Does OAL change if different nose bullets used?

[Mike in CT]

I am loading 9mm and switching from a round nose bullet to a flat nosed Montana Gold bullet.

Does the shape of the bullet nose effect Case Overall Length? I was loading at 1.169 and noticed that with the new bullet I had to back off my seating die. Wondering if that will adversely affect pressure? seems that with the flat nose bullet, less seats into the case and likely less pressure.

Mike

[Bubber]

I am loading 9mm and switching from a round nose bullet to a flat nosed Montana Gold bullet.

Does the shape of the bullet nose effect Case Overall Length? I was loading at 1.169 and noticed that with the new bullet I had to back off my seating die. Wondering if that will adversely affect pressure? seems that with the flat nose bullet, less seats into the case and likely less pressure.

Mike

Mike, The olgive (curved sides, I think) of the flat nose bullet may be close or hit the rifleing of the barrel if OAL is to much. Seen one at a Steel challenge match that would pull the bullet if trying to rack out the last unfired round after a stage. Left the bullet in the rifling. Luckily it would not chamber the next round. later be careful rdd

[lcs]

I am loading 9mm and switching from a round nose bullet to a flat nosed Montana Gold bullet.

Does the shape of the bullet nose effect Case Overall Length? I was loading at 1.169 and noticed that with the new bullet I had to back off my seating die. Wondering if that will adversely affect pressure? seems that with the flat nose bullet, less seats into the case and likely less pressure.

Mike

[lcs]

Yes

[kevin c]

The cartridge over all length will change depending on how the different style bullets contact the seating die. If they all reliably contact with the meplat (tip) in the deepest part of the die, the OAL will be the same. If they contact on the ogive of the bullet (side profile) then the OAL will change because the contact will be shallower to a degree that will vary with profile.

Varying OAL's can definitely influence pressure and feeding.

[superdude]

http://www.38super.net/Pages/Overall%20Length.html

http://www.38super.net/Pages/Bullet%20Design%20and%20Feeding%20Reliability.html

[Mike in CT]

Superdude

Thanks for your post and links. That answers all my questions!

Mike

[rfwobbly]

Does the shape of the bullet nose effect Case Overall Length? I was loading at 1.169 and noticed that with the new bullet I had to back off my seating die. Wondering if that will adversely affect pressure? seems that with the flat nose bullet, less seats into the case and likely less pressure.

Mike -

IMHO OAL is very misleading. We only care about the external measurements because in some very few guns the bullet might get tangled up in the rifling. What a reloader is primarily concerned about is maintaining a safe chamber pressure. In that sense, it's the position of the bullet's base that matters. In other words the concern when you swap bullets is to keep the same volume inside the case. Look at the cartoon below...

So if you're happy with your old load, you can easily maintain that (or come very, very close) by doing some simple math to seat the new bullet to the same depth (provided the barrel will accept it).

As reloaders, we really only talk in terms of OAL because we can't physically measure where the base of the bullet is, once it's inside the cartridge case. Follow? It's sort of like talking on and on about Italian spaghetti, when all of us understand it's really about the meatball !

Hope this helps!

Edited April 24, 2011 by rfwobbly

[CocoBolo]

We can actually get an accurate measurement of seating depth but it takes 3 measurements or 4 if you are comparing two bullets. Measure the case height and the bullet height add these toghether then subtract the OAL of the loaded round to get seating depth.

Most of the time we are not dealing with that but rather a problem with them not fitting in the gun, aka won't go into battery then its a matter of figuring out what it will eat, and how much powder to feed it. Starting out low and working it up, and we call that working up a load. This is common since those guys that write the load book don't use the cheap bullets we buy, who shoots Sierra's.

[sigsauerfan]

that's a fact .

i've loaded tons of RN and FP to date, i've got a bunch of JHP to try recently, they're the tallest 9mm bullet nose to base i've ever loaded compared with the RN and FP's i've loaded in bulk in the past.

in fact, those JHP's are 0.030 longer, wich forced me to adjust my seating die and lower the powder charge .

thing is that , if i want to keep the aol that works good in my gun, i must reduce the charge of powder, given the fact that i elected to load the JHP to the same aol, that means more space is used inside the brass, raising the pressure and velocity up.

kind of a ''start over again'''.

what i do( to keep the aol intact ) is i removes 1 grs of powder for each 0.010 added inside the case(not an absolute rule depending of the burning rate).

at the end, chrony will tell.

example: my RN's were (0.640) loaded at 1.130aol with a 3.8 powder charge good for a 920-950 fps.

now i load the JHP (0.670) at the same aol (1.130) but i've reduced the powder charge to 3.4-3.5.3.6 grs and will chrono to see how it goes. i guess the 3.6 load might be on the hot side, 3.5 should be in the ballpark. again,chrony will tell.

Edited April 24, 2011 by sigsauerfan

[Mike in CT]

Thanks for all the replies and good to see CocoBolo reply, I have read many of your posts in the reloading forums.

I made up a number of test rounds and went down to the range today for some initial testings.

Since I was going from the longer bullet to the shorter one case volume was of less of a concern. I found that all 3 of my test lengths fed fine and none of the cartridges showed any signs high pressures.

I am going to load some additional rounds and try to get the chrono out tomorrow.

Mike

[rfwobbly]

Since I was going from the longer bullet to the shorter one case volume was of less of a concern. I found that all 3 of my test lengths fed fine and none of the cartridges showed any signs high pressures.

Mike -

That is a good thing too, because you said earlier you loaded at 1.169". If the new bullet had been longer, then by trying to get the same seating depth you'd be in big trouble.

Actually. IMHO your choice of OAL is a separate second issue. 1.169" is the SAAMI max, the longest length most 9x19 mags will accept. While you're working up new loads I would encourage you to look at an OAL in the 1.125 to 1.150" range. Why?

• All magazines have a manufacturing tolerance. What if one of your competition mags (unbeknownst to you) will only accept a cartridge of 1.167" ? You could be getting random feed issues and never know why. A cartridge of 1.169" might scrub on the interior and cause Lord knows what kinds of bothersome issues.

• All reloading presses produce an OAL tolerance. Even the best reloading equipment often produces competition cartridges to a tolerance of (say) +/-.003". That means if you aim for 1.169", your shortest cartridge might be 1.166", while your longest would come in at 1.172". Now maybe the 1.172" is only 1 out of every 50 you load, but it's still there like a time bomb waiting to trip you up on the starter's box.

On the other hand, if you had an OAL of (let's say) 1.160", then your +.003" cartridge would come in at 1.163" which would clear the tight mag and never be able to harm you.

Additionally, a bullet sitting deeper in the case is much less likely to get knocked off center when it hits the feed ramp. It's simply got a greater percentage of its total length held tight by the case. So nothing but good comes from having moderate length OALs.

Hope this stimulates some good thoughts.

Edited April 24, 2011 by rfwobbly