80= .3563 for the 45-70

.3563*200= 71.25gr for the T-Rex

I'm not worried at all about the pressures with 5744 but with the velocities, I dont want it to go to fast. So what estimated velocity will 71.25gr of XMP 5744 and a 535gr HP yeild?

I'd try 55 grs and work up slowly. As I said, this worked well for me in the 500A2 with a 650 gr BMG bullet and you have much more case capacity. By the way, I'd cast those .590 Mini's out of Lynotype and size them to .586, as I've had the most consistently positive results with it. If it works then try heat treated wheelweight metal and finally 1:20 tin/lead.