Help me with my COAL

darcy32171

darcy32171

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I have a Savage Axis 22-250. I use IMR 4895 powder and Hornady 55gr V-max bullets.
I made a shell to check my COAL. The measurement is: 2.469
By the Hodgdon site, my OAL should be 2.350
Should everything be fine? Just lately I noticed about six shells that the shoulders were split.
I`ve heard of guys that make up shells for pinpoint accuracy using the COAL measurement. How does a guy accomplish this when your OAL is .119 under???
Thanks,Darcy
 
darcy32171 said:
I have a Savage Axis 22-250. I use IMR 4895 powder and Hornady 55gr V-max bullets.
I made a shell to check my COAL. The measurement is: 2.469
By the Hodgdon site, my OAL should be 2.350
Click to expand...

The 2.469" COAL cartridge that you made up, I am guessing that this was the "touching the rifling" COAL?

The COALs given in load manuals are determined by several factors, almost none of which have anything to do with your rifle's chamber or my rifle's chamber:

- the SAAMI specified COAL (so that cartridges fit in and feed from a magazine)
- the location of a cannelure (crimping groove) on a particular bullet
- with shorter bullets, to ensure that enough of the bullet is in the case so that there is adequate grip
- or, suprisingly often, what length the gunwriter/ammo-developer happened to choose (possibly what worked well in _his_ particular rifle)


Should everything be fine? Just lately I noticed about six shells that the shoulders were split.
I`ve heard of guys that make up shells for pinpoint accuracy using the COAL measurement. How does a guy accomplish this when your OAL is .119 under???
Thanks,Darcy
Click to expand...

Loading a COAL longer than the one published in the book is fine.

Case necks will split after the cases have been loaded several times. This is not unusua or surprising, this is a common end-of-life behaviour for brass. You can pull the ammo down, or if you can safely fire the ammo (if you carefully single-feed it).

Have a split form in the _shoulder_ area (the part where the "necking down" happens), or in the case body, *is* unusual and should be investigated to determine what the problem is.

Tuning COAL (more specifically, tuning the amount of "jump" between the bullet and when it makes contact with the lands) is one of the tools in a precision loader's toolbox, and can be used to make ammo more accurate. Having said that, making a bullet just touch or just barely touch the lands, does not necessarily nor automatically make the ammo more accurate - it could make it worse. Try it, test it, and see (there is a bit of trial and error in this game!)
 
Yes my COAL I mentioned was just touching the lands. With the powder/bullet combo....the seated depth is 2.350 which is .119 less. I guess to be correct, 20 thousand off the COAL is: 2.449 so I`d be .099 less. Is this quite a jump to the lands? I`ve heard of guys saying they want the bullet to be roughly .015- .020 off the lands.
If I make my OAL longer, this increases the space between the bullet and powder. What would a guy notice by increasing this space between bullet and powder???
 
20 thou jump is a pretty reasonable thing to try.

Some bullets tolerate jump well, you can load them to magazine length, be jumping 100 thou or more, and still be very accurate. Other bullets can be very "fussy" and need a lot of tuning to get good results.

All other things being equal, increasing a cartridge's OAL will increase the volume in the case, which will reduce the peak pressure that the load will generate. This will also reduce the velocity generated. It may increase the accuracy, reduce the accuracy, or have no effect on accuracy. It might make the variations in shot shot-to-shot velocity less consistent, or more consistent.

It's probably a good idea to start your load development 20 thou off the lands (if it is important to you that you be able to feed rounds from the magazine, check that it fits - usually Savages are pretty generous in the length of their magazines so this almost certainly won't be a problem)

IMR4895 is a good powder choice. Start at the recommended start load, load several (3? 5? 10?) of each charge weight as you work your way up towards the max published load. Observe the accuracy of each powder charge weight. Keep an eye out for pressure signs (read about this in your loading manual(s)) and stop if/when pressure signs appear. Enjoy your shooting.
 
rnbra-shooter said:
20 thou jump is a pretty reasonable thing to try.

Some bullets tolerate jump well, you can load them to magazine length, be jumping 100 thou or more, and still be very accurate. Other bullets can be very "fussy" and need a lot of tuning to get good results.

All other things being equal, increasing a cartridge's OAL will increase the volume in the case, which will reduce the peak pressure that the load will generate. This will also reduce the velocity generated. It may increase the accuracy, reduce the accuracy, or have no effect on accuracy. It might make the variations in shot shot-to-shot velocity less consistent, or more consistent.

It's probably a good idea to start your load development 20 thou off the lands (if it is important to you that you be able to feed rounds from the magazine, check that it fits - usually Savages are pretty generous in the length of their magazines so this almost certainly won't be a problem)

IMR4895 is a good powder choice. Start at the recommended start load, load several (3? 5? 10?) of each charge weight as you work your way up towards the max published load. Observe the accuracy of each powder charge weight. Keep an eye out for pressure signs (read about this in your loading manual(s)) and stop if/when pressure signs appear. Enjoy your shooting.
Click to expand...
Thanks for the info! Acually, the reloads I`ve done are very accurate right now. You are correct about the Savage magazine. Even though my load is very accurate, I thought a guy might be able to squeeze abit more (tighter group) by playing with the OAL/COAL. At the moment: 100 yards/ 3shots I can cover the size of a dime.
 
