Max powder charge or max Velocity

[2clicks]

When working up a new load which do you regard as most relevant? Max velocity or Max powder charge?
Example:
Sierra's manual may say
1-7 twist colt AR15 69gr smk 25.5grs Rl 15 @. 2,800 Fps max

Do you load to 2,800 Fps and stop even though you your powder charge might only be 24grs or do you load to 25grs even though the velocity might be 2,900 Fps? Yeah I know all the different variables play a part but generally I've loaded to about 50fps less than max velocity, but recently realized that twist ratio in manual test rifles are 1-7 twist so in my 1-7.75, 1-8 &1-9 twist barrels I might be shorting myself on some higher velocities in my slower twist barrels... Thoughts and experiences appreciated

 

[steve123]

Re: Max powder charge or max Velocity

Google "ladder test" or "OCW test".Load what your rifle likes.

Every rifle is different,even two of the same.

 

[Bacarrat]

Re: Max powder charge or max Velocity

Neither. I load for max accuracy. And what it says in the book is what their combination is. Most of the time, it's not what your combination is.

 

[2clicks]

Re: Max powder charge or max Velocity

Yeah I got all that, I just did a ladder test for my Eliseo RTS GAP 260 yesterday and out of 10 shots got a 1" 3 shot group in the sweet spot at 600 yrds seemed like 43.3 grs of H4350 and a 140 Berger at about 2850 FPS is the ticket. One side note even though the numerical sequence is off on the group the recorded velocities are near identical for the 3 shot group even though the charges were .3 grains different.

Posted those for any non believers.

Also I can clean the 300 rapid fire stage of the NMC with 23.5 IMR4895 load with a 68 Hornady BTHP. That load is around 2700 fps. I guess I can just load em til the primers flatten and if they hold good groups at 3200fps its cool??? Probably not.

I'm looking for an explanation of why that would be safe or wouldn't be safe for an Ar. Like I said I have 3 ar's and each has a different barrel twist ratio and of course none of their accuracy nodes will be exactly the same. But there must be a reason Sierra used a 1-7 twist for their testing maybe they realize the fastest twist crates the most chamber pressure therefore any max load they publish will be safe in any other version of ar barrel with a 1-7 or slower.

EXCEPT my Hornady manual uses a 1-9 twist Ar-15 and their max loads MIGHT create unsafe pressure in my 1-7.75 Krieger match rifle for their published max load.

So in the quest for some indepth understanding, which MIGHT be the better indicator of the safe chamber pressure? Max velocity or Max powder charge. Somebody has to know one should have more bearing on the situation than the other. I've been at this Ar shooting game since 1989 Parris Island, And I've been reloading for Match rifle shooting for about 12yrs. I guess I'm looking for a bit more of a detailed explanation of which is the better indicator and why.

Thanks Gents...

 

[TexIndian]

Re: Max powder charge or max Velocity

As a safety factor, I stop adding powder when my velocities reach those I see listed for max pressure loads in the reference manuals. My chamber may be tighter, etc, so when I see my velocities equal the test loads, I figure my pressures are about the same, too. (Obviously, I look for pressure signs even before I get to the test velocities.)

For me, max pressures and velocities are things I consider only for safety purposes. Like Bacarrat said, accuracy is what we look for, and the key to that is consistent velocities, not max velocities.

 

[rcamuglia]

Re: Max powder charge or max Velocity

What a handloader needs to do is load test ammo from a chosen, known to be safe, starting charge of powder. Incrementally increase the charge for each case or set of cases depending on what kind of test you like to do. Load test ammo even past published maximum loads. You don't have to shoot them.

Shoot the rounds from lowest charge to highest while carefully looking for signs of over-pressure. Ejector plunger mark on the case head, sticky bolt lift, etc.

STOP SHOOTING the test ammo as soon as a case is fired that shows pressure signs. That load is max for YOUR rifle.

All rifles are different. Published max velocities and max charges are general guidelines for safety. Some barrels are "slow" and some are "fast". Chronographs are not foolproof. Stopping once you hit a "published velocity max" even though you are under the published max load with no signs of over-pressure may be stopping too soon.

Stop when you find pressure and load for accuracy beneath that threshold.