Apparently my rifle shoots fine...

[SinistralRifleman]

I went shooting with a firearms instructor I know yesterday to practice some 100+ yards rifle shooting. We had an MGM Precision rifle target at somewhere around 150-175 yards. I was having a hard time hitting the center flag open, observing my impacts through my scope and the instructor observing through the spotting scope, my groups were consistently 3-4" high and 3-4" to the right. I thought for sure my zero was off, as The instructor wasn't having much trouble hitting it consistently, and trying the rifle he was using I had more consistent hits at range.

So I went to the range this morning to reconfirm zeros on both my rifles. My 20" has a 3-9X MKIV MRT TMR on it sighted in at 100 yards, and my 16" has a Leupold CQT sighted in at 50. I check both their zeros today and both were still on. I didn't have trouble hitting the steel plates out to 300 this time. The only difference today was the lack of mirage from the heat, and less wind. At the range yesterday I definitely noticed more mirage though the 9X than the CQT on 3X. Can the quality of an individuals eyesight exaggerate the effect of mirage on shooting? My groups were consistent when I wasn't hitting the intended area, so I don't think it was a problem with bad technique. Suggestions, thoughts?

On another note, my 20" rifle is more accurate than I would expect it to be. With a chrome lined 1:9 twist barrel and factory cheap ammo here is my target from 100 yards today:

[No.343]

Jim Owens has some good material in his books about mirage. I am out of town and don't have them with me. I think he has some excerpts on his web site.

I went shooting with a firearms instructor I know yesterday to practice some 100+ yards rifle shooting. We had an MGM Precision rifle target at somewhere around 150-175 yards. I was having a hard time hitting the center flag open, observing my impacts through my scope and the instructor observing through the spotting scope, my groups were consistently 3-4" high and 3-4" to the right. I thought for sure my zero was off, as The instructor wasn't having much trouble hitting it consistently, and trying the rifle he was using I had more consistent hits at range.

So I went to the range this morning to reconfirm zeros on both my rifles. My 20" has a 3-9X MKIV MRT TMR on it sighted in at 100 yards, and my 16" has a Leupold CQT sighted in at 50. I check both their zeros today and both were still on. I didn't have trouble hitting the steel plates out to 300 this time. The only difference today was the lack of mirage from the heat, and less wind. At the range yesterday I definitely noticed more mirage though the 9X than the CQT on 3X. Can the quality of an individuals eyesight exaggerate the effect of mirage on shooting? My groups were consistent when I wasn't hitting the intended area, so I don't think it was a problem with bad technique. Suggestions, thoughts?

On another note, my 20" rifle is more accurate than I would expect it to be. With a chrome lined 1:9 twist barrel and factory cheap ammo here is my target from 100 yards today:

[George]

Russ, free float handguards? If not, maybe you were torquing the bbl somewhat when you were shooting at the PRT. I have found similar reasons after the fact when something didn't add up about the POI of a known zeroed rifle.

[SinistralRifleman]

Russ, free float handguards? If not, maybe you were torquing the bbl somewhat when you were shooting at the PRT. I have found similar reasons after the fact when something didn't add up about the POI of a known zeroed rifle.

Yes, the barrel is free floated.

I posted this same question on another forum, and their conclusion was mirage combined with my vision problems is likely the cause. I need to read up on dealing with mirage. If all else fails I can use the old fire and adjust method of shooting with the mil marks in my scope

[George]

If you are sighted at 100 yards and shooting at 150 yards, the issue could have been parallax related. Where you getting your eye centered behind the scope, or was there some pupil offset occlusion going on?

[SinistralRifleman]

If you are sighted at 100 yards and shooting at 150 yards, the issue could have been parallax related. Where you getting your eye centered behind the scope, or was there some pupil offset occlusion going on?

Possibly, but I don't think I was off center by much. It is possible my corrective lenses weren't as centered in front of my eyes as they should have been, I have heard this can cause similar problems too.

[bigbrowndog]

Light bends!!!!!! when there is mirage and wind you will think that the target is one place because that is where your eye sees it. However, the mirage and wind are causing it to appear further downwind from where it actually is, and then the wind will of course cause your impact to shift as well.

I know this and still I cannot remember it when i'm shooting.

Trapr

[Helmut]

close your eyes and use the force

[George]

I am not sure I believe the mirage and wind pushing that mirage at 150 yards will cause this much error. At 300+ I could see it being a large enough factor, but this short of a distance makes me think not unless you had a heckuva' wind going.

[Religious Shooter]

From your target I wouldn't call that zeroed at 100 yards. Shoot at least five to ten shots to determine where you are hitting at 100 yards.

Where you holding center of mass on the target?

With a true 50 yard zero, .243 BC, 3200 fps, 2.7" bore to scope height you are supposed to be around... +2.4"@150 yards.

With a zero at 40-41 yards with the above bullet you are at... +3.9"@150 yards. At 50 yards a 40-41 yard zero is +.5"@50 yards.

If you are +.25" at 50 yards you have a ~43-44 yard zero which at 150 yards is +3.3". Which happens to be within the +3-4"@150 yards you were getting.

If you aren't spot on at 50... if you are off by .25-.5" at 50 yards your calculated elevation at 150 yards of +2.4" can be off by up to +1.5".

[SinistralRifleman]

From your target I wouldn't call that zeroed at 100 yards. Shoot at least five to ten shots to determine where you are hitting at 100 yards.

