Why are .40 cal bullets different

[Paraguy]

Was curious if anyone could explain why all my UMC target rounds have a rounded nose bullet and the .40 cal has a flat nose.  All are FMJ target loads, seems to be the same for Federal Eagle as well.  Not an Earth shattering issue, but it is something I just can't figure out.

[twyacht]

Hmmm......

There's this:

http://www.firearmsid.com/Bullets/bullet2.htm

Than there's this:

http://www.gsgroup.co.za/articlepvdw.html

Scroll down to Sketch 5:

Thinking the reason is penetration results, (based on this guys research), larger African game rounds, which are solids. Interesting stuff.

Like the wadcutter, semi-wadcutter, style, bullets. Maybe the bullet "guru" will chime in....

Interesting question.

[Fatman]

This is the most plausible explanation I've seen (had to find it again, had the same question myself a while back):

The truncated bullet is shorter. They were designed to work in a 9mm sized frame and magazine and a round-nose is too long. A side benefit is that the bullet has the same shape with or without a hollow point, so there's no difference in feeding characteristics.

http://boards.straightdope.com/sdmb/archive/index.php/t-534729.html

[tombogan03884]

Truncated cone bullets, like wad cutters, are supposed to leave a cleaner hole in paper targets .

[Big Frank]

I had some .45 ACP ammo with truncated cone bullets, but usually there round nose.

[Sponsor]

[GUNS-R-US]

I'd be curious what the bullet weights are. A 165 gr vs 180 gr.? Not all .40 cal is flat nose. I would think is could have something to do with case depth vs length, a flat nose bullet should be shorter overall length than a round nose bullet of the same weight. Just some guesses...... 

P.S. I assume the UMC is 9mm?

[ellis4538]

I'm going to have to agree with fatman in that the .40 was designed to work in the 9mm length platform therefore the bullets used in .40 ammo need to be more compatable with the 9mm length magazine or is that clip?  I always have trouble with that one!   LOL

Richard

PS:  Doesn't mean they can't make different configuration bullets for 1911 style pistols and others but they are having trouble keeping up with things as it is.

[Paraguy]

I'd be curious what the bullet weights are. A 165 gr vs 180 gr.? Not all .40 cal is flat nose. I would think is could have something to do with case depth vs length, a flat nose bullet should be shorter overall length than a round nose bullet of the same weight. Just some guesses...... 

P.S. I assume the UMC is 9mm?

The flat nose rounds are .40 180 gr. UMC yellow box.  Most of the target rounds I have used are rounded nose in UMC, except the .40.  It was $70 for a 250 round box at Wally World.  Felt bad since my preference is to by from the small guy locally, but that was too much of a difference to pass up.