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Thoughts on zeroing

Having spent time in the military and working at a public range I learned that most people don’t understand zeroing sights or optics.

I always found it humorous when some of the regulars at the range would have a new rifle or new optic and invite me to come over and try their new gun. I’d fire a shot and tell them something like, “Cool rifle, but it is impacting 4 inches left for me.” The response I would get would be a coy line much like, “Well why don’t you go ahead and dial it then.”

I like to imagine that I keep all my firearms combat ready, but realistically I would never choose to use some of them in a fight. I wouldn’t grab the 10/22 for obvious reasons. While I would trust a Garand in a fight, it would be far from my first choice. One of the most critical things I think of as part of being “combat ready” would be the simple ability to hit what you are aiming at.

I like to think of the quality of a zero on a firearm as one of several states. I don’t think I’ve seen other people talk much about this, so I want to lay out what I think it.

  • Unzeroed
  • Mechanical Zero
  • Battle Sight Zero (BZO) or Reduced Range Zero
  • Fine Zero
  • True Zero (or proofed zero)

Unzeroed: The least desirable state for a firearm sights to be in. Hopefully an unzeroed firearm will impact close to where you aim, but there is no way to know with out test firing or checking the bore axis to the sights against a common index.

Mechanical Zero: The sight is centered either mechanically or optically. On something like a micrometer adjustable sight, mech zero may be obtained by counting the total number of clicks and adjusting it half way. On scope you could count clicks or use a mirror to get the crosshair centered in the tube. Centering a scope via scope adjustment may not be the same as optically centering.

Generally, one a well built firearm, mechanical zero will be close to right on. On cheaply built guns, not likely. If you have something like a rifle with a 30MOA canted base for long range shooting, the mechanical zero on the scope will deviate from a proper zero because of that.

It used that a brand new, out of the bolt, Colt AR15 or M16 generally didn’t need adjustments from mechanical zero when sighting in. But as of the last few years this no longer seems to be the case.

Battle Sight Zero (BZO) or Reduced Range Zero: There are all manner of reduced range zeroing techniques. Rarely you will see 10m zeroing targets. Often reduced range zeroing in militaries is done at 25m. For the longest time the USMC liked to use 36 yards for a reduced range zero on the M16A2/M16A4. The idea of a reduced range zero is to easily reproduce a longer range fighting zero at reduced ranged. It is easier and faster to zero at 25 meters than 300. Negligible effect from wind, easier to change and inspect targets, etc. The downside is that ANY minor error at this reduced range will be magnified at farther ranges. Say if a soldier was impacting 1 inch left at 25 meters, they might completely miss a hostile enemy at 300 meters. That could cost lives.

I consider a BZO an acceptable zero. I’ve found that with a 14.5 inch AR15 firing M855, if I impact 0.3 inches low at 25 yards, I will be right on at 300 yards. This lets me quickly and easily sight in any similar carbine at the very common distance of 25 yards. I used to have a scoped rifle where my 100 yard zero was 2.6 mils different from my 25 yard zero. I could dial up 2.6 mils and be right on at 25 yards. This allowed me to double check that zero with that gun at reduced range.

A BZO often won’t give you a perfect zero for the farther distance, but they should be close enough. The now common 50/200 zero is a good example. Zeroing at 50y or 50m isn’t going to give you a perfect dead on zero at 200, but it tends be close enough for practical work.

I would not hesitate to go into combat with a firearm that has a BZO. I would prefer a finer zero, but a BZO is functional.

Fine Zero: Simply put, a fine zero is zeroed at the range the firearm is intended to be sighted in at, and is adjusted as closely to being perfect as possible. A magnified scoped rifle might be fine zeroed at 100 yards. Something like a M16A2 or M4 Carbine with CCO would be fine zeroed at 300 meters. Often people going into combat never get the chance to fine zero and must just rely on a BZO.

Sometimes you are limited by the precision of the adjustments. As an extreme example, the leaf sight on my M203. Each click of the windage knob adjust the impact by 1.5 METERS at 200 meters. So if I fire a shot and impact 1/2 METER left of my point of aim, I can’t adjust closer than that. But a fine zero will be as accurate as precise as the sights allow.

A fine zero is preferred over a BZO as it will have removed any error from the BZO and have been tested out to the preferred sighting distance.

True Zero or Proofed Zero: You don’t tend to hear about this outside of precision shooters, longer range hunters, or snipers. People who have to shoot at multiple distances, or an unexpected longer range distance may take the extra step to true or proof their zero.

This is less about the zero, and more about the knowledge and preparation the shooter has made for long distance shooting. Truing or Proofing is finding out where exactly you will hit or the adjustment you need for the various ranges you might be shooting.

Simple example, I used to shoot 565 yards with a 4x ACOG. 565 yards is about 516 meters, so I should have been able to use the 500m mark in the ACOG. Instead, with my firearm and ammo I needed to use the 600m mark to impact where I wanted to hit. Had I only relied on the stock marking I would have always missed.

