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Reloading for reduced case volume cases?

3K views 23 replies 10 participants last post by  68c15 
#1 ·
I keep asking this but I’m not getting any answers:

If the case you use for a load is smaller in capacity (as measured with water and compared to the SAAMI specification for case volume) can you just reduce all the loads in a reloading manual by the percentage difference in volumm?

The specific situation is 7.62 x 39 RWS cases are smaller than SAAMI spec’s by about 8%. Can I just reduce the starting and max loads by 8% and still be safe and expect the same result as if the case volume was not reduced?

Opinions are not needed by the unknowing. I need an expert’s opinion based on facts as he knows them. Any experts out there?

I emailed Hodgdon but got no response back, yet.

The RWS brass is excellent brass but the walls must be thicker as the case volume does not match SAAMI. Even once fired cases resized are still undersized internally. I have 300 of these cases so discarding them is NOT an option. RWS cases were the only ones I could find new.

LDBennett
 
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#2 · (Edited)
I have to thank Joost van Leeuwen for running the software QuickLOAD against my problem. He ran several cases for both H335 and IMR4227. My need was to determine if my 8% reduction in the listed loads in reloading manuals caused excessive pressure in my reduced volume RWS 7.62 x 39 Russian cases. He ran the program for both powders. In a nut shell, reducing the loads by the 8%, that is the case volume reduction, I found I did not exceed the listed max pressures. In addition:

1). The velocity I would get from a 99% fill of my cases using H335 gives less velocity that a 92% fill of IMR4227. At 92% fill the IMR 4227 does not invade the bullet space. H335 is off the table as a choice of powder.

2). My 20.5 grains load of IMR4227 (39,456 psi) does not exceed the the max pressure allowed (40,900 psi) by Hodgdon.

3). I certainly do not want to use more than 20.5 grains of IMR4227 as it I will exceed the Hodgdon max pressure allowed.

4). By using an 8% reduction from the listed reloading manual loads (which is the reduction in case volume) I stayed under the max pressure listed by Hodgdon and my loads are safe.

As it turns out in my first attempt at load development that the most accurate load was the 20.5 grains of IMR4227.

I thank Joost again for the printouts of the results and his help in assuring me I am not creating over pressure loads.

LDBennett
 
#4 ·
I took a chance using the 8% reduction in powder volume and got no signs of excessive pressure in over 100 loaded up rounds. But that means nothing as pressure signs can be impossible to read. How flat is flat when it comes to primers??? When you get discernible signs of excessive pressure you are usually WAY over pressure. Getting this data from this program, which he calibrated with listed Hodgdon data and pressures, is reassuring. Anyone doing wildcat cartridge load development NEEDS QuickLOAD!

Anyone who wants to see the printouts which have a huge amount of data on them can PM me and I'll email them to you. They need to be studied to realize the implications.

LDBennett
 
#7 · (Edited)
"Opinions are not needed by the unknowing. I need an expert's opinion based on facts as he knows them. Any experts out there?"

I was about to thank you for the question and the research you have done so far, until I read this. IMO this forum is basically an entry level question/answer type forum and to ask for "expert opinion" only on "advanced ballistics" is silly (or showing off?)...

Try here; http://www.shootersforum.com/ballistics-internal-external/
http://benchrest.com/forumdisplay.php?6-Centerfire-Benchrest
http://forum.accurateshooter.com/index.php?board=21.0

I'm sure there may be an "expert" on one of these forums.
 
#8 ·
mlkld:

This forum is open to anyone. I included that statement to avoid getting opinions. I wanted facts not opinion. In the end I got an individual that was well versed in a piece of software I was not aware of, QuickLOAD, that gave me facts not opinion or wild guesses. My concern was to avoid going over the accepted pressures for this round so as to avoid damage to my gun or me. A guess by the less knowing does not assure that.

How else am I to avoid getting a bunch of opinion not based on fact unless I ask for an "expert"? If you could not offer facts then I did not want to hear from you or anyone else that had opinions on this topic. My search for an "expert" on this forum was not in vain. I got my factual answer.

