What speed are the bullets ? And why ?

[LONG RANGE CAPT]

What speed are the bullets going and is there any reason why they would slow down.

 

The rifle is a 6.5x47 lapua, 25 inch barrel.

 

data as follows:-

 

Humidity = 74.2

 

1001 mb

 

Temp = 3 deg C

 

Wind slight R-L at 2 mph

 

 

The bullet 123 gr senar.

 

charge 37.5gr RL15

 

Zeroed at 100m and grouping 1/4 inch,

 

The rifle was hitting the gongs centrally at the following distances consistently

 

At 410m milrad 23 clicks

 

At 510m milrad 34 clicks

 

At 744m milrad 65 clicks

 

 

Interestingly when I looked at my other cards that have worked for same load in the past the data is as follows:-

 

Chart at 2915 fps (data taken at 15 deg C)

 

At 410m = 19 clicks

 

At 510m = 21 clicks (+1 for temp)

 

At 744m = 55 clicks (+2 for temp)

 

 

Chart at 2880 fps (data taken at 20 deg c)

 

At 410m = 21 clicks

 

At 510m = 31 clicks (+1 for temp)

 

At 744m = 58 clicks (+2 for temp

 

 

 

What would cause the bullets' to slow ?

 

Has anyone else experienced this ?

 

 

Kind Regards

[MJR]

Rob, I think it's temp related. At 410 MTR, 35 fps is making 2 clicks difference on your 'known' data. You were shooting at 17 degrees lower temp than your 20c figures. I'd say a lower velocity could easily be explained at approx 2fps velocity drop per degree c and explain your need for extra elevation.

 

Is your 2915/510 Mtr data correct?

[MJR]

Forgot to say. I'm about to re chrony my known 308 load. I chronyd it at 15 c initially and thought it would be interesting to see what it is at 0 c or colder?

[foxing2night]

Rob were you shooting up at glens????

 

If so you have to be very mindful of the wind in that valley,,

 

I would say that the valley was your problem,,,

 

One wind direction and it goes uphill from left to right and over the top and down hill from

right to left,,

 

It is never a true flat direction and that is what you need for testing your loads???

 

Glen and myself have got used to it??, but I think that it may cause you some trouble,,,

 

At the lower distances i have not found much if a difference with my loads?? a click here and a click there but not much to worry about,,

but when you extend the range then this is were the difference will show up as regards to the temp on the day and the humidity,,

 

Now dont take this the wrong way, i think that you would be better off using a paper target and not a 10inch steel gong????,,

 

What i am trying to say is that a small bull will give you a more defined result, the problem with a gong is that how do you know that you have hit it write in the middle????

 

And you use them funny mill scopes :D Much better with 1/8 moa elevation and 1/4 windage ( heads down incoming )

 

Was you also taking it in turns with others to hit the plates???? did they have the same trouble as yourself?????

 

Let me know how you get on with it????

Rob have you not got a set of cards for just winter and summer temps??

Darrel

[Canadian F-Class Guy]

One of my favorite explanations in the world: Paroxysmal Gravitational Surges. Say it with a straight face and people will believe you.

[Dan534]

Temperature (as in powder temp), it the same symptoms as before with your 6.5 and mine shooting at the same time. 3 degrees is very cold. Also did you check the mod as it did the the same thing when the mod loosened?

[Offroad Gary]

Same rifle?

Seating depth?

Round count between trials, barrel wear changing results?

[LONG RANGE CAPT]

Same new rifle.

 

Cleaned in normal way.

 

Three different ammo batches all of which performed at about 2880 Fps on previous testings.

 

No vertical wind - only wind R to L at 2mph

 

Only difference was it was 3 deg C

 

Is RL 15 temp sensitive ?

[gbal]

What speed are the bullets going and is there any reason why they would slow down.

 

The rifle is a 6.5x47 lapua, 25 inch barrel.

 

data as follows:-

 

Humidity = 74.2

 

1001 mb

 

Temp = 3 deg C

 

Wind slight R-L at 2 mph

 

 

The bullet 123 gr senar.

