Chronograph speeds not working out for drop

[wnc-coyote]

Ok guys. I was testing some new loads for my 243 yesterday.
Specs for gun and load.
26" factory varmint contour rem 700 in hs precision stock.
4-16 vortex pst mil 1.900 scope height


Load.
105 a-max
45.5 gr rl-26
WLR primer
Rem brass
.025 jump.

Ok here's where I am lost. Previous load was 44.8gr rl-22. Chrono showed 3025av. For this load and shot properly to 600.

New load of rl-26 chronoed at 3005av. So after conferming zero I went to my first spot at 570. Put values into ballistic app and came up with 2.95mil actual drop was 2.3mil. Then I stepped back to 740 app called for 4.53mil actual drop 3.6mil. Double checked across three different app. Istrelok, AB, and ballistic ae. All were within .1 mil of each other. I am using litz g7 of .252. So at this point I changed velocity to march drop. Came up with 3300. I really don't think my chrono is off that much and seriously doubt I am pushing a 105 at 3300. However this velocity works out for both 570 and 740. Zero was reconfirmed at 100 dead on. So what could I be missing. I know people are getting good speed from rl-26 but could I possibly be running 3300?

 

[7mmShooter]

With RL-26 in a 243 with 105s, I don't believe 3300 is out of the question at all. I know a couple guys over on Snipers Hide that are running the 105 Hybrids over 3400 with rl26...

http://www.scout.com/military/snipe...rl26-and-105-in-a-243-at-3400fps-update-dtacs

 

[Engineering101]

I'm getting 10% more power out of a 30-06 with RL-26 than should be possible with no pressure signs. You are about 400 ft lbs past Hornady data which is 19%. Hard to imagine that big of an increase. Kind of odd that your chrono read this same bullet correctly before and now doesn't appear to. A misaligned chrono will always read slow but it would have to be pretty far off to read that slow and you would be able to see that just by looking through it. What kind of chrono do you have?

 

[wnc-coyote]

Sorry forgot the chrono. It's a shooting chrony f1 master. I have not chronoed the rl22 load in about a year. Chrono has also not been used in about 8 months or more.

 

[cowboy]

Sorry forgot the chrono. It's a shooting chrony f1 master. I have not chronoed the rl22 load in about a year. Chrono has also not been used in about 8 months or more.

I will make a couple of suggestions.
- Borrow a tried and true chrony
- Either shoot that F1 and put it out of it's misery or send it back and have it recalibrated.

Been there - done that.

 

[wnc-coyote]

Trust me a knew chrono is in the not to distant future for sure. I guess my main concern right now is to make sure I have not missed something stupid that could be screwing my results. Because I am still skeptical that I am truly at 3300fps.

 

[RockyMtnMT]

The chrono is top of my list. I would also check the zero. You may do a little better if you zero at a longer distance. A slight error at a 100y zero can make a large change down range. The good news is you have app matching your drops so you can shoot it confidently.

Steve

 

[wnc-coyote]

Checking zero was the first thing I did. Zero was dead on 5 shots all inside a 3/4" bullseye.

 

[RockyMtnMT]

If everything matches up other than the vel, then you are in good shape. We got a magnetospeed and solved those issues. Never knew if we had good data or not. Never knew what to change to get drops to match. Pretty frustrating.

Steve

 

[Wedgy]

It took a little while to realize it but my friend did me a huge favor when he shot my F1. No more crazy readings. The F1 can raise more questions than it can answer.

 

[Lpart]

Another approach is to collect real life data at the range and use a ballistic calculator to adjust you velocity. Aaron Davidson's calculator works very well and now always do this for final data when I feel I am close. Here is his you tube video on the suject.
https://www.youtube.com/watch?v=dWpTVbXlspk

Also Google trajectory validation.

 

[Wedgy]

I read this with interest and tried some RL26 with great results so I have to say thanks. I was using the Cutting Edge Bullets 100 grain .243 and not able to get over 3040 without ejector marks with various powders including H1000. My load was running 3015fps .4 MOA with IMR7828 which I have a ton of and it's always available The gun is a long action 26" barrel 7 twist. I worked up in half grain increments getting to 47.5 with no ejector marks, bolt lift, primers slightly flattened. I only loaded to 47.5 or I would have kept going but I think I found a good node. At 47.0 was 3220fps and 47.5 was 3227 and the two bullets were 1/2" apart on my 400 yard target. All the others went up in velocity as the charge went up so I think I'll work in this range. I'm still a little curious how far it would go but it's just about to go compressed at 47.5 and 3220 is plenty fast. But I'm still a little curious to see how far under the pressure limit I am.
Federal brass
Fed210M
2.400 base to ogive
2.942 base to tip
Magneto Speed
67F
9mph wind 3oclock

 

[wnc-coyote]

Wedge, Thank you for posting your results. That helps me feel better about my results. I thought I had something really screwed when it only took 3.6mil at 740. It may become a do all powder for me. So far I have worked up great loads for 25-06, 7mm rem, 260, and am going to start with 270wsm and 30-06 next. It is crazy how well it has done with all these cals. I have never had a powder that would do well in that's many calibers.

 

[Wedgy]

I need to test its temp sensitivity as it gets hot here, over 100F, and some of my other loads don't hold up. If this does it's going to be a go to powder for me.