An unsuccesfull load.

[wolfsburg_de]

I agree with the other posters that muzzle blast could cause erroneous readings but OP, does your chrono support metric SI units and is it possible the mode got switched? 450 m/s is about 1475 fps which is very stout indeed. My wife once turned salmon fillets into cat food when she had her instant read thermometer set to *C instead of *F. You do NOT want salmon to get to 130*C!

[The_Shadow]

BravoSherpa, I hope you didn't take offense to what we have written...but there have been many good points raised with respect to the chronograph readings.  Please if you have your manual, have a look at it.  I have included a link for the Shooting Chrony MODELS: F-1*, M-1* manual.  Here is the info for feet per sec and Meters per sec;
You cannot change the standard of measure on the F-1 and M-1 Chrony units. The F-1 Chrony will show AL in FPS and the M-1 Chrony will show A.L in MPS.  M-1* Notice there is a period between the A.L for the meters per second model.

http://www.shootingchrony.com/manual_F1M1.htm#sos

Hope you are able to work out the issue and get correct readings from your chrony!

[Benchrst]

I agree with the other posters that muzzle blast could cause erroneous readings but OP, does your chrono support metric SI units and is it possible the mode got switched? 450 m/s is about 1475 fps which is very stout indeed.

That's certainly something to look into, but I'm thinking that 180 HAP + 9.5gr 800X + stock length (assumed) AF barrel = 1,250 ish range.

If he managed 1,475 outta that setup I'll eat my hat 

[DM1906]

I agree with the other posters that muzzle blast could cause erroneous readings but OP, does your chrono support metric SI units and is it possible the mode got switched? 450 m/s is about 1475 fps which is very stout indeed.

That's certainly something to look into, but I'm thinking that 180 HAP + 9.5gr 800X + stock length (assumed) AF barrel = 1,250 ish range.

If he managed 1,475 outta that setup I'll eat my hat 

It's not that far off the mark, with a longer, aftermarket barrel. If it's a Storm Lake 6" (not ported) barrel, it's possible. 8.7 gr. under a Remington JHP at 1.250" runs about 1225 FPS in my 5.2" barrel. 10 gr. with the same bullet and length goes 1495 FPS from my 6.5" Ruger revolver. This from my own testing. 9.5 gr. under a HAP bullet (same size, dimensions and BC as the XTP) in a 6" SL barrel wouldn't be that far off of 1475 FPS. I wouldn't fire these in a stock Glock barrel, but they weren't remarkable in my revolver, other than the velocity. If we put everything at the ragged edge of the margins of error, it's certainly possible. Stranger things have happened.

[Benchrst]

If we put everything at the ragged edge of the margins of error, it's certainly possible. Stranger things have happened.

That's a true story