Why am I getting my best accuracy at or near max charges?

[IMtheNRA]

I found a few loads that my handguns seem to like and most of them are at or close to maximum published charges in 9mm and .44 mag. I don't mind using up a bit more powder to make quality ammunition, but I'm wondering why I have better luck with warm and hot loads than I do with mild ones. Any ideas?

 

[ArchAngelCD]

IMO it's because the published Max charges today are middle charges from yesterday. The mild (starting) charges of today are too low for most calibers and thus inaccurate.

 

[IMtheNRA]

I was wondering about the physics of this phenomenon. What happens to make the point of impact of these loads more consistent?

 

[caz223]

From what I've seen it isn't how hot the load is, but where the bullet is in relation to the powder.
I've had the best accuracy when the powder is from 3/4 full to where the powder alllllllmost touches the bullet base. I've previously chalked it up to powder curve and/or position sensitivity.
Who knows?

 

[Hook686]

The Shadow Knows !

 

[41 Mag]

In some cases the extra pop received by the base of the bullet allows it to actually flatten and fill the groves a bit more giveing a better seal and better grasp of the rifling. This is especially true of a lot of the cast bullets. This will in effect give better accuracy to some loads.

If you slug your barrel and then measure against a new jacketed bullet this might give you an indication of which bullet would be more accurate at a lower velocity or load. Also just due to the fact that a jacketed bullet has a diameter stamped on the end of the box doesn't mean that it will always measure out to that exact diameter. Some are in fact a few thousands under which sometimes depending on the actual bore of your barrel will be significant enough to make a difference. The bullet makers have acceptable tolerances on their products just as do the barrel makers.

 

[Crimp]

It's not always the case. For instance, Nosler's Reloading Guide lists a min, mid and max load for each of the powders. They place an asterisk near the load that has the best accuracy found for that powder and bullet combination.

Here's some of the data on the listing for their 185gr JHP:

Bullseye - *min
AA #2 - *min
Green Dot - *max
W231 - *max
SR7625 - *max
AA #5 - *min

The only possible 'gotcha' I found in this system is that HP38 is also listed and has the asterisk beside the minimum load. That seems strange, as we're told that HP38 is the same powder as W231. Perhaps the tester shot W231 in the morning and HP38 in the afternoon - after a liquid lunch?

 

[Walkalong]

It can depend on burn rate and which powder as well. You need to get whatever powder you are using to a pressure it performs well at. Lets say you are shootng the .45. You may get great accuracy with AA #5 at max .45 velocities, but not quite as good at lower levels while you can take AA #2, Clays, WST, etc, and get outstanding accuracy at lower velocity levels. Lots of things come into play obviously, but I think this is overlooked at times. The right powder for the right app. That is one thing folks like about W-231 and the .45. It gives very good accuracy over a wide range of velocities in the .45. Very easy to find a good load with W-231 in the .45.

 

[ranger335v]

"I was wondering about the physics of this phenomenon."

Each powder burns "best", or more consistant within a certain pressure (tempature) range. While going too far will raise pressures too much, going lower than the ideal range will produce inconsistant pressures. That makes for inconsistant velocities and accuracy. Simple physics at work.

To reduce the velocity and recoil of your rounds use light charges of a faster powder to get more consistancy, not lighter charges of a slower powder.

 

[K3]

There's also the issue of barrel harmonics. IIRC, there was a pretty good thread on it with a link to some serious info.

 

[SSN Vet]

To reduce the velocity and recoil of your rounds use light charges of a faster powder to get more consistancy, not lighter charges of a slower powder.

so it was worth getting out of bed this a.m., as I learned something new (and practical).

 

[Virginian]

When I shoot cast bullets, which is a lot, I will usually finish with ten wax gas check loads. I started this because it takes out any leading that might happen. I have found that with some loads, especially with lighter bullets, it appears that I get slightly better accuracy with the wax checks. My theory is that is takes up some free case volume. I have no empirical proof however.

 

[moosehunt]

If you are referring to lead bullets (you didn't say) it could very well have to do with bullet hardness. A harder cast bullet requires more preasure to properly obturate. I had exactly the same issue with a .44 Mag and purchased cast bullets. If I cast softer bullets (less antimony and tin), then I could get the good accuracy with light loads, otherwise, with the harder "store bought" stuff, I had to stay up pretty high on the power scale. The bullets sold as "Coyboy" are softer and usually obturate at the lower preasures. I got the softer bullets by adding pure lead to wheel weights, thus lowering the ratio of antimony, which of course is the primary hardening agent. But, remember, if you get some softer bullets, be forewarned that if you load them hot, you'll likely get a lot more leading. So, try some softer bullets for the lighter loads, but use hard bullets for hotter stuff. Could well address your issue.

 

[IMtheNRA]

Wow, thank you for all this great info and insights. BTW, I use jacketed bullets only.

 

[Steve C]

Hand load accuracy is where you find it and is often specific to the gun. Change guns or load components and your results will likely vary.

I've often found that as the load gets hotter and pressures get higher you reach a point where the velocities become more consistent over the chrono as measured by Standard Deviation. Load manuals generally set their max load at a point where if loaded beyond that level the pressures, velocities and accuracy becomes erratic and not necessarily the "maximum" SAAMI allowable pressure.

 

[Grizzly Adams]

There are to many factors to say that its the powder charge alone. You could possibly change one component, such as the brand of primer, in your load and find that a much lower powder charge will be more accurate.

 

[kennedy]

I found the same thing in .308 rem 700, with 150gr matchking bullets the min load is most accurate, but with 168 gr the max works best, I am using H4895 powder. go figure?

 

[okeybug]

They used to tell us your best accuracy would not come from full power loads. You would get the best accuracy if you reduced your load by a grain or two. Due to fear of law suits, reloading companies have purposely reduced full loads. Just check out the older manuals and your see I'm right. Plus some of those power loads might not work in old guns not made for powerhouse loads

 

[Run&Shoot]

Besides bullet base expansion and optimum pressure/burn rate I think another factor is consistency.

The more powder you have the less effect a .1 gr variance will have, right? So a 20.0 gr load will be less affected by a 0.1 gr variation between cartridges than a 4.0 gr load.

This principle works somewhat between powders as well as ranges within one powder.

The less percentage of variation the more consistent the pressure and velovity, resulting in better accuracy.