Perhaps "expert" was too harsh. All I wanted was no opinion and only facts. As you can see by the few responses I avoided the opinions. The responder contacted me via a personal message and email. I posted his results for those interested to see. Sorry if it offended you.

LDBennett
 
#9 ·
We have all levels of expertise here, from entry level to expert, and questions and answers on all levels.

Glad you got your answers. I'll have to check that QuickLOAD software out.
 
#14 ·
"In the end I got an individual that was well versed in a piece of software I was not aware of, QuickLOAD, that gave me facts not opinion or wild guesses. "

^ this is the statement that concerned me. I've had several of my calibers ran through quickload and the data it predicted was well above any other data I've seen. Again, quickload data should be approached with caution just the same as any other source of load data.
 
#15 ·
To be clear the H335 data was first compared via the software to standard case and load data from Hodgdon and it matched. Then IMR4227 load data was compared to standard case and load data from Hodgdon and it matched. Both loads where then run in the software with my bullets and the reduced volume of my cases for both H335 and IMR 4227. The H335 load showed you could not get enough of that powder in that reduced case volume to make a useable load. The IMR4227 gave the best result in the program and showed that the pressures did not exceed the limit presented by Hodgdon.

On top of that I had already shot the 8% reduced from max IMR4227 load by working up from a starting load almost 2 grains less than that load I eventually found to work best in my gun. At no time were there any signs of excessive pressures.

But that software is better than someone's wild ass guess or opinion.While not really "fact" it is better than a guess considering what the provider did for me. I, of course, would have liked a Ballistic lab to check the load for me but since there is none anywhere close to me and that effort would be a bit over top for this case I chose not to pursue it.

In conclusion, I started with a reduced load to accommodate the reduced case volume. I made up loads from several grains less than the calculated max load and worked up to the calculated max load which accommodated the 8% case volume reduction. I found no signs of excessive pressure. To validate the safety I got the software calculation that showed the pressure low enough to be safe and discounted H335 as an alternative.

Now, how much safer than that can I be??? Is someone's opinion or guess worth more than what I did? Why should I not state I did not want opinions (for which someone got upset about)? I wanted to avoid opinions. I have my own which I had already exercised. Validation by software seems perfect in my situation.

If I were developing a wild cat cartridge with no place to start even my effort would probably be a little short of totally safe.The software might give you a good place to start. But that is not what I did. I took reloading manual data, reduced it by 8% to accommodate less case volume of 8% and tested it from a safe starting load. Validating it with software is frosting on the cake.

LDBennett
 
#17 · (Edited)
To be clear the H335 data was first compared via the software to standard case and load data from Hodgdon and it matched. Then IMR4227 load data was compared to standard case and load data from Hodgdon and it matched. Both loads where then run in the software with my bullets and the reduced volume of my cases for both H335 and IMR 4227. The H335 load showed you could not get enough of that powder in that reduced case volume to make a useable load. The IMR4227 gave the best result in the program and showed that the pressures did not exceed the limit presented by Hodgdon.

On top of that I had already shot the 8% reduced from max IMR4227 load by working up from a starting load almost 2 grains less than that load I eventually found to work best in my gun. At no time were there any signs of excessive pressures.

But that software is better than someone's wild ass guess or opinion.While not really "fact" it is better than a guess considering what the provider did for me. I, of course, would have liked a Ballistic lab to check the load for me but since there is none anywhere close to me and that effort would be a bit over top for this case I chose not to pursue it.

In conclusion, I started with a reduced load to accommodate the reduced case volume. I made up loads from several grains less than the calculated max load and worked up to the calculated max load which accommodated the 8% case volume reduction. I found no signs of excessive pressure. To validate the safety I got the software calculation that showed the pressure low enough to be safe and discounted H335 as an alternative.

Now, how much safer than that can I be??? Is someone's opinion or guess worth more than what I did? Why should I not state I did not want opinions (for which someone got upset about)? I wanted to avoid opinions. I have my own which I had already exercised. Validation by software seems perfect in my situation.

