Weird Velocity numbers

[Grizzdude]

I just started load developing for a new bullet in my 338 lapua. I Noticed yesterday while shooting a 12 shot string 4 groups of 3 and starting with the lowest charge my velocity continually gets lower and lower with each shot even though I'm going up in powder charge. My last group produced 1/2" at 200 yards so today I loaded up 9 rounds for 3 groups of the same powder charge. Same thing happened with the velocity, High at first then gets lower and lower. Ended up with a ES of 114 and groups no smaller than 2" at 200 yards. Does this sound like my rifle needs to be copper cleaned? The rifle has about 350 rounds through it but it's had about 300 rounds since last copper cleaning. Just don't understand why the FPS would keep getting lower.

 

[BLDTYLRY]

How long are you waiting between shots?

 

[Grizzdude]

I was shooting them about 30 seconds apart, just a couple hours ago I shot two more 3 shot loads, this time I waited about 1 minute between shots and with the first load I had an ES of 11 and the second had an ES of 5. This time in each group two shots were very close under an inch but each had a flyer making total group size about 2". So I'm not sure if waiting between shots helped even out the FPS or the chrono was acting weird with the sun hitting it. I still need to work up the powder charge, I'm still about 2gr away from manufacturer load data and still see no pressure signs. Maybe as I get up in charge the groups will start to shrink.

 

[BLDTYLRY]

With that big of a round I'd wait at least 2-minutes between shots when doing load development.

 

[CK_32]

I had the same thing with POI doing my 308.

Higher I went up the lower the POI got. Thought that was odd. All shots times 2 min apart.

 

[BLDTYLRY]

I had the same thing with POI doing my 308.

Higher I went up the lower the POI got. Thought that was odd. All shots times 2 min apart.

Did you get chrono numbers? Maybe you mixed up your loads and shot them in reverse order?

 

[CK_32]

No chrono. And that's what I thought but I don't think I did. Made sure to put them in order in my shell box and put the card labeled with info on top to not mix them up.

I also hope not too because that would mean I got a node at 47gr not 43 lol

 

[Grizzdude]

With that big of a round I'd wait at least 2-minutes between shots when doing load development.

I'm starting to think this was my velocity problem, I'll be loading up some more hotter loads tomorrow and I'll go by the 2 minute rule. I think I'll have to revisit the load that gave me a ES of 5, see how it does tomorrow.

 

[dustinoif3]

Are you using an electronic or beam scale? Maybe you bumped your beam and its sitting funny on the table? Or if its electronic maybe the batteries are getting low or sometimes I notice if I leave my cheaper electronic on to long it'll start reading messed up.

 

[Grizzdude]

Are you using an electronic or beam scale? Maybe you bumped your beam and its sitting funny on the table? Or if its electronic maybe the batteries are getting low or sometimes I notice if I leave my cheaper electronic on to long it'll start reading messed up.

thanks for the post, I use a beam scale that I constantly zero every time I use it. I was doing some more load development today and I am starting to see the groups shrink up as I get closer to manufacture load data, I just shot a 1.25" group at 200 with one of the loads. I noticed my FPS were 2900, 2902..... then the sun hit the chrono and it showed 2918. So I think it was a combination of the sun hitting the chrono too. In the morning when I was getting the variation in FPS the sun is shining through trees so sometimes the chrono is in the shade the next minute it could be in the sun.

 

[dustinoif3]

Yeah I wonder if my chrono does the same thing. My pet load shots lights out but my chrono said I had a nasty spread of like 48fps. Anyways my last couple loads I've put together for other rifles I just input a guess fps from the loading manuals. Input it into shooter and use the adjusted mv option when I dial dope in it initially gives me. If my poi is high or low I throw the adjusted moa at given yardage into and it spits out the adjusted. Works pretty slick. I HATE dragging the damn chrono out there to sometimes it not even freaking read. I should sell it and buy more powder and bullets.

 

[FunkBass2008]

Are you using an electronic or beam scale? Maybe you bumped your beam and its sitting funny on the table? Or if its electronic maybe the batteries are getting low or sometimes I notice if I leave my cheaper electronic on to long it'll start reading messed up.

This came to my mind as well. 114 is a pretty large ES. Are you weighing each charge?

 

[Grizzdude]

This came to my mind as well. 114 is a pretty large ES. Are you weighing each charge?

oh yeah each charge is carefully weighed out.

 

[Heretoimproveforhunting]

Are these compressed loads? I don't have personal experience with the 338, but in instances of compressed loads I have experienced reduced velocities above a certain load point, without getting pressure signs. I also wondered the reason, as it was a new experience to me and someone here on the hide indicated it could be from an uneven / incomplete burn of the powder, on account of the compressed nature of the load