Cyril Waterworth's reloading data page for the .303-25.

Specs For The .303-25

Cyril Waterworth's reloading data page for the .303-25.
Cyril Waterworth’s reloading data page for the .303-25.

Q: I own a .303 and a .303-25 both are on the Lee Enfield No. 1 MK III action. I enjoy using both rifles and must reload if I am to continue to do so, particularly the .303-25. Recently, I bought a bag full of .303-25 cases in a gun shop. With regard to maximum case length for the .303-25, I’ve been given different lengths from different sources. A reloading manual gives a maximum case length of 56.44mm.

On the internet I found the maximum length to be 55.44mm. I have Simplex Master reloading dies, but the booklet that came with them had no specs for case length. The once-fired brass I purchased has an average case length of 56.28mm. When I bought the .303-25, it came with 60 rounds of Super factory ammo, the case length of which measured an average 55.18mm. After one firing the cases lengthened to 55.38mm. All of the cases chamber easily. What is the maximum case length for the .303-25?

If you can’t tell me, how do I determine the maximum length? Are there any warning signs for overlong cases before you get a faceful of gas and maybe miss the stag of a lifetime? Evan Lapworth

A: My Practical Reloading Manual lists the maximum length for the .303-25 case as 56.20mm. By the way don’t take too much notice of everything you read on the internet as it is a source of much misinformation.

You are lucky to have a Simplex 7/8×14 die set as you can neck .303 cases down to .303-25 in one pass through the full length die without any problem. A Lyman full length die wouldn’t do this and it was necessary to neck cases down to .270 before necking again to .25.

Oversize cases won’t enter the chamber. You will only get a faceful of gas if you overload your cases. In the interest of safety, reloads should be limited to 45,000 PSI pressure. The .303-25 will kill deer if you place the bullet in a vital area .

For deer I recommend a strongly structured bullet 100gn bullet like the E-Tip or Nosler Partition and AR2209 powder. Work up from 39gn to a maximum of 42gn which delivers a strong 2914 fps from a 635mm barrel. Do not exceed the maximum charge in your Lee Enfield rifle.




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Nick Harvey

The late Nick Harvey (1931-2024) was one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He wrote about firearms and hunting for about 70 years, published many books and uncounted articles, and travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject was unmatched. He was Sporting Shooter's Technical Editor for almost 50 years. His work lives on here as part of his legacy to us all.