That was my best group out of the several I shot. When I am consistently that close to the center, especially at 100 yards, I usually call it good. I've driven myself nuts trying to get a group perfectly placed on the target, chasing it around with 1/2MOA clicks. The rifle is clearly more accurate than I am, trying to get it any better is limited by my shooting ability. Frankly I was amazed it grouped so well, as 2MOA is typical with a chrome lined barrel and standard 55 grain FMJ as opposed to 3/4MOA.

I use a 100 yard zero with this rifle as that's what the BDC turrets are made to work with. I pull the target in closer to minimize my human error and see if the bullet is as low as it's supposed to be and centered, and it is. I'm fairly certain the 1/2" low and to the right at 100 is more me than a bad zero.

Where you holding center of mass on the target?

Yes, with a 100 yard zero 150 is the re intersect point

[George]

Russ, RS has a point about that inch+ to the right group at one hunnert' You should be centered on the aim point to be truly zeroed.

Here is a chart showing what a typical 55gr at 3125 fps does downrange when zeroed at 100 yards. Minus a half inch at 150 is about where it winds up.

55gr_100yd_zero.pdf

Your slight zero error coupled with a half inch extra drop and any optical offset from your multiple lenses pretty much explains it to me when coupled with the slight hold wanderings present in a field position versus bagged on a bench.

[SinistralRifleman]

I'll go try some more at the range tomorrow and try not to let the normal weekend mutants that congregate there distract me.

With 1/2 MOA Adjustments 1 up and 1 to the left should be good...in theory

Edited May 26, 2007 by SinistralRifleman

[George]

Russ, with that zero, a dead center hold at 150 on a 4-5" PRT opening has you hitting barely an inch from the right edge of the scoring hole. Any other misalignment whatsoever and it's 50/50 chance as to whether the shot is pulled into the center of the scoring zone, or off the edge of it.

[bigbrowndog]

using a 50 yd zero is not really good, there ar far too many variables that can cause bullets to go astray further downrange. you really should zero at the furthest distance you have available. as RS stated .25" and even less ascew one way or the other at 50, doesn't exactly corellate to twice that much at 100, it can be more!!!!

If you can't get good consistent groups, centered. Try letting someone else who is a better shot than you try. It may be all the gun is capable of, a good cleaning can do wonders as well.

Trapr

[SinistralRifleman]

Went back to the range today. One click left for windage got the group centered around the middle.

I forgot that my elevations clicks are 1MOA not 1/2. 1 Click up put it too high, so I left elevation where it was. Close enough I suppose.

[George]

About 1 MOA is the amount you needed there. At 150 yds this was 1.5 inches. See what I mean. Even with a centered hold, it was a random factor as to whether you hit the plate or the face of the PRT with the original zero.

I'll bet ya' bang that PRT center 10 for 10 from a good rest now ;-)

[SinistralRifleman]

The windage clicks are 1/2 MOA and the Elevation Clicks are 1 MOA on the MKIV MRT I have. IIRC I was told they made them like that so you can get 800 yards of elevation in one full turn rather than two.

I hit the gopher targets a few times at 300+ today when my nerves were steady enough. These are only about 4" across. The larger plates at 200-300 I didn't have trouble with.

[George]

BTW, ifn'ya go ahead and add that 1 click up of elevation, you will be about 3/4" high at a hunnert' which is a lot better downrange zero for the .223 anyway. It will be just about on at 200 depending on just how fast your 55's really are going. This a better 3gun zero IMHO. 1.5" high at 100 is also a great zero for dead center holding on most anything out to 300 and just over.

Always verify at least the windage at longer distances. 100 is barely enough to see the error creeping in.

[bigbrowndog]

just because the adjustment is 1 moa, doesn't mean it will move it 1 moa. it could be more or less, I would vote for taking the 1 moa up. and see what happens if its too much, readjust back down. As George said, verify at the longest distance available.

Trapr

[SinistralRifleman]

The rifle in question with the 3-9x MKIV was zeroed at 100 yards. One click up actually put it just over 1" high at 100 yards in the several groups I shot. I understand simply turning one click might not result in true adjustment sometimes, so I turned past where I wanted it then turned back down. With the same result.

The other rifle I was talking about that was zeroed at 50 yards is my 16" with Leupold CQT. I reconfirmed zero on it and it is good for windage and elevation at 50 yards. This zero works well enough for me hitting the larger targets out to 300 we encounter in 3 Gun.

The 20" Rifle with 3-9x, I usually save for matches like the Ironman where there will be more shooting at distance on smaller targets.

[jobob]

I recently was advised by one of the top 3-gunners that sighting dead on at 50 yards is a good zero. That zero shoots about 2" high at 100 yards. Being old fashioned and set in my ways, I use the same procedure I use on my hunting rifles, 3" high at 100. That gives me a zero around 275 and about 2 or 3 inches low at 300. At 100 - 200 yard steel plates I hold in the lower 1/3 of the target for good hits. 350 hold is the top of the plate. That trajectory is similar to the 50 yard zero method. Either will work well. The 100 yard zero would, I think, cause hold over problems at 250 or 300 yards. On the other hand, you don't have to think about holding slightly under at the 100 - 200 range.

BTW, that 55 gr. Fed. AE is a great load. I get about 1" 10 shot groups with it at 100 yds.