Does It Shift? Testing Positional POI Shift and Rail Flex

[@danielmattera4298]

I absolutely BLEW a competition at a course. Sights dead on, pull trigger, miss x 4-5 times. I was getting really upset because 5 minutes ago the gun was zerod. Lifted the gun off the barricade and nailed the rest of the plates with perfect hits off-hand. Couldn't figure it out. About an hour later it suddenly clicked that I had rested the gun on the suppressor, not the rail. When I put my hand on the rail to stabilize the gun, I applied enough pressure to send the round over the targets despite my reticle remaining the same. This stuff is SUPER important and your study is awesome.

[@seanoneil277]

Sorry about that stage, but in hindsight -- isn't it awesome when you can sort out what happened, and learn something very valuable in the process? Good job on the detective work.

[@danielmattera4298]

@@seanoneil277 Without a doubt! I was really frustrated since the whole class I had been shooting great, and I had just pushed it to 400-450 yds prior to the class (10.5 w/Eotech). It was a good humility check and a reminder in the future. I feel we learn best from failure, and better to fail in a unimportant competition than in the real world.

[@stephenlopez5497]

Excellent video and explanation. For those that say this isn’t a realistic test obviously haven’t trained enough on positional shooting. I wrench down on my sling and on barricades every chance I have. In Run and Gun events, we do not have the luxury of bags so slings and applying force on the handguards are a must. Until now, I didn’t realize the zero shift would’ve been that significant. Just more influence to open up the cone of fire.

[@seanoneil277]

Great topic, Jim. I remember Jay at Ridgeline talking about handguard/rail choice being important for a precision AR, because of flex/distortion of the handguard. Whether from a sling, or bipod load, or barricade stop load, or from light/laser stuff at the muzzle end helping things want to flex. Sling tension and POI shift is something that gets covered at Appleseed shoots, when the shooter is advanced enough to isolate the sling as the source of deviation (versus unstable platform/fundamentals otherwise). I experienced it myself at my 2d Appleseed shoot and began experimenting with where I anchored the sling at the forend. Best for sling use is 6:00, but that position is bad for other sling use especially because it makes the rifle roll away from you when tensioned up against your torso. The 10:30 QD position is best for that rolling, but adds too much twist when tensioning the sling. All related to the issue you're discussing above, combined with how the sling tension affects the shot alignment during and through the shot process. Jay mentioned it to me because I've got my offset mounted on the rail. "Check how that zero behaves under load," he said. I'm using a BCM MCMR on that rifle -- he said they are good rails but a little flexy and so I should check the load deflection.

[@parisshoots154]

Try this at dusk. Pick a target around 100 yards away. Turn your vis laser on. Go prone with bipod, and look through your ATACR on 8X at the target, note the laser position in the reticle. Then put the rifle on a bag just in front of the magwell in the standing position. Look through your ATACR on 8X at the target, note the laser position in the reticle. See if the laser position in relation to your reticle has changed. I’ve see anywhere from .2 to .4 Mil vertical POI laser shift on quality rifles/rails depending on how much weight you have hanging off the end of the rail (bipod/light/LAM). While this will show vertical rail deflection not all 100% of that shift translates to the barrel nut and causes actual POI shift, but some of it does. Give it a try.

[@veracitysolutionsllc]

That’s a solid test for rail deflection for enablers. Try that same thing with a pen laser taped or clamped to the barrel. That will show a more accurate representation on POI shift when shooting.

[@Runningmancs]

Nice explanation. I learned this the hard way at the last barrel and hatchet match at jtac. Had my suppressor on barricade and threw me completely off target.

[@kiteokoh2652]

Great video. POI shift is why on precision gas guns I only use the seekins IRMT3 or the M4e1 enhanced paired with a SGT of Arms arca handguard

[@Quality_Guru]

Very impressive video as I never even considered that there would a POI shift from the handrail nor from the pressure of tightening the sling. I would like to see a test perform at a short distance (25 yards) to see which technique and/or equipment can be used to reduce wobble from the shooter.

[@KennyRodgers930]

LWRC Monoforged Upper for the win 🤙🏽

[@altairibnlaahad9348]

LMT Monolithic as well.

