.303 British and .45-70 Government Cartridges compared.

“Smelly” Conversion

A No4 Enfield .303 converted to .45-70 Government
A No4 Enfield .303 converted to .45-70 Government

Q: I like the Lee Enfield action with 10 shot magazine and wonder if it would be possible to convert one to .45-70? It would make a devastatingly effective gun for everything from pigs in lignum to sambar in brush.
Freddy Jeffery

A: Important factors in determining whether a conversion is feasible are the dimensions of the bolt face, action length and width of the side rails, together with the working pressure of the proposed cartridge by comparison with the original. Some people want to convert an action to a magnum cartridge that generates chamber pressures much higher than those for which the action was designed. This is can be dangerous, particularly if the action is a very old one. In the case of the

.303 British and .45-70 Government Cartridges compared.
.303 British and .45-70 Government Cartridges compared.

.303 British and .45-70 there is no problem because the .303 works at higher pressure. The rim diameter of the .45-70 is larger than the .303 – 0.608″ against 0.540″, but it shouldn’t be difficult to modify the extractor to handle the 0.608″ larger rim. Case length shouldn’t pose any problems either since the .45-70 is just a bit shorter than the .303. The Lee Enfield magazine may need a little work to feed the fatter case, but a good gunsmith should be able to carry out the conversion without too much trouble.




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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.