Moving POI barrel getting faster?

[Randoman5]

I took my Remington 700 SPS Varmint to Thunder Valley Precision today. Things started out very well. I'd never shot beyond 220 yard before but got first round hits at 200,300,400,500,600 and 700. But before long things got a little interesting. I started missing and my POI kept getting higher and higher. Eventually I guessed that my MV was off in my ballistic calculation.

I dialed the scope to where I was hitting again and changed the MV in the calculator until the holdovers matched what I was seeing. As I kept going the POI kept creeping up. I fooled with my calculator again.

When I ran out of ammo the POI still seemed to be moving up and according to my calculator I'm shooting FGMM 168s at 2820 FPS.

My scope rings and bases are torqued to spec and as far as I can tell solid as a rock. Is it possible I'm getting that kind of speed and that as the barrel breaks in it's getting faster? Or should I start looking at other things to explain this?

 

[COLOSHOOTR]

You could see some velocity increase from barrel heating up and possibly a temperature increase of the ammo but it should not keep going up and up. Any increase is usually fairly small and should not give you such inconsistent numbers. Did it vary from shot to shot or did it change slowly over time? Did it also change at closer range or just longer ranges? What kind of scope and mounts do you use? Is your scope tracking properly and returning to zero?

To start I would check your scope mounts again. I put a pencil line on my old fixed 10 set up and found the scope was moving under recoil as the pencil lines were now off. Also check to be sure you're action is properly torqued down as that could cause variations too.

 

[Lowlight]

Over the years we have seen and read about some strange "dope" issues with Thunder Valley.

Guys using much less dope than the distance would suggest.
I have never been there, but I am curious to go as we have read about this before and I want to see if there is something making all these guys use less dope than anywhere else.

 

[Randoman5]

I didn't know about that. It's really interesting. I'll have to look around the forum for similar instances. I'm not sure where else I could shoot that far so a direct comparison will probably have to wait.

My rifle is still very new. I put rounds 71 through 160 through it today and I've heard that new barrels get a little faster as they break in. I'm just not sure. It did get about 20 degrees warmer over the course of the shoot. If I believe what my calculator is telling me I gained about 60fps over the course of the 90 rounds I shot and my Remington barrel is hurling bullets 140fps faster than it says on the box.

 

[Lowlight]

Factory 308s rarely have this increase in speed being talked about.

You might see it with a custom Tube, but a factory stick usually not gonna increase in MV like that.

I think a lot of that is put on everything... it becomes a blanket line of thinking.

But we have seen people who could not jive their data to Thunder Valley post on here, which makes me think something is going on there.

 

[MoBoost]

It has little to do with muzzle velocity, but a stress point in action, barrel, scope mount or stock.

 

[Randoman5]

Hmmm......

I think I'll try re-torquing everything and go to the local range with a chrony and run a box test. I don't really plan on using anymore 168s. I'm planning to load up some 155 Scenars, but I'll get everything dialed in for sure and go back and see where I'm at.

The trouble is there are a lot of variables here, notwithstanding the TVP mystery.

 

[STLSteve86]

Chrony some 168 if you have more in the same lot.


Sent from my iPhone using Tapatalk

 

[sakobob]

how did you come up with the 2820 as your velocity? not say its wrong but that is damn fast for fgmm.
on a side note you may have something in your ballistic calculator off, scope hight,or your scope it self may not be tracking.
i have many rounds down range there and the straight range (from the benches) the 1k is 1000yds it has been hit with
every laser from a cheap bushnell to a couple of terrapin and it comes to 1k.
now the winds and temp rise are another issue. i have had a 1k hit in the mourning with x dope and later in the day have to
take off .3 in the heat of the day. a kestrel is your friend there.

 

[Randoman5]

how did you come up with the 2820 as your velocity? not say its wrong but that is damn fast for fgmm.
on a side note you may have something in your ballistic calculator off, scope hight,or your scope it self may not be tracking.
i have many rounds down range there and the straight range (from the benches) the 1k is 1000yds it has been hit with
every laser from a cheap bushnell to a couple of terrapin and it comes to 1k.
now the winds and temp rise are another issue. i have had a 1k hit in the mourning with x dope and later in the day have to
take off .3 in the heat of the day. a kestrel is your friend there.

When I left elevation at 1000 was dead on at 10.4 mils. In my shooter app that works out to 2820. I don't think it's right either. I took that same formula and was on at 700 600 and 200.

That's why I posted. I'm a bit confused. One quick correction. I missed my first 2 at 500 way high using 2680 like it said on the box. I corrected and got to closer to 2750. Then it was dead in at 500 600 700 and 1000. But as I shot it slowly drifted higher again. I was shooting fairly quickly. The gun did get hot.

