Varying Adjustments at range?!!!

[Josh189]

I recently added a DM kit to my HS Precision stock, and took it shooting to OGC. While the 100yd zero was fine. I took it to the 200m range. Now I usually come up 2 minutes and a 1/4 minute windage and we're in business. This time I had to come up 3.5 minutes and 3/4 windage. I was shooting consistent, but am I reading too much into this? My initial thought was, a mag kit shouldn't mess up my data at 200. I just want to know if anyone has experienced this before, or if my scope just took a crap.
Specs:
Remington 700 SPS .308 (Bull Barrel) Took the Bipod off.
HS Precision Stock and Mag Kit
Glass is a Nikon Monarch 4x16x42SF, 1.5" mount on a weaver 20 moa rail.
Hornady 150, G1 model.

Any help is appreciated.

Thanks,

J.

[UnaStamus]

You can have variations based on the stock and what the action is doing in the stock. My concern would be to make sure that the stock is bedding/secured correctly and securely, the barrel is free floating, and the receiver is torqued into the stock at the appropriate torque values. Variations in torque can affect your zero.

The other questions are what you were zeroed with for ammo, what temp you did that initial zero with on that particular load, etc.

[JJ]

You can have variations based on the stock and what the action is doing in the stock. My concern would be to make sure that the stock is bedding/secured correctly and securely, the barrel is free floating, and the receiver is torqued into the stock at the appropriate torque values. Variations in torque can affect your zero.

The other questions are what you were zeroed with for ammo, what temp you did that initial zero with on that particular load, etc.

^this.

From the sounds of it, you either had an issue with the barrel touching somewhere and/or torque incorrectly to the action causing stress, or you now have the barrel touching somewhere, or improper torque on the reveiver. Bolt actions can be very particular to how they are assembled in to the stock, the DM bottom kit may be applying pressure in the middle of the action, that was not previously present.

[farmerj]

That is why on a good rifle you use a torque wrench to tighten not only the scope, but the stock as well

Was the bipod also just removed?. Or on the initial zero too?

It sounds like you might have several things stacking into the equation. Torque issues, bedding issues, changing the magazine, ammo issues ( some weather related), bipod....

[Josh189]

First off, Thanks for the replies.
Same ammo for all zeroing. I torques to 60in/lb, same as before. Temp was a bit warmer at 75-80 degrees but it was what 60 Sunday? 20 degrees shouldn't bring me another minute and a half adjustment.
I'll double check the velocities on the ammo tonight but the website says 2820-2649ft/sec.
I have never zeroed with my bipod from a bench. I use the bipod more or less to hold the rifle up so I can work on it. I need to get a better one for actual shooting. Is there a break in period after changing the bottom metal?

[JJ]

.
I have never zeroed with my bipod from a bench. I use the bipod more or less to hold the rifle up so I can work on it. I need to get a better one for actual shooting. Is there a break in period after changing the bottom metal?

I would be more inclined to believe the action is not seated properly, there should not be a break in time changing the bottom metal. I would take the action out of the stock and look for abnormal contact and reseat the action. A bit of metal shaving between the lug and bedding block, tension from the magazine kit against the action, or something of that nature would be my guess.

Ensure gun is unloaded
Stand stock pointed upward on the buttpad
Insert action into stock
Insert bottom metal
Hand tighten action screws (forward action screw first)
Lightly bounce the stock on the buttpad to ensure everything is seated
Retorque ((forward action screw first)

[farmerj]

Yes, 20° can give that much of a change.

It's keep watching guys with zero's from shooting in July try to hunt deer in November.

[Holland&Holland]

Yes, 20° can give that much of a change.

It's keep watching guys with zero's from shooting in July try to hunt deer in November.

You can get a 20 degree swing between opening shooting hours and mid afternoon on the deer stand. Do you seriously change your scope settings for temperature adjustment in the stand?

[farmerj]

Yes, 20° can give that much of a change.

It's keep watching guys with zero's from shooting in July try to hunt deer in November.

You can get a 20 degree swing between opening shooting hours and mid afternoon on the deer stand. Do you seriously change your scope settings for temperature adjustment in the stand?

It's a factor you need to be aware of.

Talking mod (minute of deer), most won't ever change a thing.

When you are getting to the brass tacks of it like he's talking trying to get the same poa and the same poi, yes it needs to be compensated for.

[Holland&Holland]

Yes, 20° can give that much of a change.

It's keep watching guys with zero's from shooting in July try to hunt deer in November.