While I was in the Corps, when we shot the rifle range, we would note our true zero for each distance. Windage adjustment might change due to how we held our rifles, elevation might be slightly different as well. So one persons 500 yard zero might have been setting the rifle rear sight to 5, another might need to set their A2 rear sight to 5 plus 1 click.

You might have a great gun with an a great cartridge and your ballistic calculator spits out a hold over for some distance, but when you actually shoot that distance you may find you need a different adjustment or hold over. Accounting for that is truing or proofing your zero. With out proofing, that drop chart or BDC is just a suggestion, not a fact.

A very few ballistic calculators give the ability to put in your proofing results to calculate a corrected drop chart to ensure you will hit when you need to hit.


Not that simple, isn’t it?

Surplus Milkor M32 Multishot Grenade Launchers for sale

https://www.machineguncentral.com/ViewDetails.aspx?p=2512–b2b01f92-3540-4206-a27a-bd2575391936

Milkor is selling off 53 M32 Grenade Launchers there were Army trade-ins. So for a mear $15,000 you can own one too. At that price, might as well get two, one for each hand.

Shame these are not the newer, upgrade, M32A1s. Those have a 3 inch shorter barrel, and are upgraded to be able to take higher pressure rounds.

Sometimes I think I am the only person in the world that isn’t in love with the M32. My biggest complaint is that it is large and bulky. It is twice the weight of a M79, and about 4 times the weight of a M203 or M320. Whom ever carries the M32 will likely have another weapon as a primary weapon. I didn’t care for the design of the stock and the optic. The stock pivots to allow for the high angle necessary for farther shots. The stock on the one I used would flop around. I really didn’t like that. In photos and videos I’ve seen of others, the stock seems to lock in various angles, so that might have just been an issue with the unit my platoon had. The optic was good, but not great. It was just a red dot you manually had to adjust for range. I had a few complaints about the optic. First it relies on the user making an accurate range estimation. If the user is wrong they have to adjust the sight again. Secondly when firing at near maximium ranges, the optic is tilted nearly 45 degrees and is aimed right at the barrel. You then won’t be able to see the target through the optic and then have to keep both eyes open to do something like the Bindon Aiming Concept to transpose the dot and the target together.

For example, in the above pictures, you see how a 40mm is nearly at 45 degrees for a 400m shot. Using an offset sight or a multi-ranging holographic sight like the discontinued M40GL allows for easy of aiming while aiming. Putting the optic right over the barrel ended up with you pointing the optic right at the barrel.

My last gripe is a training and use issue. In the Corps, I never saw anyone able to really use one fast or efficiently. I never saw anything that made me believe that the average infantryman was going to actually load and fire 18 rounds a minute through one of these. Loading always seemed slow and awkward. But to be fair, we received these mid deployment and there was never any real training time given to them.

Still, it is a very cool weapons system. One of the biggest merits we found with it was that due to its’ spring loaded cylinder, you could advance it to the chamber you want. We sometimes loaded up (in order) 2 green star clusters, 2 parachute flares, and 2 HEDP rounds. When we had to warn locals or do escalation of force, the Marine with the M32 could easily do a snap shot firing off a green star cluster to gain people’s attention and warn them. If instead, it was night time and we needed light, they could advance the cylinder twice and fired off a parachute flare or two. Should we need the indirect fire or to strike an area target, the cylinder would be advanced to the fragmentation rounds to lay down some death.

At night, it would a whole lot of fun, and kinda handy to be able to spin in place while firing parachute flares in order to light up the sky with a new constellation, albeit a temporary one.

Still, from my experience there was nothing we did with the M32 that we didn’t do as well with the M203. We certainly didn’t miss it when we turned it back in before the end of our deployment.

All that said. If I had the money to burn, I’d buy one of these surplus guns. Hell, I’d buy two, one for each hand.

Sometimes I wonder if MLok and Keymod are a step backwards

Today I was messing with some of my Surefire weapon lights and started to write a review of a VFG. That got me back to a line of thought where I wonder if these newer attachments systems are a step backwards from the 1913 picatinny rail.

Now don’t get me wrong, the new modular handguards have many merits. But lets back track for a moment.

Back in the day we either didn’t mount stuff to our weapons, had to use proprietary mounts, or clamped stuff on. You can find pictures of hose clamps holding Maglites on M16s and MP5s. Special equipment like the AN/PEQ-2A IR Laser and the M203 sights had their own unique mounting systems.

When the 1913 Picatinny Rail showed up, we installed these heavy quad rails and started attaching everything to our firearms.

Now your standard screw on rail mount could hold its zero fairly well. Often with in a minute of angle, if the person installing it was consistent.

Then things got really nifty, we got all sorts of quick detach mounts that held their zero.
Now, you could have a red dot and a magnifed scope ready and zeroed for your long arm. You could mount stuff like lights, lasers, bipods, as you needed them.

But quad rails are large, heavy, and when poorly made can be sharp as a cheese grater. Keymod and MLok, along with their predecessors allowed for lighter, thiner, slicker firearms.

