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Be careful, myths about pressure signs.

 
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  #22  
Old 05-05-2008, 02:37 PM
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eddybo,

I'm waiting on a couple of paydays, then QL will be on my own computer. I will learn it inside and out, and may ask you some about it more then. I know it does a lot of things. You can also customize it to your brass capacity too which can greatly affect pressure.

From your above post, you seem to have a handle on velocity vs. pressure, and even better (something some handloaders never grasp) is the effect of burn rate on pressure.

I write on online BB's a lot about the .280Rem and the loading I do. Most often I'm told I'm loading way too hot. I tell them I've loaded that way for years with no probs...they say my time is coming one day. Now with QL I have something to back up what I say is safe, and out come the computer software poo-poo'ers. Well, let me tell ya. NASA doesn't shoot rocket after rocket to get the actual data for a real launch, they use prediction software like QL. It's good, tested, solid technology. It works.

I love reading people say "I'm at book max, and it's 200 fps slower...this data is way too optimistic." No, you just don't understand how to read it. They all know that lots of powder can vary, sometimes greatly, yet they think they're supposed to get the same velocity with the exact same powder charge and bullet. Why?

I load this way. I'll use my .280 as an example. Nosler data says I can get 3150 with 57grs of R-19 in a 26" bbl. Hornady says with their 139 and 57.4grs of R-19 I can get over 3000fps in a 24" bbl (Hornady doesn't give exact velocity, they step theirs ever 100fps). Now I got two sources telling me that 139/140 class bullets and R-19 can get between 3000-3100fps in a 24" bbl. (I figure the loss of @ 50-75fps from Nosler's 26" to my 24" bbl and QL bears that out along with other data I see online.) Now, I start my loading by working up from abut 55 grs of R-19. I know that all .280 data is produced at 60K psi. I know the SAAMI for the .270Win is 65K psi, so it's safe to load it up to .270 pressures if I want, or keep it down to 60K and have that extra cushion. I load up to .270 pressures. So basically, I get back the 50-75fps I lost with Nosler's 26" bbl. Now, I simply work up to my target velocity, and the number of grains of powder are only used to get me a reference for a starting point, and if I am at 3100-3150 when I hit 57 grains, then I'm at max. If I hit 3100-3150 at 56 grains I'm at max. If it take me 59 grains (which it does in my then that is max regardless of the listed max powder charge in the book. The "real listed max" is the max velocity. And now, as a final check I consult QL. It tells me my velocity with the 140 BT is around 62K psi but takes over 60grs of R-19 to get it. (why the powder charge is not the way to look at QL) The pressure is even lower with the 139 Hornady due to shorter bearing surface. So, all the data I have indicates that I'm safely in the good on pressure at velocities many say you can't achieve. When you run the numbers using the faster burning powders many of these folks use, then you see why. Even stepping up in burn rate just a tad to H4350, the same velocity gives as much as 2K psi more pressure. And to the other end, R-22 will give about 2K psi less pressure at the same velocity as R-19. In fact some data I have here on my work computer that someone sent me suggest that you can run the 139 Hornady over 3100fps in a 22" bbl and still be under 65K psi. Many loaders that simply look at book data will tell you that's impossible and asking for a nuclear holocaust! You suggested, and I concur, you must match the powder to the bullet wt and case capacity, and if you do, you can get great results.

I also concur with the original poster in that many times people think they see pressure signs, when in fact they're misleading. The oversized firing pin hole making cratered primers is a classic example. A rough edge on the bolt face creating "shiny spots" is another. Even flattened primers can lie, as the different manufacturers have greatly differing hardness, and many factory offerings flatten primers.
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  #23  
Old 05-05-2008, 03:22 PM
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Join Date: Jun 2007
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Eddybo

Guess what I am saying is too many times we see QL used in another way, that will build a false sense of safe load or max pressures when reality might be just the opposite.

"Someone run QL for me and see what my pressure will be this weight powder"

QL says that this is the pressure this load must generate!"

No, QL does not compensate automatically for different seating depths, (want to have fun run QL on our famous 75 gr V550 and 300 WSM with 125 BTIP and change the seating depth .100 and see how much pressure drops). That is highly probable also in single shot version. it does not know which primer you are using which can change pressure 2-3k alone. Plus it has a default H2O capacity that might be right on or might be way off one way or the other.

QL allows you to change the bullet friction coefficiant function and alter the pressure and velocity also.

If you use QL smartly to try and figure which powders and likely loads and then work up like you said that is a great use. However, we are seeing more and more people asking and trying to say this is the "definitive exact load" and start there or this is "the Pressure of a given load", when in fact reality is that is just a WAG based on the default settings of QL, with no seating depth variance, no primer info, no H20 capacity info etc.

That is dangerous in creating a false sense of confidence or a false sense of that is unsafe.

Any way that is my take.

Used smartly it is great, used dumbly well that is another story.

BH
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  #24  
Old 05-05-2008, 03:38 PM
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Quote:
I went to shoot in the rifle with the new ammo and found that the 129 grain bullets made my bolt stick that I could only get it open after 5 seconds.
Was it only the first two rounds or did all of them stick? The reason I ask is that most of us old timers were taught by our Dads to put a lot of oil in and on our rifles. Perhaps your Granddad oiled it up real good for you so you wouldn't have a rusty gun. Oil in the chamber can cause the case to slide back instead of gripping the sidewalls. (So can water if you decide to hunt in the rain.) This causes extreme rear bolt thrust.
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  #25  
Old 05-05-2008, 03:42 PM
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Man you better watch it the pressure police will get ya
There are people out there shooting loads that are dangerously hot that could be getting better velocity using safer loads. Matching the componants together seems to be the key. QL allows you to envision the results. I dont even post the velocities I get with my 30/06AI and 208 A-Maxs lest the pressure police come knocking, even though I am pretty sure the load is within saami spec. If someone tried to get the velocities that I have obtained with different componants things could get dangerous pretty fast. There is a post near the top today regarding .308s at seemingly impossible speeds with heavy bullets. I think that performance near that listed is posssible safely with normal pressures, even though at first glance I thought it was a dangerous situation. Some small changes in componants and 2800fps in a .308 with 190gr bullets becomes a bomb.
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  #26  
Old 05-05-2008, 03:49 PM
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Bountyhunter, you posted while I was already responding to .280rem. I am pretty sure I ran QL on that exact load as you defined with a longer seating depth, I maybe even ran it using moly back when it was a hot topic. I do not think I ever was ever able to get that load to pressures that I felt were safe or even close to safe in a factory rifle. I do not think the issue was whether it could be safe in a rifle in a special cut chamber, which maybe could be done using high but probably safe pressures...ie a couple of reloadings. To me the issue has always been what can happen when someone uses this load in a factory rifle.
I am not going to rehash that here. Maybe we outta just let dead dogs lay.
I do see how QL could be used as you say, but I do not think that it was used as you think. In fact I think that it was purposefully used as intended, to allow people to see what would happen with a specific load under a given set of paramaters. I do not remember who posted the results in that thread but I am almost positive they were correct.
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