Muzzle velocity and temp powder

[shooterfpga]

If i have 4fps of variance between 0* & 125* would i enter 4fps for my variance? How does that compute per degree of change?

[postal]

Is this what you actually measured? It would likely be quite a bit more even with varget- (a continuation of that thread I guess?)

I dont recall, but I think from 35 deg to 110 deg I noticed a MV change of about 40-50.

However, if you reload, and you shoot 10 rounds through a chronograph, your ES (extreme spread) from slowest to fasted will all depend on your anal retentiveness... My ES is in the mid 20's FPS which is fine for most practical shooters though BR guys would scoff unless they hit single digits.

So- Consider that- your ES on the same day, same ammo has a ES of 25+ FPS... And you want to learn how to plot a 4 fps difference? Even BR guys dont get an ES of 4 fps with 10 rounds unless Lynn Jr tells me I'm wrong.

Simple approach is to have 3 charts (if you normally shoot at the same location) 1 for for cold weather, 1 for moderate and one for hot weather. If you have an "in between" weather day- look at the 2 charts and split the middle.

Once again, your true issue is the Density Altitude. And a Kestrel and shooter app will cover those- and you can can also plug in your expected MV correction from temp conditions.

[shooterfpga]

Sorry dinner time. Short answer is definately not 4fps. Im seeing 5.45fps difference per every 1*.

When dinner is over ill revisit. I like your explaination.

[Rbutler]

personally 4fps gets chalked up as a wash. In perspective, put into your calculator your velocity and right down your drop at 100 yards and at the max range of your firearm, do the same with the velocity +4fps, i highly doubt you can shoot the different.

example my 308
my standard load

@1k has a drop of 294.5
@1500 - 943.8

+4fps
@1k - 293.6
@1500 940.6

so 1 inch at 1k your talking 1/10 of 1 MOA. if you're that accurate kudos!

[shooterfpga]

I think all of this extended thinking is hurting my brain and making my formula muddied. I think i need to log some more data and go back to a traditional chart like suggested above before i revisit trying to adjust it automatically instead of manually.

[shooterfpga]

My es is the same 20-25fps difference but i only use the avg for figuring out anything.

[postal]

My es is the same 20-25fps difference but i only use the avg for figuring out anything.

What I've noticed winter to summer if you keep your ammo out of the sun which is important.... It makes a difference but not much for practical distances which is easy with cold moderate and high temp charts. If you shoot a big bore extended range like 1500+ is where you see it make a difference.

To be honest I only run 1 chart for moderate weather... it's of such minor significance.

[shooterfpga]

What I've noticed winter to summer if you keep your ammo out of the sun which is important.... It makes a difference but not much for practical distances which is easy with cold moderate and high temp charts. If you shoot a big bore extended range like 1500+ is where you see it make a difference.

To be honest I only run 1 chart for moderate weather... it's of such minor significance.

Maybe i should just do it how i normally do. Sounds like the extra charts, logs and math isnt worth it.

[kcstott]

So how are you measuring this 4fps difference??

[postal]

Also, the chart you posted on the other thread shows 168 SMK... for longer distances, people either use the 175 SMK or the hornady 177 (very similar higher BC than the 168) or the VLD for longer range.. which personally I dont like the VLD since they want to be jammed into the lands... unloading a live round becomes problematic.... round sticks in rifling, brass pulls out.. dumping powder in your action and need a cleaning rod to knock out the bullet.... Seen it happen about 4 times.....

[shooterfpga]

I use both 168gr and 175gr. 168gr (600 under) 175gr (600 over) im just currently using 168gr right now. I had to temporarily stop using 175gr as they kept unseating as you experianced with vld. I also have a 6.5 creedmoor running 140gr amax.

[shooterfpga]

Its definately not fun trying to clean out all the powder from the chamber and then rod out the bullet.

[kcstott]

Also, the chart you posted on the other thread shows 168 SMK... for longer distances, people either use the 175 SMK or the hornady 177 (very similar higher BC than the 168) or the VLD for longer range.. which personally I dont like the VLD since they want to be jammed into the lands... unloading a live round becomes problematic.... round sticks in rifling, brass pulls out.. dumping powder in your action and need a cleaning rod to knock out the bullet.... Seen it happen about 4 times.....

I don't know who told you to have the bullets touching the lands but even if that's what the mfg said i wouldn't do it.

I always start .005 off the lands and start playing with it from there. I,ve had loads that wouldn't shoot worth a damn until i gave it 1/8" of free bore.

[postal]

I don't know who told you to have the bullets touching the lands but even if that's what the mfg said i wouldn't do it.

I always start .005 off the lands and start playing with it from there. I,ve had loads that wouldn't shoot worth a damn until i gave it 1/8" of free bore.

It all depends on the bullet you shoot.

It's very common that smk shoots well with a 25-30 thou jump.

It's very common the VLD doesnt shoot well until it's jammed into the lands.

I do not and never have shot VLD's but have seen others using them that jam the lands and had to unload.... and have seen them pull apart 4 times now.

Currently swapped my 308 for a 6.5 creed with hornady Amax 140 with a 15 thou jump.

VLD specifically is known to tighten up groups when jammed into the lands- no others I recall.

[kcstott]

It all depends on the bullet you shoot.

It's very common that smk shoots well with a 25-30 thou jump.

It's very common the VLD doesnt shoot well until it's jammed into the lands.

I do not and never have shot VLD's but have seen others using them that jam the lands and had to unload.... and have seen them pull apart 4 times now.

Currently swapped my 308 for a 6.5 creed with hornady Amax 140 with a 15 thou jump.

VLD specifically is known to tighten up groups when jammed into the lands- no others I recall.

If thats true it sucks, as that severely limits your powder charge ability.