You can get a 20 degree swing between opening shooting hours and mid afternoon on the deer stand. Do you seriously change your scope settings for temperature adjustment in the stand?

It's a factor you need to be aware of.

Talking mod (minute of deer), most won't ever change a thing.

When you are getting to the brass tacks of it like he's talking trying to get the same poa and the same poi, yes it needs to be compensated for.

Understood. So going a different route. If one zeroed in July and then again in November what kind of change in POI could one expect? I suppose one could leave their ammo sitting in the sun for awhile in july and really get some variance but I have done this with my deer rifles and really can't tell the difference.

[Josh189]

.
I have never zeroed with my bipod from a bench. I use the bipod more or less to hold the rifle up so I can work on it. I need to get a better one for actual shooting. Is there a break in period after changing the bottom metal?

I would be more inclined to believe the action is not seated properly, there should not be a break in time changing the bottom metal. I would take the action out of the stock and look for abnormal contact and reseat the action. A bit of metal shaving between the lug and bedding block, tension from the magazine kit against the action, or something of that nature would be my guess.

Ensure gun is unloaded
Stand stock pointed upward on the buttpad
Insert action into stock
Insert bottom metal
Hand tighten action screws (forward action screw first)
Lightly bounce the stock on the buttpad to ensure everything is seated
Retorque ((forward action screw first)

You may be right with something between the lug & block. I'll try re-seating/torqueing and go out again this weekend, see if anything changes. I appreciate the help.
I will post back after this weekend and update the results. Thanks again.

J.

[jshuberg]

A 20* difference in air temp doesn't effect a .308 round anywheres near 1.5 MOA at 200 yards. That's a 3" difference. I just made a 20* change in my ballistic calculator for a 175 SMK bullet with a MV of 2603 ft/sec, and at 200 yards the difference is 0.1", or roughly 0.05 MOA.

If anyone blames a 20* temperature change for a 3" miss at 200 yards, they're looking in the wrong place.

My guess like many other here is that the action isn't bedded properly. What group size are you getting at 200 yards?


Sent from my iPhone using Tapatalk

[Josh189]

A 20* difference in air temp doesn't effect a .308 round anywheres near 1.5 MOA at 200 yards. That's a 3" difference. I just made a 20* change in my ballistic calculator for a 175 SMK bullet with a MV of 2603 ft/sec, and at 200 yards the difference is 0.1", or roughly 0.05 MOA.

If anyone blames a 20* temperature change for a 3" miss at 200 yards, they're looking in the wrong place.

My guess like many other here is that the action isn't bedded properly. What group size are you getting at 200 yards?

My initial grouping size was a little under 1". I say initial because it was close to non-member closing time and after I had booked it down to change my target I had to rush my last shots, so my grouping opened up to 3". But it was shooting pretty consistent. I was just a little scared after adding an extra minute and a half adjustment from my usual 200yd settings.

[farmerj]

A 20* difference in air temp doesn't effect a .308 round anywheres near 1.5 MOA at 200 yards. That's a 3" difference. I just made a 20* change in my ballistic calculator for a 175 SMK bullet with a MV of 2603 ft/sec, and at 200 yards the difference is 0.1", or roughly 0.05 MOA.

If anyone blames a 20* temperature change for a 3" miss at 200 yards, they're looking in the wrong place.

My guess like many other here is that the action isn't bedded properly. What group size are you getting at 200 yards?


Sent from my iPhone using Tapatalk

So YOU are claiming that temperature has nearly zero effect on bullet rise or fall?

[andrewP]

A 20* difference in air temp doesn't effect a .308 round anywheres near 1.5 MOA at 200 yards. That's a 3" difference. I just made a 20* change in my ballistic calculator for a 175 SMK bullet with a MV of 2603 ft/sec, and at 200 yards the difference is 0.1", or roughly 0.05 MOA.

If anyone blames a 20* temperature change for a 3" miss at 200 yards, they're looking in the wrong place.

My guess like many other here is that the action isn't bedded properly. What group size are you getting at 200 yards?


Sent from my iPhone using Tapatalk

So YOU are claiming that temperature has nearly zero effect on bullet rise or fall?

I am in no way even versed in this subject (reading to learn, and out of curiosity), let alone an expert like some of you folks. That said, and yes, I realize I'm being somewhat pedantic here, it sounded like a piece of software was making that claim, not him. Presuming said software has produced accurate results in the past, unless the numbers were entered incorrectly, you could reasonably expect the results to continue to be accurate in the future, especially when changing only one variable.