Ballistic data 25/06 and 300 Winchester Magnum

[Dr Ray]

I need some advice!

I have handloaded by 300 Winchester Magnum
Info
Lapua cases

Powder AR2225 - compressed

Loads as per data sheet

I have included the Hornady ballistic coefficient data

For long range shooting - 1 Km
What bullet weight for the 300?

The 195 Grain has a very little velocity variance

 

[cash_tx]

34" barrel? Wow!

 

[Dr Ray]

34" barrel? Wow!

Sorry 24 inch barrel

 

[cash_tx]

Is the barrel a standard 1:10 twist? If so, i think anything in the 180-210gr range would work good (probably right around 200gr).

 

[Dr Ray]

Is the barrel a standard 1:10 twist? If so, i think anything in the 180-210gr range would work good (probably right around 200gr).

Yes standard 1 in 10

I thought the 195 grain bullets because of the small variation in velocity.but; I’m not experienced in long distance shooting.
Hence I’m asking for advice,
Ballistic coefficient for the 208 is better but will it be as accurate at 1 km as the 195 grain

 

[Dr Ray]

I would really like assistance in which bullet weight

Pretty please [emoji120]

 

[Bob Nelson 35Whelen]

Yes standard 1 in 10

I thought the 195 grain bullets because of the small variation in velocity.but; I’m not experienced in long distance shooting.
Hence I’m asking for advice,
Ballistic coefficient for the 208 is better but will it be as accurate at 1 km as the 195 grain

@Dr Ray
What about the 212gn ELD or one of the very sleek Berger's
Bob

 

[TMac]

Yes standard 1 in 10

I thought the 195 grain bullets because of the small variation in velocity.but; I’m not experienced in long distance shooting.
Hence I’m asking for advice,
Ballistic coefficient for the 208 is better but will it be as accurate at 1 km as the 195 grain

Your instincts are spot on. Once you get way out there, the velocity variation, or more properly standard deviation, becomes a major component. If your SD varies much, the further you shoot the more vertical stringing you will see regardless of inherent rifle accuracy.

The other huge factor is calling the wind, that’s where the higher the BC the better due to a little less correction being needed. That way if your wind call is off, it hurts just a little less. A good wind call will beat a more accurate rifle with a poor wind call most of the time.

Some absolute accuracy can be sacrificed for a low SD and your hit percentage at 1K will actually go up. It’s a different game than hunting.

 

[Dr Ray]

Your instincts are spot on. Once you get way out there, the velocity variation, or more properly standard deviation, becomes a major component. If your SD varies much, the further you shoot the more vertical stringing you will see regardless of inherent rifle accuracy.

The other huge factor is calling the wind, that’s where the higher the BC the better due to a little less correction being needed. That way if your wind call is off, it hurts just a little less. A good wind call will beat a more accurate rifle with a poor wind call most of the time.

Some absolute accuracy can be sacrificed for a low SD and your hit percentage at 1K will actually go up. It’s a different game than hunting.

Thank you I really appreciate the help

 

[Dr Ray]

@Dr Ray
What about the 212gn ELD or one of the very sleek Berger's
Bob

My shooting pal, Ron uses those and 240 grain bullets.

Concern is that Bergers get a bit hard to get

 

[TMac]

Thank you I really appreciate the help

Have fun with it. I shoot to 600 yards, so I can get away with fairly large SD’s and if I can make fair wind calls I am shooting OK. That practice really helps me hunting when faced with 350 - 400 yard shots, which is almost my limit. 1K is a whole different game. It can get humbling fast.

 

[Dr Ray]

Well in my case I have to out shoot Ron (my shooting buddy)! LOL!!

 

[TMac]

Well in my case I have to out shoot Ron (my shooting buddy)! LOL!!

In that case the 195 gr. load has promise. If it holds 1moa or close to it with 10 or better yet 20 shots and a SD in the single digits, Ron could be in trouble. For beating buddies, you can usually get away with a little more error, both in accuracy and SD. So I’d bet a 10 shot 1 1/4 moa ish load with a SD of 12-15 ish, would position you for a win, unless Ron is a LR competitor.

 

[Dr Ray]

Your instincts are spot on. Once you get way out there, the velocity variation, or more properly standard deviation, becomes a major component. If your SD varies much, the further you shoot the more vertical stringing you will see regardless of inherent rifle accuracy.

The other huge factor is calling the wind, that’s where the higher the BC the better due to a little less correction being needed. That way if your wind call is off, it hurts just a little less. A good wind call will beat a more accurate rifle with a poor wind call most of the time.

