Weird ProChrono Readings

[buffalorancher]

I wasted a couple of hours this afternoon trying to get some 95 gr. Ballistic Tips to shoot in my 6-284. I found a decent load but it was right at 3200 fps, I had hoped for more. Anyway, I am using a ProChrono that is about 6 months old and I noticed I keep getting readings of exactly the same fps. in different strings. For example, at 50.5 grains of RL-22 I had 3341, 3410, 3333, 3350, and 3367. At 51 grains I had 3341, 3367, 3375, 3392, and 3410. And finally, 51.5 grains yielded 3410, 3401, 3375, 3385, and 3375. The constant repeating has me baffled but I never had a missed reading. If you notice I have a 3410 at each of the powder weights and three readins of 3375. My other chronograph is an old Chrony that i could compare velocities with but I am tired of burning up barrels looking for a bullet that will expand at low velocities and still stay together in flight. Has anyone experienced this??
Thanks
Lance

 

[britz]

Pro crono's are hit or miss on their quality. I had one that worked fairly well for about 4 years and then it just stopped giving me consistant readings.

 

[royinidaho]

As I read the first couple of sentences of you post I expected the problem to be that successive readings were repeated as in 3375, 3375 3350 3325 3333.

I really don't think your chrono is a problem. Maybe ES and SD but most probably not the chrono.

If you keep going, and still have a barrel, you'll probably find that there is a narrow band of velocities that keeps reappearing. It would be interesting but completely useless to find out.

JFF I'd try a slow burning ball powder like AA 8700 or US 869 and see if the ES doesn't shrink a bit.

Just my tho'ts

 

[buffalorancher]

Roy,
Using RL-22 I have not found a load with an ES or SD that was very good at all in any bullet weight. In fact the best load was using H4350 and 107 SMK. This shot well but it pressured out at 3050 or something like that. I have a 30 inch barrel so I thought I might try some Retumbo or something else. My barrel is an ABS barrel and Mike D. at ABS said I would be able to shoot this for many rounds more than a standard barrel so I guess I'll find out sooner than later. The repeating velocities still have me troubled as what are the odds of a bullet going exactly 3410 with three different powder weights.
Thanks
Lance

 

[royinidaho]

The repeating velocities still have me troubled as what are the odds of a bullet going exactly 3410 with three different powder weights.
Thanks
Lance

Lance,

What are the odds of that? I'd say, in your case, 100% cause it happened. Those kinds of things nag at me also and I've had a few.

I was pretty much in the same boat with a 338 RUM. No powder gave an anywhere near acceptable ES. At 200 yds it was shooting 1/2" at 830yds it strung them vertically so bad that I got to chasing the hits and could never hit anything. ES was random and just under 100 fps.

I jumped clear out of the "box" and threw in some US 869 and ES dropped to +/- 1 consistently and still achieved the accuracy. For the first time in forever I could fine tune by neck tension and seating depth and actually measure the results.

BTW, what barrel is used for the ABS wrapping?

 

[buffalorancher]

Roy,
My ABS barrel is a Rock 5r 1-8.2. I am going to Omaha tomorrow and will visit Cabelas to pick up a couple different powders and if i don't get anything I like I will go back to the Match Kings and mediocre velocity I guess.