T3 338WM, confirm my #'s, crazy chrony

T

thepitchedlink

Regular
Super GunNutz
Rating - 100%
255   0   0
Location
Lumby Town!!
Hey guys, my chrony seems to be acting up, I'm getting 200fps spreads so I'm not sure what to believe
225g Hornady SP's
H4350, 69.5 and 70g. I'm getting 2720 up to 2863
H4831 75 and 76g. I get 2713 up to 2795
thanks
 
Have you got a friend that has a chrony you can try? Your numbers look right to me but the ES seems extreme.

I see on Accurate Reloading that one fellow quotes 2915 our of a 25" Pre-64 M70 with 72gr of IMR 4350. That's in line with what you're seeing.
 
You are quoting two powder weights and two velocities. I don't understand - are they linked? In that case, are you wondering why the velocity doesn't increase at the same rate?
Otherwise, what is your spread for each powder weight, and how many shots?
 
I have shot about 20 of each powder at each weight and my shoulder is getting sore. My quiestion is "Has anybody else shot a T3 in 338 WM with these powders and weight?" and if so, what velocities did you get? I am starting to suspect that my chrony is not working properly and I would like to know where the speeds should be. I suspect that mid 2700's is where they should be and these high 2800's are the chrony. thanks
 
silly question but are they all loaded the same, neck tension, seating depth.
are these compressed loads at all? sorry i don't shoot a 338.

if you have a tight neck and the bullet is seated in the rifleing your going to have higher pressure which = higher velocity.
also, what primer are you using? that might be the culprit.
 
Thanks Dan, that's what I'm going to do today. It has done this before, I think it might have to do with overcast days. I will shoot a bunch of .22's today and see what happens, thanks
 
Keep in mind the effect ambient temp. has on pressures/velocity. I took a .270Wby to the range that shot 140gr. Tsx's in the 3350 fps range. On a particularly warm day first shot through the gun clocked 3412, second 3493,
there was no third! Later in the fall same loads were back in the 3300's.

If your ammunition is sitting out in the sun, or a round is sitting in a hot chamber a while before firing it can have signifigant effect on pressure and in turn velocity.
 
Well, no crazy numbers today. I set the chrony up in the shade and only had 2 errors, and that was when the sun went behind a cloud. When the sky is blue it seems to work fine. My .22's went through at 1140-1160, now the box says they are 1280 at the muzzle. My chrony is about 15' in front of the muzzle, so there is 100-140 fps difference there. Can't say if it's the chrony or the ammo, I'll have to find someone else with one and try the same loads one after the other...thanks for the replys. Oh ya, numbers are in the high 2700's, low 28's just like they should be, but the spread is about 25fps, not 225!
 
It would be a bit of a miracle if the bullets went as fast as what is said on the box. I will bet on your chrony.
 
I've seen chronys crank out some consistant but totally bogus numbers. A guy I was shooting with was wringing out a HS Prescion rifle in .300 WSM. He had some suggested loads from HS, and a pile of part boxes of premium factory loads.
The handloads were cranking out Weatherby speeds without showing pressure signs. They weren't even close to max loads by the book either. Being the kind of guy that takes detailled notes he tried the factory loads that he had chronographed on a previous day. They were coming in a couple hundred high as well. Going back and forth and doing a bunch of head scratching the numbers started drifting back to sanity, and eventually the factory ammo matched the previous session. We concluded that it was a lighting thing, but who really knows? I do know I wouldn't bet the farm on chrony results if they don't make sense, without repeatting the test on a different occasion.
 
I can attest to needing proper setup and conditions. When my 9mm pistol was pushing 124gr rounds out at 1600 fps I knew something was up. The suggestion of using quality .22lr is a great one.
 
You must log in or register to reply here.
Back
Top Bottom