Question about changing powders

You might get lucky but I would start at the starting load and work my load up you may even find a better load than what you got now

Sounds like a reasonable plan, and benchmark is on my list to test. Each powder having it's own character I hope it turns out to hammer for ya.

The only flaw in your thinking is that it may not work at all. Then again, it might.

The velocity as a bullet leaves the barrel is not a major determiner of the accuracy of a particular load or load development would be easy. The characteristics of the burn rate and pressure curve of a power charge, along with the bullet scraping its way down the barrel in response to that pressure curve makes the barrel vibrate, not the final velocity obtained. Now that doesn't mean your plan won't work, but the only way to know is to try it and see. I'm curious to know how it goes, so post your results.

Benchmark is - by the relative burn charts - a faster powder than H335. However, the Hornady book (and likely others) have data for Benchmark in the .223 Rem and a 40 grain bullet. The same book shows the H335 giving about 200 fps faster velocity. But if you do everything by the rules, you will not get hurt. Will it be better or worse accuracy? I'm just an old man, not a seer.

buy a chronograph and work up the loads with the new powder like it is your first time.

Problem with trying to match velocity without regard for load data (not that you were proposing that) is that some powders can safely produce higher velocity than other powders when each is loaded to maximum recommended levels. So if your "try to emulate this" load is near max with a particular powder, and the max recommended load of another powder doesn't produce the same level of velocity, you may be tempted to exceed max trying to chase identical velocity.

If you work up your new load by the book, you may find a load that shoots as well as your "baseline" load, but the velocity may be different (or it may not).

Well stated.

Aletheia said:

The velocity as a bullet leaves the barrel is not a major determiner of the accuracy of a particular load or load development would be easy. The characteristics of the burn rate and pressure curve of a power charge, along with the bullet scraping its way down the barrel in response to that pressure curve makes the barrel vibrate, not the final velocity obtained.

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The velocity in most reloading manuals is useless because you will never shoot that same bullet, through the same barrel, with same same atmospheric conditions. The load data is only helpful for you to identify max/min powder charges.

if you don't have a chrono, I would suggest googling the OCW method. Many of the top competitors in long range shooting use this method to identify accuracy nodes for a given powder and bullet.

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

There is a lot of information on this method if you google it. The idea is that you will find a velocity plateau of .5-.6 grains where an increase or decrease in powder wont change the POA (meaning the velocity is not changing. Once you find this node, you choose a load in the middle for your powder charge. Then, if you need to, start adjusting your seating depth and neck tension to tighten up the groups.

What is important to understand about this method, you are not looking for the tightest group initially. You are just looking for a set of consecutive groups whose POA (center of group) is approximately the same.

I found this method extremely helpful in developing my loads quickly. Hope it helps you.

For me, this is a major factor in handloading; trying different components and working up a load. Yes, powders burn differently at different speeds and temperatures, bullets even of the same design weight and shape will preform differently but I don't think there is any downside to experimenting with different components, using manual guidelines of course, and there are even "scientific" methods of testing the loads. I would probably not reload if I was limited to one powder, one primer and one bullet. That would be really boring...

Good choice on the 8lb of Benchmark. It's all I use in 223 anymore.

I rarely get best accuracy with max loads but I've found 40's and Benchmark are the complete opposite, in my guns anyway. Every 40 grainer I've tried performs best close to max or at max.

I'm thinking the best way to get an accurate load using the same bullet and same rifle would be to try and find the powder charge of Benchmark that duplicates the velocity of the load I have with H335.

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I concur.

In the "mini-drought" of reloading components in the early-1980's, I had trouble getting power. I ended up developing a .223 Remington load that would hit the same aim-point using IMR-4198, IMR-3031 or Winchester 748. I suggest you work out a Benchmark load that delivers the same velocity and point of impact as your prior loads. The knowledge that you can pick up any magazine and know it will hit the same spot on the target is a quality all its own.