All good, right?

Now, we can remove and reattach something from MLOK and Keymod handguards, and still they will tend to hold their zero.

In military testing, they reported that KeyMod had an average shift of 4.9 MOA shift and M-LOK 1.3 MOA.

That is probably why we still see rail on the tops of uppers and we don’t see KeyMod or M-LOK scope mounts.

So, what point am I really trying to say? I’m saying that M-LOK and KeyMod are not really QD. That is a step backwards.

I keep a Harris BRMS bipod on an ADM mount. That way I can slap it on a rifle when I need it, and take it off when I don’t.

Some years back I bought a brand new Surefire Scout light, and I remember planning to put a QD mount on it so I could just move it from rifle to rifle with out having to buy another one.

So now I have guns with KeyMod and M-LOK. I have to buy little rail section so that I can put my Bipod on them. If I want to quickly be able to move a light, laser, or grip, I have to mount another rail section.

The step backwards with these new systems is the loss of quick disconnect. We can certainly live with out that, but it was very nice to have.

I’d love to see a replacement or upgrade to MLOK allowing us to quickly remove and reattach items with out loss of zero. Then I think we will have the best of both worlds.

Finished the M203 side folding project

My hobby is to spend my money on pointless projects.

So a while back I bought a M203. I got the classic underbarrel design as that is what I really wanted. But I know that it isn’t practical for me to be leaving a M203 on a rifle, so I got a LMT stand alone mount. This let me use the M203 by it self, while retaining the ability to quickly remove the M203 and put it on a rifle should I choose to.

Picture from 2 weeks ago when I was talking about rear sights.

The LMT stand alone stock is pretty awesome, but I then decided that I wanted a folding stock.

Many people here, would just say, “Howard, why don’t you buy the FAB M203 folding stand alone unit?”

Image result for fab m203

Well I have a few answers to that:

  • The FAB unit is not quick detach. I can not easily remove the M203, and mount it on a rifle.
  • I am told you have to remove the backplate of the M203 to mount it on the FAB unit, and swap that back out should you want to rifle mount the M203.
  • Lastly and most importantly, I think the FAB until is fugly and looks like old tapco crap.

Now, the FAB FD-203 is probably a great product, but I have no interest in it. Cause it is even uglier than I am.

So when I saw that KNS made an adaptor that would allow for mounting the new Sig folding stocks, I got interested.

The KNS adaptor allows for replacing a buffer tube with a rail section. This allowed me to install a SIG side folding collapsing stock.

Now lets take a look at that first picture again:

Is it a perfect setup? No. You can’t easily reload while the stock is folded as the barrel will catch on the stock. The SIG collapsing stock is slow and awkward to adjust length. But I like this. It is smaller to pack, feels handier, and just looks cooler.

I can also remove the SIG stock quickly with a Torx bit to have a pistol grip only 203.

Final thoughts:

KNS rail adapter is well made and awesome. I wish it was cheaper, but it was worth it.
SIG Side Folding Collapsing Stock is nice, but not great. Little awkward to use, could be nicer.
And M203s are always fun.

New toys for my 203

Spent more money on stuff I don’t really need. I picked up a couple more sights for my M203. Fortunately I was able to get some open box items and didn’t have to pay full price. M203 accessories are expensive!

First, lets take a look at the L3C Rail Mounted Quadrant Sight.

The L3C is set up like any other quadrant sight, but attaches to a side rail instead of the carry handle. I intend to modify this one to have a red dot in place of the iron sights.

In the Corps, we felt the leaf sight was good enough for most purposes, but the quadrant sight was prefered when you are trying to hold a higher level of precision. Not only does it adjust out to 400m, unlike the leaf sight that stops at 300, it made hitting smaller targets, like putting rounds in a window easier.

This sight I received had a huge amount of play in it. I found the screw that holds the pivoting section was loose. Tightening that took all that slack out of the sight.

Next up is a KAC M203 Leaf Sight.

The KAC unit is much lower profile than the rail grabber M203 sight. It is standard issue in the USMC.

The leaf sight allows for adjusting from 50m to 300m with the M203. This sight is much lower profile than the rail grabber I am currently using.

Here it is beside the current rail grabber sight. You can see the milled aluminum body of the KAC sight looks sleeker and (to me) stronger than the rail grabbers stamped steel body.

The main thing I don’t like about the rail grabber is that huge honking knob sticking out the side.

So the next time I go to the range, I am going to replace the rail grabber with the KAC sight and rezero. The A2 windage knob on the KAC sight makes it easier to adjust.

The only downside I could see with the KAC sight over the rail grabber is that the KAC sight can not flip back farther from its upright deployed position. The rail grabber leaf can move farther. That makes me think that if it were dropped, the leaf sight on the KAC would be more likely to be damaged. But, I don’t ever remember seeing on of these damaged while I was in the Corps. Probably a non-issue.

Anyways, just felt like sharing.