Ruger American Rimfire - Radical POI Shift

[Emmanuel of Arms]

Hi All,

New guy here. I was hoping you all could help me understand what is going on with one of my more finicky firearms, and maybe advise if it falls within normal range of deviation.

As a baseline, let's talk about my reference gun. My trusty Ruger 10/22. It exhibits what I'd consider a normal amount of POI shift, very much inline with what I've seen with my 9mm carbines. Maybe .5-3 MOA of shift with different ammo. Not so much that I couldn't make a dope sheet, and put a few clicks on the optic to adjust. Especially important in this day and age where you don't know what will be on the shelf.

Now on to Mr Troublemaker. My Ruger American is exhibiting an what I'd consider an unreasonable amount of POI shift at 50 yards. Like 3 mils. Each mil is 3.38 MOA, then double that because MOA is an inch at 100 yards, and we're talking roughly 3*3.38*2 = 20.28 inches of shift at 100 yards. Holy crap! Is that really normal?

Before we get to the data, let's talk about gun setup.

Ruger 10/22 Takedown

• TacSol XBR barrel. However the factory barrel exhibits comparable performance.
• Factory trigger. I think it has the auto-bolt release plate in it.
• Sig Romeo 5 (2 MOA dot)

Ruger American

• All factory, trigger is adjusted down to minimum pull.
• I've tried a number of rimfire scopes because I thought that was the problem. I took the mil readings based on a BSA mildot scope, then switched back to a trusted Simmons 9x32 that has served me well on the 10/22. Both scopes required consistent holdover for different ammo.

For the sake of this experiment, both guns were zeroed with the same ammo at the same distance. More below:

• Federal 40gr 1200fps (baseline)
  • Both guns were zeroed with this. Groups were fine. Roughly 1" groups off an improvised rest at 50 yards.
• Winchester Super X 36gr 1280fps
  • 10/22 - Shoots a tad high. Maybe half an MOA. Has not been so much that I can't hit what I'm shooting at @50yds with the same point of aim.
  • American is already shooting a mil maybe 1.5 high.
• CCI Stinger 32gr 1640fps
  • 10/22 - Shoots high, maybe 2 or even 3 MOA high? I hold low within the body of a critter at 50-75 yards to get a clean hit.
  • American shoots a full 3 mils high. I've made a few clean shots with this hold over, but mostly at totally stationary targets. Moving shots I'm not quite there trying to count mils and holdover while only having a 3 second shot window.

I've tried other ammo like Aguila Super Extra, Norma, Velocitor, MiniMags, etc... I did not take the time to dial in on paper with those. Just noted the POI shift was enough to not run them in the American. Also, sorry to mix MOA and Mils. That is the adjustment and/or instrumentation that I used on each gun at the time of measuring the results. Thanks.

 

[Armored farmer]

I voted ammo, but....no expert though.

 

[BigBL87]

I don't think you double the number, so that does change the calculus a little bit. A mil is a mil and MOA is MOA regardless of the distance. So, 3 mils converts to 10.31 (rounded) MOA. At 50 yards that's 5ish inches, at 100 yards that's 10ish inches..

So, still a significant difference in drop BUT not as huge. I used Strelok to chart out absolute drop for each. You're looking at about a 1.5 inch difference in absolute drop at 50 yards between Automatch and Stinger, and about 5 inches at 100 yards assuming all other things are equal. That isn't really a valid assumption, as the powder burn rate of the different ammos can affect how close to their listed velocity they get in an equal length barrel, but all in all that shouldn't make a huge difference. All that said, I'd your mil measurement is accurate, you are sing a bigger shift than you probably should...







My bigger question is how you are getting the mil measurement? Is that based off of using the mildot scope at maximum magnification? If its not at maximum magnification or FFP, then the holdovers won't be true to the mildot reticle as far as the actual mils between each dot.

Really, knowing the inch difference of the POI would be alot more helpful.

 

[Emmanuel of Arms]

I don't think you double the number, so that does change the calculus a little bit. A mil is a mil and MOA is MOA regardless of the distance. So, 3 mils converts to 10.31 (rounded) MOA. At 50 yards that's 5ish inches, at 100 yards that's 10ish inches..

So, still a significant difference in drop BUT not as huge. I used Strelok to chart out absolute drop for each. You're looking at about a 1.5 inch difference in absolute drop at 50 yards between Automatch and Stinger, and about 5 inches at 100 yards assuming all other things are equal. That isn't really a valid assumption, as the powder burn rate of the different ammos can affect how close to their listed velocity they get in an equal length barrel, but all in all that shouldn't make a huge difference. All that said, I'd your mil measurement is accurate, you are sing a bigger shift than you probably should...