Some absolute accuracy can be sacrificed for a low SD and your hit percentage at 1K will actually go up. It’s a different game than hunting.

Wind would straighten out the coat on a curly coated retriever
Gusts something like up to 50 km per hour - big ravines and high in the hills

The BC of the 195s grain Hornady bullets not quite as good as the 208s.
But I look at the variation in the velocities.
Hmm
I’ll get the data soon

 

[TMac]

Wind would straighten out the coat on a curly coated retriever
Gusts something like up to 50 km per hour - big ravines and high in the hills

The BC of the 195s grain Hornady bullets not quite as good as the 208s.
But I look at the variation in the velocities.
Hmm
I’ll get the data soon

I’d run a ballistic calculator for both bullets at the hi and lo velocities. Then compare the expected drop “error” due to velocity variation for a given bullet at 1k. Hi - lo for the same bullet = what I’ll call drop “error”. Compare that to the wind drift difference for both bullets at hi and lo velocity at 1k the same way. You are looking for the variation in accuracy induced by differing velocities for both drop and drift for a given bullet. That should inform your choice.

That said, with the wind you are talking about, your best bet is to stalk closer to the target lol. Thats a lot of wind. With that much wind I really don't have a sense which one will prove the best. At lower wind velocities, I am pretty sure the 195 wins due to low velocity SD. Have fun.

 

[Dr Ray]

I’d run a ballistic calculator for both bullets at the hi and lo velocities. Then compare the expected drop “error” due to velocity variation for a given bullet at 1k. Hi - lo for the same bullet = what I’ll call drop “error”. Compare that to the wind drift difference for both bullets at hi and lo velocity at 1k the same way. You are looking for the variation in accuracy induced by differing velocities for both drop and drift for a given bullet. That should inform your choice.

That said, with the wind you are talking about, your best bet is to stalk closer to the target lol. Thats a lot of wind. With that much wind I really don't have a sense which one will prove the best. At lower wind velocities, I am pretty sure the 195 wins due to low velocity SD. Have fun.

But I'll also be shooting at sea level to 500m.
I worked out the density altitude for the 1 km ->> yikes 3600-3800 ft at 26 degrees Celsius (79 F) but it gets a mighty lot higher than that!!

BUT!! the density altitude will be more likely well above that when summer comes. We in the far north of Oz don't really have a winter - just a cool dry. The altitude is 2000 ft for the Back Valley range
The range is used for military training, sniper training, and police training. Obviously this is not flat country as expected for a rifle range - targets are set out to 2.5 k.

 

[TMac]

Pretty area. Sounds like quite a challenge. You may want to factor in spin drift and Coriolis effect too. Especially if you are trying any of those longer shots over 1K. But at 1k they will have an effect. I hadn’t considered the high humidity, that may start tipping the scales to the higher BC bullet more than I’d considered. Looking forward to hearing which bullet you choose.

 

[Dr Ray]

Pretty area. Sounds like quite a challenge. You may want to factor in spin drift and Coriolis effect too. Especially if you are trying any of those longer shots over 1K. But at 1k they will have an effect. I hadn’t considered the high humidity, that may start tipping the scales to the higher BC bullet more than I’d considered. Looking forward to hearing which bullet you choose.

Thanks for those tips.
I think I’ll need to use my Sako 338 after 1 k.
Humidity here is a big thing!
Right hand barrel twist is better here in the southern hemisphere.
I will start testing groupings at sea level soon at Kurrimine Beach range not far from Cairns - about 90 min drive but worth it.

 

[TMac]

As to which boom stick is best over 1k, probably come down to the fastest barrel twist. You are running into the reasons the 6.5 CM, the PRC cartridges, and a number of others came about.

Also the larger the bullet the easier it is to see where it splashes if you are not on target. That and seeing the trace are where a good spotter comes in.

 

[Dr Ray]

My 300 Winchester magnum

I need some advice!

I have handloaded by 300 Winchester Magnum
Info
Lapua cases

Powder AR2225 - compressed

Loads as per data sheet

I have included the Hornady ballistic coefficient data

For long range shooting - 1 Km
What bullet weight for the 300?

The 195 Grain has a very little velocity variance

View attachment 532551

Barrel length 643mm -> 25.3 inches
Case length (Lapua) 2.611 inches
208 grain grain Hornady 3.6155 inches
195 Hornady 3.510 inches
Density altitude (say on average 4250 ft)
Pressure 54,400CUP
center of barrel to center of scope 2.1325 inches
I'm interested in shooting to 1 km