Chrono surprise?

[hawkeye1]

Have you ever had a go-to load that you liked, but was surprised at the velocity you were getting when you finally ran them over a chronograph?
I have been shooting 45 Colt with 7.1 grains W231 and a 200 grain LRNFP. Today I ran ten of them over my chrono and was only getting 600 fps. How can that be? They are mild but had no idea they could be that low. My other loads were all about the velocities I expected, but not these 45 Colts. These readings are nowhere near what the manuals call out. Any thoughts? Just how low a velocity can you go?

[44Blam]

Be VERY careful with big boolits going that slow. They don't splatter against steel and will bounce back at you! Ask me how I know... :-o

[Winger Ed.]

Check how they got their data, and how different your handgun is from what they were shooting:
Compare barrel length, maybe your cylinder gap is larger and bleeds off more pressure than theirs,
what they sized a Lead boolit to, what alloy, or see if they used a test barrel that may- or may not be vented* at all.
Even different brands of primers will give different speeds sometimes.

If you stack up a few things different that the lab. used in their data, you'll get noticeably different results too.

*
Its a cut ahead of the chamber to duplicate the cylinder gap of a revolver.

[greenjoytj]

Was the powder all down at the base of the bullet?
If the revolver was held pointing down then swung up to point at the target the powder will be clumped at the bullet base so you will see 100 fps less MV than if the powder was bunched up against the flash hole. Just like you’ll see during a powder position sensitivity test.

Weak battery in the chrono?
Under size bullet diameter allowing a lot the gas blow by?

[almar]

Have you ever had a go-to load that you liked, but was surprised at the velocity you were getting when you finally ran them over a chronograph?
I have been shooting 45 Colt with 7.1 grains W231 and a 200 grain LRNFP. Today I ran ten of them over my chrono and was only getting 600 fps. How can that be? They are mild but had no idea they could be that low. My other loads were all about the velocities I expected, but not these 45 Colts. These readings are nowhere near what the manuals call out. Any thoughts? Just how low a velocity can you go?

This is pretty coincidental! I was wondering the same thing with the same powder and cartridge just last week when i tried it too. I was using a 230 gr RN though.

[zarrinvz24]

I've had a chrono surprise, but never one like that. My first attempt at loading 45ACP using Ramshot True Blue resulted in 11-1200fps loads with 230gr FMJ j-bullets. Needless to say, I didn't believe it and ran a few more over the chrony to make sure. I discontinued firing those shortly thereafter and returned home and pulled them all apart. I'm still not sure exactly what happened but it was a valuable lesson in "starting low and working my way up" - don't just interpret data for a desired velocity and call it good.

[hawkeye1]

I hadn't thought of powder position. I store all loads bullet down, then load the gun bullet down. Wouldn't think it would make that much difference, but that's what keeps this hobby interesting. I will run some more over chrono trying from muzzle up,to muzzle down. Will report results. Thanks much for your input.
Side note: all bullets are wheel weights, sized .454, with Lee FCD.

[charlie b]

^^^^be careful of this.

My first surprise was also with a .45Colt Ruger BH. I was shooting a lot of different loads in it, light to heavy, just for grins.

I had some Blue Dot so loaded up some stiff loads. Ruger only loads from the manual (Sierra I think) with the 255gn cast (Lee). Shot two cylinder loads, around 1200fps or so. Then one round went off and scared me. Recoil much more. Chrono said 1575fps!! Being a bit dumb at the time, and not knowing about Blue Dot's issues, I decided to test my hunch at the time.

Raised the pistol to point up and slowly lowered to level and fired. 'Normal' 1200fps or so. Next round pointed pistol down and raised it up. BANG! 1550fps! Carefully fired the rest of that load and did not use Blue Dot in the .45LC again!

[country gent]

My question is How did the extreme spread and standard deviation look? My second is Was there a lot of unburned powder in the gun after firing? The powder charge and shorter bullet may have created an ignition issue. The old go to load for 45 colt was 7-8 grn unique under a 250 grn bullet. This load took up a lot more of the space in the case.

How did the load shoot nice round groups or vertically strung.

On the plus side if its a good shooting load then recoil should be very light and controllable

[44MAG#1]

Surprizes come in all shapes and sizes. I posted on here one time about result I got with two different lots of Alliant 2400 and was picked apart on it.
ALL the other components were THE SAME including the REVOLVER and both "lots" were choroned back to back.
Assuming velocities from published data is not very reliable. Although it is better than nothing it is still unreliable.

[hawkeye1]

In response to Country Gent's questions. Shot to shot was very close. Groups are nice. And almost no un burned powder at all.

[gwpercle]

Sometimes ignorance is bliss .
All this time you believed you had a good load ... now you know the true fps and what does that mean ... it's not a good load ? It's still good , just because you now know the real velocity that doesn't change the performance . Reload another batch and retest or just say to heck with it ... I like the load as is .
Gary

[country gent]

Okay then you my have a "slow" gun.

I came into a batch of LC 852 when I was shooting high power. Was very consistent in both my M1As but about 100 fps between the 2, after a local match we set up and tested in a bigger sample of rifles same chrono same ammo just different M!As a couple were 150-175 fps different from the others.

[lar45]

I've had a chrono surprise, but never one like that. My first attempt at loading 45ACP using Ramshot True Blue resulted in 11-1200fps loads with 230gr FMJ j-bullets. Needless to say, I didn't believe it and ran a few more over the chrony to make sure. I discontinued firing those shortly thereafter and returned home and pulled them all apart. I'm still not sure exactly what happened but it was a valuable lesson in "starting low and working my way up" - don't just interpret data for a desired velocity and call it good.

A little thread drift here, sorry.
If you were using military brass, that could have been the problem with the 45 acp loads.
I had some go 1300fps by accident with TZZ brass. I backed way down and worked back up slowly...

[fredj338]

I doubt powder position makes that much diff. I would verify my powder charge was actually 7.1gr. You should be well over 600. A chrono is always an eye opener.

[RKJ]

Not with my guns, but a "fast" compound shooting the then new small diameter carbon arrows and a 4" overdraw (My pull is 30" but with the overdraw I was shooting 26". I thought I might have been shooting 280-300 FPS, shot it over a Chronograph and it was like 220. Ruined that bow for me, I never shot it again. The bow was plenty fast enough for me before I knew the speed but once I saw that I couldn't bring myself to pull it out of the case.

[Mal Paso]

Surprizes come in all shapes and sizes. I posted on here one time about result I got with two different lots of Alliant 2400 and was picked apart on it.
ALL the other components were THE SAME including the REVOLVER and both "lots" were choroned back to back.
Assuming velocities from published data is not very reliable. Although it is better than nothing it is still unreliable.

I had a "warm" batch of 2400. I was shooting Elmer's load in my 6" 629 and got 1604 fps. Ran 3 more just to be sure and all were within 10 fps, sure does burn well at that pressure. Brass was a little stickier than I care for. Started buying lots and testing and most were fairly close. That warm lot, someone must have been adding the nitroglycerin "to Taste".