N-133 with low humidity

R

Richard

Member
I used to believe that N-133 was hard to tune with low humidity. But over the last several years I no longer believe that. Since tuners became legal I have had no problems whether the humidity was 10% or 80%. Are others finding this to be the case? I go with pre weighed charges which I think makes a difference. the XBR powder throws better but I cannot get it to agg. 133 throws rather poorly and I think that is part of the problem. It needs to be weighed.
Any thought on this?
Richard Brensing
 
If it works for you, that is all justification that is required. Your equipment interests me. Tell us about your tuner, in detail, and what sort of velocity are you loading 133 to? Also, how long is your barrel, and what does it weigh?
 
Boyd,
I am using a 12oz Loker tuner on my LV rifle. I have to flute the bbl to make weight. Bbl length is around 21.375 Having 3 different Lv rifles I just take out bbl material until I can make weight for each one. I am shooting around 3250 fps. Darrel makes a lighter tuner but I have found the heavy tuner gives a wider tune window.
Richard
 
Richard said:
I used to believe that N-133 was hard to tune with low humidity. But over the last several years I no longer believe that. Since tuners became legal I have had no problems whether the humidity was 10% or 80%. Are others finding this to be the case? I go with pre weighed charges which I think makes a difference. the XBR powder throws better but I cannot get it to agg. 133 throws rather poorly and I think that is part of the problem. It needs to be weighed.
Any thought on this?
Richard Brensing
Click to expand...

Right on, mate. N133 does not throw well, and anyone who has a powder thrower that claims one tenth accuracy with this stuff ......well, I'd like to see it.
I either use the Chargemaster or weigh each charge with N133 - it's not worth the risk.
 
Humidity

I have for a while been going to post this set of questions but just never got around to it. Ill start here.
1. I acknowledge that humidity plays a part in shooting.
2. Snipers for long range have to figure it into their equations, though I dont know what it does or what part it plays. They dont load as they go they are preloaded so it could only have to do with the bullet flight.

Question
1. For short range BR why does humidity play a part?
Just because we load a the range and therefore our powder is subject to the humidity and we trap the humid air in the case?
2. While I know most dont preload BUT if a person could preload like some of the 30BR guys would that eliminate humidity or at least make it a null factor since all the ammo could be produced in a climate controlled enviornment?
Once the cases are sealed the outside humidity should not have an effect on the burning powder.

What say you
 
I believe it's more of a matter of what's going on atmosphere wise than what is happening inside the cartridge. I came home from a match with 20 rounds left (So I could do some testing) that was shooting nice mid-ones. These rounds gave me around .3 worth of verticle at home. Turned the tuner about 3 numbers and it fell right back into tune. At the match it wasn't a matter of "set it and forget it" I was having to twist the tuner all day to stay competative. The reason I pre-weigh is that I don't want my groups lying to me and make a bad call on where to set the tuner.
I have given up on trying to figure out why and how atmospheric conditions affect tune. If you can trust your groups your rifle will tell you what it wants.
Richard
 
In order to isolate what humidity is doing, wouldn't you have to hold temperature constant? How much did temp. vary during the match, and how did it compare to when you shot at home? Could the temperature of the ammunition have been different because of how/where it was stored? I am not doubting your conclusion so much as looking for more information.
 
Boyd,
I have came to the conclusion that it would be very difficult to tune a rifle by temp and humidity. I tried that for a couple of years and did not have much luck. I don't even get out my meter anymore. To say a certain temp-humidity will require a set amount of powder does not work(for me anyway) Barometric pressure,density altitude, all come into play. Using Loker's tuner was the best thing I have found. I will try to get pics soon.
Richard
 
Richard said:
I believe it's more of a matter of what's going on atmosphere wise than what is happening inside the cartridge. I came home from a match with 20 rounds left (So I could do some testing) that was shooting nice mid-ones. These rounds gave me around .3 worth of verticle at home. Turned the tuner about 3 numbers and it fell right back into tune. At the match it wasn't a matter of "set it and forget it" I was having to twist the tuner all day to stay competative. The reason I pre-weigh is that I don't want my groups lying to me and make a bad call on where to set the tuner.
I have given up on trying to figure out why and how atmospheric conditions affect tune. If you can trust your groups your rifle will tell you what it wants.
Richard
Click to expand...


Right on Richard!