[@PewPewDaily]

Excellent video! I know you work with/shoot for SOLGW, but can you or have you done this same thing with the Cobalt rail/receiver set build that you made a video on a few months back? Is the outcome the same/similar?

[@ant337]

great info. Never thought about POI shift due to positioning. yay another thing to obsess about!

[@LONEWOLF_LCD]

Another Great Vidja…… very informative,I’ve found that you are correct in rail shifting…. I also found that some rails have more than others. I will say that the Ripcord LDR1 rails have less flex than G’s rails and “Combat” rail had a bit more flex, I’m guessing do to the short alum barrel nut. The MCMR rails was a happy med it did not flex as much. Just remember it was a small batch, and diff rail lengths. The BCM 15 flexed more than the 13” which is physics the LDR1 15 did flex more than the 11.75 again physics and the amount of pressure on the rail. Using a flexy bipod (you know who you are) causes more flex in the rail do to loading more than say a Harris or Atlas…… just a bit of my experiences not trying to jump into your content……

[@LeifyGuy]

Realized today I wasn't seeing your videos, had to re subscribe...

[@prone_wolf8871]

I was going to put the broadsword and bcm upper and rail head to head for shift due to weight on the rail.....put 50 pounds on the bcm rail and no change.....Im not going to test the broadsword 😂...... So far loving the broadsword...upper to lower fit is the tighter then typical. (Tightest i have)..upper to barrel fit is very tight. I thermaly set mine. with proof and riflespeed..... ao far it's being an excellent combo....haven't done good accuracy testing yet ... But out breaking in the rifle it printed under 3/4 for 5 shots at hundred..with 77 grain sig and razorcore.... Going for ten to 40 shot disperstion tests soon....

[@SAA6ix]

This has been something that i have been looking into.. you say “ALL” have shift, which i agree.. but have you tried the Seekins IRMT line?

[@maddawgmr]

I did a deflection test with my broadsword (and the 6max) and the most I could get mine to move across all positions was less than .3 mils (less than an inch) on the broadsword. 4/5 positions were .2 or less.

[@darrinlenton]

Thank you 🙏

[@Clockwork0nions]

I can’t help but feel this video is a result of the previous comment chain we had a couple of weeks ago 😂😂😂

[@SM-tg7yw]

I know it’s a point of debate when it comes to precision SPRs. But I’m going to ask anyway. How often do you clean the barrel and how?

[@wilcoxblues27]

One thing to think about as well is that the flex within the rail itself may not be the issue. At the end of the day the force exerted on the barrel nut and upper receiver may be the cause of the POI shift. In theory the rail its self shouldn't matter much, if it was not attached to the barrel at the barrel nut. The SOLGW probably does better because it strengthens the interaction of the rail with the upper, which should cause less influence to the barrel. Just another theory

[@veracitysolutionsllc]

That is what is happening. This was part one of another set that Jimmy and I have talked about. The leverage from the rail is applying pressure to the barrel nut. Essentially the longer and heavier the barrel the more pressure applied to the receiver tenon. When leverage is applied to the rail it affects the barrel position. You’re thinking right

[@seanoneil277]

What you're discussing is the mechanical cause. So you & Jim both are discussing the same thing. The load translates from the handguard back to the rifle through the mechanical connection -- handguard to barrel nut, or if monolithic then it translates to the entire upper then outward from there. This is why handguard makers try to make the handguard-to-barrel nut connection as sturdy and as lengthy as possible before the rail's free floated section starts. It's why monolithic uppers were designed. The deviation in POI vs POA is due to the flex under load, and it happens pretty much as your discussion said. But the bigger unsaid point from Jim's video is that you have to be self-diagnostic enough, and skilled enough already, to be able to isolate rail flex as the cause. Because otherwise it may be from shooter fundamentals. If you're still developing a repeatable fundamental platform, you're not going to be able to Dx rail flex as a separate cause of shot deviation.

