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Hot weather and zeroing


30-6
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Yesterday was very hot and the only option I had to zero my .223 after a clean.

With a 1 in 10 twist ( sauer 100 ), it seems to love 40g v max, but I want to use 55g v max also. Previously, 40 and 55g were not that much different in impact points.  Using benchrest bags off the bonnet of my car I had a really good support. With the 40g I could get 25mm bullseye at 100 ( actually was 107 ) yds every time. When I went to the 55g the impact points went right a bit and opened out to about 50 center to center.

I noticed a heat mirage with the naked eye, I could not with the scope. The barrel and silencer, especially the silencer was very hot, like a frying pan, I did try to let it cool between shots. 

Could this have contributed to the poor grouping of the 55g ?

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In a nutshell yes it’s possible I have a moderator cover on my silencer for the same reason, A 1 in 10 twist would favour a lighter bullet it might be your rifle doesn’t like the 55 grain bullet you’re using try some different Bullets, another thing is your barrel free floated if not as the barrel heats up it will cause your groups to shift

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17 hours ago, 30-6 said:

Silverfox 1 - the barrel is free floated, and the fore end is very stiff. Sauer do very good composite stocks. 

How does putting a cover on a moderator help keep it cool ? Wouldn't a cover keep heat in ?

It doesn’t keep it cool it stops the heat Mirage of the moderator when you’re looking through the scope

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17 hours ago, 30-6 said:

I might have given the wrong impression. When I said I could see a heat mirage, I meant as I looked across the field towards target due to being very hot day, and not coming off barrel / moderator.

Mirage can cause problems with the point of impact especially if the Mirage is very bad it can look like the targets moving so your aim point could be different every time you shoot

having said that it’s probably not the Mirage that’s affecting you as you would notice it more through your scope then with the naked eye

Edited by silver fox 1
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Its wrong to generalise but ten rounds in quick succession will most probably shift the point of impact progressively on any sporting barrel as it heats up. Most people don't realise how slowly a serious target rifle shoots his 10+2 rounds. Half an hour or more at least.

Unlike you who was probably rattling off three or four shots a minute

You may interpret that as opening up the group or it could just be your rifle doesnt like the 55gr load you are using as much as it likes the 40gr load.

If anything it should be the other way, the 55g should be easier and less fussy to load than the 40g. Lighter bullets and higher velocity usually make rifles more fussy to load for.

Its quite normal for a different weight of bullet, or even a different brand of the same weight to move the POI

I think you just need to do a bit more load tweaking 

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