Overall Length Implications

[1979Standard]

How important have you found overall length to play in regards to reliability and accuracy (not to mention safety issues from too high of pressure)?
What are the implications specific for pistol?
What are the implications specific for rifle?

I have read that reliability and accuracy can be inversely proportional for longer vs shorter OAL.

Here are the SAAMI specs for 9mm I found, but the listed min OAL is 1.000 and max OAL is 1.169 which seems like a large range from what I have read about safety/reliability/accuracy due to OAL variance.

http://www.saami.org/PubResources/CC_Drawings/Pistol/9mm%20Luger%20-%209mm%20Luger%20+P.pdf

Here is the load data from Hodgdon where they used OAL of 1.150:

http://www.hodgdonreloading.com/data/pistol?&CartridgeName=9mm+Luger&OrderBW%5B%5D=124&Manufacturer%5B%5D=Hodgdon&Powder%5B%5D=CFE+Pistol

I have a real small T-square ruler that goes down to 1/64", but I guess a digital caliper is really required for what I need to be doing with 9mm.

[JMP]

It's different from gun to gun as headspace and fit vary.

[klewan]

Go as long as you can, and still fit in the magazine. Measuring with a yardstick just doesn't cut it in reloading....1/64"on a ruler, Shirley you jest!

Get a dial caliper, .001"

[1979Standard]

Go as long as you can, and still fit in the magazine. Measuring with a yardstick just doesn't cut it in reloading....1/64"on a ruler, Shirley you jest!

Get a dial caliper, .001"

I am planning to get the caliper, but was hoping to get a digital one since they are easier to read the .001" than the dial models. Any reason to go with a dial model instead of the digital?

Here is a link to the small ruler I have with 1/64":

http://www.harborfreight.com/6-inch-stainless-steel-pocket-ruler-93684.html

[brettkeating]

Any reason to go with a dial model instead of the digital?

Cheaper, and less things can go wrong or break. I'm usually a fan of avoiding electronics when the benefit is small.

[MrElectric03]

A dial caliper will never die, I've found them to be more accurate as well. Not sure if anyone else has had the problems I've had finding batteries for those damn digital ones but a couple times I've been working at mine sites and after work I'm running around town looking for those stupid things.

[klewan]

OP, now you know why to get the mechanical caliper....want to try something that is really hard to read; get a vernier caliper. Probably one person in a thousand knows how to use those...spell correct has highlighted 'vernier', so that doesn't know either....Gave you the perfect setup with 'Shirley you jest', and you blew it. Somebody here will know...

[BigBronco]

A digital has the ability to zero an any given point. This becomes very useful when using a bullet comparator.

[twotacocombo]

Here are the SAAMI specs for 9mm I found, but the listed min OAL is 1.000 and max OAL is 1.169 which seems like a large range from what I have read about safety/reliability/accuracy due to OAL variance.

9mm Luger can be loaded with a wide range of ammo weights, from under ~65gr to ~147gr. This is why the OAL can vary by over 1/8". The lighter bullets need to sit far enough in the case to still get a grip on it, and the heavier ones need some room out front.

[jameshenry]

Don't call me Shirley!!

[mark501w]

You get what you pay for in measuring tools. I've checked my Chicom with my micrometer gauges & found them off as much as .0015 over 2" , May not be much but NWaS for casting. Go to eBay you can get some deals on dial calipers.

[thenodnarb]

Dial caliper is the way to go for reloading. I really like my Lyman set. You don't really read the whole number IME. You are mostly looking at the dial to meausre your lat 2 digits. when you seat a 30-06 for instance, you don't have to check to see if you are at 2" or 3". You just check your tenths once and then go by the dial each time for that cartridge. You get used to seeing the dial in a certain spot for a given OAL. You can also check for bullets that are out of round by spinning the bullet while measuring, and watch the dial go up and down.

Also anything digital can have weird fluctuations and wandering. Obviously quality will trump these generalizations, but I wouldn't trust a digital that might not be zeroed correctly. heck it might be human error. As already said: Batteries die....often. Digitals mush have a high self discharge rate.

Dials all the way!

[1bulletBarney]

I bought a 6" digi caliper from Harbour Freight, my friend has a Starrett 1" calibrating rod, checked the caliper... dead nuts 1.000" I can live with that... $14.00 with a 20% off coupon.

I have a couple of those 6" machinest rulers, would not use those under any circumstances to determine OAL.

[1979Standard]

Alright I am buying a dial caliper as soon as I can get to the store. Thanks guys.

I was originally posting because I was curious more about how precise within the SAAMI range I should try to be and why it would be important to be so precise.

[Enfield47]

Different shaped bullets will have a different COL so load to the length the bullet manufacturer recommends. This will apply for both rifle or pistol. You don't want your bullet smashed into the lands as this may cause an unsafe pressure spike when fired. It also isn't fun having a bullet jammed into the lands so that when you have to pull back the bolt to get it out, it pulls the bullet out of the case and dumps powder into your action and magazine.