.40 cal: why the flat shape?

ericsaysgo · April 7, 2009, 11:58 PM

can anyone tell me why just about every .40 caliber bullet has a flat face while just about every 9mm and .45 is round nose? thanks for sharing.

armsmaster270 · April 8, 2009, 01:23 AM

45 also come in a SWC they work good and punch a clean hole the 357Sig is that way too.

CowTowner · April 8, 2009, 09:08 AM

As is the 40 S&W's daddy, the 10mm Auto.

**Unclenick** · April 8, 2009, 09:12 AM

A flat meplat (the tip of the nose) is both more damaging in tissue and cuts cleaner, easier to score holes in paper targets than round nose bullets. Round nose has the advantages of being easier to feed in most guns and having a higher ballistic coefficient for shooting longer distances. Some bullets that appear to have flat noses in photos are actually expanding hollow points when you turn them sideways and look in. Some, like the truncated cone, are solid. Round nose is the older, more traditional bullet style, so it has been a default shape for designers of basic non-expanding full metal jacket and solid lead bullets since before the Civil War. It comes from taking the shape of a round musket ball for the front of the bullet. Other old designs, such as Minié balls have a more pointed shape achieved by using an arc for side view of the bullet nose profile. The points are for still longer range ballistics, but today are much longer and sharper in shape than the Civil War projectiles and have boattail angled bases for still longer range shooting.

freakshow10mm · April 8, 2009, 09:32 AM

The .40 is based off the 10mm. The 10mm was designed with a flat meplat FMJ bullet due to the feed ramp geometry. It has nothing to do with the terminal performance of the bullet type on live tissue. It has to do with feeding geometries.

Cosmik de Bris · April 8, 2009, 04:34 PM

The .40 was designed to go in a 9mm platform so the OAL of the .40 has to be the same as a 9mm so that it fits in the mags etc. They have to shave a bit off of the front in order to make it fit.

RidgwayCO · April 8, 2009, 06:11 PM

My take on this is that the .40 S&W has a relatively short max COL of 1.135" (which is interesting in that it was designed to be used in pistols firing the 9mm Luger with a 1.169" max COL). I'm pretty sure that a round nose bullet of conventional ogive would be unsupported at the case mouth if seated to meet that 1.135" COL. Plus the flat nose bullet allows you to keep the COL down while simultaneously providing as much gripping area on the bullet as possible. You don't want the bullet of that already high-pressure round seating itself deeper on the rough journey from the magazine, up the feed ramp, and into the chamber.

For what it's worth, all of the bullets in Speer Manual #14 for the .40 S&W are flat nose or hollow point.

Archie · April 8, 2009, 06:18 PM

The 9x19 and the .45 ACP were designed in the very early part of the 20th Century. The bullet shapes are traditional.

The .40 S&W was designed in the 1980s or 1990s. Bullet technology has been much advanced.

Shoney · April 8, 2009, 11:00 PM

As RidgwayCO stated the flat point and hollow point give better grip in the case, especially for light weight bullets. However, the larger surface area of the bullets sidewall yields better accuracy!

April 8, 2009, 01:23 AM	#2
armsmaster270 Senior Member Join Date: November 25, 2008 Location: California Posts: 1,951	45 also come in a SWC they work good and punch a clean hole the 357Sig is that way too. __________________ http://www.armsmaster.net-a.googlepages.com http://s239.photobucket.com/albums/f...aster270/Guns/ Retired LE, M.P., Sr. M.P. Investigator F.B.I. Trained Rangemaster/Firearms Instructor & Armorer, Presently Forensic Document Examiner for D.H.S.

April 8, 2009, 09:08 AM	#3
CowTowner Senior Member Join Date: October 17, 2007 Location: Cowtown of course! Posts: 1,747	As is the 40 S&W's daddy, the 10mm Auto. __________________ NRA Chief Range Safety Officer, Home Firearms Safety, Pistol and Rifle Instructor *“Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life......”* President John F. Kennedy

April 8, 2009, 09:12 AM	#4
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	A flat meplat (the tip of the nose) is both more damaging in tissue and cuts cleaner, easier to score holes in paper targets than round nose bullets. Round nose has the advantages of being easier to feed in most guns and having a higher ballistic coefficient for shooting longer distances. Some bullets that appear to have flat noses in photos are actually expanding hollow points when you turn them sideways and look in. Some, like the truncated cone, are solid. Round nose is the older, more traditional bullet style, so it has been a default shape for designers of basic non-expanding full metal jacket and solid lead bullets since before the Civil War. It comes from taking the shape of a round musket ball for the front of the bullet. Other old designs, such as Minié balls have a more pointed shape achieved by using an arc for side view of the bullet nose profile. The points are for still longer range ballistics, but today are much longer and sharper in shape than the Civil War projectiles and have boattail angled bases for still longer range shooting. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; April 8, 2009 at 09:24 AM.

April 8, 2009, 06:18 PM	#8
Archie Senior Member Join Date: May 26, 2000 Location: Hastings, Nebrasksa - the Hear Posts: 2,209	History The 9x19 and the .45 ACP were designed in the very early part of the 20th Century. The bullet shapes are traditional. The .40 S&W was designed in the 1980s or 1990s. Bullet technology has been much advanced. __________________ There ain't no free lunch, except Jesus. Archie Check out updated journal at http://oldmanmontgomery.wordpress.com/

April 8, 2009, 11:00 PM	#9
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	As RidgwayCO stated the flat point and hollow point give better grip in the case, especially for light weight bullets. However, the larger surface area of the bullets sidewall yields better accuracy! __________________ I pledge allegiance to the Flag - - -, and to the Republic for which it stands….Our Forefathers were brilliant for giving us a Republic, not a democracy! Do you know the difference??? and WHY?http://www.wallbuilders.com/LIBissue...les.asp?id=111

April 7, 2009, 11:58 PM	#1
ericsaysgo Junior Member Join Date: September 5, 2008 Posts: 6	.40 cal: why the flat shape? can anyone tell me why just about every .40 caliber bullet has a flat face while just about every 9mm and .45 is round nose? thanks for sharing.

April 8, 2009, 09:32 AM	#5
freakshow10mm Junior member Join Date: January 23, 2008 Location: MI Posts: 1,398	The .40 is based off the 10mm. The 10mm was designed with a flat meplat FMJ bullet due to the feed ramp geometry. It has nothing to do with the terminal performance of the bullet type on live tissue. It has to do with feeding geometries.

April 8, 2009, 04:34 PM	#6
Cosmik de Bris Member Join Date: December 15, 2008 Posts: 65	The .40 was designed to go in a 9mm platform so the OAL of the .40 has to be the same as a 9mm so that it fits in the mags etc. They have to shave a bit off of the front in order to make it fit.

April 8, 2009, 06:11 PM	#7
RidgwayCO Senior Member Join Date: March 22, 2008 Location: Western Colorado Posts: 244	My take on this is that the .40 S&W has a relatively short max COL of 1.135" (which is interesting in that it was designed to be used in pistols firing the 9mm Luger with a 1.169" max COL). I'm pretty sure that a round nose bullet of conventional ogive would be unsupported at the case mouth if seated to meet that 1.135" COL. Plus the flat nose bullet allows you to keep the COL down while simultaneously providing as much gripping area on the bullet as possible. You don't want the bullet of that already high-pressure round seating itself deeper on the rough journey from the magazine, up the feed ramp, and into the chamber. For what it's worth, all of the bullets in Speer Manual #14 for the .40 S&W are flat nose or hollow point.