Weird Chrony results!

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boomer2

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I went out to the range today with my Win Featherweight in 6.5x55 to try out some new loads. I wanted to try the 100 gr Sierra Hollow Point, in Federal Cases, with Fed 210 primer and IMR 4350 powder. Loads were taken from Nosler 5th edition. I loaded up the following with book fps and then the fps average of my 3 shots at a temp of 0C (32F)
Grains book actual
44 gr 2819 2577
45 gr ---- 2430
46 gr 2973 2446
47 gr ---- 2572
48 gr 3127 2571
Note: no signs of pressure, no problems lifting bolts, no flattened primers.

I did not expect to get the same as the book value, but I sure did not expect to get a drop after 44 gr. :confused: What is the reason for that? Unfortunately, I deleted the first 3 shots after shooting and getting the average of the Chrony before I noticed this effect shooting the 45 grain ones. Surely I couldn't have made a mistake 3 times copying the values down, and then an additional mistake copying the average down? My thinking that it should have been 2377? I never made this mistake the rest of the day (ie 5 for 3).
Unfortunately none of the loads proved to be accurate anyway, but I sure would appreciate some ideas why the first three are funky, and why the others are so far off book values. By the way, I tested some 30-30 loads at 1850, 30-06 factory fed 180's @ 2450, 30-06 win factory silvertip 180's @ 2370 so the Chrony seems to be working OK.
 
HeadDamage:
Test barrel 23 inches, my barrel 22 inches. That would account for some difference, but not the vast difference nor the sudden drop after 44 grains.

Beater:
Good idea. However, last weekend I did a similar test using IMR 4350 and 95 gr VMax Hornadys. None of them grouped either, but the speed increases were consistent and fairly linear. Results below average of 5 shots.
44 gr 2435 fps
45 gr 2516 fps
46 gr 2698 fps
47 gr 2782 fps
48 gr 2821 fps
49 gr 2949 fps
You would think if the powder was too slow for 100 gr HP Sierra that it would be too slow and erratic for the Vmaxs also?
 
At one time I was a huge 6.5x55 reloading nut. I found that IMR4350 worked for 100gr to 140gr bullets just fine in my winchester featherweight. I was getting over 3000fps with the 100gr bullets just fine to. I don't think I have my old load data any more but maybe you need to experiment with some different primers or check that the chrony is working properly.
 
Try RL-22 very consistant, Those loads you tested are slow for the 6.5 I would be looking for those velocities with 140-150 gr bullets, I get 2600 fps out of RL-22 and 140 Hdy SP at 46.5 gr of powder.
 
yes, i would thing that from my 6.5 experiance, you should be getting more speed with the lighter bullet. 4350 IS the powder for 140s in the sweed as far as im concerned.
id try something a step or two faster burning.
another thing that may have caused your probs would be different crimp tightness?
slower powder, lighter bullets, if some were not crimped tight it may make that diff.
slow powder can do some funny things sometimes.
 
There are a number of other factors that could affect the readings. Low battery, the cold temperatures, etc.

The readings could actually be accurate. What was your extreme spread? Shooting more than 5 rounds would give a better statistical probability thingy.
 
I always shoot a minimum of 5 rounds over the chrony to get my avg. and occassionally I do get a totally odd ball number with I disregard. An example of this was one round in a string of 5 with my .45-70 Ruger #3 that gave a reading of 4300fps with a 400 gr bullet.
 
I had similar results a couple of times, and found out that varying light conditions dureing the day, position of the sun, clouds, rain etc were causeing a lot of very erratic readings. Also the same loads and components fired out of two different, though same maker, rifles will have different velocities. I finally hooked up a couple of 12 volt bulbs over the chrony diffusers and that got rid of most of the problems. The best way I found to get rid of the problem completely was to get rid of the chrony and develop loads to the point that they were the most accurate and don't worry about velocity (just another thing to drive you crazy). As for the books and bullet drop tables that go with them, take it all with a grain of salt. None of this stuff is written in stone and is only meant to be a guideline to help you achieve your accuracy requirements. Testing what your assembled components will do at any given range is up to you to find out. bearhunter
 
your loads for 06 180 gn @ 2370 seem aufully low as well. maybe the cold was affecting battery voltage. try keeping a spare battery in your pocket and swap them back and forth.
 
Well, I went back to the range today to do some shooting (6.5x55 in Win Featherweight) with my daughter and her friend. Since I had the 100gr Seirra HP already, I thought I would load up a light load for them to shoot. As before, Federal cases, Fed 210 primers, Sierra HP 100gr, and 44 gr of IMR 4350. This is the lightlest load in Nosler's latest book and showed the most promise from the last shooting episode. The load grouped not too bad, 1-1.25 inch @ 100 yds. A friend had his chrony there and it was exactly the same (2577 fps) as what I had measured 3 weeks earlier! The only thing I noticed is that after shooting, the exterior of the fired cases had a smokey, dirty appearance...extending down about 2/3 of the case length. I usually see this around the neck area only. So what does this mean? Is there not enough pressure to expand the case to the walls of the chamber? How would that increase velocity over higher grains of powder? If I continue to use this load is this dangerous or could it lead to problems later on? Unfortunately I only loaded 44 grains of powder so I do not know if the trend would reverse itself as it had done before ie 45 and 46 grains having lower velocitys. Thanks guys.
 
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