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Similar burn rate

 
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  #15  
Old 08-25-2013, 07:40 PM
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Re: Similar burn rate

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Originally Posted by Lefty7mmstw View Post
The biggest problem with a closed bomb test chart or even a simple powder rate chart is there isn't any real world data there to differentiate how powders act while being constricted differently, how much load is on them, how much pressure you will hit at peak, etc..
A good example of two rather similar powders having differing burns in different calibers is rl22 and I7828. In my 7rem they are similar with 7828 acting slightly faster with mid weight bullets. In my 300 win I 7828 is slightly slower burning than rl22. In my 270 using identical charges (on the run up) of I 7828 and rl22 (since the books do) a top charge of rl22 loosened a primer pocket while I 7828 is a 1/2 moa load and well within pressure bounds. I've fired 200 of them in the last few years.
A burn rate chart can get you in the right class of powder, but using it to approximate charges is downright foolish. A better route is to find data in a slightly smaller cartridge or data with a slightly faster powder and consider your starts from there. You need the constriction and basic loading of the powder to make any sort of educated guess. Also do not substitute ball and stick powders as the bullet weight and pressure slow the two powder types down differently.
I am not saying the chart is perfect and can give me an accurate way of predicting min and max loads. In fact, this chart lists H4350 as a slightly slower powder than RL17 and my experience in my 300 WSM showed the opposite. RL17 gave me the same pressure signs that 1 gr less of H4350 did with same bullet, primer, etc.

However, knowing that RL17 was "similar" to H4350 gave me something to work with. At the time there was zero published data for a 180 gr bullet. Alliant had 165 gr bullet data which also gives something to work from. So i started about 10% lower than the listed max H4350 data showed and I ended up exceeding that by about 2 gr.

I am not saying that you can map and swap powders based on a burn chart. I am saying you can use them as a guide to determine a reasonably safe starting point.

Let's consider RL33. There is not a shred of data out there as far as I know, yet Alliant has been selling it for over a year and it is not to be found laying around on any shelf. Folks are buying it by the truck load and using it.

Based on info I've read in this forum as well as some other searches I did and comparing to similar powders in the same cartridges, I came up with some reduced break-in loads for my 300 RUM, 6.5 WSM and 6-284. My velocities were right in line with what might have been expected for those loads.

You gave an example of powders with available data. What would you do if you wanted to experiment with RL33?
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  #16  
Old 08-25-2013, 11:37 PM
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Re: Similar burn rate

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Originally Posted by Iclimb View Post
Thanks for the info. How so?
Short answer, both nitrocellulose (found in single base propellants) and nitroglycerin (found, in addition to nitrocellulose, in double base propellants) are high explosives. This means they detonate (the flame front when they burn moves faster than the speed of sound through the substance).

They are stabilized for use as smokeless propellants, so that they deflagrate (flame front moves slower than the speed of sound) instead, when used in a firearm.

Under certain conditions, they will revert to detonating, and this can damage/destroy your firearm (and you). One condition that has, VERY RARELY but not zero frequency, been demonstrated to cause this is a slow burning powder that is loaded under the minimum charge. It happens infrequently enough that it is very hard to characterize, but often enough that we know it CAN happen.
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  #17  
Old 08-25-2013, 11:38 PM
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Re: Similar burn rate

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Originally Posted by MontanaRifleman View Post

You gave an example of powders with available data. What would you do if you wanted to experiment with RL33?
I have run up rl33 in the lh 7stw and lh 300 rum with heavy bullets. I did comparisons vs. retumbo and other similar powders available and used their data with the 7stw subbing in the 171 barnes for the 175 speer. What I found with the 171 wasn't spectacular, with my rifle eating 82 and 84 grain charges and being slightly over-pressure (slightly heavy lift and flattened primers without loosening pockets or deforming the head) with 86 grains. The accuracy wasn't terribly great, but I suspect that is my rifle's 10" twist with the long hp style bullet. My rl 50 groups, rl25 groups, and retumbo groups also confirmed the edge of stability also with the 171 barnes, with ammo turning in .25 moa at 100 one day (with rl25 mostly) and 2 moa + from the same box of ammo another day. With all the messing around with the lh stw, I've already got 300 confirmed holes in paper (saved targets) with another 100-200 rounds fired on top of that. She's turning in .5 moa 5 shot groups at 100 yards with 82 rl25 with the 140 accubond, so I'm sure she's just about shot out.

With the lh 300 rum and the 225 grain hornady the Retumbo top was 89 grains for hodgdon with a 220 partition, sierra runs 89 h1000 with their 220's, and the 300 roy 220 grain data on the rl33 poop sheet shows 89 grains with a 220 sierra, so I simply walked up from 89 grains and finally got good acuracy/ good pressure at 95 grains rl33. The load is turning in 1.1" at 200 in a 9" 300 rum without a brake in flaky wind so I think it'll do. The load has tenatively chronoed ( still need to get it over the oehler) at 3,000 fps which is 130 fps faster than rl50 would do without the compression being asinine. We ( my brother also shot a 300 rum for a bit ( he had a heavier rifle and a brake- pansy)and he was rolling some test loads in nosler brass as a secondary reference) did get rl50 to 3,000 fps with the 225 hdy, but the extra powder compression was beginning to make the seating plug dig into the bullet.


