40 cal. length

[bearfoot]

on wipedika, a diagram says the length is 1.135" unless wipedika has a wrong diaghram. but that`s w/ an included radius. so the actual length cannot be measured unless i have the rad./points on the bullet and use trig. to figure out the dim./length from the radius top to the flat of the bullet. i can`t find another specfications chart for the s&w 40 cal. bullet from the bottom of the case to the flat(top) of a 180 gr. ball bullet. read an article that rechambering a round for 7 days moves the bullet back into the case .014 thousands. which is causeing problems w/ the fireing of the ammo if the bullet moves to far into the case rechambering every day. best to fire the bullet or dispose of. the article states that usually doesn`t cause problems w/ a 9 mm because the powder stops the bullet. thanks for the specs., or location to check them.

 

[bearfoot]

w/ micrometers i have measured the ammo i have, and then checked the rechambered round, but the most it has moved in was .007 thousands. and thats w/ winchester white box. so i just have fired off the rounds. just measured WWB/ 180/ ball, it measures 1.122 of an inch. federal/155gr./hydra shok is 1.121 of an inch. should have done that before i posted a thread. just wanted to get the correct/ excellent help from the forum.

 

[Titegroups]

You're over-thinking things, you should be a bit concerned about OAL changing if you cycle the ammo all the time but realize this has gone on for years before internet hype brought it to the forefront of attention of some. Keep in mind just because one box of ammo got set back .014 doesn't mean the next box or next round will set back with the same consistency. Ammo can vary. A small set back is unlikely to cause a serious overpressure situation. Engineers figure in safety factors when designing.

 

[Coastie762]

Bearfoot, I looked in three reloading manuals, the maximum overall length listed is 1.135", regardless of bullet weight or shape. That would, I presume, be the SAAMI specification for the cartridge.

Repeated re-chambering of a loaded round can cause bullet set back. The amount varies depending on the amount of neck tension. Some calibers seem to be noted for a greater potential of setback, the .40 and .357 Sig among them.

One can increase the amount of neck tension during reloading by using a smaller expander plug or an undersized sizing die. For instance, EGW makes an undersized sizer die for the .40 S&W. It works very well as designed, but does increase the sizing effort. When using this die, I use a little Imperial sizing die wax every 5-10 cases to ease the sizing force required.

 

[firecracker6]

As a preface, I reload 40 but it's not my bread and butter so I'll take a back seat to those for whom it is. There's no way to know for sure how much repeated chambering will set the bullet back. It's going to depend on what kind of firearm it is, what kind of brass your using, what bullet is involved and occasionally, how much powder is in the case --though personally I do not care to count on the powder to eliminate bullet setback. I suppose if you chamber the same round often enough the bullet could get setback enough to cause a problem perhaps even a dangerous one in an extreme case. It could definitely cause an accuracy problem though (if extreme accuracy is what you want). It could also cause a feeding problem if it got bad enough. Improper COL is one of the main causes of feeding problems in reloaded ammo. If memory serves me correctly, the max length of a 40 round is 1.135 from the base to the tip regardless of the bullet involved (like the Coastie has already said). The 40 cartridge is different from 9mm in that it doesn't offer much room to play with regarding COL. Personally, I measure my carry ammo once in a while. If I find one a little short I light it off. I like to change my carry ammo once in a while anyway. You can increase the neck tension by using a U (undersize) die (again like the Coastie said). My only experience reloading w/ a U die is w/ 38 super. I use it when I shoot 9mm bullets as both my 1911's cause some pretty serious setback. A U die is going to work the brass more which will shorten case life (once again, like the Coastie said). Personally, I wouldn't fool w/ a U die for the 40. I don't think .007 in. is enough to worry about.

 

[Coastie762]

One other item to consider is the fact that for the most of us (well, at least me) our handloads only get chambered once, then fired. Setback in this instance (assuming a properly assembled round) is probably not a big deal. Carry loads are another matter, how often you load/unload your pistol and cycle your carry ammo may cause this to be a bigger consideration for you.

You can test your handloads by making up a few dummy rounds with your desired bullet and length. Load them into a magazine then chamber them as you would normally do. Measure them after each chambering and note the amount, if any, of setback you experience and how many times it takes to start the setback process.

 

[firecracker6]

What Coastie said.