OAL - what's your precision factor?

MarkGlazer · October 19, 2013, 07:03 PM

Guys, I have been at my bench today reloading my Makarov CZ-82. I'm frustrated with the inconsistency in the lead cast bullets that I purchased, have been measuring them and batching by size then adjusting my die accordingly to arrive at a specific OAL during the load process. I immediately ran out of patience today and decided to take a different tack.

My logic went as follows; both the Lee and Hodgons' data call for a minimum OAL of .965 (Titegroup powder, 3.3 grains), a factory round is .975 (usually my targeted OAL) and the diagrams for a Makrov round in the Lee manual is .982 while Lyman is .984 (no data from them for a 95 grain cast lead round with Titegroup), so why do I care about achieving consistent OAL as long as I am above the minimum and below the maximum? As such, I loaded 150 rounds on my single stage press with that "attitude." I ran every round through the weapon, cycling manually, without incident.

So, do you really care about your OAL if you are within min and max?
Going forward, should I have a specific, targeted OAL set or continue on with my "new attitude?"

I would appreciate your views on this matter.

Thank you.

Nick_C_S · October 19, 2013, 08:23 PM

Well you need to start by doing the "plunk test" in your barrel to make sure you're specific gun is going to chamber them properly.

Once your OAL has passed the plunk test, for what you're doing, there's no reason to get too wrapped up in COL. We loaders tend to overthink this.

Setting COL does two things; 1: It ensures (if done correctly) proper chambering; and 2: it sets a consistent internal case volume for consistent discharge pressure (can still vary with different brass).

For everyday shooters, good enough is good enough. When you start loading match rounds, we can talk again

Mike / Tx · October 20, 2013, 04:52 AM

The biggest thing I look for when loading auto rounds is that I am above the minimum lenght. I don't want more of the bullet shank shoved down in the case than necessary which might jack up pressure. If I am over and they still fit whoopee. As for being exactly the same length, I learned a long time ago that is a headache I am not looking to find again. Even being .003" longer or shorter, they will still shoot better than I can hold them most of the time.

m&p45acp10+1 · October 20, 2013, 05:46 AM

I go for not too long for the magazine, and not so short they hang up on the feed ramp. I prefer to load in the longer side. They tend to feed better. Note I do not reload for my 9mm Mak. It makes brass disappear, and steel cased ammo is cheap when ordered in bulk. I would just check to make sure they feed properly, and loaded rounds extract easily. If they do not extract easily then check to make sure you removed enough flare, and they are not too long. Most 9 mm Mak guns have a generous chamber tolerance so you would probably exceed magazine length before making the bullet touch the lands.

Nick_C_S · October 20, 2013, 03:27 PM

Quote:

As for being exactly the same length, I learned a long time ago that is a headache I am not looking to find again.

Yep! I've measured factory rounds that vary +/- .005 (.010 total variance), or more.

Taking this measurement down to the nth degree is going to achieve nothing but a headache. The bullet shape distorts (especially lead) when it is seated in the press - which shouldn't matter in theory, but yet it does. It's not a perfect world. There's going to be variance.

On high-end rounds, I allow myself +/- .005. On everyday shooters, I allow myself +.010 / -.005.

October 19, 2013, 07:03 PM	#1
MarkGlazer Senior Member Join Date: February 19, 2013 Location: Atlanta, Ga Posts: 329	OAL - what's your precision factor? Guys, I have been at my bench today reloading my Makarov CZ-82. I'm frustrated with the inconsistency in the lead cast bullets that I purchased, have been measuring them and batching by size then adjusting my die accordingly to arrive at a specific OAL during the load process. I immediately ran out of patience today and decided to take a different tack. My logic went as follows; both the Lee and Hodgons' data call for a minimum OAL of .965 (Titegroup powder, 3.3 grains), a factory round is .975 (usually my targeted OAL) and the diagrams for a Makrov round in the Lee manual is .982 while Lyman is .984 (no data from them for a 95 grain cast lead round with Titegroup), so why do I care about achieving consistent OAL as long as I am above the minimum and below the maximum? As such, I loaded 150 rounds on my single stage press with that "attitude." I ran every round through the weapon, cycling manually, without incident. So, do you really care about your OAL if you are within min and max? Going forward, should I have a specific, targeted OAL set or continue on with my "new attitude?" I would appreciate your views on this matter. Thank you. __________________ non ministrari sed ministrare

October 19, 2013, 08:23 PM	#2
Nick_C_S Senior Member Join Date: March 21, 2013 Location: Idaho Posts: 5,522	Well you need to start by doing the "plunk test" in your barrel to make sure you're specific gun is going to chamber them properly. Once your OAL has passed the plunk test, for what you're doing, there's no reason to get too wrapped up in COL. We loaders tend to overthink this. Setting COL does two things; 1: It ensures (if done correctly) proper chambering; and 2: it sets a consistent internal case volume for consistent discharge pressure (can still vary with different brass). For everyday shooters, good enough is good enough. When you start loading match rounds, we can talk again __________________ Gun control laws benefit only criminals and politicians - but then, I repeat myself. Life Member, National Rifle Association

October 20, 2013, 04:52 AM	#3
Mike / Tx Senior Member Join Date: April 8, 2000 Posts: 2,101	The biggest thing I look for when loading auto rounds is that I am above the minimum lenght. I don't want more of the bullet shank shoved down in the case than necessary which might jack up pressure. If I am over and they still fit whoopee. As for being exactly the same length, I learned a long time ago that is a headache I am not looking to find again. Even being .003" longer or shorter, they will still shoot better than I can hold them most of the time. __________________ LAter, Mike / TX

October 20, 2013, 05:46 AM	#4
m&p45acp10+1 Senior Member Join Date: May 3, 2009 Location: Central Texas Posts: 3,930	I go for not too long for the magazine, and not so short they hang up on the feed ramp. I prefer to load in the longer side. They tend to feed better. Note I do not reload for my 9mm Mak. It makes brass disappear, and steel cased ammo is cheap when ordered in bulk. I would just check to make sure they feed properly, and loaded rounds extract easily. If they do not extract easily then check to make sure you removed enough flare, and they are not too long. Most 9 mm Mak guns have a generous chamber tolerance so you would probably exceed magazine length before making the bullet touch the lands. __________________ No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.