"Return-to-Zero" Mounts: Fact or Fiction?

[blackscot]

Well now that I'm running a scope, I have a need-to-know -- Can I take it off to use the irons and really expect to replace it without re-zero'ing?

I like to maintain proficiency with the irons as well as an optic -- for obvious reasons -- as well as sometimes to shoot 3-gun in the "irons category" just for shitzngiggles. Having previously always had some kind of red dot in a cowitness set-up, it was just a matter of turning the unit off. No longer with the scope, however, which must be got out of the way before flipping up the rear BUIS.

Having recently zero'd my new scope, I thought I'd check here before thoughtlessly taking it back off and then find I need to go through the procedure all over again.

FTR, I have A TR24 on a Bobro mount, but it along with most others tout the return-to-zero capability.

Let me know of your experiences, good, bad, or ugly.

Thanks.

[HuttoAg96]

I recently picked up a GG&G accucam from my EOTech so I could do the same thing - shoot both optics and irons classes at local carbine matches. In the day or so I had to play with it, it seems to come right back to zero every time. Will that last over time? I guess we'll see.

[sammage]

The LaRue mount for my Aimpoint RTZ'd fine.

[Kchen986]

The A.R.M.S. Mount that came w/ my ACOG ECOS RTZ's fine. Zeroed at 100, after a dozen removals and placing back on, the ACOG is still zeroed.

[C4IGrant]

Do throw levers retain and repeat zero? Yes and no. Can a non-lever mount repeat and retain zero? Yes.

I once took my T1/DD mount off my gun. I re-installed it and couldn't tell if there was any shift. No witness marks were used on the mount and I did not use a calibrated torque wrench. I just guessed.

The question you have to ask yourself (when dealing with non-magnified optics and ball (service) ammo is how would you know? How would you know if your optic is repeating and retaining zero? I mean, you have a 4MOA dot, shooting out of a 2MOA gun using ammo only capable of 3MOA. Couple this with the fact that MOST people don't shoot all that well and there is just no way to verify that you are retaining or repeating zero.

Throw levers that have a half inch to an inch of rail contact will do the best job of retainng and repeating zero IMHO. So your BOBRO mount is GTG.


C4

[blackscot]

.....How would you know if your optic is repeating and retaining zero?.......

......So your BOBRO mount is GTG.

Well to provide some possibly needed context, I zero as best as my ability, equipment, and patience permit. This translates to shooting off a sandbag, and adjusting the little dialies until I've convinced myself that the shot placements are as repeatable as my dim eyes and shakey hands can achieve. Certainly not a scientific approach, but basically works.

On this basis, I can then reliably hit 8-inch steel plates at 200 yards at 1X (on a good day anyway). If misses are persistent -- and it's not windy and I'm not tired -- then I suspect the zero of being off.

Glad to hear from a Primary Source that the Bobro should have no trouble fitting the bill -- thanks.

[Robb Jensen]

I've used Bobro for a few years now including a lot of prototype stuff. Got a very tall 30mm one for 3gun on the way to me now. Thus far I have noticed a measurable shift. When I install the scope back on the gun I mount the scope mount on the rail and push it forward and then lock down the lever. With a 1-4x scope I've never noticed it shift.

[BaileyMoto]

Can't say i have noticed shift with my Larue mount (on my mk12), but I guess I could do a more comprehensive test to verify.

[JSantoro]

This is sorta in the realm of "what it means," such as what it actually means when an optic is tagged as "parallax-free." It's absolutely impossible to make anything in which light passes through glass bo be parallax-free (SCIENCE!). In the end, it basically means that the manufacturer has made it as parallax-free as the physical laws of the universe allow it to be. Like with anything measurable, there's a low end (failure), the desired goal, (threshold) and a high end (objective).

With mounts, what the phrase "return-to-zero" really means is that, when you remove the mount for whatever reason, so long as you remain consistent in your remount procedure (same gun, same place on the gun, same method each time), you should see no more than a .5MOA shift.

If you consistently see greater deviation than that, that's a FAIL.

If you consistently see it meeting .5MOA deviation, your mount(s) has achieved the THRESHOLD. It's good, solid, within desirable tolerances.

If you see it consistently showing devaition less than .5MOA or even NO deviation, you are a bastard and I hate you. Not really, your mount is simply achieving the OBJECTIVE.

Everything is subjective to how drunk the little old lady in the factory is that day, what the QC practices of the vendor in question are, sunspots, and the unanticipated appearance of the Spanish Inquisition. There are vendors that do a good job of of keeping those instances to a minimum. After that, you have intangibles like the differeing intensity levels of Silly-Straw Chromosomes that any given user might have....there are always unaccountable, indefinable variables.

This is why ADM, LR, BoBro, and a few others are heartily recommended. It's not fanboy-ism, it's the fact that there is a measurable incidence of their equipment (with all other things being considered equal) consistently meeting and usually exceeding threshold.

EDIT: For clarity, in most instances, all one'll see on a performance spec is threshold/objective, so anything not meeting threshold is considered to have failed.

[ucrt]

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I've removed my T-1 w/ ADM several times at 50-yards and still maintain a good 1-3/4" group. I always apply forward pressure to the mount when tightening the lever.

I have removed a scope mounted in the Chicom Burris PEPR and it returns within an 1" at a 100-yards but I retorque it and position it forward for each install.

I have pretty much proven to myself that my ADM does return to zero BUT after I remove a sight, I always verify it is back on target. I just look at the RTZ "claim" as one that should at least get me back on the paper possibly saving me time and ammo while I verify my zero.

But maybe it's just me...

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