An unsuccesfull load.

[BravoSherpa]

I made a small batch of 10mm shells that resulted in a low velocity projectile with a fairly hefty recoil. I used a 180 gr. Hornaday HAP bullet, 9.5 gr. Hi-Skor 800-X, CCI 300 LPP. The powder filled a lot of space in the shell casing and I'm sure it was compressed with the bullet seated, this was towards the high end of the published load data. When fired my chronograph was registering an average of 450 fps, much lower than I expected. I was shooting a Glock 20 gen IV with a stock 17lb spring, only mod is a Storm Lake barrel.  I had fired a few factory rounds with my chronograph just to make sure it was giving solid data, seemed fine.

I'm guessing the powder ignited slowly and pushed the bullet out at low velocity and then continued to burn, possibly at an accelerated rate, after the bullet left the barrel; as mentioned I was getting a good kick. Only guessing though, I'd like some analysis from more experienced loaders.

I'll probably make one more batch with the minimum published charge just to see what happens, but probably the last load with 800-x, what a pain that stuff is to work with, got plenty of other powders to use. 

[The_Shadow]

I can assure you if you were loading 9.5 of 800X that reading on your chronograph was incorrect!
That loading would have yielded in excess of 1300 fps  (example;180 HAP with 9.3gr =1331 Kimber Target II-5" barrel) in testing.
800X 9.4 grains under the 200 Grain XTP, 350 CCI LP, seated to 1.255"  (As shot from my S&W 1006 5" barrel, 1254 fps)


You were likely too close to the chronograph, sometimes the blast and powder particulate can affect readings as does poor light conditions, and battery conditions!  You need to be at least 8' minimum and 10' to 12' is needed with the upper end loads.  Your shots should also be 4" above the sensors but 6" to 10" works well.  You need to shoot level over the sensors.

Also remember the sensors see the bullet to start and stop the timers, some people actually blacken the bullets with a permanent marker so it will see the contrast as the bullet passes.

[BravoSherpa]

I agree Shadow that the velocity should have been very much higher which is why I was so shocked to see the chronograph ring up 450 consistently over every shot.  The chrono had a brand new battery and it was at least 12" away, I seemed to be getting expected results with a few other different loads including a factory load.  Maybe it was some weird thing with the sun hitting the sensors at an odd angle just as I was shooting these rounds.

I'm pretty perplexed so I'll probably be reloading some more with original charge and some lesser measures, maybe I'll mix in some 350 CCI primers along with the 300s I was using.  I'll also have to experiment with the chrono at different distances and at a different time of day.  Gotta get to the bottom of this!

Edit: One other piece of data.  COL=1.26"

Edit2: Also interesting about the bullet color, this load was the only one I shot that day with a copper jacket, everything else was a dull hard-cast.

[Benchrst]

I'd be inclined to stick with standard primers for now and concentrate on the chrono issue.

Recoil should have absolutely told you velocity was not 450fps 

[sqlbullet]

I'm guessing the powder ignited slowly and pushed the bullet out at low velocity and then continued to burn, possibly at an accelerated rate, after the bullet left the barrel; as mentioned I was getting a good kick. Only guessing though, I'd like some analysis from more experienced loaders.

Physics is not on your side with this.  The velocity of the 9.5 grains of gas ejecta would have to be 250,000 fps in order to make up the recoil difference.  Smokeless gunpowder is not capable of that kind of ejecta velocity without a very exactly engineered nozzle, if at all.

As has been mentioned, your chronograph readings were definitely wrong.

[14 GT-500]

So what was your fps?? I know were mine Guns would be with that charge and its not poking along!

[basic]

The maximum in Hodgens reloading is 8.7grains.
BULLET WEIGHT
180 GR. SIE JHC
Starting Loads Maximum Loads
Manufacturer   Powder   Bullet Diam.   
C.O.L.
Grs.   
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Hodgdon   800-X   .400"   1.260"                  8.7   1,210   30,000 PSI

9.3 is quite a bit over.

If I want more I'll grab my 44mag or rifle.

[DM1906]

Definitely something wrong with your chronograph method. 12" is MUCH too close. 6' is often too close. 8-12 FEET would be more reasonable. When I shoot "magnum" rounds through my chrono at close rage, I occasionally get a "double-tap" (and the screens get blown off, so I don't use them). Meaning, it will record the bullet, then the ejected powder residue. Too close with subsonic rounds register errors, because the gas gets there before the bullet. If your chronograph is capable of capturing high rates of fire in strings, check the record previous to your low reading (it may have an accurate reading or an error). A 180 gr. bullet over a compressed 800X load should have damaged the case, and perhaps more. Just for reference, a 9mm Luger round fired from a .40SW/10mm pistol (or a .40SW from a .45ACP) will hit 600+ FPS (and they're accurate, too).

[The_Shadow]

Yes I hope BravoSherpa meant to say 12 feet and just hit the " marks by mistake...

[DM1906]

Yes I hope BravoSherpa meant to say 12 feet and just hit the " marks by mistake...

I agree, but he had opportunity to correct that after your first reply. The factory rounds should have read similar (most are marginally transonic). I suspect something else amiss, though. Either it is bad 800X (doubtful), wasn't 800X, or there was a LOT less powder in the case. It meters so poorly, it's possible to get a bridge in the measure for some light loads, and is why every load of 800X must be hand weighed, which you know. It doesn't even trickle well. If several loads were hitting 450 FPS consistently, I don't suspect that is the problem (velocities should be all over the place). 800X is a good powder, but a real PITA to work with. I use it, but rarely, for that reason alone.

[Benchrst]

"good kick" + no mention of failing to cycle has me thinking something's up with the chrono or his setup.

450 fps even possible?

[DM1906]

"good kick" + no mention of failing to cycle has me thinking something's up with the chrono or his setup.

450 fps even possible?

That's the problem. Too many variables that don't add up. Good point about the cycling. A load only able to muster 450 FPS (actual) wouldn't cycle, and wouldn't have "good kick", at all.

[Pumpkinheaver]

I agree that you need to be further from your chrono than 12 inches. Back on up and try your load again.

[blaster]

I was getting similar very low speed erratic readings choreographing some 300 Black Out  sub sonic loads. I was using a MagnetoSpeed chronograph. (mounts on the barrel like a bayonet) when I put the suppressor on the AR pistol and mounted the chromo on the can, I started getting correct readings. my guess was that the muzzle blast was causing the problem.

[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!