View attachment 1004196

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View attachment 1004194

My bigger question is how you are getting the mil measurement? Is that based off of using the mildot scope at maximum magnification? If its not at maximum magnification or FFP, then the holdovers won't be true to the mildot reticle as far as the actual mils between each dot.

Really, knowing the inch difference of the POI would be alot more helpful.

You are right. I derped the math up by multiplying by two. The deviation on the American vs the 10/22 still seems wild. I will see if I can turn up any paper. Or I will try to make some tomorrow, weather permitting.

I had the magnification on the mildot scope set at 12 out of 24, when zeroed and kept it there during shooting. The Simmons I used for comparison was a 9 power, and not graduated for mil or MOA.

As far as the theory goes, is the accuracy of the graduations on a MIL or MOA scope really predicated on using it at full magnification? That bend my brain a bit and makes me question why adjustable power scopes have graduations?

Obviously I am still learning here an appreciate the input.

 

[BigBL87]

You are right. I derped the math up by multiplying by two. The deviation on the American vs the 10/22 still seems wild. I will see if I can turn up any paper. Or I will try to make some tomorrow, weather permitting.

I had the magnification on the mildot scope set at 12 out of 24, when zeroed and kept it there during shooting. The Simmons I used for comparison was a 9 power, and not graduated for mil or MOA.

As far as the theory goes, is the accuracy of the graduations on a MIL or MOA scope really predicated on using it at full magnification? That bend my brain a bit and makes me question why adjustable power scopes have graduations?

Obviously I am still learning here an appreciate the input.

I'm not as well versed as some on here, so someone may jump in to correct me, but...

If a scope is first focal plane, where the reticle changes size as you change the magnification, then the reticle and its markings should be accurate across the entire magnification.

If a scope is second focal plane, the reticle stays the same size no matter what magnification you're at. If that is the case, mildot and/or ballistic reticles are calibrated for one magnification in the scopes range, typically maximum magnification.

This picture shows the difference pretty well:



So, with the FFP mil dot reticle above, no matter what magnification you are the space between the dots is 1 mil (assuming a standard mil dot reticle). That's because the reticle changes size with the level of zoom and as such it stays consistent.

With the SFP mil dot, only at max magnification is the space between the dots actually representative of 1 mil because that is what the reticle is calibrated for. Anything below that magnification and the distance between the dots is actually more than 1 mil.

That's not to say SFP mil dot or ballistic reticles aren't useful otherwise, just not accurate for measuring MOA or Mil unless at full magnification OR you happen to have a ballistics program like Strelok to help you figure out.

In the example below, the scope is calibrated so that the mil reticle is accurate at 9x magnification, and the target is at 50 yards. Notice how at different magnifications the "inches of space" at the target distance between the dots is different (the blue number) as well as the bullet drop. That is why at 12x power the dots on your scope wouldn't actually represent a mil. In reality it would be approximately half a mil I think. So, instead if a 3 mil difference in POI you'd be looking at about a 1.5 mil POI shift, in which case I think you'd be coming out about right based on my absolute drop charts above.

Alot of what it comes down to is the understanding that MOA and Mil are not an absolute measure of distance, but rather a measure of division of an imaginary circle.

 

[Varminterror]

Not for nothin’, as they say, but you’ve made three errors:

1) 1 Mil = 3.44moa, not 3.38.

2) 1 Mil at 100yrds subtends 3.6”, not 3.38” (and 1moa at 100 doesn’t subtend 1”, it’s 1.047”, hence the difference between 1mil = 3.44 moa = 3.6” at 100yrds).

3) Your doubling math was wrong - you didn’t express your units so your math doesn’t yield a real value. If you measure 3 mils with your reticle at 50yrds, you do NOT multiply 3 * 3.6” per Mil at 100yrds * 100yrds / 50yrds (noting here, you used 3.38” per Mil at 100 and also that 100yrds /50yrds represents the doubling scalar, 2, which you used). You doubled TWICE. 3 mils at 50yrds would be 1.8” per Mil at 50yrds * 3 mils = 5.4” at 50yrds, which you could then double to be 10.8” at 100yrds. OR you can realize that 3 mils at 50 is still 3 mils at 100, and we know 1 Mil is 3.6” at 100, so 3 mils is 3.6*3 = 10.8.