 

charge 37.5gr RL15

 

Zeroed at 100m and grouping 1/4 inch,

 

The rifle was hitting the gongs centrally at the following distances consistently

 

At 410m milrad 23 clicks

 

At 510m milrad 34 clicks

 

At 744m milrad 65 clicks

 

 

Interestingly when I looked at my other cards that have worked for same load in the past the data is as follows:-

 

Chart at 2915 fps (data taken at 15 deg C)

 

At 410m = 19 clicks

 

At 510m = 21 clicks (+1 for temp)

 

At 744m = 55 clicks (+2 for temp)

 

 

Chart at 2880 fps (data taken at 20 deg c)

 

At 410m = 21 clicks

 

At 510m = 31 clicks (+1 for temp)

 

At 744m = 58 clicks (+2 for temp

 

 

 

What would cause the bullets' to slow ?

 

Has anyone else experienced this ?

 

 

Kind Regards

 

20 15 3 temp

 

410 21 19 23

510 31 21 34

744 58 55 65

 

510/15 seems very odd at 21-was it really 31,or close to that,which would be more consistent...but a 17 degree celsius drop to 3 will reduce fps in most if not all reasonable loads,some powders a bit more than others.As you'd expect 20/15 are pretty close on warm days,with the possible oddity mentioned.

george

[Offroad Gary]

The reason i was reccomended varget?

[Dan534]

Mayan calendar, sign of the end of the world??? Maybe? just throwing it out there... Or proof RL15s temp sensitivity which would effect most powders at that cold temperature.

[gbal]

The reason i was reccomended varget?

Probably-I think I recall some US tests where R15 was middling on cold effects (?50fps lss over quite a large range for 308?),and varget was among the least sensitive to cold...most of the data is on higher temperature effects -Africa or Mid West varminting.

george

[gbal]

One of my favorite explanations in the world: Paroxysmal Gravitational Surges. Say it with a straight face and people will believe you.

.... with Transient Cryogenic Aberation,and they'll call you 'Professor'

 

George

[gbal]

Forgot to say. I'm about to re chrony my known 308 load. I chronyd it at 15 c initially and thought it would be interesting to see what it is at 0 c or colder?

OK-that will be comparative data,esp if using the same powder.There seems to be some jocularity about your scope clicks-what scale are they on-like 1/8 or 1/4 (of...) per click -hard to estimate your actual drop without that...and see if it's in the ball park for estimated velocity reduction effects due to cold at longer range...

 

george

[foxing2night]

Rob, I have just been out today to test a new front bag rider,,

 

Temp -2

Powder Varget

Bullet JLK 130g

 

Group size .263

 

Dont use rel15 any more as i found that it was temp sensitive and varied from lot to lot

and it was bloody dirty,,,

 

Rob, I find it hard to visualise your targets as you and Dan are working in new money,

i am still in pounds shillings and pence (1/8 elevation and 1/4 windage MOA)

 

What i would say is that air density and a loose sound mod will have big effect on your results,,,

 

I found that using my br rest so that i could take out the human error as much as possible and a papper target with a more defined aiming point, my charts are as accurate as i could possibly get them,,,,,

One set of summer charts and one for the winter,, but as i have said there is not a lot of difference between them??,

 

Rob if you ever want to have a go with my Br rest the bag rider that David at the shooting shed makes they are detachable in seconds,

So to swap over from rest to bi-pod is a breeze,, really does give me rock solid hard data,,,

 

All the best, Darrel

[gbal]

OK-that will be comparative data,esp if using the same powder.There seems to be some jocularity about your scope clicks-what scale are they on-like 1/8 or 1/4 (of...) per click -hard to estimate your actual drop without that...and see if it's in the ball park for estimated velocity reduction effects due to cold at longer range...

 

george

 

My apologies-you do say milradians quite clearly.So 410 yards is a couple of clicks,from 20 to 3C..and Darrel has 'summer/winter charts',from a measured target ,so if he can just quantify the 'not much difference between them' for about 400 yards, you should have some kind of confirmation/not....bearing in mind the gong is perhaps less precise for small variations.

 

george