If I were developing a wild cat cartridge with no place to start even my effort would probably be a little short of totally safe.The software might give you a good place to start. But that is not what I did. I took reloading manual data, reduced it by 8% to accommodate less case volume of 8% and tested it from a safe starting load. Validating it with software is frosting on the cake.

LDBennett
I agree that you took the proper approach for the situation you had. There's no disputing that. My comments weren't aimed at you, they were aimed more to potential future readers.
Again, a normal quickload projection will yield higher charges than hodgdon, Hornady, nosler, etc. I just wanted to point that out for any new hand loaders that read this thread.
 
#18 ·
Funny, when we compared the QuickLOAD results with reloading manuals they pretty much matched. There are a lot of variables and get one wrong and it may throw the results off. If I had a new wild cat and ran the program Id start low and work up to the info from the program.

LDBennett
 
#20 ·
68c15:

I did not mean to exclude you or anyone from viewing the problem (and the results). I just did not want a bunch of opinions since every one has one. I hope you learned something from my post. I knew the reduced volume, just like military cases, requires reduced charges. Everyone knows that and I did not need to get that opinion many times. It really worked as no one respond with an opinion until I published the results from Joosh who responded with a personal message and subsequent email correspondence.

Then someone got bent that I asked for expert advice and not opinions. Then others offered up that the software was flawed when Joosh ran test runs using data from a reloading manual to calibrate the software. I explained all that and even offered, to anyone that wanted them, screen shots of every software test he ran. And I still got the comments about the software. Joosh was super thorough and did exactly what I would have done if I had the program. And we were coming in with data from shooting that said that the pressures probably were OK. But I wanted validation which the calibrated software gave me. I had no idea software like this had progressed to the level I saw when I reviewed the result. I was familiar with an older crude mathematical process from an old NRA book but thought it too cursory.

The internet can be a wonderful information supplier but it can also bring out unwanted or unneeded comments from what amounts to anonymous poster (Unless a person uses their real name, as I have from day one, they are anonymous). Perhaps the warning about the software giving hotter loads than expected was needed but I took it that the software validation we did of my loads was inaccurate and unsafe.

Sorry about the rant but I try to help people understand and there is always someone who makes negative comments. But I come to help and I'll not be stopped in that effort. A little bitching clears the air for me.

LDBennett
 
#21 ·
Thanks for the great research, LD. My first thought when I started following this thread was that, since the pressure is directly related to the mass of powder burned and the volume available for expansion of the gasses produced, this should be a no-brainer. But it's really not a linear relationship. Some powders burn faster when the pressure increases, some slower. It's hard to predict, even with good software and validated models. This whole discussion has been a good learning experience for me and others. :)
 
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#22 ·
rawright54:

I too thought it might be P1V1= P2V2 where P is pressure and V is volume. I thought that the pressure was directly related to velocity. But that is too simplistic as the pressure is an impulse not a steady state condition. It turned out that linearly reducing the powder charge by the 8% reduction in volume still left the pressure in the safe area but a little more powder and that may have not been true. I think the quickLOAD software gives results that are usable to a point but you still must start low and work up the powder charge watching for pressure signs. It was helpful that Joosh calibrated the software against listed Hodgdon data and got a match. This all validates that my loads in the reduced volume cases are safe. That is all I wanted to do.

I also wanted to see if H335 was an alternate choice which the software showed it was not. You could not get enough H335 in the reduced volume case to match the performance of IMR4227 because of the reduced case volume. I eliminated all the other choices from the Hodgdon Reloading Center Data as I could not find any for sale in my area. I had the IMR4227 and H335 (a favorite powder of mine).

It's too bad the brevity of this thread was ruined by those being critical of the process and my attitude and all the excess explaining I had to do to justify the process and the results. But hey, that's the internet for you. I'm glad you got something out of it.

LDBennett
 
#23 ·
I had no problem not commenting on this until you got your answer. I am a novice reloader and couldn't be of any help on this. As my dad always said no one will know how dumb you are until you open your mouth.
 
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