Min OAL to use for 147 grn FN 9mm

[canuck9]

Hi Guys

Im new to this website and like it a lot. Well done.

I have been loading 9mm RN 147 grn Frontier CMJ bullets and using 3.5 grn of Titegroup. Now I want to try FN 147 Frontier CMJ bullets. My question is what should my new measured min OAL be? I figure that I shouldnt be loading at the old bullet depth setting because whatever bullet mass was removed from the front of the bullet, to make it a flat nose, had to be added to the back end of the bullet, thereby making the bullet sit deeper in the case. This I expect will change the pressures produced. My Lee reloading manual doesnt provide the answer.

Thanks

[sdm74]

Listed in my book is 1.10

[Edubya]

Hi Guys

Im new to this website and like it a lot. Well done.

I have been loading 9mm RN 147 grn Frontier CMJ bullets and using 3.5 grn of Titegroup. Now I want to try FN 147 Frontier CMJ bullets. My question is what should my new measured min OAL be? I figure that I shouldnt be loading at the old bullet depth setting because whatever bullet mass was removed from the front of the bullet, to make it a flat nose, had to be added to the back end of the bullet, thereby making the bullet sit deeper in the case. This I expect will change the pressures produced. My Lee reloading manual doesnt provide the answer.

Thanks

I've been told not to use minimum COL. Set a bullet in a once fired case and drop it into the chamber. Make sure that the case goes all of the way in. It might push the bullet into the case a little bit as the bullet hits the lands. Either pick the bullet out by the rim or gently and slowly insert a dowel up through the muzzle end and remove the bullet. Subtract .003" from that length and that would be a safe starting point. Shot ten of these and examine the primers to insure they are not flowing. You can decrease .003" at a time and each should be chronographed and recorded, keeping an eye on the primers. The 1.1" is a minimum COL and not necessarily what your load or gun will like.

Remember, the 9mm is very sensitive to COL and .003" can make an overload very dangerous.

EW

[rfwobbly]

Mr Canuk -

• 147gr in a 9 is a weird beast. If you consider that every safety aspect of reloading revolves around 'safe chamber pressure', then you really want to stop thinking in terms of OAL and start considering the depth of the bullet's base inside the case. Now of course that can't be directly measured, so we talk in terms of OAL, but all the while you should be thinking bullet depth. In other words, we say OAL, but what we really mean is 'OAL minus bullet length'.

In 115gr bullets we are forced to use shorter OALs to simply get enough of the bullet into the case to hold it firmly in place. That is not the case with the 147; the bullet is so much longer it just ain't a problem. In fact the bullet is so long that you have the opposite issue... finding enough room for powder!

So what you really want to do is explore a method to measure the maximum permissible OAL for that bullet in your barrel. One such method is outlined above by Edubya.

• You are correct. A new bullet always changes the chamber pressure. Sometimes lowering it; sometimes raising it. No one knows. And that's where the "starting load" comes in. Beginning 10% below max has been shown to cover a host of ills. If you'll load 5-10 rounds at each of several incrementally higher loads, then you can shoot those and check for accuracy and "pressure signs". Stop when the shot groups stop getting tighter. A chrono can also be a huge help in avoiding dangerous pressures.

Hope this helps!

Edited June 29, 2011 by rfwobbly