25/303,what powder and how much

[PAT303]

I have a 25/303 that I want to shoot cast in,I have a 258418 lyman mold as well as a RCBS 120grn bore rider,the trouble is I have no load data for this calibre.How can I measure it's capacity as one way is to compare to a similar cartridge,from memory the 30/40 Krag case was necked to 257 so it would be a very close match.Can anybody give me some info so I can get started.Thanks alot Pat

[JeffinNZ]

I think 303Guy has one. Hey PETE!!! Ya got ya ears on?

[303Guy]

The 303 Brit equals the 308 Win in case capacity. I've only fired 120gr paper patched boolits in it. I'll look up what limited data I have and report. It's similar to the 250 Savage for cast and stuff.

[Southern Son]

Pat,
Don't know if you have seen the ADI site, but they have 25/303 listed.

http://www.adi-limited.com/handloaders-guide/

[PAT303]

What do I start with?. Pat

[303Guy]

The only record I have for a paper patched boolit is;

case capacity - 47.7gr AR2209
powder charge - 36gr AR2209
boolit weight - 121gr
boolit type - smooth side paper patched bore-rider
primer - Fed 210 LR
cases - W-W Super
OAL - 73.5mm

[45-70 Chevroner]

I think but am not sure 10 grs. of Unique works in just about any medium to large capacity case. Do some extrapolation and start low about 8 grs. to start with. As for slower burning rifle powder I venture not to say or guess. Of course this is not a guessing matter

[Al_sway]

I have a .25-303 Improved and I shoot two styles of cast bullets through it- one is a 100 grain Loverin style FN, PB,and the other is a 117 grain RN, GC.
I am not familiar with the mould number you quoted, so I have no idea of the weight or style.
I load the 100 grain FN with any number of fast powders for light plinking and rabbit loads. Around 5 grains is generally used.
The 117 grain bullet is often loaded with 12 grain of Unique for a very pleasant practice load around 1600 fps.
Since yours is not improved, you might want to start at 10 grain Unique.

[grouch]

I shoot cast in my 257 roberts, and my best loads are so far down the velocity scale as to be very safe. I use 10gr of H110 behind CBE's 25790 bullet. Not great in wind but good for 1" for 5 shots at 100yds. I'd try up and down from there.
Grouch

[runfiverun]

i would just start at 12-13 grs of 2400 and work from there.
18 is good in a 308 with a heavier bullet but a bigger bore.
the 303 case is big enough that it'd handle 20+ but you have to account for bore size.
if you have a 10 twist i'd think @ 15 ish would be best accuracy.

[303Guy]

Curiously, one will see them being called 25/303, 25-303, 303-25. They're not the same. Not exactly anyway. The one I have is a straight 303 Brit necked down to 25 using the same shoulder angle so the neck shoulder junction moves forward. I think it will chamber most of the other variants unless there are some with the shoulder moved forward. But that makes no difference to the load data (the improved being more of a 257 Roberts class). Mine is a Sportco barrel. The 25/303 is a very under-rated cartridge for some reason. The ADI load data doesn't do it justice. In reality it lies between the 257 Roberts and the 250 Savage in performance. Another way of looking at it is it is equal or very nearly equal to the 243 (similar velocity with the same bullet weight and even similar powder charge).

[Certaindeaf]

I shoot cast in my 257 roberts, and my best loads are so far down the velocity scale as to be very safe. I use 10gr of H110 behind CBE's 25790 bullet. Not great in wind but good for 1" for 5 shots at 100yds. I'd try up and down from there.
Grouch

Grouch, that's interesting.. I always thought H110 was essentially the powder to not reduce by over 10% of maximum or somesuch. Those are some great groups though.

[runfiverun]

for some reason h-110 tends to behave itself in cast rifle loads.
i have seen quite a few loads for it,and usually use it as starting data for aa-1680.
i don't ever recall seeing W-279 data though.

[grouch]

Certaindeaf, you're right - that's what the maker says about H110. Then they list loads for 32 - 40. I only know that a friend has been using it since the early '60s, and that I've shot upwards of 20 lb of it without incident and with good results in 30 30, 30 40, 308, 30 06, 303 Brit, 6.5x55 and 257 roberts, always with fairly light loads. For what it's worth, it didn't show much promise in 45 70.
Grouch

[Certaindeaf]

Well heck, learn something new every day! That's good to know.

[303Guy]

Just a quick question, why would we want a light plinking load from a small calibre such as the 25/303? Nothing wrong with it in principle but the calibre has the potential for a pretty reasonable velocity with a pretty heavy for calibre boolit with a slow powder load. I'm not sure what would work well in the 25 but I do know what works well in the 303. I would like to transpose that sort of performance across to the 25. I was getting in the region of 1800fps with heavy cast in the 303 using AR2208 (Varget). I'd like a load something like that but with a filler that forms a wad behind the boolit. I know paper patching can do magic but these are getting on to the rather small side for greater than teenage fingers to patch! Don't get me wrong, I'm still pretty young but I do have trouble operating these new fan-dangled gadgets called cell phones! (Designed by youngsters with feminine little fingers ... mutter mutter ... !)

Anyway, velocity limitations would be the same with heavies and lights so why not go with the heavies? They're actually still pretty light at 25 calibre.

(One more question, why in heck does my spell checker flag me when I try to spell caliber the right way?)

[PAT303]

Well I loaded 5 rounds with 15grns of 2207(H4198) and five with 16 and we'll see how they go.It is a very good looking round and the 120grn chambers with the gas check just above the shoulder so it does look promising.The rifle has a 1-12 twist so having it on the slower side might help accuracy. Pat

[303Guy]

Mine is a 1-in-10 twist. Did you use Dacron filler? I don't know what twist is best for 120gr boolits. Lighter powder charges may allow a slower twist than expected due to the lower destabilizing muzzle blast.

It is a nice looking round. I'm looking forward to your results.

[stocker]

For 120 grain J-bullets a twist of 1/9 is ideal yet 1/10 is the norm. Myvote would go to 1/9 if you can find one. I have had a series of 257 Roberts and 257 Ackley Roberts rifles with 1/10. Accuracy declined slightly in the standard chamber with 1/10 once I went heavier than 115 grains. The extra velocity in the Ackley chambered rifles maintained accuracy with 120 grain bullets. Have shot no cast boolits in any of these rifles as they were purpose built. So, not sure what the result would be with cast at moderate range and velocity.

[303Guy]

A cast boolit tends to be shorter than a j so slower twist will work. I never got round to testing for accuracy.

There bullet stability calculators out there but I've found them a pain. They ask for the nose length and radius but won't accept what you tell them!

Anyway, I've found something at http://www.lasc.us/Brennan_2-3_Twist.htm

Max boolit length for a 12 twist is given as .83" (21mm) for the 25. My 118gr boolit is 26mm long. Too long it seems, for the 10 twist! But then again the 60gr spire point bullet is too long for a 16 twist hornet yet is shoots it very accurately for a long distance.

I suspect that a wad type filler improves stability by keeping the muzzle blast away from the boolit base at muzzle exit. When I pull out my 25 I'll be trying AR2209 with wheat germ filler.