longer oal

[jdwmyr]

When seating bullets out further then the C.O.A.L how do you know how much more powder to add without going over pressure

 

[MTBULLET]

1. read manual
2. read again
3. seat depth DOES NOT dictate "powder charge"

 

[g0rd0]

as MTBULLET stated follow the manuals!
If you choose to add extra powder sooner or later you will have the "big bang".
It will just be a matter of when, how much distruction and if anyone gets hurt.
Read the book, follow the book and leave the dart throwing to the pros

 

[varmintH8R]

All true, and I agree.

It is also worth noting that even published max loads can be higher than what your particular rifle will digest (while keeping decent brass life). This is especially true if you are using different primers, COALs, etc than what is published.

If I am going to change OAL of a known load, I will always reduce my charge and work back up, looking for pressure signs as I go. And I personally never "work up" over a max published load, regardless of a lack of pressure signs.

 

[kcebcj]

When seating bullets out further then the C.O.A.L how do you know how much more powder to add without going over pressure

To answer your question there is no set rule saying if you move the bullet this far you can add this much powder and stay within limits so.......

This is just an example of what kinda goes on.

In Quick Load.
300 WM
27 inch barrel
210gr Berger
COAL 3.340
70gr IMR 7828
Velocity 2916 fps
Chamber Pressure 60,751 psi (Max pressure 62,366 psi)

If you move the bullet out to a COAL of 3.600 the chamber pressure drops to 53,076 with a velocity of 2824 fps with all the settings above. You bump the powder to 72.8gr's, chamber pressure 60,340 psi with a velocity of 2936 fps your about back where you were. There are other factors here that effect chamber pressure (jump to lands etc.) and things that effect accuracy so take all of this with a grain of salt am just trying to keep it simple.

What is important is the ability to move the bullet around in and out to find the most accurate jump safely and maintain a decent velocity.

Loading manuals give you the data that they found using the listed COAL and you should not load any hotter then what they list as max with that COAL and bullet. The second you change the COAL the reloading numbers no longer apply accurately. There are other important factors evolved and every rifle is different and one should not leave the guidance of the loading manuals until enough experience has been gained with the proper tools to do so safely. Always when making a change in seating depth drop back a couple grains and come back up and the same practice should apply when using the manuals COAL and working up to a max load. Learn to recognize pressure signs which is always not a sure bet shoot through a chronograph and pay attention to the feel of the rifle when working up near a max.

 

[jdwmyr]

thanks for the reply's. I guess i had some wishful hoping going on for a formula to help me out. I'm playing with a 6.5 creedmoor with 140gr VLD's to see how accurate i can make it, by doing all the right things with the ammo. problem is i live far away from our shooting range so till i put together a mobile reloading station its difficult to make up rounds and drive back and forth 5 times a day to try them out. just looking for good info to help minimize the trips back and forth, and making up unneeded rounds.

 

[g0rd0]

I cannot help you with loads, I do not have that caliber. But, I can give you a hint. I live 45 min. drive to the range so when I have a new load idea this is what I do. Size and prime my cases, weigh up 5 charges of each and put them in separate little baggies (marked of course) and bring the lot to the range along with my bullets, loading block and a funnel.
I then start with the lowest 5 and pour in a charge, place the bullet on the mouth of the case and chamber it, repeat 4 more times, retrieve the target and make my notes. Then go to the next weight and keep going.
This sounds like a hassle but, it saves a lot of driving and if you are lucky like me the range you use will be free of other people so that you can take your time

 

[jrsolocam]

I start midway between the starting load and max load from the manual. Then work up 1/2 grain or grain until I find pressure. Find pressure, back down and start looking for accuracy. Sometimes with a longer OAL you can safely exceed published maximums, sometimes you can't.

 

[Kennibear]

There are too many variables to make a hard and fast rule about exceeding C.O.A.L. and adding powder. If the bullet is seated out and jams the rifling then the maximum charge could be LESS! For some monolithic bullets seating deeper allows more powder to be loaded as the initial resistance (inertia + friction) is lower as the jump to the rifling helps lower the friction of engraving of the bullet.

Predictions aside, you seat a bullet out longer to improve accuracy and if you drop some pressure then more powder becomes an option. But adding powder can kick the accuracy back to square one also.

My thoughts are to seat the bullet out close to the rifling. Check for accuracy. Check to see if the round feeds through the mag. Check the pressure signs. If it is all good then I bump the bullet closer to the lands and try again. Repeat until the bullet seats home or the accuracy falls off. Then think about changing the powder charge.

The exception is with cast bullets I seat into the rifling and adjusting the powder charge. I have never had a cast bullet shoot off the rifling.

KB

 

[boomtube]

When seating bullets out further then the C.O.A.L how do you know how much more powder to add without going over pressure[/QUOTE

There is no such formula, if there was it would be included in every loading manual.

The basic premise of your question is false; seating closer to the lands runs initial pressure UP, not down. Rifles are not high intensity-small capacity handguns and the seating effects are quite different. A longer 'running start' before engaging the rifling allows bullets to engrave the lands much easier than otherwise.

Most factory rifles shoot most bullets seated from 20 thou off the lands to as much a six times that much. Tuning the seating depth/OAL can be as critical to good accuracy as tuning powder charges.