Home Forums Hunting & Shooting Competitive Shooting Tiny groups at 300; so so at 100? Paralax???

This has happened to me twice now. Shooting prone in the field with a bipod I have shot close to a one inch 5 shot string at 300 yards.

But I have never done any super tiny groups at 100. Do I have my paralax adjustment screwed up??? I usually forget to tinker with it. Its a loopy 3.5x10 M1

A friend of mine swears up and down that his other friend has a particular rifle that does not stabalize boolits until they are past 250 or so... to which I cried baloney!

I've got a round that won't stablize till its 300 or beyond, but is super at 600 and 1000 and in between...

I've adjusted parallax the correct way, not using the settings on the dial, and its just the way it is...

I'm convinced some bullets just take longer to go to sleep, especially long skinny, high BC boattails.... like 90 jlks in a 223

Really????
Man! You got me scratching my haid now...

How can it be? from an engineering standpoint...

I ain't crying foul, its just I'm from Missouri so to speak

Dixie,
Sierra is in Missouri too! I read about this in a Sierra loading manual. They call it "Gyroscopic Precession".
They claim it is similar to somone throwing a football.
Long skinny bullets are affected by this more than short fat ones.

Man you got me laughing so hard! Next time I am at the range I am gonna pull that one out and throw it on my bud... Gyrscopic Precession! Dang! between that and metplat and coriollis how do we ever git on paper???? LOL

Thanks! I am going to look that one up.

Parallax can be unadjusted as long as you stay behind the center of the scope...... Its only if you nod off to a side that it'll affect you.

As to reasons why to an engineer.... sorry I'm far from that, I only report what shows up on paper in real life and could care less why it shows up.

Much like a chrono telling you this is the lowest ES/SD, and will be your best load ,but the target telling you the load sucks, go with paper...

Jeff

BTW when the chrono says perfect and the paper says no, I personally think you have the load balanced but not in the sweet spot of the barrel, such that if you keep the low es and sd, and bobbed the barrel half in inch at a time you'd find you would get into the sweet spot AND have the best of the chrono...

My 1K BR rifle has shot a best of 5/8" at 100 yds. It's best 1000 yd group is 3.5," and it has shot several 4" or better. It's not uncommon at all for long, high BC bullets to moa better at longer ranges.

Blaine

Exactly what i've seen, on a smaller scale distance wise though.
Thanks for the backup.

Jeff

My old Winchester 300 does the same thing. The 240 grain shoot into 1 inch groups at 100 and 1 1/2 inch groups at 300. Go figure.

Wayne

Yet lots of folks will happily call 3 of us liers...

Who cares? That old Bull Rifle was designed for long range, and I've even had guest shooters get the same result with bullets as light as 168 grain Sierra Match. Results is results, right?

Wayne

Its why I always say the paper doesn't lie....while books, chronos and the net can...

I attribute it soley to parallax. Someone with lots of coin will have to set up some optical screen targets in a series and pass each round through the series to make a believer out of me. In other words, show me the numbers, and the numbers must come from the same 10 rds measured at each range. Putting 10 rds thru a paper target at 100 yds, and then another 10 rds at 500 are two completely independent and unrelated events. If one has garbage at any point along the path, he will have garbage for the rest of the journey. There are no ion trails out there that will cause one's bullets to converge as they move further down range.

Another potential aspect is having targets that fit ones sights at each range. I.e. at 100 yds the bulls eye will be 1/4 inch when using my 257 with its 24X scope. Move to 400 and a 1 inch bull will fit the cross hairs almost perfectly. Consistently shooting small at each range will typically improve ones performance. 1Minute

It can be parallax except those like Blaine and myself shoot up to 10K rounds a year and know how to take that out... Its not in our case, related to the scope...

Its simply the bullet not going totally to sleep. Very common with high BC bullets.