So somewhere in the mix, you used the wrong scaling factor and then used improper proportional math, so you ended up with “almost” the 200yrd dispersion estimate. Not the 100yrd estimate you were after.

4) I’ll throw in a fourth “bonus mistake” here - stop considering your targets and dispersions in inches. Just live in mils or minutes. The only time inches matter is when you have your hands on the target and a ruler to measure the group. For everything else, the reticle replaces your ruler, and you have no means to measure in inches, only in mils or MOA.

 

[Varminterror]

As far as the theory goes, is the accuracy of the graduations on a MIL or MOA scope really predicated on using it at full magnification? That bend my brain a bit and makes me question why adjustable power scopes have graduations?

Yes, in a second focal plane scope - unless otherwise indicated in the manual or on the magnification ring itself - typically the reticle is only properly proportioned at the maximum magnification.

Many of us consider that second focal plane scopes should not include graduated reticles for this reason. However, additional math can be done by the shooter to correct their readings with the reticle. For example, in a 6-24x SFP, a Mil dot reticle will have 2mil wide gaps when set at 12x, instead of 1 Mil wide (center of dot to center of dot). At 6x, the dots will be spaced 4mils on center.

In a first focal plane scope, this scaling doesn’t happen - one Mil is always one Mil.

I had the magnification on the mildot scope set at 12 out of 24, when zeroed and kept it there during shooting. The Simmons I used for comparison was a 9 power, and not graduated for mil or MOA.

Confirming this: assuming this is a second focal plane optic, unless you have a very odd 6-24x optic, at 12x, those Mil dots are calibrated only for 24x, so when you measured 3mils at 12x, it was really measuring approximately 1.5mils.

 

[Emmanuel of Arms]

Yes, in a second focal plane scope - unless otherwise indicated in the manual or on the magnification ring itself - typically the reticle is only properly proportioned at the maximum magnification.

Many of us consider that second focal plane scopes should not include graduated reticles for this reason. However, additional math can be done by the shooter to correct their readings with the reticle. For example, in a 6-24x SFP, a Mil dot reticle will have 2mil wide gaps when set at 12x, instead of 1 Mil wide (center of dot to center of dot). At 6x, the dots will be spaced 4mils on center.

In a first focal plane scope, this scaling doesn’t happen - one Mil is always one Mil.



Confirming this: assuming this is a second focal plane optic, unless you have a very odd 6-24x optic, at 12x, those Mil dots are calibrated only for 24x, so when you measured 3mils at 12x, it was really measuring approximately 1.5mils.

Super interesting to me that they would make a scope where the graduations are calibrated to a zoom level that is effectively unusable in all but the brightest conditions (it’s a cheap scope). But I see your point that I may have doubled the mils, and then accidentally doubled my math. So I may be at 4x, which as the other gentleman pointed out effectively puts me out to 200 yds.

I am shooting some paper now and hope to have it posted soon. Then we can see if the theory matches the results. Thanks.

 

[Varminterror]

@Emmanuel of Arms - this is largely an example of “you get what you pay for,” combined with “caveat emptor.” Lots of people get lured into buying 1” tube 6-24x40mm second focal plane scopes with milling reticles (even worse when they have 1/4 IPHY adjustments) thinking they are buying something capable of long range shooting, but then realize a 1.7mm exit pupil is crap for low light, the SFP correcting math sucks, and 1” tubes often don’t actually offer enough internal adjustment for long range shooting with many common “new shooter” cartridges.

But you’re wrong to state the reticle graduations are not usable except for at the calibrated magnification. As I stated above, all other magnifications can still be used, there’s just one more step of math to be done to scale for zoom. If you read 3mils at 12x in a 24x calibrated scope, the ratio of 24/12 gives you the correct reading - 1.5 mils. If you read 1.5 mils at 8x, the ratio is 24/8, so the corrected reading is 0.5mils.

 

[Emmanuel of Arms]

Attached are the groups I shot today. Funky math notwithstanding, my observations about the American shifting about 5” at 50yds remain accurate. As you can see, the variation with the 10/22 is manageable.

The 10/22 was zeroed with stingers and I also shot the federal bulk. They were so close that i opted not to shoot any super extra. The American was zeroed for winchester super x, but i am out of that so I substituted aguila super extra which i find comparable. I also shot federal bulk and the stringers.

 

[CoalCrackerAl]

Ok after all this fancy talk. Is your scope rings and base tight?

 

[Emmanuel of Arms]

Ok after all this fancy talk. Is your scope rings and base tight?

