Ok, I have been looking at most of the rifles that are for sale on the web. My question is, I have noticed that the 3 inch all have shorter barrels. The 3 1\4 all have 26 and 28 inch barrels. Why is this?

Just thinking. The 450/400 3 1/4 came first as a black powder round. The 450/400 3" came out designed for cordite. Just wonder if the intended powders resulted in the different length barrels?

I'm sure one of the double experts will have the correct answer.

My guess would be when the 3 1/4" case was common so were longer barrels of the black powder express rounds. Most .450 and .500 bpe have 28" barrels. They were of lighter steel and longer for higher velocity. That would be my guess.
Cal

My vintage 450/400 3 inch has 26 inch barrels.

Cal and Ramrod are probably correct as it was a transition from the black to NE. I have owned 3 450-400 3 1/4 BPE's, all with 28 inch barrels, as well as 4 450-400 3 1/4 NE guns. The NE guns had 28 and 26 inch barrels. Interestingly enough, the one very early cordite underlever hammer NE had 26 inch barrels but weighed 13lbs 6oz! Wrong barrel contour and placed on a heavy frame. Shot like a house of fire and recoil was very mild.

Dutch

Would a longer barrel be needed for better combustion with the older BPE rounds?

I would say the 450/400 3 1/4 was more popular in Webley built guns for the trade and they tended to have 26 - 28" barrels. Many of the 3" guns were Jeffery's and all the those I have seen had 24" barrels.

My 2 cents.

The fact is the 450/400 3 ¼ inch started life as a black powder express rifle and most will have 28 inch barrels, the Cordite 450/400NE 3 ¼ inch came out the barrels were still mostly 28 inch. The 26 inch barrels chambered for the 450/400NE 3 ¼ inch with 26 inch barrels came later as they found the 28 inch barrels were not needed to get the velocity.

When buying a vintage 450/400NE 3 ¼ inch with 28 inch barrels make sure it is not a Black powder rifle being sold as a nitro rifle, or re-proofed black powder rifle for a weaker load of smokeless powder.

The 450/400NE 3 inch started life as a full nitro cartridge so any 450/400NE 3 inch is automatically proofed for nitro powders. I have never seen a 450/400NE 3 inch rifle with barrels longer than 26 inches. I would be suspect of any 450/400 3 ¼ inch rifle with 28 inch barrels, and would certainly make very sure it was not a re-proofed black powder rifle.

There are many pitfalls for the unschooled when buying vintage double rifle. If you aren’t sure get advice on any double rifle that has 28 inch barrels to avoid getting stung with a black powder rifle being sold as a nitro rifle.

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I have seen a Lyon & Lyon and a Jeffery that the dealer thought were 3 1/4 (why would he not know?) and both had 24" barrels. They certainly handled well but I think the loss of velocity increases the marginality of the calibre for dangerous game.