So, if a guy gets the bullet seated where it is .020" off the lands and this also creates more room between the bullet and powder which = less pressure, a guy should re-develope a another load increasing the powder charge to see if the groups get even tighter?
The reason I was looking into all this was the splitting of the shoulders which I thought was a "headspace" problem. By getting the bullet .020 off the lands and increasing the space between the powder and bullet should help this?
 
Sorry, I tried numerous times to get a real good pic. This is all I could get. Like I had mentioned, the neck is perfectly fine, just the shoulders.
splitshell.jpg
 
darcy32171 said:
Sorry, I tried numerous times to get a real good pic. This is all I could get. Like I had mentioned, the neck is perfectly fine, just the shoulders.
Click to expand...

cgn-splitneck-markedup.png


If that's the split, that is unusual. Does the split appear after you've made the ammo, or only after you've fired the round? What brand/type of brass? How many firings since new? Is it a "split" (i.e the brass is broken all the way through), or more of a "crinkle"?
 
The split is actually just on the inner left of the circle. Its not a crinkle, more of a definite line. The brass is Winchester and loaded maybe 4-5 times. Yes I have read before that re-load life is usually around 5 times, but I`ve seen split necks, not the shoulders. Hard to tell if the split goes right through. Its enough to make me not want to reload it anymore. I just would like to ballpark the cause.
 
darcy32171 said:
What program do you use to insert the circles,arrows and print on pics?
Click to expand...

http://markup.io/ - it is *really* slick, you bookmark it to your toolbar. Then when you are on a webpage that you'd like to annotate, you click your "markup" bookmark, which allows you to do some basic drawing on top of the web page.

When you are done you can "publish" the marked-up copy (it gives you a scrambled-up short URL, which has both the original web page plus your annotations). In the two that I did, I couldn't get CGN to load up the scrambled-up URL so I took a "screenshot" and that's what I used.


Getting back to your ammo:
- nice sharp photos!
- your brass sure is shiny and bright
- the first picture seems to best show the cracks. Is that fired brass, that has not yet been sized?


Cracks in that location are unusual. I can't immediately think of a rifle or ammo problem that would cause this. Perhaps the brand or lot of the brass you are using, was not properly annealed at manufacturing time; if so, you could try a different brand or batch of brass.
 
rnbra-shooter said:
http://markup.io/ - it is *really* slick, you bookmark it to your toolbar. Then when you are on a webpage that you'd like to annotate, you click your "markup" bookmark, which allows you to do some basic drawing on top of the web page.

When you are done you can "publish" the marked-up copy (it gives you a scrambled-up short URL, which has both the original web page plus your annotations). In the two that I did, I couldn't get CGN to load up the scrambled-up URL so I took a "screenshot" and that's what I used.


Getting back to your ammo:
- nice sharp photos!
- your brass sure is shiny and bright
- the first picture seems to best show the cracks. Is that fired brass, that has not yet been sized?


Cracks in that location are unusual. I can't immediately think of a rifle or ammo problem that would cause this. Perhaps the brand or lot of the brass you are using, was not properly annealed at manufacturing time; if so, you could try a different brand or batch of brass.
Click to expand...
Thanks, I try to tumble every batch. These are "numerous fired" brass and they were full length resized before I had noticed these marks.
Before you gave me this website, I tried my hand at "paint" but gave up...I was horrible lol.
 
I could post a pic of my target, but way too many confusing holes in it lol. I should have put up seperate targets for each batch of shells. By Hodgdon`s site: IMR 4895 and 55gr Hornady Vmax bullet at 34.5grains of powder, the OAL is 2.350.
.020" off the lands is: 2.449. I made 5 shells using this OAL but leaving the 34.5gr powder alone. My reloads at 2.350 were a little better having the bullet jump to the lands.
Question I have is: If Maximum powder charge is 36.5gr with an OAL of 2.350, does a guy disregard this maximum charge if the OAL is 2.449? I`m thinking increasing the space between bullet and powder would = less pressure so a guy should work up the charge to take up the extra space. Of course watching for signs of pressure all the way. So I wonder what the maximum charge would be with an OAL of 2.449?
 
darcy32171 said:
Question I have is: If Maximum powder charge is 36.5gr with an OAL of 2.350, does a guy disregard this maximum charge if the OAL is 2.449? I`m thinking increasing the space between bullet and powder would = less pressure so a guy should work up the charge to take up the extra space. Of course watching for signs of pressure all the way. So I wonder what the maximum charge would be with an OAL of 2.449?
Click to expand...

All other things being equal, then yes; but it is a pretty minor effect. ***BUT*** all other things are not equal; there are enough other differences, that are potentially much bigger effects, that you should probably start by ignoring the fact that you're loading slightly longer (so tending toward _slightly_ lower pressure) than the manual. Work up the load as you normally would. If you choose to exceed published load data, do it on the same basis as you would/wouldn't do so for a COAL of 2.350".

Use a chrono, if you have one. Pay attention to all the various pressure signs.
 
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