Power equivalent

[jr612]

Hey everyone, although this is my first post I've spent much time here reading and trying to learn as much as I can. I've been reloading for about 2 years now so I'm not new to this but I do have some questions. My main question is about reloading cb for my m91/30. I've read about the "universal loads" for .30 military rifles and that's what got me thinking. I've been using RX-15 with my 150gr spitzer rounds. I like RX-15 and have been looking into using it with a 200gr lyman 314299 cb. I read that 26gr of RX-7 is a good powder for that boolit, so I looked at the burn rates to see if RX-15 would work as well but that's where I seem to be missing something.

I guess what I'm asking is, how can I know how much of a difference in burn rates is too much for the powders to be considered interchangeable or equivalent? I hope this makes sense and thanks in advance. I don't like to deviate from published data so I'm a bit leery about trying this with out getting some advice first.

[runfiverun]

there is no interchange or equivelant.
even amongst powders of the same burn rate category they flip flop in burn rate depending on application.
you are applying pressure and gas volume to a bullet they are not the same.

you could use an equal peak pressure [in fact that's all you got] but you are not going to get the same results.
if it worked like that we would only have one powder for everything.
even black powder has different grades for different applications.
it has the same pressures but different gas volumes.

[ku4hx]

I feel certain more knowledgeable CB rife shooters will chime in, but in my 43 years of loading, I've never used burn rate tables to determine powder suitability. I've done my share of experimentation, with varying degrees of success, but I always start with published data. Pretty much always end there too.

Using burn rate to determine powder suitability and/or interchangeability is sort of like using BTU content to pick the fuel for my truck. I think I'll just stick with what's recommended.

[jr612]

So far the only published data I've found is in Lymans 48th edition but mentions nothing about using RX-15. So if burn rate is not a suitable means of determining what powder works, what is? Keep in mind that I don't have a chronograph.

[DrCaveman]

Jr612

This is a delicate issue, one which most here don't like to dive right into due to respect for others' well being. Unlike lawyers, I find the people here to care more about maintaining our ranks uninjured than to avoid lawsuits.

That being said, there is probably more information about experimental loads on this site than anywhere else. My attitude is that if someone else here hasn't tried it, it's prob not a good idea. I have violated that quite a few times, however, and let me say that I didn't come away with anything that I wasn't already warned about...here. No disasters, but also no groundbreaking new awesome insights.

There are burn rate charts that list powder equivalents (burn rate) instead of ranking everything against one another. I find this a bit more useful but you still must exercise caution and let go of any arrogant presumptions. Meaning: no max loads for uncharted territory. I'll see if I can find a link to the particular chart I am thinking of, it may provide some insight to RL-15 similar powders. Not equivalents, just similars.

[runfiverun]

rx-15 is reloader-15 or rl-15.
it's similar to other company's powders.
it's in the 4064 burn rate family.
it would probably do fair at 28-30 grs.

[DrCaveman]

Runfiverun

Is your new profile pic a dog? I know it is the obvious guess but I am honestly not sure. Looks half cat, half dog, half raccoon.

Dang cute. And fierce.

[wv109323]

RX-7 and RX-15 is two powders made by the same company. They may overlap some but there is enough difference that they produce the two powders. I would stick with published data.
I would go to the manufacturer's web site to see if they have published data for what I would like to load.

[runfiverun]

yeah a puppy.
i should start a thread about it.

[jr612]

rx-15 is reloader-15 or rl-15.
it's similar to other company's powders.
it's in the 4064 burn rate family.
it would probably do fair at 28-30 grs.

I had a feeling this was so because much of the load data for IMR-4064 is very similar to that of RX-15


RX-7 and RX-15 is two powders made by the same company. They may overlap some but there is enough difference that they produce the two powders. I would stick with published data.
I would go to the manufacturer's web site to see if they have published data for what I would like to load.

I've looked and looked over my manuals hoping to find somewhere were they have data for both powders side by side but have yet to find anything. I'll keep looking though.

[waksupi]

Lamar, are you sure that's a dog? I thought it was a punk rocker gopher!

[runfiverun]

i think so,,, little girl put it on.
he's plenty pissed though.

[DrCaveman]

Id bet that the lions share of possible 7.62x54r loads has not been published in manuals. A little, sure, but this is a cartridge not explored by the masses due to (previously) cheap milsurp. Of course there are many within this site who have in fact tried & developed good cast loads with said cartridge. Just saying that if printed, reputable recipes are part of the requirement, you will prob sell yourself short.

Listen to runfiverun, try his suggested load. I trust that guy.

[MT Chambers]

You will note however that not all powders in that burning rate work as well with reduced loads ie: ball powders.

[runfiverun]

the good thing about a lot of cast loads is that there is not a lot of data.
the good thing about most low and medium vel cast loads is they are lower pressure.
sometimes you have to do like the lee manual does and extrapolate a little data from a similar sized cartridge.
if you look and find a load that is acceptable in the 308 and the 30-06.
you can be assured it will be safe in the 303 brit,the 7.7 jap,the 7.65 argie,the 7.5x55 swiss,and the x54-r case also.
sometimes you can/need to trick the powder into thinking it is being used in a smaller case by using a filler.
the filler is only needed when you are having vertical stringing,
this is really velocity variations and the filler is patching that up.

[jr612]

sometimes you have to do like the lee manual does and extrapolate a little data from a similar sized cartridge.
if you look and find a load that is acceptable in the 308 and the 30-06.
you can be assured it will be safe in the 303 brit,the 7.7 jap,the 7.65 argie,the 7.5x55 swiss,and the x54-r case also.

That's exactly what I did. After thumbing though my manuals I was able to find some load data for .30 cal cartridges which had both rx-7 and rx-15. The ratios were all within .2gr. So based on that published data I can conclude that a by adding 6.3gr to the rx-7 load I should have a usable load for the rx-15. It looks like you were spot on with your 28-30gr recommendation. You sir are the man.

[DrCaveman]

You will note however that not all powders in that burning rate work as well with reduced loads ie: ball powders.

While I still trust run's suggested load, mtchambers brings up an excellent point, one which I need to learn more about...or rather, commit it to memory. Powder grain shape makes a BIG difference in load options and suitability. If you are gonna make powder substitutions based on burn rate, make sure both powders are the same shape.

On another note, I now understand why my 91/30 was all sloppy with cosmoline when I got it. Just pulled out my brothers gun after sitting for about 16 months, and apparently he didn't clean it the last time he shot, and I know he shot some silver bear. Prob also shot some of my corrosive Russian milsurp.

Black barely describes the bore... Have you ever been spelunking and had everybody turn off their lights for a fun minute? That's what I experienced looking down the bore. Of course there was a faint glimmer of light from the chamber end where my light was shining, but you get the idea.

Spent about 45 minutes soaking, scrubbing, and cleaning, repeat. Looks like I am about halfway there, I can finally see metal. I think I need to man up on my solvent strength.

Don't forget to oil that bore when done cleaning! Also don't trust your little brother to clean his own gun ;)

[runfiverun]

that's where things get tricky, a lot of ball powders do not reduce well.
and some of the same group do.
the 4350's for example, bad idea to reduce them [except accurates 4350 does pretty well]
aa-2230 has given me outstanding results reducing it in most cartridges.
and their 1680 has shot some teeny little groups in the 0-6 for me.

others like aa-2700, H-414, and wins 760 are more in need of a case full of powder with a bit of compression.

dr. a box of paper patched rounds down the barell will scrub it shiney again.