WARNING - 4955

[Calvin45]

I bought a fair share of 4955 when it first appeared, drawing a blank on what cartridge I wanted to use it in, think 6 Comp Match. There is nothing linear in loading, but my first thoughts were this powder is way faster than what it was advertised at. I shelved it and sold it to a guy with advice.
Then 2 yrs later I revisited 4955 and this time i found it way slower for my application than anticipated and of course did not have the case capacity to make it work, fire sale again.
Both times, the buyers loved it.
Losing 4166, 4451 and 7977 hurt, and heard good about 8133 too!

Thanks for sharing! And for not just assuming there's nothing to my observations.

I agree…non-linear is a fantastic way to word this, and it is indeed true about any pressure curve…but some powders absolutely are less linear than others, with an exponential jump 4955 is one of them, in my conclusion. Non-linear x 10, while the boring old single bases are much more predictable (I tested 4 other powders also in 1 grain increments like an idiot - old reliable imr 4064 progressed very consistently and "linear", more predictable than any of the others)

I also did a stupid thing treating a 243 like a belted magnum regarding ladder increment sizes and acknowledge that.

I will say, what you're saying about published burn rate not matching your experience at all and being different from cartridge to cartridge is something I've also experienced with SUPERFORMANCE powder - I give up on pinning it down, it's a progressive burn rate double base so it's just a little weird - even hornady acknowledged it's got a narrow window of optimal performance but wheee it works it really works. That's been my experience with it. It's either entirely unsuitable for an application or it rules the roost!

This also seems the case with 4955 a bit - the burn rate I've experienced is entirely at odds with what's published on charts and the quickload data that quiet Texan was kind enough to share also reflects a powder that has a much slower burn rate than what was revealed to be the case upon actually shooting the stuff and reading the chronograph

In my experiences it's faster than 4831

 

[MSURunner]

This was the QL pressure curve for probably about the last "safe" load with 4955. It's 48.0 gr, and using the HBN coated 75 gr X on a 22" it projects for 3270 fps. 60700 psi.

This is your 51.0 gr load. 3485 fps projected. 74960 psi.

This is one of the powders recommended by Barnes for the 80 gr TTSX, RL-17. This is 46.0 gr and projects to 3390 fps at 58960 psi.

I think that what you have experienced is shown in these graphs pretty well. IMR4955 pressures up much more quickly, and dissipates that pressure more quickly as well. I would surmise that it would thus hide pressure signs a bit more that one that stays at peak pressures longer. Not gonna beat a dead horse on don't go too far, too fast. I think that QL or GRT (FREE) are invaluable in load development efficiencies because of this data that you can pull from it related to how a powder pressures up. Is it gonna be perfect? No, as seen in that it didn't perfectly nail your velocities, but it would have given you a warning that it's going to be snappy on the high end and probably would have made your loads a bit more conservative.

 

[Calvin45]

View attachment 446688
This was the QL pressure curve for probably about the last "safe" load with 4955. It's 48.0 gr, and using the HBN coated 75 gr X on a 22" it projects for 3270 fps. 60700 psi.

View attachment 446689
This is your 51.0 gr load. 3485 fps projected. 74960 psi.

View attachment 446690
This is one of the powders recommended by Barnes for the 80 gr TTSX, RL-17. This is 46.0 gr and projects to 3390 fps at 58960 psi.

I think that what you have experienced is shown in these graphs pretty well. IMR4955 pressures up much more quickly, and dissipates that pressure more quickly as well. I would surmise that it would thus hide pressure signs a bit more that one that stays at peak pressures longer. Not gonna beat a dead horse on don't go too far to fast. I think that QL or GRT (FREE) are invaluable in load development efficiencies because of this data that you can pull from it related to how a powder pressures up. Is it gonna be perfect? No, as seen in that it didn't perfectly nail your velocities, but it would have given you a warning that it's going to be snappy on the high end and probably would have made your loads a bit more conservative.

Much obliged.

you say that you can account for hbn with quickload? I didn't know that. Learn something every day…

I don't know that I'd say the graph lines up..if anything I was apparently doing even worse for pressure.

Because the ql prediction for the 51 grain load you've shared is exactly 150 feet per second slower than what my primer buster load read out.

 

[Petey308]

Much obliged.

you say that you can account for hbn with quickload? I didn't know that. Learn something every day…

I don't know that I'd say the graph lines up..if anything I was apparently doing even worse for pressure.

Because the ql prediction for the 51 grain load you've shared is exactly 150 feet per second slower than what my primer buster load read out.

the difference in velocity can easily be fixed by calibrating the Ba in QuickLoad.

The things QL doesn't allow you to account for, such as chamber dimensions, case shoulder bump, neck tension, primers, primer seating depth, twist rate, different lots of powder, etc, etc, can be accounted for by adjusting the burn rate (Ba) for the particular powder. Differences in all those things mentioned effectively change the burn rate of the powder due to how it directly affects it.

You also change this figure when using QL for actual load development methods such as OBT.

I think you'd find that if you adjusted the Ba to match your actual MV, you'd still find it was at an excessive amount of pressure. I'd do this for you and post it, but I'm not at my computer at the moment.