Haha, yes. I just double checked to be sure. This amount of shift has been consistent across multiple optics mounted on their own separate pair of rings.

The BSA optic and rings which were previously on the American are now on a marlin 60 and doing fine.

 

[BigBL87]

What distance are they zeroed at? And is that the same distance you're shooting at?

 

[Emmanuel of Arms]

Yep, zeroing and the groups recorded were both done at the same bench.

The bench is 50yds up range from the berm.

 

[CoalCrackerAl]

I put loc-tite on my Marlin 60's rails where the rings meet the dove tail. Scopes like to walk from the action working. Had to do the same thing for my wife's Savage 64.

 

[BigBL87]

OK, so the 10/22 being zeroed for the Stingers and the American being zeroed for the Winchester/Aguila may be part of it. If you're zeroing both at 50 yards, the ballistic curves are a bit different.

The Stinger at advertised speed will JUST be starting to drop ever so slightly at 50 yards when zeroed for that distance, hitting its high point just short of 50 yards. The Winchester/Aguila on the other hand, because of the lower velocity and heavier projectile, in order to be zeroed at 50 yards will need to be shot with the barrel pointed higher than with Stinger and will have a less-flat ballistic curve.



So, what does this mean to our question... On a rifle zeroed with Stingers, the scope/barrel alignment to zero will have the barrel flatter than if it were zeroed with the Federal. So the Stinger will hit about right on, and in theory the Federal will be dropping though probably not by an insane amount yet at that distance. One is just starting to drop, and one is dropping a bit more.

On the other hand, with a rifle zeroed for the Federal, the barrel will be pointed "up" more in relation to the plane of the scope based in the ballistic curve of the slower, heavier round. At 50 yards, the federal will already have been dropping from its peak for 15 yards to get to that POA/POI. You shoot the lower weight, higher velocity round at that same barrel angle in relation to the scope and it may very well still be climbing or hitting its peak at 50 yards.

Now, I'm not sure that explains 5 inches of difference, but at least logically (if what I laid out made sense) a noticeable higher impact would make sense given what each rifle was zeroed for.

 

[Barbaroja]

I expect different POI for different brands of ammo, with different speeds and projectile weights. I’d say sight in for the most accurate round you have and just use it

 

[CoalCrackerAl]

I like the BDC reticle for different rounds.

 

[Emmanuel of Arms]

OK, so the 10/22 being zeroed for the Stingers and the American being zeroed for the Winchester/Aguila may be part of it. If you're zeroing both at 50 yards, the ballistic curves are a bit different.

The Stinger at advertised speed will JUST be starting to drop ever so slightly at 50 yards when zeroed for that distance, hitting its high point just short of 50 yards. The Winchester/Aguila on the other hand, because of the lower velocity and heavier projectile, in order to be zeroed at 50 yards will need to be shot with the barrel pointed higher than with Stinger and will have a less-flat ballistic curve.

View attachment 1004426

So, what does this mean to our question... On a rifle zeroed with Stingers, the scope/barrel alignment to zero will have the barrel flatter than if it were zeroed with the Federal. So the Stinger will hit about right on, and in theory the Federal will be dropping though probably not by an insane amount yet at that distance. One is just starting to drop, and one is dropping a bit more.

On the other hand, with a rifle zeroed for the Federal, the barrel will be pointed "up" more in relation to the plane of the scope based in the ballistic curve of the slower, heavier round. At 50 yards, the federal will already have been dropping from its peak for 15 yards to get to that POA/POI. You shoot the lower weight, higher velocity round at that same barrel angle in relation to the scope and it may very well still be climbing or hitting its peak at 50 yards.

Now, I'm not sure that explains 5 inches of difference, but at least logically (if what I laid out made sense) a noticeable higher impact would make sense given what each rifle was zeroed for.

Hrm.. I think what you’ve stated is sound, but only in the context of determining the secondary zero and thereby the bullet’s trajectory in relationship to the aiming plane at various distances. The same reason the 50/200 RIBZ is so popular on AR platforms, because it results in a flatter trajectory along the aiming plane. So to your point, I agree the ammo you choose (and height of the optic) to zero with also will affect your secondary zero and overall trajectory at different distances.

Imagine both guns had been bore sighted in a vise, no optic. Would that really have resulted in a different outcome at 50 yards? I think the American would still be off by 5”.

I think it needs warrantied tbh. It’s already been in twice for magazine/feeding issues, which was resolved by replacing the warped stock. And it is the only firearm I have out of, i donno, 15 or so that behaves so erratically.

