I would like to know what loads you guys are using in 303 British. I will be using Hornady 174 grain fmj boat tailed bullets, winchster large rifle primers, and would prefer to use IMR powders. I have IMR 3031 and IMR 4895 on hand, but if another one has more potential, that's fine too. The rifle is a SMLE no. 4, mk1. Thanks!

Either 3031 or 4895 is just fine. Just look in the Manual for loads.

My son is using Reloader 15 in his 303 with the Hornady FMJ bullet (he uses the same powder in his 308s so it was a natural to try). Looked at the Alliant Powder web site for info and use a load about 4 or 5 grains under max. Makes for a very pleasant shooting load.

When you resize the brass try to neck size only as the 303 cases seem to really stretch and can separate just above the case head if continually FL sized.

Most stuff in load books is pure folklore, but when Ackley said the Enfield 303 Action was springy, he was right. The bolt body is thin, long, and the lug(s) are in the rear. This compression of the bolt allows the 303 brass to be stretched. I calculate this stretch to be ~.003" and proportional to chamber pressure.

The SAAMI registered headspace for the rim in the chamber of a 303 Brit is loose as a goose. The drawing of the rim: The cartridge rim is .064 - .010" and the chamber is .064 + .015".
This means the headspace can be vary .025" and still be in spec.
[defining "headspace" as a relationship between brass and chamber]

Then there is the problem of 303 Brit Enfields gaining headspace.
The No4 Mk 1 and No 4 Mk 2 rifles take bolt heads marked:
No 4 bolthead sizes:
0 - .629 to .625 in.
1 - .625 to .630 in.
2 - .630 to .635 in.
3 - .635 to .640 in.

These bolt heads are getting to be very hard to find in the US or Canada. Some surplus bolt heads show up, but without extractors and do not have the threads clocked to the extractor position. Preparing these heads takes lathe cuts with fixturing.

What does it all mean?
You can shoot the 303 with it's registered pressure and get almost 308 like performance and short brass life.
Or you can shoot the 303 with slow powder and get almost 30-30 performance and long brass life.

really not concerned with long brass life... if i only get 2-3 loadings out of each cartridge, thats fine. was looking to see if anyone had a good load worked up in either of these two powders.. thanks for the info though!

Since that corresponds to the 30/40 Krag.. my loads for that round are 25 grains of SR 4759 or 30 grains of IMR 4198... either 180 or 168 grain match bullets in mine..

not top velocity but both are decent and accurate 200 yd loads...

I had an SMLE once, I could get no more than two reloads per case, sometimes only one.