why winchester brass and primers only?

[toooldtocare]

I found some load data for my 121 grain cast boolits. Why Winchester brass and primers only?

[I'll Make Mine]

Different brass has different wall and head thickness, meaning different case volume -- which can change pressure. A "tighter" case will increase pressure, and starting from a near-maximum load, could cause a dangerous condition (pierced primers, head separations, etc.). Likewise, different brands of "identical" primers will have different levels of temperature, particulates, and gas production, so can alter the earliest part of the pressure-time curve. Combine a "hotter" primer with "tighter" brass, and a load that's perfectly fine in Brand A cases and with their primers could seriously damage a rifle and/or shooter if loaded into Brand G cases with Brand R primers.

Given your load data presumably originated with Winchester, it's only natural that they'd state this caution as "use only Winchester cases and primers" -- the powder is probably Winchester, too, and it's pretty likely the data originally called for Winchester bullets (possibly jacketed instead of cast, though cast will usually give lower pressure for the same weight, other factors equal, because of lower engraving effort and barrel friction, so is likely to be a safe change).

Follow proper load development process (reduce any published load -- usual figure is 10% -- and work up in small increments to your best accuracy and/or maximum pressure, then start over if you change any component -- even lot number for powder or primers, some say), and you should be fine using that Winchester data with, say, Norma cases and CCI primers.

[Gohon]

I found some load data for my 121 grain cast boolits. Why Winchester brass and primers only?

A little more information on what your talking about would be beneficial in not having to guess what your question really is.
What did the load data actually say about brass and primers? Did it say if you use something other than Winchester brass and primers we will find you? Or was it more in line with Winchester brass and primers were used for load development?

[toooldtocare]

sorry. Its a 121 grain cast bullet. The data is from Lyman reloading hand book. here are the specs
#356402
bullseye powder suggested starting grains 3.7 --950 fps--21,600 c.u.p.
max grains 4.4--1125 fps--32,00 c.u.p.
for this load they say use only winchester primers and cases

[bowenrd]

You should re-read the book. It tells you what THEY used for load developement. It is not telling you that you HAVE to use that brand of components.

Look at the list of components used. They used CCI and Winchester primers and they used Federal and Winchester cases.

All the book is telling you is what they used for each load. I think you are trying to make it complicated more than it is.

[Shiloh]

Start at 3.6 or 3.7 gr.
Work up from there. If it doesn't cycle the pistol, go up a little. Look for pressure signs as yu move up. For me, I stay in mid range of loads. If it cycles reliably at 3.7, you could leave it there.

Shiloh

[toooldtocare]

You should re-read the book. It tells you what THEY used for load developement. It is not telling you that you HAVE to use that brand of components.

Look at the list of components used. They used CCI and Winchester primers and they used Federal and Winchester cases.

All the book is telling you is what they used for each load. I think you are trying to make it complicated more than it is.

Ok maybe i misunderstood what it meant. Actual wording is "Designates use of "

[fredj338]

Changing any component will change the result. So if you want near exact results, use exactly what the data indicates. It's only really going to matter as you get closer to max data.