Anyone know why my Chrony would go coo-coo?

Doc

Strange chronograph results today at the range. Tested two .38 revolvers and two 9mms, a P38 and a Marlin Carbine.

Results for the 9mms seemed about what I expected. Winchester "white box" from Wal-Mart ran 900 FPS from the Walther and 1250 from the rifle. I thought the pistol velocity a tad low but it is marked as "target and range" ammo so it's not hot loaded at all.

Then I tried some Winchester 115 +P+ ammo. From a 4" pistol I have gotten around 1300 with this load, so it seemed close when the 5" Walther clocked 1350 with it. (1350 from a 9mm, wow). This stuff registered 1450 from the 16" Marlin.

The problem was with the pair of revolvers. Both S&W Military & Police models, one with a 5" barrel and the other a 2" snubby. Using Remington 125 grain +P ammo, the 5" gun clocked a very consistent 1150 FPS. Low of 1143 and a high of 1157. But this seems too fast. The specs on this load call for 925 FPS.

I switched to the 2" pistol and got the exact same results. This can't be right. The 2" gun should have given up some velocity.

Either all the readings were off and I only think the 9mm tests were about right, or that Remington ammo is some magical stuff going 200 FPS faster than the factory claims regardless of barrel length.

Any ideas on what was happening? I thought maybe the battery could be tired but would it give results like these on a dying battery? Why give obviously bad results only for one caliber? Odd.

almanac

Maybe battery, but results seem pretty normal before the +P. Stranger things have happened. Sometimes things just are. No sense in trying to figure them out.

LaidbackDan

Tailwind ???[;)]

1911a1-fan

factory data will vary from your data, when and where they get their data can make a great difference in comparison to your data, elevation being the biggest factor, temperature, and humidity will play a big role

high elevation will lower velocity

lower temperature can lower velocity, but depends on the powder, vihta vuori powders can increase in velocity when temperature is lower

humidity can decrease velocity

so where and when was their test done in comparison to yours?
i have received very conflicting data when shooting the same bullet out of a glock vs. a 1911, fjm's i gained velocity in the glock, Rainier's i lost velocity when comparing the two, each gun is different

here is the proper procedure for cronoghraphing a bullet when you want consistent data

take your handgun ready to shoot across your crony, tilt the barrel back, tap the gun three times to seat the powder all the way back in the case, slowly lower the gun down to the sight plain across the crony, each and every shot fired, you can get as much as 20-30 fps increase by this method, but it is the most consistent way, but keep in mind powders used may have different results

also wwb is a cheaper bullet, while their results may be a guide line, they can and will change powder from time to time, they use whatever they have the most of

glabray

I find the inexpensive chronos to be unreliable at best. They are very fussy about lighting, muzzle blast, etc.

Doc

1911fan- OK, I understand temp and elevation and all that but 200 FPS? That's a lot of variance. And only with one caliber and not another?

beantownshootah

A few of those results do seem a bit odd to me.

WWB 115 grain 9mm from a full sized pistol should clock in at around 1100 fps. 900 is on the slow side and I'm a little suprised by that. But echoing what 1911fan said, I know Winchester subcontracts out its WWB ammo to a variety of manufacturers, so its conceivable that you just got a slow batch.

1350 fps for 9mm+P+ sounds about right. People like to mock the 9mm, but the hottest 9mm loads (like that one) really aren't that much slower than ordinary 357 Sig loads. A hot 9mm really is 85% of the way there to 357 magnum ballistics. Corbon claims 1350 fps from a full sized gun for its 9mm+P, and having shot some of it before, I believe it!

In terms of the .38s, the usual figure I've heard is 50 fps per extra inch of barrel all else being equal. But its possible that in your case the longer barrelled gun has a wider cylinder gap and/or slighly wider bore accounting for the similar ballistics.

As for the .38+P, 1150 fps definitely sounds high, but it isn't completely crazy.

Corbon claims that its 125 grain +P .38s will get 1125fps out of a full sized gun, and supposedly their numbers are legitimate. So why should Remingtons be all that much worse?