40 S&W Strange Results

T

Thomasq

Inactive
I just started working up some loads for my SIG 229 in 40 S&W. The results have me totally puzzled.
I am using Longshot with 165 Gr Jacketed HTP and 155 Gr Hornady XTP.
I started with 7.3 gr and stepped up to 7.7 with the 165's and 7.5 to 9.1 with the 155's. None of the loads showed any pressure problems on the spent cases.
My problem is with the velocities I am reading with my old Pact Model 1 Chrono.
With the 165's the velocities started at 2118 with each increase in powder went down until they got to a low of 1921, The 155's were similar in that they started at 1750 and stepped down to 1612 with each increase in powder. I know that it is impossible to get that velocity from a 40 S&W so I am looking for what could be causing the erroneous readings. I first thought I was getting muzzle blast so I moved the screens to about 25 feet and got similar results. Thinking it was the Chrono I fired some 22LR and got readings within 1 % of the published speed for the round.
It was a bright sunny day both times which I know is not ideal.
Any thoughts?
Thanks.
Tom
 
I would bet the "bright, sunny day" and the light reflecting off the bullets is the culprit. And the .22LR won't reflect in the same way.
 
You didn't freak-out about 2118 fps and kept on firing rather than try to fix the problem?
Google and the manufacturer can also be of great help--and, with a smart phone, both are usually available at the range
 
"You didn't freak-out about 2118 fps and kept on firing rather than try to fix the problem?"

I wouldn't have freaked out, either. In a .40 handgun with those bullets there's absolutely no way to get that kind of velocity. He would have blown cases or a damaged gun LONG before he even approached that.

I would have immediately investigated the batteries, too.
 
At 25 feet, the usual culprits for misreadings shouldn't be involved.
But after changing batteries, try shooting through a large piece of cardboard to block and prevent the chrono from reading anything other than the flight of the bullet.
A .40 has a lot more powder and gases than a .22 to confuse the readings.
Might help.
 
Mike Irwin
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Click to expand...

After much pondering I have decided the advantage that enables humans to conquer the world and get to the top of the food chain is our belongings:
1) a stick
2) clothing
3) a dog

1) explains why we men are obsessed with guns.
2) explains when women think about fashion more than men think about sex.
3) explains why we hate to throw meat scraps in the garbage.
 
Thanks for the responses.
I kept shooting because a day at the range collecting bad data is still a day at the range--all practice is good practice.
The chrono had new battery.
I have heard back from Pact and they say 5-10 feet downrange should be sufficient. The bright sun is most likely the culprit. They suggested canting the sensors 60 to 90 degrees left or right to increase the contrast of the bullet against the sky.
 
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