Best Powders: Short Barrel 270+280AI

[Unckebob]

I am the proud owner of two rifles I assembled that have 20" barrels. One is a 270 (cheap to shoot and plenty for deer) and a 280AI (exotic project). Normally, I would look at reloading manuals and start with the temperature stable powders with the best velocities. But, I suspect the best powders for velocities in a 20" barrel may not be the same as the best powders with the 24" barrels used for developing the book loads.

I have some H4350, H4831sc and Staball 6.5 on hand, and I would be willing to try to find other suitable powders assuming they are availabl.

Considering the cost of components, what powders would be "most likely to succeed" in a 20" barrel? With only 20" of barrel to work with, velocities matter,

 

[onlybrowning]

What bullet weights in each?


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[Dman86]

I really like 7828ssc in my 280ai. I also tried Reloader25 and IMR4831 but ran out of case capacity before hitting pressure. 7828ssc gives good velocity with small kernel sizes.


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[Dman86]

I may be oversimplifying things, but my powder selection process is now looking up the powders available to buy on the quickload sheet I attached. I choose the one with the best velocity and between 100-105% case fill. The reloader 25 shows good velocity but gets there when the case is filled 111% full which in real life means you are crunching powder a couple grains before that max load. The 7828ssc gets good velocity at 103% which is right around perfectly full with a seated bullet or slightly compressed. Understanding the case fill% column was a big lightbulb moment for me in powder selection.

 

[Dman86]

It looks like I accidentally posted the file for 180eld-m. I can’t see the full file names on my phone. One of these two is the 162eld-m. The main concept though is look for a powder with good velocity at realistic case fill%.

 

[Unckebob]

What bullet weights in each?


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150s & 160s

 

[onlybrowning]

150s & 160s

I think I’d start with H4831sc and go from there. Since you have H4350 on the shelf, I’d try that too.


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[Orchemo]

7828 SSC gave me very good velocity with 150 gr and small ES.

Also 7828 SSC had less muzzle flash than 4350

 

[BrBa]

For your 280AI, the faster burning powders like H4350, RL16 and N555 should have a complete burn in a 20" barrel. I haven't played with Staball 6.5 but that's a similar burn rate. RL17 might be worth a try if you don't mind some temp sensitivity.

H4831SC is known for small groups but not top end velocity.

 

[wyosam]

I’d just try both H4350 and H4831 with both. Either will probably work just fine, might get a touch more velocity with 4350, but probably not enough to make a real world difference. I’ve just never been impressed with StaBall. Regardless of marketing, its far from temp insensitive, just less so than traditional ball powders. Pretty dirty, too.


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[35WhelenAI]

Find the safe load that shoots best for accuracy and consistency, and if it's an appropriate powder to begin with, it'll get a good velocity. In the same vein, if velocities matter, a few more inches of barrel length to begin with solves the problem. The powders you name are all in the ballpark for being appropriate.

Faster or slower powders do not care what barrel it's in, it's all burned up and pressure peaked well before it gets anywhere near the muzzle. All you will get with a faster powder is less muzzle flash from less powder burning overall.