Home Forums Hunting & Shooting Ask The Gunwriters Which 6.5 mm bullets are two diameter?

Which bullets were two diameter and then re-designed back to a more conventional configuration? I just hung a 129 grain Hornaday Interock BTSP in the lands and it appears like I got one bullet that was not two diameter in a box where the rest were or a different ogive. Not sure how this could happen except if they are swaged in two steps. These were blems so that may be the reason. This was not a compressed load, it is possible I just didn't seat it fully but this is unlikely.

I have no idea. However, an old timer told be years ago that the 264 winmag used a two diameter bullet years ago.

The last box of factory Winchester 140-grain .264 softpoint ammo I bought, maybe 4-5 years ago for an article, still had the two-diameter bullet. I read somewhere that the original Remington 140-grain .264 bullet was also 2-diameter, but have never used any myself.

Rem's 140gr that Mule Deer mentions is also 2-diameter bullet.

That's the one I remember as well, the 140gr Remington. I forget if it was a round nose or just a fairly blunt SP? Although I may be confusing that with a different bullet.

I recall reading about those two diameter 6.5 mm bullets, and if IIRC it did have something to do with the 264 Win. Mag.. While we're on the topic of 6.5 mm bullets; who was it that once made single diameter 6.5 mm bullets that were .263 diameter ? Speer comes to mind but my memory is pretty hazy.

Speer

I picked up two boxes of Speer .263 120 grain 6.5 mm bullets for a song at the local gun shop quite a while ago. I haven't tried them yet, but at the price I figured I'd take a chance. If they don't group well, I will just use them for ringing steel and some offhand practice. I've always been curious why these bullets were originally .263 inch...was it in deference to some old rifles that were made a little tight? I don't know.

I believe Remington's bullets in their factory loads for the 6.5 Rem Mag were two diameter also.....?

Interesting, I'd be curious to hear why as well.

I've got some of the old .223" Hornet bullets, and understand the reason for those with the smaller Hornet groove diameter, but wasn't aware of a similar condition for a 6.5 caliber.

What is a two diameter bullet?

I've never figured that out either. It seems that all bullets would be "multi-diameter" once they get past the shank.

So how many diameters do they have?

I'm guess one for each reduction in diameter from bearing surface to the tip.

Right, but how many is that?

A two diamster bullet is caliber size at the base and bore size towards the ogive, most are divided at a cannelure. How many diameters I don't know, but two if you omit the taper. This was in deference to the short throat on the .264 and later the 6.5 RM. It was an effort to reduce pressure but caused problems for reloaders who were not aware of this and switched components. Bob Hagel was the first person I recall to write about this in Handloader magazine (can't find the article though). It led to the rumor that the 264 produced erratic pressure which didn't help it's popularity.

The Hornaday 160 was a two diameter bullet that may have gotten changed to a conventional design, I'll have to measure them again. I was not sure about the 129 and 154s though, but don't have any of the old 129s around to measure.

This. Two different diameters in the straight shank of the bullet; it has nothing to do with the bullet nose taper or a boat tail. The straight section is stepped down at some point, with the front section smaller diameter than the rear. It's essentially the same idea as a bore riding cast bullet design that employs a long straight nose section at bore diameter (for example .300" for a .308" bullet) that rides on the lands of the rifling.

If a guy "can't figure it out", one can always ask or go look it up.

The reason for the two diameter bullet for the 264 was not to reduce pressures. The purpose was to allow Winchester to build the rifles with a short throat. The short throat was configured to produce good accuracy with the 100 grain bullet while the 2D 140 was designed to allow the bullet to be seated out yet still fit the short throat. I had to reset the cursor 3 times to type this. WTF? GD

Here are some old Two-Diameter Noslers..

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Learned a couple of things. Throating for the 100 grain bullet makes sense as the 264 was touted as a dual purpose varmint/big game cartridge. I don't believe Bob Hagel mentioned this in his load work up and review of the 264.

Those Noslers are unique, I thought the Zippeedo was their first boat tail but those partitions look like they pre-date them.

The .263 diameter bullets were for the .256 Newton and some European 6.5mm's with a .256 x .263" groove & bore diameters.