PS: Thank you for all of the ballistics data. I am going to have to learn to use those tools in the future.

 

[BigBL87]

Hrm.. I think what you’ve stated is sound, but only in the context of determining the secondary zero and thereby the bullet’s trajectory in relationship to the aiming plane at various distances. The same reason the 50/200 RIBZ is so popular on AR platforms, because it results in a flatter trajectory along the aiming plane. So to your point, I agree the ammo you choose (and height of the optic) to zero with also will affect your secondary zero and overall trajectory at different distances.

Imagine both guns had been bore sighted in a vise, no optic. Would that really have resulted in a different outcome at 50 yards? I think the American would still be off by 5”.

I think it needs warrantied tbh. It’s already been in twice for magazine/feeding issues, which was resolved by replacing the warped stock. And it is the only firearm I have out of, i donno, 15 or so that behaves so erratically.

PS: Thank you for all of the ballistics data. I am going to have to learn to use those tools in the future.

Ya, the thing that is weird about it to me is it is only 1 specific ammo, and it still seems to group fine with it. If it was really erratic and wouldn't group, I'd think it was something mechanical but I dunno, kind of grasping for an explanation at this point, haha.

 

[Varminterror]

@Emmanuel of Arms - it really seems to me that you’re making much ado about nothing.

Different ammo will print to a different POI. Nothing more than that, nothing less. As long as each ammo type shoots small and the zero remains consistent for that type, you really don’t need to care so much about the offset between them. Record the POI shift or rezero when you change. Many of us do this regularly, and it’s really not so complicated - nor does it need to be.

 

[Emmanuel of Arms]

Ya, the thing that is weird about it to me is it is only 1 specific ammo, and it still seems to group fine with it. If it was really erratic and wouldn't group, I'd think it was something mechanical but I dunno, kind of grasping for an explanation at this point, haha.

I’m going to see if I can turn up any other hypervelocity 22, like maybe some yellow jackets or something to further investigate. In the mean time, I think I’ll reach out to Ruger and see if they have anything to say about it. Appreciate everyone jumping in to put their noodle to it.

 

[Ru4real]

@Emmanuel of Arms

I think the bolt return spring or bolt is lighter, or both, in the 10/22.

And the “benefit” is that the stingers print closer to the federals, because the stingers are leaving the barrel of the 10/22 slower than the American, because the blow back bolt begins to travel rearward sooner in the case of the 10/22.

Said another way, if you shoot 1640 fps stingers and 1200 fps federals out of a bolt action 22, the stingers will print higher than the federals at 50 yards, always. Gravity and flight time and all that jazz.

 

[Emmanuel of Arms]

@Emmanuel of Arms

I think the spring or slide is lighter, or both, in the 10/22.

And the “benefit” is that the stingers print closer to the federals, because the stingers are leaving the barrel of the 10/22 slower than the American, because the blow back bolt begins to travel rearward sooner in the case of the 10/22.

Said another way, if you shoot 1640 fps stingers and 1200 fps federals out of a bolt action 22, the stingers will print higher than the federals at 50 yards, always. Gravity and flight time and all that jazz.

Good points made on bolt action vs blowback. Wish I had a chrono to test that theory...

As an extension of that thought, I had wondered if...

• The 10/22 shooting out of a short 12" massively thick TacSol XBR barrel made a difference. Probably no harmonics at play, and a little less velocity (I'll quote a chart below. It's not as much as you'd think.)
  • Mitigating factor: The 16" factory barrel, though I've only done limited testing, gives similar POI to the TacSol barrel.
• The American has a 24" barrel. Is it really possible that harmonics are at play with 22LR?
  • Wrinkle: My 24" Marlin 60's don't shift this much. Though I should shoot more paper tomorrow to quantify. Understanding that by your theory, the Marlin 60 is giving up some velocity per the blowback action, even tho the barrel length is the same.

Chart from ballisticsbytheinch for various 22LR ammo. I am always shocked by how relatively flat things are down to 12", but I've not verified their testing method as far as fixed action vs auto.

 

[BigBL87]

I guess one thing you could try is zeroing the American for the Stingers, and then repeat the experiment. See if the difference is as big. I'd venture to guess it probably won't be, but I could be wrong.

Barrel length is another variable I hadn't even considered, the longer barrel of the American may maximize the performance of the Stingers such that you end up with a greater difference in velocities than out of a shorter barrel.