 

[Lowlight]

That is part of the problem, you are trying to shoot and play with the computer at the same time.

Next time, just shoot, get your dope and have it centered up on target and ignore the computer.

The go home and play with the computer based on your drop and impacts. By attempting to do both you're not gonna do either very well.

 

[Lowlight]

Also if you really want to diagnose this,

You should be including all the data for the day, like this was your data book.

We need more than you are telling, guessing what you used, and where the other ranges lined up is not gonna work

As an FYI, to get 10.4 mils at 1000 yards with Federal 168gr ammo, I have 2725fps, it's right there.

 

[redirt78]

That is part of the problem, you are trying to shoot and play with the computer at the same time.

Next time, just shoot, get your dope and have it centered up on target and ignore the computer.

The go home and play with the computer based on your drop and impacts. By attempting to do both you're not gonna do either very well.

Good advice, I tried to play with all the numbers while it was both my first attempt at using a ballistic calculator and first few times out at long distance. Get a good solid zero then go by what the bullet is telling you, make note of it then later on you can play with the computers on the couch at least until you get good information to put in and familiar with it all. Trying to do it all right off the bat can easily cause numbers to be off.

 

[parkervbar88]

this is why a routine barrel cleaning regime is needed. the more copper build up the moe pressure spikes you get

 

[Randoman5]

Hmmmm. Yeah. I need a data book and a kestrel. I'm pretty new at this stuff and I have a lot to learn. There's a big difference between theory and practice.

Just out of curiosity what elevation is that?

I had 200 feet plugged in and I think that's around where I was.

Do you have a specific smart phone app that you'd recommend. I use shooter. Mostly just to play around until yesterday.

 

[Randoman5]

this is why a routine barrel cleaning regime is needed. the more copper build up the moe pressure spikes you get

Barrel was cleaned when new for manufacturing remnants and still has less than 200 rounds. You think copper build up is an issue?

 

[Lowlight]

Pretty much sea level, it's not enough to throw it off, it's inside 1000ft, 200, 400, 600ft above will not move it that much. The software is not the problem, all Apps use the same engine, with only minor variations between the programs. It's the user input that screws it all up. Heck JBM is free use that.

Barrel cleaning has nothing to do with it, it's a 308, you can go a whole lot of rounds without cleaning. 500 to 1000 rounds between cleanings is not uncommon.

List the dope you used if you have it.

 

[Randoman5]

Moving POI barrel getting faster?

This is what I ended up with.

It's set up with a full value 10mph wind but there wasn't actually much wind

 

[Lowlight]

Is all that right ?

You said you ended up with 10.4, that shows 10.1 ?

Are the other ranges correct, or is the computer all you have and you didn't write anything down ?

 

[Randoman5]

Sorry. I screwed up and posted the wrong one. I was playing around with the elevation to see how much difference it would make. As it's posted right now is exactly what I had.

You are correct. I wrote nothing down like an idiot.

Sorry for the mistake. And thanks for the help.

 

[sakobob]

Randoman if there is another open range day hit me up and will be glad to give you a helping hand down there.
with any luck my 308 will be up and running. you damn near drive rite by me. also there is another shoot at rayners in oct.

 

[Randoman5]

Randoman if there is another open range day hit me up and will be glad to give you a helping hand down there.
with any luck my 308 will be up and running. you damn near drive rite by me. also there is another shoot at rayners in oct.

I'll have to take you up on that.

 

[YJSONLY]

Pretty much sea level, it's not enough to throw it off, it's inside 1000ft, 200, 400, 600ft above will not move it that much. The software is not the problem, all Apps use the same engine, with only minor variations between the programs. It's the user input that screws it all up. Heck JBM is free use that.

Barrel cleaning has nothing to do with it, it's a 308, you can go a whole lot of rounds without cleaning. 500 to 1000 rounds between cleanings is not uncommon.

List the dope you used if you have it.

What is jbm app? I cannot find it in my store (Apple)

 

[Lowlight]

JBM is a website not an App...

JBM

 

[YJSONLY]

JBM is a website not an App...

JBM

Ok thanks.

 

[Randoman5]

For reference this is what I started with.

There was one adjustment in between. In each case shots were either on target or or just off the edges of the 12"x12" plate at 1000 or 700 and then started falling quite a bit over the target. When this happened I adjusted until elevation was back on target and then went back to the program and tweaked the speed until it lined up with what the bullets were doing. Each time I shot at other targets using the new formula to confirm it was correct and each time the bullets were back on target.

The only thing I could think of is that the conditions or velocity changed or something on the rifle moved so that it was changing my zero in a way that was temporarily repeatable and wasn't effecting windage which is also possible.