ballistic coeiffiencey

tommyboy26

Any know the ballistic coeiffiency and muzzle veliocity of hps 155gr .308 ammo?


tommy

(please forgive the spelling:o)

dev110

Ezridax wrote: »

The 155 gr bullets in .308 are a great round, as with all HPS ammo. They have an average MV of 2950 fps from a 30" barrel..... They have a BC of 0.445


HPS AMMO ONLY



100yds - 200yds - 300yds - 500yds - 600yds - 800yds - 900yds - 1,000yds

- 0

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1

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4.5 ---- 10.75

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13

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22.5 ---- 27.25 ---- 33.5 - MOA

- 0

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4

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18

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43

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52

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90

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108

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134 - Clicks

This is what Ezri was getting with a 30" 1-12 twist

tommyboy26

dev110 wrote: »

This is what Ezri was getting with a 30" 1-12 twist

Im using a 30" lilja with a 1in13 twist so should be close

dev110

Ye you should be very close to that. The 1-13 is a more suitable twist for the 155's but not much higher.

tommyboy26

dev110 wrote: »

Ye you should be very close to that. The 1-13 is a more suitable twist for the 155's but not much higher.

When i put all the data in strelok calculator it say 1000yards is 30.62moa???

dev110

Data from a Ballistic calculator is only a guide line to get you close.
The data from Ezri is real testing.

Temperature at that distance will make a difference. Not much but it will

tommyboy26

dev110 wrote: »

Data from a Ballistic calculator is only a guide line to get you close.
The data from Ezri is real testing.

Temperature at that distance will make a difference. Not much but it will

Im tryin to figure out will a 20moa rail do me or should i get a 30moa rail. With the rail i have now from zero only has 26moa of elevation.

dev110

20MOA rail will do fine

tommyboy26

dev110 wrote: »

20MOA rail will do fine

I actually just rechecked it. From zero it has 24.5moa to top and 28.4moa to bottom. the thing is i was told it was a 20moa rail on the rifle but dont think it is

dev110

I'm not sure how you would check if it is a 20 MOA rail.
Someone might be give you an idea of what to do

BELOWaverageIQ

The 155 HPS-tr is using a 155 Sierra MK
BC of 0.45 above 2700fps
If it was taking 33.5moa at 1000 then they were doing just below 2900, I'd say 2850-2875fps.
https://www.sierrabullets.com/index.cfm?section=store&page=item&stock_num=2155

Cass

A 20 MOa does not always give you 20 MOA, but close to it. So if you have 28.5 MOA from bottom of scope to your 100 yard zero the rail will remove between 16-20 MOA of that. Meaning your zero will be between 8.5-12 MOA on your scope leaving you with 41 - 45 MOA on your scope. As you only need a max of 36 MOA with ANY 30" barreled rifle any most any target ammo you will easily make the distances with a 20 MOA rail.

ALso a 30 MOA rail not allow you to come down low enought o attai a 100 yard zero. Can be important for returning to zero for comps, rifle checks, etc all of which are done at 100 yards usually.

As to HPS. The average MV from Carmichael's is usually around 2950. Having chrono'd some rounds they averaged 2917fps with some dipping below, and other above. Heat, cold, headwind, etc all play a part so the 33.5 MOA stated above, and used as the basis for the 25 yd safety card is applicable to the day it was shot on.

tommyboy26

Is there anyway to know if the rail i have now is a 20moa rail? i cant see anythin on the rail that says what moa it is. the back of the rail is higher than the front but the top of the rail looks level should it not be inclinced slightly????

hope that makes sense

Cass

The top of some actions are flat. So when a 20MOA rail is mounted with the rear of the rail higher than the front its obvious.

Other actions though are slightly "sloped" on the rear of the action so require a slightly higher rear height than front height to keep the rail (where scope mounts) level. So even though the rail looks inclined it is actual not a 20 MOA rail but 0 MOA.

All that aside. If you are using 28.4 MOA to achieve a 100 yard zero i guarantee the rail is not sloped/inclined. It is a 0 MOA rail. No .308 target rifle fitted with a 10/20/30 MOA rail takes that much adjustment of the scope to find its 100 yard zero.

clivej

I got the calipers out and on a 15MOA x 4 1/2" long rail the difference between front and back was 1/2mm. Its only a cheap rail mind so don't take the messurement as gospel.