[DOK]

I have run two separate tests for the same load and achieved significantly different velocity readings.  There are two differences between the two tests; the initial test used WSR primers and the temperature as 86 degrees, the second test used CCI std. small rifle primers and the temperature was 46 degrees.

Using W296 powder and 360gr. LBT with gc, the loads/velocities were:
23.5grs. = 1405fps and 1289fps
24.0grs. = 1425fps and 1317fps
24.5grs. = 1465fps and 1339fps

Considering primer and temp. were the only differences, my questions are "would the temp delta cause this significant a difference?" or "should I suspect the CCI std. primer contributed to the effect of the temp?".

I appreciate my best method would be to test with WSR primers at 46 degrees, but the good old Iowa weather isn't that cooperative.  I use a Redding powder measure and Dillon digital scale, so feel confortable the powder measure is consistant.  I use RCBS .454 dies (not 45L) and seat and crimp separately.

Appreciate any comments,

Respectfully,

 

[Bill Lester]

DOK,

I'd say this was more component change than temperature change. I've chrongraphed several loads in the summer and again in winter to test this idea. Specifically I've compared two .30-06 loads, two .41 Magnums in a Marlin, and two factory 125-grain .357 Magnum loads. The greatest spread was with Federal .357s at -65 fps on a sub-freezing day in Feb. 1992 compared to over 85 dgrees the previous August. John Barsness has an article in the new Handloader using several rifle cartridges that pretty well duplicate my own results.

 

[DOK]

Bill,

Thanks, based on your input,  I'll run a test using both WSR and CCI std. primers with the same loads on the same day.  I thought I'd seen articles (Taffin?) that referenced H110/W296 as sensitive to cooler temps, although I'll certainly admit, 46 degrees isn't very cold.  

Respectfully,

 

[MikeG]

Keep in mind that it's the ammo temp that matters, not the outside weather.  You can keep the ammo in the car till it's time to shoot, or run experiments where you cool it down with ice, etc.  Then you can make side-by-side comparisons in the same range sesssion. That would seem to be the best way to eliminate variables.

 

[DOK]

Mike,

I like your suggestion.  I'll try the different primers on the same day and if that doesn't sufficiently account for the delta, I'll do the car/ice trial -- very good suggestion.

Respectfully,

 

[Bill Lester]

You could even put one of those little, clip-on refrigerator thermometers into the cooler to know the exact air temp at which the ammo has been stored.

 

[DOK]

Bill/Mike,

I've loaded 23.5grs. and 24.0grs. W296 -- selected because they had the least ES when tested.  I used WSR for five loads and CCI std. SR for five loads. I weighted (Dillon digital scales) each load so they should be accurate to the tenth of a grain.

Clean gun, clean me, I'm anxious to see what happens today -- temp is currently 45degrees.

Respectfully,

 

[DOK]

Bill/Mike,

The velocity delta I referenced doesn't appear to be a result of primer performance.  Today's test 3 results are as follows:

23.5grs. WSR primer: 1290avg & 21ES
23.5grs. CCI primer:  1310 avg & 21ES

24.0grs. WSR primer: 1334avg & 13ES
24.0grs. CCI  primer: 1329avg & 19ES

This test supports the results from my previous test 2 that was noticeable lower than the innitial test 1.

23.5grs. CCI primers test 2 = 1289fps
             CCI primers test 3 = 1310fps
24.0grs. CCI primers test 2 = 1317fps
             CCI primers test 3 = 1329fps

The next thought was "is the Chrony accurate/consistent?"  As a reference point, I fired 5 factory 300gr. jacked rounds which are rated at 1600fps -- results were 1648fps avg and 22ES.  So the Chrony doesnt' appear to be registering low.  I agree with your previous suggestion that the temp. should not affect the velocity, certainly not to the extent noted.  The Chrony is positioned the same distance each time, so the inital, higher velocities should not have been achieved by hot gases affecting the results.  

I'll throw another ringer in -- my initial tests were with W296 and Lil'gun with the rest of the components being the same.  Literature led me to expect similiar velocities and that's what happened:

W296 24.0grs. = 1425fps
Lil'gun 24.0grs. = 1448fps

The point being that there is "some" validation of the higher velocity readings.

Anyway, appreciate the help and for the time being, I'll use test 2/3 as the appropriate results and rerun the tests when it's 85 degrees -- just to put this to bed if possible.


Respectfully,

 

[Southpaw]

DOK,
An interesting tidbit. I talked to one of the guys who make your 360gr'ers.  They said they use Winchester SR's.  Also on thier site, the only powder they show in their load data for any bullet in the .454 is W296.  I'd be curious to know what other loaders suggest and why.  Maybe we'll get some more input on this new thread.  That was a good idea.  Out of curiostity, did you fire-lap your barrel, or slug your cylinder to check dimensions?  I wonder if some of the accuracy/velocity differences might be related to something other than primers/powder/temperature.

God bless,

(Edited by Southpaw at 12:57 pm on May 24, 2001)

 

[DOK]

Southpaw,

I have not had the occassion to lap any of my barrels -- simply wasn't aware of the potential until I read Mr. Marshall's book.  I typically shoot 44mag and 5000/6000 rounds a summer, so I'm not sure if I'm not already lapping the barrels via normal wear and tear?  I do plug my barrels and have found them to be pretty consistent -- I use .430 44mag and .452 454 bullets. If I go up to .431/453, I get noticable increase in leading.

Respectfully,