approaching max charge??
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CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
In working up in strong rifles, often the practical limit is brass life.
Loose primer pockets are not found at some repeatable threshold of one firing.
The first measurable increase with dial calipers with a 180 degree spin in extractor groove is a repeatable and fairly exact threshold. This is well below any loose primer pockets with one shot. Vernon Speer in 1956 writing about how to write a load book said to back off 6% from any change in the brass. In some cartridges with temperature stable powder, I have backed off as little as 3% for my personal use. That would be in 7mmRM with H4350 I backed off 2 grains from 72 to 70 and have used that load in many rifles I built and factory to kill many animals.
H335 is not as temp stable, and in a 223 if I found an extractor groove expansion threshold at 30 gr, I would back off the full Vernon Speer 6% safety margin to 28 gr as my usable max load for bolt actions and single shots. My non adjustable gas semi auto guns have addition constraints.
In working up in strong rifles, often the practical limit is brass life.
Loose primer pockets are not found at some repeatable threshold of one firing.
The first measurable increase with dial calipers with a 180 degree spin in extractor groove is a repeatable and fairly exact threshold. This is well below any loose primer pockets with one shot. Vernon Speer in 1956 writing about how to write a load book said to back off 6% from any change in the brass. In some cartridges with temperature stable powder, I have backed off as little as 3% for my personal use. That would be in 7mmRM with H4350 I backed off 2 grains from 72 to 70 and have used that load in many rifles I built and factory to kill many animals.
H335 is not as temp stable, and in a 223 if I found an extractor groove expansion threshold at 30 gr, I would back off the full Vernon Speer 6% safety margin to 28 gr as my usable max load for bolt actions and single shots. My non adjustable gas semi auto guns have addition constraints.
Hodgdon uses a lot of Winchester brass which has higher internal capacity. If you are not using the same brass, your max charge will likely be noticeably less. In my experience, Remington, Lapua, Norma, and Nosler brass have less capacity and will generally max out with less powder. Probably anywhere from 1 to 3-4 grains less. Just a thought.....check your brass against the loading data. 
All manuals, including Hodgdon's site, reflect the conditions on the day of the test using the exact components indicated. The bullet weight in the important pat, not the brand or the construction.
Hodgdon's 25.3 Max for a 55 grain bullet at 3,203 fps Max, will not bother your rifle. Hornady factory 55 grain V-Max ammo runs hotter than that. MV is 3240 fps.
"...start the next loads at .1gr?..." Begin with the Start load and go up by half a grain to the Max load.
Hodgdon's 25.3 Max for a 55 grain bullet at 3,203 fps Max, will not bother your rifle. Hornady factory 55 grain V-Max ammo runs hotter than that. MV is 3240 fps.
"...start the next loads at .1gr?..." Begin with the Start load and go up by half a grain to the Max load.
In my experience, this is the way it works. At or above max listed load, accuracy usually starts to get worse. You will see this clearly using the OCW method.
FYI, OCW is the method usually used for best accuracy at a given distance. Ladder loads are best for finding the ideal pressure node...
I'll admit that I was one of the guys saying 25gr is GTG or better yet good to approach slowly . After looking at Hodgdon and my Lyman 49th that has the 60gr V-max at 25.8gr max charge and the fact I shoot two loads at 25 and 25.5gr ( though AR's )
I'm going to keep with my statement that working up to the 25gr charge looking for pressure sings as you go should not be a problem . In situations where I'm not completely confident in the charges I'm about to approach . My load work up will be something like .5gr increments to the point the confidences starts to lessen . At that point I'll drop to .3gr and continue to max in the .3 increments .
So It would look something like this , 5 shots each
22.5
23
23.5
24
24.3
24.6
24.9
25.2
I'm going to keep with my statement that working up to the 25gr charge looking for pressure sings as you go should not be a problem . In situations where I'm not completely confident in the charges I'm about to approach . My load work up will be something like .5gr increments to the point the confidences starts to lessen . At that point I'll drop to .3gr and continue to max in the .3 increments .
So It would look something like this , 5 shots each
22.5
23
23.5
24
24.3
24.6
24.9
25.2
You know I keep forgetting you are shooting a 223 chamber AND you are using magnum primers . IMO the Magnum primers are not needed in a small case like the 223 but that's me . I see you get better groups using the magnum primers but that could be as simple as the magnums are giving that little extra pressure as if you are loading .5gr or 1gr more of charge weight .
Did you ever find your MAX COAL with the 55gr V-max ??? The fact you have a 223 chamber and use magnum primers . "IF" you proceed up past 24gr I'd want to be sure your seating depth is not close to the lands . At least .020 off but .040 would give me a little more comfort . I'd also consider going back to the CCI #400 if you're going to push past 24gr .
