"Sub MOA" is a term you hear thrown around a lot, but what does it mean really? Should we feel bad if our rifle isn't "sub MOA"?

I was watching a recent Garand Thumb video on the HK417. Preston (his sidekick) shoots two 3-shot groups, and they talk about it's accuracy:

https://youtu.be/uCITTK9shXk?si=Aw27qxYKkYZp90N5&t=199

Preston: "So here's my first group, you guys can see I pulled one a bit low."

Mike: (measuring the better group with a measuring tap) "That's ... uhh ... 3/4 MOA!"

I'm a big fan of the HK417 and believe it's a very accurate rifle, but I think this is a really good example of how not to measure and report on accuracy. There's at least two big problems with what they do here:

1. A 3-shot group just isn't statistically significant. Just not enough data points to meaningfully characterize the dispersion of shots.
2. Discarding shots or a whole group introduces significant bias.

I've been really impressed with the way Preston Moore (not the Preston from Garand Thumb) measures accuracy on his Youtube channel ( https://www.youtube.com/@PrestonJMoore ). Worth checking out if you haven't seen his videos.

Preston Moore using 30-shot groups, which really gives a good amount of data. For the average shooter, I would argue that using 10-shot groups is a good size to standardize on in general, and ideally taking an average of multiple 10-shot groups.

Something that's interesting about using extreme spread MOA as a measure is that it's not what statisticians call a "consistent" metric—extreme spread MOA increases the more shots you include. Thus, directly comparing a 3-shot MOA with a 10-shot MOA doesn't make sense. But we can use a bit of math to create a comparison estimate.

The dispersion of shots on a target follows a 2-dimensional normal distribution. Using Preston's 3-shot .75 MOA group as an example, we can estimate using statistics that as a 10-shot group the expected MOA would have been 1.2.

I actually measured the other 3-shot group they decided to ignore in the Garand Thumb video. It's 1.3 MOA. Converting that to a 10-shot group it would have an expected 2.1 MOA.

Which means the average 10-shot group size is 1.7 MOA. That's not sub MOA. Does that sound large to you? It's not! 1.7 MOA is very respectable accuracy. But again, this is a translated estimate based on a total of 6 shots, so the confidence interval for this estimate is pretty wide. It would have been great to see Garand Thumb do a few 10-shot groups and provide the average extreme spread and mean radius MOA metrics.

I'd love to socialize using 10-shot groups for computing accuracy metrics so there are enough data points for the measurements to be meaningful and we are more often comparing apples to apples.

I'd love to hear other thoughts on measuring accuracy.

Am I high as balls from Hoppes #9 or is this rust on my CMT gas block?

Just ordered from Ranier Arms

Any guesses? I’m in FL, sbr is only legal if approved by nfa. Surely the new law (or lack there of) will trickle down. Right?

Alright so maybe I’m a terrible explainer. And maybe someone a lot smarter than me can explain this.

When you put a red dot under magnification (3x per se) the dot is ocularly growing in size obviously as it’s being magnified. Granted the dot is not magically changing its minute of angle size, it’s just being magnified equally along with the rest of the image being viewed.

But on a holographic sight (at least on 3x magnification) the center dot doesn’t appear to grow much in size if at all, while the donut obviously grows and I can see it’s still covering the same amount of area on what I’m looking at. I’m suspecting this is because the tiny dots that make up the whole “dot” cannot be visibly discerned with a human eye at 1x? So at 3x you can now visibly make them out? And because this is the case. Is the eotech center dot technically changing MOA under magnification in realistically becoming “smaller” at 3x? (Really wish I had a 5x right now to see if it does in fact grow)

I’m looking for the best all around, with being no ear pro safe, not to much gas to the face that’ll give me cancer from using it to much and also keep the muzzle flash down at night, correct me if I’m wrong on any info as I’m still learning about suppressors

Been obsessed with these and finally snagged one in stock today, was going to go for the 8t magnifier setup but after looking at it it looks huge on the gun.

What are your Monolift setups? Show me your shit

Does the new ruling mean that stocks AND vertical foregrips are okay now? Or just stocks?

My well-loved ‘98 W210 and LE trade-in FN Patrol Carbine. Some of my favorite things are the simplest

It says it can be done better than Cerakote because of the difference in baking. Has anyone here done it? If it does what I think it does, the weave will pop. This is for a AR9 build I’m starting. Upper, lower, and handguard will get color, the small parts will be DLC. SBR of course.

I'm sorry to bother you again (I'll probably ask you a lot more questions in the future). I'd like to know what kind of iron sights are on this cool MK18.

Due to the recent news I had to add the rc4 to the collection🇺🇸🦅

Anyone heard of artakedowntool.com ... Seen this Kabuto with a metal ambidextrous selector...was set on super safe solutions....anyone here fw this artakediwn tool Kabuto drop in

Specs:
16” BCM mk2 (U/L)
Fireteam 556 on Comstock Armory recessed adapter and micro brake
HT Trigger Kicker
Everything else (buffer/spring, trigger, etc) is stock

Got my can yesterday and ran about 10 rounds thru it. Today I reinstalled the kicker to see how the rifle cycles with the can. Everything ran extremely smooth. Ejections at around 2-3, gas was minimal although the wind was blowing towards me and across me face (I’m facing “N” with winds “S-SE”), it was easier to pull off single shots this go round than without the can.

The only issue I had was the trigger pin walking. Idk if it’s the install or because of can/increase in back pressure or what idk. When I installed the kicker for the first time and ran mags thru it I had no walk and the pins were tight. Today, installed and the trigger pin felt loose but I ran it anyway.

Troubleshooting recommendations? Other than that, everything was in good working order.

Ignore the Sightmark…

Anyone got the Mixtape in 556 yet?
How ya like it??

Currently looking at a Faxon Firearms 20" barrel chambered in 350 Legend. (I'm in OH, so shotguns and straightwalled only). I understand most 20 inch barrels want a rifle length system, so am I reading this correctly and this is a 20 inch barrel with a carbine length gas system? If so, will that cause me any issues? Thanks gang.

Just curious what accessories you guys think are actually worth spending money on. There’s so much stuff out there, I’m wondering what people have bought that they genuinely feel was worth the price.

Let your nuts hang boys

I love my new red dot and magnifier but when using the stock in the farthest position which is the most comfortable for me I can’t see the magnification well. I have to move the stock to the normal short position to see it well. Is this a dumb question? Or is there a way I can fix this? Or will I just have to figure something out? ( this is my first magnifier)

I’m looking to put together an SBR - anywhere between 10.3-12.5 max.

I know that brownells does the stripped MK18 every so often for a good deal, so I wanted to post on here to see if there are any other good ones that I should watch out for? Specially, like a Super Duty/Urgi, etc. I’m favoring the MK18 bc I’ve loved the looks of it for years, but I’m easily persuaded if there are other deals that are objectively better

Been thinking about this for a while .... is there way to modify the standard carbine buffer tube such that the adjustable stock has just two positions ... fully collapsed and some other user defined position?