Shooting Accuracy

[DamnRinella]

I am enjoying this as well

 

[deerkiller]

My last hunting rifle was consistently 0.65 MOA 3 shot groups sandbagged in from the bench with 165 TTSX. That's not a "best" number that was the average of 5, 3 shot groups.

I will say I disagree with the guy who said only 5 shot groups count. 5 shot groups are a better indicator for target rifles with heavier barrels but for anything thinner than a #4 contour the heat tends to cause some POI shifting after 2-3 rounds. I don't like taking ten minutes in between shots either.

"I" think you are mistaken

 

[Northwinds308]

Hey I probably came off snarkier than I meant to, I need to use the internet less when I'm sleep deprived.

That was really interesting, thanks for the detailed information. I'd buy the cold shooter explanation, that makes a lot of sense.

I do shoot long range regularly so this will give me a new way of collecting data for hit probability. I didn't think the 5/10/30 round strings would show as drastic a difference as they did between test.

The part that I have trouble getting my head around is the heat not affecting accuracy. So to qualify for a course I've assisting with the shooters have to shoot 1 MOA at distances of 1-400 meters, 1.5 MOA at 500, and 2 MOA at 600 with a .308 Win platform.

Same group of people took a very high end .338 LM, shot 2 deliberate 5 round groups, then fired 25 rounds in a "sustained fire" role, then 2 deliberate 5 round groups. The second set of groups was not equal to the first, they were pretty well double the size.

 

[Formidilosus]

Same group of people took a very high end .338 LM, shot 2 deliberate 5 round groups, then fired 25 rounds in a "sustained fire" role, then 2 deliberate 5 round groups. The second set of groups was not equal to the first, they were pretty well double the size.

No issues. It’s all discussion. I need a note under the bottom of my posts that says “everything written should be taken in a conversational tone”. Ha


As for the above, my initial thought is shooter fatigue. 338L recoil, especially with brakes for 45 rounds is not to be taken lightly.

 

[Northwinds308]

No issues. It’s all discussion. I need a note under the bottom of my posts that says “everything written should be taken in a conversational tone”. Ha

Well if that wasn't the most relevant thing I've read all day, thanks for the new insight. I'll have to try that with my custom rifle when it's finished.

So your philosophy on it is shoot a 10 round group from a mechanical rest, which should give you an 85% probability of your rounds landing within that cone. Did I understand that correctly?

Sorry for stealing your thread OP, I like getting into the weeds when it comes to ballistics.

 

[Formidilosus]

So your philosophy on it is shoot a 10 round group from a mechanical rest, which should give you an 85% probability of your rounds landing within that cone. Did I understand that correctly?

Yes, mostly. For a better than 95% certainty you need 30 rounds on the same target. Really doesn’t matter how many how many rounds per group to get there, just 30 rounds.

What I generally say, is most people do not want to nerd out about this stuff. Ok cool, I get it.

The easy button is to use scopes that work correctly (vast majority do not), and rifles that generally do not have issues. Then-

1). Bore sight rifle.

2) Fire one round at 100 yards. If it is on paper-

3) fire 9 more for a ten round group.

4). Adjust to bring center of group to center of point of aim.

5). Fire another 10 round group.



At this point you will know the true precision of the rifle system, will know if there are any underlying issues with the rifle, and that you have a solid zero.

 

[Northwinds308]

Then you will know the true precision of the rifle system, will know if there are any underlying issues with the rifle, and that you have a solid zero.

Awesome thanks for explaining. I've shot a box test with my current scope and it tracks very well. I'll have to give this a try when I get my new rifle. I have a friend getting more into the weeds with this too and I'm helping him do some handloads. I'll have to give this test a try with his rifle.

 

[DamnRinella]

i changed a few basic things and in the order that helped

1 the table at range seemed a bit wobbly lean back and the bench shifts. Low and behold they had wooden supports you could ask for to support bench

2 bag under the butt of rifle

3 new timney elite hunter trigger

Shot 3 groups of 3 right around 1 moa. Others I was practicing on keeping eye through scope while reloading and being faster for hunting and accuracy suffered some.

Next steps I need help with if the experts don’t mind. I have the 16.5 inch rem 700 sps tactical and shooting hornady 308 178 eld x. What velocity drop should I expect with this shorter barrel? Using for strelok to assist with DOPE card. Thx!!

 

[bitbckt]

I usually figure about 50 fps per inch of barrel in a .308.

 

[DamnRinella]

Thanks I notice strelok uses bullet speed instead of muzzle velocity. Is it the same in their mind?

 

[DamnRinella]

I usually figure about 50 fps per inch of barrel in a .308.

Can this be right? So a 24 inch barrel is 2600 for this ammo. So 2225 for my rifle, seems slow. I edited as I did bad math earlier.

 

[bitbckt]

Can this be right? So a 24 inch barrel is 2600 for this ammo. So 2225 for my rifle, seems slow. I edited as I did bad math earlier.

It very well could be. Factory ammo isn't typically loaded with powder fast enough for a short barrel. A 20" barrel with a 178gr bullet would probably be somewhere around 2400-2500 hand loaded with W748, but factory ammo loaded for a 24" barrel using (say) IMR 4064 isn't going to reach appropriate velocities in a short barrel.

Since you're asking, I assume you don't have access to a chrono or enough distance to measure your dope directly?

 

[EastMT]

You don’t lose nearly as much as pay people think, but you do gain muzzle blast. Here’s a test of cutting a barrel in 1” increments starting at 28”.

Sorry the bottom one should be up top.


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[EastMT]

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″) Introduction Released by Winchester in 1952 (and adopted by NATO in 1954 as the 7.62x51mm NATO), the 308 Wi…

rifleshooter.com

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[bitbckt]

Nice, thanks for that coop.

 

[EastMT]

Here is another all the way to 13.5”, not too shabby really if you wanted a 308 hunting pistol.


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[DamnRinella]

Funny thing is the default settings map to what i shoot at 300 yards but want to learn more about 300+. Is the bullet speed the same as muzzle velocity on strelok?

 

[Jimbob]

I have a rem 700 sps stainless and cut the barrell to 18.5". Tried a bunch of ammo and really wanted 165 grn accubonds to work but the rifle likes 180 interlocks better.

With the factory hornady interlock I can get the bullets to touch consistently and over all range sessions it is very close to 1 moa.

Don't be afraid to try different bullet brands.

 

[ChrisAU]

The barrel was cooled down to ambient temperature for each 5 round group.

So if heat doesn't affect the accuracy, what is the point of this? Just playing devil's advocate @Formidilosus

 

[Formidilosus]

So if heat doesn't affect the accuracy, what is the point of this? Just playing devil's advocate @Formidilosus

The testing organizations protocol.