There's also the possibility that the round that caused the issue had some other differences you're unaware of that compounded the issue and why it appeared so much different than the ones before it.

 

[MSURunner]

the difference in velocity can easily be fixed by calibrating the Ba in QuickLoad.
You also change this figure when using QL for actual load development methods such as OBT.
I think you'd find that if you adjusted the Ba to match your actual MV, you'd still find it was at an excessive amount of pressure. I'd do this for you and post it, but I'm not at my computer at the moment.

^Quote trimmed for context^

I adjusted ba to more closely match the velocities (ended up around .5200, up from .4910). This should always be the last thing you do after measuring EVERYTHING else and truing to single data points is never a good idea, but it ended up projecting for 3586 fps at 82570 psi. So, yes, you were definitely up there!

 

[Calvin45]

^Quote trimmed for context^

I adjusted ba to more closely match the velocities (ended up around .5200, up from .4910). This should always be the last thing you do after measuring EVERYTHING else and truing to single data points is never a good idea, but it ended up projecting for 3586 fps at 82570 psi. So, yes, you were definitely up there!

yikes!!! Thanks.

 

[MSURunner]

yikes!!! Thanks.

No problem. FWIW, it has 49.0 gr at 3468 fps at 74680 psi with the adjusted Ba

 

[asd9055]

No problem. FWIW, it has 49.0 gr at 3468 fps at 74680 psi with the adjusted Ba

Just out of curiosity, what weighting factor and shot start pressure are you using? Default, or did you adjust?

 

[Calvin45]

No problem. FWIW, it has 49.0 gr at 3468 fps at 74680 psi with the adjusted Ba

That checks out

 

[Calvin45]

Let the record reflect:

I, Calvin45, do hereby acknowledge that going from 45 to 49 grains was a monumentously stupid thing to do and I **** well knew better.

I still do not comprehend how 49 and 50 showed zero signs or reluctant extraction before 51 did this. I still do not trust 4955 at all.

I will be smarter in the future

 

[asd9055]

Let the record reflect:

I, Calvin45, do hereby acknowledge that going from 45 to 49 grains was a monumentously stupid thing to do and I **** well knew better.

I still do not comprehend how 49 and 50 showed zero signs or reluctant extraction before 51 did this. I still do not trust 4955 at all.

I will be smarter in the future

Show me a person who has not messed up and I will show you someone who has not tried enough. We just hope, when we do make a mistake, is not serious.
Thank you for sahring, I think we all learn something, or at least got reminded to be more carefull

 

[Petey308]

^Quote trimmed for context^

I adjusted ba to more closely match the velocities (ended up around .5200, up from .4910). This should always be the last thing you do after measuring EVERYTHING else and truing to single data points is never a good idea, but it ended up projecting for 3586 fps at 82570 psi. So, yes, you were definitely up there!

Agreed. You measure EVERYTHING you can first and double check that it's all accurate. Only then do you start adjusting Ba.

And I'm not surprised you got what you got. I'm sure the HBN did help lower pressure a bit though from 82,570psi but I'm sure it was close.

And when you get close, 1gr can make a huge difference in pressure. The more expense you get with QL, the more they become very clear. It can be pretty eye opening.

 

[Petey308]

Show me a person who has not messed up and I will show you someone who has not tried enough. We just hope, when we do make a mistake, is not serious.
Thank you for sahring, I think we all learn something, or at least got reminded to be more carefull

Yep. We all mess up and learn valuable lessons from it.

It definitely helps to know what the actual problem was too. Hopefully by making this post it has shown blaming the powder alone was not correct. The same thing could potentially happen with other powders.

It's always great when no real harm occurred during the lesson lol.

With that said, I'm off to surely make a mistake of my own at some point today lol. Hopefully there's no harm done when it happens .

 

[milo-2]

Thanks for sharing! And for not just assuming there's nothing to my observations.

I agree…non-linear is a fantastic way to word this, and it is indeed true about any pressure curve…but some powders absolutely are less linear than others, with an exponential jump 4955 is one of them, in my conclusion. Non-linear x 10, while the boring old single bases are much more predictable (I tested 4 other powders also in 1 grain increments like an idiot - old reliable imr 4064 progressed very consistently and "linear", more predictable than any of the others)

I also did a stupid thing treating a 243 like a belted magnum regarding ladder increment sizes and acknowledge that.

I will say, what you're saying about published burn rate not matching your experience at all and being different from cartridge to cartridge is something I've also experienced with SUPERFORMANCE powder - I give up on pinning it down, it's a progressive burn rate double base so it's just a little weird - even hornady acknowledged it's got a narrow window of optimal performance but wheee it works it really works. That's been my experience with it. It's either entirely unsuitable for an application or it rules the roost!

This also seems the case with 4955 a bit - the burn rate I've experienced is entirely at odds with what's published on charts and the quickload data that quiet Texan was kind enough to share also reflects a powder that has a much slower burn rate than what was revealed to be the case upon actually shooting the stuff and reading the chronograph

In my experiences it's faster than 4831

Retracting this after reading you were using a chrono!