Experienced rifleman please chime in....

[PrecisionGuru]

Is there any true to something I was told while at the range?

Someone said that if you rest the weight of your rifle on the magazine while shooting prone, that your zero will be altered. I was wondering if this is true or if the person that told me that may have been mistaken. For 3 gun we often shoot prone out to long distances and everyone uses their mag as a monopod when shooting prone, so I don't see this being a big deal, but I was wondering if there was any truth to this statement.

 

[Ryguy]

Hmm. Seeing that the bullet comes from the chamber, I'd have to say no. The magazine may be less steady and offer more of a shift in point of aim resulting in a wondering point of impact but to change you zero, that seems unlikely. Maybe there is something I am missing and if so, I hope someone chimes in.

 

[Victory]

POI between rounds, maybe ever so slightly depending on how good you are at repeating that same position between shots.

There are always myths that revolve around shooting off of your magazine, I believe all steming from old school Military views.

 

[PrecisionGuru]

That what I was think as well but not sure info might be missing something as well. He didn't mean it would alter the zero as a result of the mag being a unsteady surface/platform to use as a monopod. He said that the bullets are pressed upward by the weight of the gun resting on the mag, and thus the zero or point of impact would differ. When I tried to rationalize his point, I couldn't seem to. Since the bullet in the chamber is not connected to the mag anymore, & the tolerance of the barrel around the casing of the bullet is so tight that I doubt the mag pressing upward due to the weight of the rifle resting on it would affect your zero. Plus the bolt carrier is dividing the mag from the bulletin the chamber which is another form of avoiding this from affecting the zero.

 

[Ryguy]

Maybe the loose chambers of WWII would allow the mag to press up on the bolt and as a result, somehow effect how the bullet sits in the chamber. This is of course, assuming WWII chambers were loose enough to be affected like this.

 

[PrecisionGuru]

Yeah, I could see that if the chamber is not built as tight fitting as they are today especially by manufactures like JP. Thanks for the feedback

 

[Victory]

Feed lips should not make contact with your bolt carrier, but not all mags are created equal, and all lowers aren't created equal. My PMAGS and USGI mags do not make contact, but have heard that with some peoples rifles some mags can.

The pressure of rounds touching the bolt carrier is maxed at what ever the spring pressure is in the mag. I can't see in a spec chamber, this spring pressure changing your POI more than the weapons natural cone of fire. If it's a solid 1 minute rifle, it's not going to suddenly become a 1.5 minute rifle from spring pressure on the bolt carrier. I dont think for the average shooter, a POI change would be noticed beyond what the rifle, ammo, and skill set combo is capable of.

Maybe a smith or someone who has conducted testing in this area will better be able to confirm or deny this.

 

[PrecisionGuru]

Good to know. Thank you for your knowledgeable feedback.

 

[Victory]

Don't take it as fact, I'm not a subject matter expert on all things AR, just a dumb Infantry guy.

 

[Redmanss]

Seen them FTF/FTE because of it on old rifles with beat to hell mags, but they don't throw rounds off because of some weird mechanical contorting of the rifle. As a former Parris Island 8531 "Range Nazi", we say all kinds of stupid shit because recruits do all kinds of stupid shit, hence that's how rumors are started. Kind of like keys for the HMMWV or chem light batteries.

[MENTION=6431]Victory[/MENTION] is spot on about the rest concerning shooting positions and whatnot, and I'll only add that the biggest change it would make would be due to lack of natural point of aim being achieved or getting too many vibrations from hard on hard contact of the weapon to the ground causing shift of POA prior to the shot being completed. Of course I'm a dumb Infantryman too, lol.

 

[elfster1234]

Any deviation from the way you typically / consistently shoot can shift your point of aim somewhat

 

[RTH1800]

This^^^^^^^
The change might be so slight as to not be noticed or it could be fairly big. Why not test for yourself? The better you shoot, the more likely you will see shift. My AR shoots differently from a bipod than bags or slung up. Shows up at 500 meters. Runs .1-.2 mil. If you can shoot well enough that .1 mil shows up, you will see changes I suspect.

 

[Echo4Bravo]

I tested this on my rifle at 100, 200 and 300 yards. I alternated between the bipod, magazine and supported. I shot 5 shot groups from each position and range. I did not notice any difference in accuracy between bipod or magazine. Sling supported changed impact a bit, but I am a tight sling shooter...

 

[MAT4-82]

Might depend on the rifle. With the AR platforms there used to be a big difference in POI between supported at forend or at mag, slung up tight or snug.
uppers and lowers were looser then. Also light barrels could be deflected. That's where float tubes came from.
Nowadays a lot of that no longer applies. I don't believe it ever effected a rifles accuracy only changed POI for a given sight setting.
Also remember when you are shooting steel rather than bullseye you are less likely to detect a minor shift in POI.