I see on the 300 rum bbl life thread you are going from 94 to 103 grains with the 230 hybrid; I think you may want to step down your first couple of loads a bit as that is a rather stiff start to the game. The rum is rather forgiving as to reduced loads as compared to some of the smaller bores with less bullet load. I went from 96 grains i 5010 to 112 grains with the 180 hornady when I was using that powder before settling at 3320 fps with 107 grains i5010. To bad that stuff went bad as it was better performing than most of what's out today. I never got to chrono the 112 grain load but I did load up a box and let my brother get the crap kicked out of him with it before I backed down.


With my 7stw ( my old sendero) and rl25 I was shooting 140 sierra's at 3350 fps and 140 accubonds at 3450 fps well before data came out. I cheated a bit there and ran it up starting with rl22/I7828 data for the stw and put a strain gauge on the rifle to confirm. With rl25 I was able to get similar speed to I 7828 using the 140 sierra with 6,ooo psi less pressure and better accuracy to boot. The pressure graphs are in the stw sub-forums if you poke around a bit.

Last edited by Lefty7mmstw; 08-26-2013 at 12:12 AM. Reason: spelling/ clarity
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  #18  
Old 08-26-2013, 10:07 AM
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Re: Similar burn rate

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Originally Posted by Lefty7mmstw View Post

I see on the 300 rum bbl life thread you are going from 94 to 103 grains with the 230 hybrid; I think you may want to step down your first couple of loads a bit as that is a rather stiff start to the game. The rum is rather forgiving as to reduced loads as compared to some of the smaller bores with less bullet load. I went from 96 grains i 5010 to 112 grains with the 180 hornady when I was using that powder before settling at 3320 fps with 107 grains i5010. To bad that stuff went bad as it was better performing than most of what's out today. I never got to chrono the 112 grain load but I did load up a box and let my brother get the crap kicked out of him with it before I backed down.

Yup, 94 gr does seem to be a little stout for a starting load. I was going to start @ 92. My reduced break-in load was 90 gr pushing the 230's and velocity was about 2700 or so. If I gain 50 fps per grain, that would put me to 2900 @ 94 gr. I think the actual gain per grain will be less than 40 fps. I'm expecting max velocity to be over 3050 in my 27" barrel. With nitriding, there should be reduced pressure. All that and AZ shooter's max of 100 gr with 2975 fps in a 24" barrel and I'm comfortable with the 94 gr start. I suspect I will max out about 101 or 102 with the nitrided barrel and velocity somewhere between 3100 and 3200. Time will tell.
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  #19  
Old 08-26-2013, 05:34 PM
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Re: Similar burn rate

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Originally Posted by MontanaRifleman View Post
Yup, 94 gr does seem to be a little stout for a starting load. I was going to start @ 92. My reduced break-in load was 90 gr pushing the 230's and velocity was about 2700 or so. If I gain 50 fps per grain, that would put me to 2900 @ 94 gr. I think the actual gain per grain will be less than 40 fps. I'm expecting max velocity to be over 3050 in my 27" barrel. With nitriding, there should be reduced pressure. All that and AZ shooter's max of 100 gr with 2975 fps in a 24" barrel and I'm comfortable with the 94 gr start. I suspect I will max out about 101 or 102 with the nitrided barrel and velocity somewhere between 3100 and 3200. Time will tell.
So basically the hornady should take about 5 grains less powder to get to pressure then, eh? I thought az had a rather loose/worn throat to take those charges when I first heard his charges but he says in the 300 rum bbl life thread that barrel is a fresh re-chamber. It seems the bergers are just somewhat more slippery in the bore and a bit more powder hungry than the hornady and sierra pills I'm used to. I concur that 40 fps per grain is a good roundabouts and possibly closer to 30 fps per grain until you get a head of steam on the load. With rl50 I started at 90 grains with the 225 hdy at 2660 ~ fps and hit 2870 fps at 98 grains; my brother ran the load compression up and went to 102 grains and we were right at 3,000 fps with that.

As to velocity with the 225 hdy and rl33, I haven't found the wall yet ( 3,000 fps @95 grains is still mild) and don't plan to at present as the rifle's starting to get a lot of rounds on her (bought used and my round count is at least a few hundred) and the hornady bullet isn't in production until at least next year; I've only got three hundred to last me until then.
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  #20  
Old 08-27-2013, 02:14 PM
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Re: Similar burn rate

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Originally Posted by Lefty7mmstw View Post
It seems the bergers are just somewhat more slippery in the bore and a bit more powder hungry than the hornady and sierra pills I'm used to.
The short bearing surfaces of the hybrids apparently increase velocity/pressure ratios. Broz reported about a 50 fps gain in velocity with the 215's over the 210's in his 300 WM.

In my RUM, I was getting 3130 with 93 gr of retumbo pushing 210's in a 26" tube. Using RL33 in a 27" nitrided tube, pushing the 230 hybrids which have a shorter bearing surface, I think there's a very good chance I'll exceed the 3130 I was getting with the 210's.
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Last edited by MontanaRifleman; 08-27-2013 at 02:54 PM.
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  #21  
Old 08-28-2013, 07:41 AM
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Re: Similar burn rate

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Originally Posted by Iclimb View Post
Gun guides 25-06 Seirra 120's. just was. Curious how powders of similar burn rate corresponded to pressures. I'll see if someone will run a quick load for me.

I got a Box of nosler accubond 180's for 30-06 and the card it came with only lists re-22, gun guide doesn't list nosler....
If you want TESTED load data, tell me what bullets/powder you want to run in your 25-06 and I'll provide you with some data I have worked up and tested in my rifle.
I have tested several powder and bullet types, unfortunately I do not own a 30-06 and the only loads I have used were for a buddy and I don't have the data anymore.

Cheers.
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