It has nothing to do with target size either, my targets are made for whatever I'm shooting, IE 300 is different than my 600 yard targets, I actually make them each time I shoot after I see what power of the scope I can see best with that day due to mirage issues unless I'm shooting at night.

Of course if you shoot diamonds, target size isn't as critical.

rost, how important is velocity with putting the bullet to sleep? I am working on a load with 115g Berger VLDs(.257) and I am not getting the groups that I want to get at 300 yards for a varmint target shoot. (Shoots really well at 100y) Should I speed it up or slow it down? Will that matter?

I am going to shoot the same load at 600y and see how it shoots.

Lastly if you are working up a load for a particular distance, do you shoot off a bench at that distance or do you load develop at 100 yards?

Do you shoot a load at different distances to see when it goes to sleep?

Sorry for all the questions.

This is my take on it.... there will be others.

Velocity only matters a lot if the twist is wrong. Stabilization becomes a problem with sleeker bullets, longer means sleaker and that means faster twists required OR running the bullet faster, which can tear the jacket apart. Shot some 64 bergers in a 7 twist once, pushed too fast and too fast of a twist, not a one ever hit paper. So there are both sides.

If I was going to run a specific bullet I always twist up for that bullet per the formulas for twist. Then I can feel safe working in the parameters of the cartridges speed without pushing safety.

How do I work up a load. I shoot the bullet I want to shoot, at the distance I want to use it at. I haven't shot more than deer rifles to test zero's at 100 yards in years. My testing all starts at 200 or 300 yards and extends out.
The first thing I do is run an audette test preferably at 300 yards. Take the fastest clump and load them up in groups of 3 or 5, shoot them at 300 to reverify, then take it straight to 600. 600 can show errors better, IE I play with neck tension, seating depth and primers at full distance. Thats IF what I take to 600 doesn't make me happy.

You also may have issues with case weights, non concentric issues and so on, that generally don't show at 100.

In fact the only reason I found that some loads didn't work at all at 300 but did at 600 was a fluke, I shoot different loads, 300 I shoot a cheaper load/bullet. But one day I was shooting a 300 yard match and it was really quick switching winds, I thoughth, heck I'll run my 600 ammo and have an advantage... not at all really, it barely would hold the 10 ring....Went out and shot it scoped at home, same thing showed.. I've also got a kick butt 300 prone load, that doesn't fair well at 600, but at 300 I've shot 5 shot groups of an inch...

Good luck, Jeff

Never been to Missouri, but the physics of what I'm reading is mind boggling. Can't even begin to imagine how one might model this phenomenon.
As I understand it, bullets leave the barrel at 2 moa and then turn 1 moa to group 1 moa?
I'm a lot more comfortable with paralax.
There was a lot of people that saw the edge of a flat planet, also.
I am sure that you are seeing the results that you are reporting, just not buying the explanation.

Guys,

This is a very interesting topic!

Hadn't heard about this "gyroscopic precession" before. Will have to look this up later.

Have found that the 160 gr GameKings and AccuBonds do pretty good @ 100 yards (.7" and .75") in my custom Sako 7MM STW hunting rifle, but do very well further out; 3" @ 400 yards and 1.6" @ 300 yards, respectively (when I do my part!).
This didn't add up to what I'd read or been told before.
(1" @ 100 = 2" @ 200 = 4" @ 300 = 8" @ 400)
The only random guess I've received of late was a question about the muzzle's crown.

Blkram, a minute of angle (moa) is a unit of angular measurement, 1/60 of 1 degree. Calculating the physical equivalent group size equal to one minute of angle can be done using the equation: equivalent group size = tan(MOA ∕ 60)*distance. In the example previously given and substituting 3600 inches for 100 yards, tan(1 MOA ∕ 60)∙ 3600 inches = 1.0471975511966 inches.
As a linear equation, 1 moa (or 1" for simplicity)at 100 yds would be 3.15" at 300 yds, and approx. 4.2" at 400 yds, etc.