 

[USACS]

Be careful what you pick up at the range. I can't tell you how many times I've heard people talk out of their asses and believe every fucking word of it. This is especially pertinent to people who are military. I'm not saying this about guys here because everything here is fine. However, every time I see a military (current or prior) person on a public range or at my gun club with an AR, I have to fight to keep my mouth shut. Most don't know more than the typical gun platitudes which are more often than not complete horse shit. Much of it is range folklore. I was a senior range NCO in my latter years, and I can't even count the number of stupid things I saw as being "typical" SOPs in units.
Sadly, all that stuff migrates to public ranges and private gun clubs. Nothing new either, because there are still Vietnam era guys and Gulf War (first one) guys giving the same "common knowledge" advice.

 

[rideHPD]

To add, a few years ago one might have thought that increased pressure on the bolt carrier from the mag might slow down its travel, increasing dwell time ->chamber pressure -> velocity -> higher POI, but with the high speed footage we have now we know that's a bunch of bunk, as the projectile leaves the muzzle before the lugs even disengage.

 

[MAT4-82]

Only one way to find out. Test it yourself!

 

[Schleifalot]

It depends.... on the kind of rifle used:

I experienced no POI shift (like minute of goon) with the AR and the SIG 550/551 rifles. We even dug in the mags through pushing down on the rifle and shoving back and forward to get balls to the ground prone. The rifle resting on the mag and the stock on your biceps, head sideways, really low prone. There was no problem hitting the kneeling goon popper up to 200m. I did no testing for tiny groups.
The AR is an excellent system, if properly built.

With HK G3 amd G36 there is definitely a big, like BIG, POI shift. With the G3 resting on the mag the groups open from 2MOA to Minute of Barn (5MOA+). With the G36 it is worse. A G36 has usually about 2MOA. With the mag touching the sandbags I had the 10 rounds scattered over the whole target at 300m. The diameter was 1 METER, like 10MOA! The same if your housing (plastic) heats up. I had a shift from center target to 13MOA left high just from the sun shining on the rifle. OK, it was lying the whole day in the sun with the right side up when not actually shot. This shat will not happen to any other rifle I know.
Hitting a kneeling goon target is a lucky stroke with your mag resting on the ground or a heated up rifle! My own experiences!
I think the mag or rounds are pushing the bolt up, so the round does not sit straight in the chamber any longer.
A friend had similar results with the HK 416 and 417.

The AK this should not be a problem, it is a MOHUMVEE douchepump rifle from the beginning. Douchepump: Shooting the AK well oiled or well watered (rained on) will result in a spotted douche pattern from your cheek up to your hairline. Nice to have a slurry of oil/water/gunk on my glasses.
But it works......

 

[dynamite1552]

I am pretty sure this comes from Army Basic Training...has nothing to do with POI shift though...When using old, worn out aluminum mags, we used too see far more double feeds and failures to go into battery when resting on the magazine. These magazines had seem literally millions of rounds and every wear point was completely worn out.
That is likely too difficult for some to relate to a private that has never held a rifle, so it gets ingrained in the military as "you won't shoot as good/qualify if you do it that way"

 

[WATERWALKER]

I think everyone has heard this AR magazine monopod myth, over and over and over... I was taught that way back in the day as well. Don't let the PMIs' see you shooting the 500 w/ a mag on the ground. I don't believe there's any truth to is as far as the AR is concerned, at least by today's standards.

Using the mag as a monopod on concrete may be an issue as far as hopping / sliding around a bit. This will vary depending on caliber. This is probably due to the concrete finish being either very smooth like a garage floor vs. a sidewalk finish. I realize this sounds a little goofy, but if you've never poured or finished concrete, take a look at a sidewalk or driveway vs. a garage or basement floor. ( I use a small piece of iso-mat (remember the rubber bitch pads?) taped to the bottom of a mag for quals and I can still hold a great group at 100 yards. After that, the prone position is a moot point.

 

[fmsniper]

in short answer, NO

 

[USACS]

The key to everything is the mag. If you have a quality in-spec mag, it's all fine. Far too many .mil and .LE groups run shit mags, or good mags that went to shit. Once a mag is fucked, it's permanently fucked. It's a wear item, but people treat them like they're fucking gold. I severely cracked a feed lip on a PMAG I'd been using for years, and some dude at the range got a visit from the Good Idea Fairy and decided to fish it out of the garbage.
I think we would all be amazed (or maybe not surprised I guess..) how much doctrine and TTP has been developed around shitty equipment.

 

[WATERWALKER]

The key to everything is the mag. If you have a quality in-spec mag, it's all fine. Far too many .mil and .LE groups run shit mags, or good mags that went to shit. Once a mag is fucked, it's permanently fucked. It's a wear item, but people treat them like they're fucking gold. I severely cracked a feed lip on a PMAG I'd been using for years, and some dude at the range got a visit from the Good Idea Fairy and decided to fish it out of the garbage.
I think we would all be amazed (or maybe not surprised I guess..) how much doctrine and TTP has been developed around shitty equipment.

Outstanding point made here. Check your feed lips often because once they've gone bad the magazine is junk. It can't be fixed, EVER. However, you can spray-paint it red (my choice of colors) and use it a training mag. If I have to spell this out I will; it is painted red so that it is not mixed up w/ your gear & / or anyone else's work gear. The benefit of keeping this fucked up mag is that it will give you the opportunity to perform many IA drills. Happy training.

I realize this post is painfully obvious, but I have been asked why I have red mags.