Gene Beggs
 
Richard said:
Boyd,
I am using a 12oz Loker tuner on my LV rifle. I have to flute the bbl to make weight. Bbl length is around 21.375 Having 3 different Lv rifles I just take out bbl material until I can make weight for each one. I am shooting around 3250 fps. Darrel makes a lighter tuner but I have found the heavy tuner gives a wider tune window.

Richard
Click to expand...
As you have learned, it takes a 10 oz or greater tuner to tune, and stay in tune, on the normal barrels we use on LV rigs. This means a barrel of 4.5# or less, which means fluting or straight turning to bring the barrel weight down. A pain!!
 
I havent recorded enough data to know what i am about to ask so please take it easy on me. Is there a general rule of thumb as to what direction you go with your powder charge (N133) as the temps rise? Say i start the morning at 28.8gr 80 degrees, were would i most likely be by the end of the day@ 91 degrees? Should i have gone up in powder weight or down, Generally?? Or is it simply, not that simple? Like i said i havent had the chance to shoot in the heat with my ppc yet, so i have no real experience. The shoot i attended in February i used 28.8gr all day, but the temps were chilly and stable. Thanks Lee
 
Skeetlee, Generallly as the temps rise so does the pressure, so if your in tune @ 28.8- 80deg. backing off a tenth or whatever is what you would do (28.7 eg).
 
One thing you might be interested in, one of the best shooters in short range Benchrest has been known to go to the line with three loads, shoot some sighters, and then choose his record load based on what he sees.

Years ago I was shooting a three day match and a friend, who had been shooting better, in the same conditions, in practice, was struggling. I suggested that he make use of the time that he would normally be spending waiting for a match to end, after finishing his group and try seating his bullets both longer and shorter. He tried .003 longer and after that, made the change and started doing much better. Looking back, I should have suggested that he do what the first fellow I mentioned does.

The bullets that we were both using were a double radius ogive design that seemed to like being into the lands farther than single radius designs. I might have suggested a smaller change for a different bullet.
 
So you fellas think that bullet seating depths can change also during the match as conditions change, or am i reading that wrong? I always thought once you found a good seating depth that was it?? I shot some bruno double O a while back and i was about 8 off a hard jam. Actually what i am finding with my rifles is that all the bullets i have tried shoot best just off a full jam. I read somewhere an article from one of the top ppc shooters that stated most ppc shooters dont jam there bullets and shoot them anywhere from 5 off to 10 off a full jam. Something about putting to much stress on the cartridge. I dont know but it make since to me. We take all kinds of measurements to keep stress out of our rifle, so why would you want to stress the cartridge?? There again fellas i speak from hear say and lack of experience. I think Krupa wrote that artical i was reading but dont hold me to that. I do find that my loads shoot the best when not on a full jam, so i dont know!! Lee
 
Arrhenius and Humidity

My current thinking is that the Burn Rate Temperature dependence is not always linear with temperature and, its moisture in combination with temperature that defines how easily the flame front propagates (catalytically-driven process of powder elongation) through the interstitial voids of the powder. Smokeless powder burns on the surface and surface moisture is an inert material that absorbs heat when vaporized.

Powder is readily charged with static electricity; and moisture is Polar; under specific highly humid conditions physical and thermodynamic properties can facilitate phase transition.

Total moisture refers to the surface moisture, bound moisture, inherent moisture and interstitial moisture is the water vapor present in the gas that fills the voids. When the moisture content evaporates cooling occurs, which reduces the temperature of reaction.

This may be some of the why and; I do believe in the general consensus that tune is best measured from POI

Ken
 
You will hear both ways, and both can be correct depending on which side of the node you are on. I set my rifles up to go down on powder as temps rise. For exapmle, if it is 75 deg in the morning and I am throwing 28.5 charges of 133, if I see verticle in the group I will up the charge until most of the verticle is gone. I try to leave .100 worth. As the temps rise it will start to tighten up. If you shoot a screamer you had better be backing down on powder because the next group might get ugly, as in a shot gun pattern. If I start out tuning and I am shooting dots I will back down on the charge to induce verticle in the group to see where I am at in the tune window and the adjust the load accordingly. Lots of ways to tune,but this works for me if I am not using a tuner. Having said that, all of my rifles now have tuners, and they work just like changing powder weights.
Richard
 
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