I did some testing of the exact same load work up . one set of loads using the #400 and a duplicate set of loads using #450 . Although the average velocities were about the same . I found the #450 had a larger ES/SD on the whole then the #400 did . Keep in mind this test was using an AR with a 5.56 chamber .
I have the notes somewhere . If you'd like I can dig them out and post them . Off hand I'm pretty sure the tests were conducted using 55gr FMJ-BT bullets and H335 .
EDIT :
I just found the data and the #400 grouped by far better then the #450 . Almost comically better . I have all the data including the targets if anyone wants to see .
Did you ever find your MAX COAL with the 55gr V-max ??? The fact you have a 223 chamber and use magnum primers . "IF" you proceed up past 24gr I'd want to be sure your seating depth is not close to the lands . At least .020 off but .040 would give me a little more comfort . I'd also consider going back to the CCI #400 if you're going to push past 24gr .
I did some testing of the exact same load work up . one set of loads using the #400 and a duplicate set of loads using #450 . Although the average velocities were about the same . I found the #450 had a larger ES/SD on the whole then the #400 did . Keep in mind this test was using an AR with a 5.56 chamber .
I have the notes somewhere . If you'd like I can dig them out and post them . Off hand I'm pretty sure the tests were conducted using 55gr FMJ-BT bullets and H335 .
EDIT :
I just found the data and the #400 grouped by far better then the #450 . Almost comically better . I have all the data including the targets if anyone wants to see .
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Clark :
I consider the chrono just another helpful piece of information to add with other info . We all know not to take one sign as being the answer . The more info you have the more accurate your conclusions "should" be
I have found a chrono helpful on more then one occasion telling me I might want to stop and look harder for other pressure signs. This was do to my velocities being much higher then they should be for a given load . On one occasion it ended up helping me see I was at or likely past max pressure . Other times it has showed I needed to change the battery
I understand there not the be all end all of signs but I do believe they can be a helpful tool for the reloader .
Case in point
These are the cases from the CCI #400 pimer test using 55gr FMJ-BT and H335
Cases on the right had a charge weight of 26gr of H335 pushing that 55gr bullet 3130fps from a 16" 1-7 barrel . The cases look good , primers not to flat but my velocity was telling me along with the charge . I was likely approaching pressures I'd better not go over . In these specific tests the 26gr charge was the largest charge I had so I never went higher that day or any day there after because of the velocities I was getting . Well that and my best group was 25gr
Another time
I have not been back to confirm this . How ever I "believe" my chrono the other day showed that my seating depth was not consistent with a 308 load . I was testing a new load and I had seated these specific bullets what I believed to be right at the lands . They should have been just touching them . While shooting over my chrono I had the worst ES/SD I'd ever had with an ES of 125fps . I was specifically testing seating depths that day and all other loads had a consistent ES/SD except the load that was supposed to be touching the lands . My thoughts right now on that is that the seating depth was not all that consistent as far as if the bullet was "in" the lands , "on" the lands , or "off" the lands . My thinking is some bullets may have been a little in the lands while others were just off the lands . Resulting in erratic velocities ??? what do you think ? I'm not sure what the issue was seeing how all the other loads were consistent , pressure seemed fine .
I consider the chrono just another helpful piece of information to add with other info . We all know not to take one sign as being the answer . The more info you have the more accurate your conclusions "should" be
I have found a chrono helpful on more then one occasion telling me I might want to stop and look harder for other pressure signs. This was do to my velocities being much higher then they should be for a given load . On one occasion it ended up helping me see I was at or likely past max pressure . Other times it has showed I needed to change the battery
I understand there not the be all end all of signs but I do believe they can be a helpful tool for the reloader . Case in point
These are the cases from the CCI #400 pimer test using 55gr FMJ-BT and H335
Cases on the right had a charge weight of 26gr of H335 pushing that 55gr bullet 3130fps from a 16" 1-7 barrel . The cases look good , primers not to flat but my velocity was telling me along with the charge . I was likely approaching pressures I'd better not go over . In these specific tests the 26gr charge was the largest charge I had so I never went higher that day or any day there after because of the velocities I was getting . Well that and my best group was 25gr
Another time
I have not been back to confirm this . How ever I "believe" my chrono the other day showed that my seating depth was not consistent with a 308 load . I was testing a new load and I had seated these specific bullets what I believed to be right at the lands . They should have been just touching them . While shooting over my chrono I had the worst ES/SD I'd ever had with an ES of 125fps . I was specifically testing seating depths that day and all other loads had a consistent ES/SD except the load that was supposed to be touching the lands . My thoughts right now on that is that the seating depth was not all that consistent as far as if the bullet was "in" the lands , "on" the lands , or "off" the lands . My thinking is some bullets may have been a little in the lands while others were just off the lands . Resulting in erratic velocities ??? what do you think ? I'm not sure what the issue was seeing how all the other loads were consistent , pressure seemed fine .
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