[@veracitysolutionsllc]

@@seanoneil277 you’re on it as usual brother. This video is but a small piece of a more detailed problem/process. Once I’ve diagnosed my equipment and if it has a shift I’ll do things to mitigate it regardless of position. Like zero it from barricade instead if prone, zero it splitting the difference between the shift etc etc. There’s so many nuances to these platforms one can see as they progress in their shooting journey. Initially we just need the users to be as consistency as possible in their abilities and then begin diagnosing nuances of the platform. But these things are good to know even for beginners just in case they may be using an unfortunately subpar designed product that is hindering their abilities.

[@seanoneil277]

@@veracitysolutionsllc Hey thanks. I try to pass along what I've learned from folks wiser than myself. Or from using what they have taught me. My puzzle these days is offset RDS and main optic zero-truing. The windage and elevation adjustments don't behave the same when the RDS is off at the 33-45 deg offset angle. I think I've got it dialed for near, then at 100 it's a pukepile. There's probably some maths and geometry I'm ignoring that could make things easier.

[@veracitysolutionsllc]

@@seanoneil277 if the optic base isn’t canted parallel to the bore then weird things can happen that farther you go out. Up close odd number of cant could work well. But as distance grows the angular error grows.

[@Advoflui]

How would you recommend someone who wants to get started into shooting start? How do you find ranges to shoot at?

[@jatollar]

Hi, I don't know if he'll see this comment and respond so I'll offer some advice. If you don't have friends that shoot, google to find a beginners class to learn basic safety and marksmanship, preferably one that will allow you to rent a gun so you can see what works for you. The easiest to find will be a class in an indoor range so probably pistol, but this is good enough to learn the basics. You could also go to a match in your desired discipline (I think this is Precision Rifle Shooting PRS) and ask around to see if there is anyone who will teach you. Shooting sports are all about teaching and learning so I think the odds are pretty good someone will help you a lot.

[@Advoflui]

@@jatollar thank you for taking the time to respond. I think that’s probably a good starting point for me to get back into it. After getting out of the military I quit shooting and it probably wouldn’t hurt just to get back into it with doing a class covering the fundamentals. I know I need to practice getting into shooting positions and getting that flexibility back.

[@W1BwY0K3VChm1uuw]

8:46 "...what people Doo-Doo...." 😁💩

[@GldenRetriever]

I can't wrap my head around test 2 (rewatched it and the explanation a few times). How are you getting POI shift with having weight on the freefloat handguard (as the handguard doesn't touch the barrel or gas block)?

[@wilcoxblues27]

I think it's because the rail is mounted to the barrel nut, so any force on the rail is transferred to the threads on the upper and that's where the flex is happening

[@veracitysolutionsllc]

@@wilcoxblues27pretty much that’s it. And the longer and heavier the barrel the more the POI shift can be.

[@wilcoxblues27]

@@veracitysolutionsllc exactly, it's just like engineering math problems with a beam supported at one end. Like you said, the more lever arm and mass you have, the higher the bending moment or torque will be at the fixed end.

[@veracitysolutionsllc]

@@wilcoxblues27 yep. I’ve seen anything from .2 up to 1.1 mil shift. 1.1 mil shift coming from Geissele mk18, 26” heavy barrel with suppressor. .2 from a 16” and aero rail and receiver.

[@wilcoxblues27]

@@veracitysolutionsllc that's wild, I can't say I'm suprised though. there was a video out with the guys at Seekins talking about this year's ago. That's why they beefed up their uppers in the front of the ejection port. Regardless of the rail, the thread tennon on the upper is going to be the weak link regardless of how beefy the rail may or may not be. Super cool to put numbers on how much shift can happen though!

[@LaCal22]

Should do a video on the tacomhq

[@codyway7424]

I always wondered how guys get away with shooting with the bipod mounted but not deployed on one stage, then removing it on the next stage.

[@jamesdrakcip9276]

I dont think rail flex would cause the POI shift shown in your video. The optic is mounted to the receiver and the barrel is secured into the receiver. The forces imposed on a free floated rail cause some degree of receiver flex, which moves the line of bore from its original position.

[@veracitysolutionsllc]

You stated it wouldn’t and then stated it would in the same paragraph. The pressure applied from the rail directly influences the pressure at the barrel nut/receiver thread junction. That pressure applied and the length/weight of the barrel can’t affect the POI shift.

[@jamesdrakcip9276]

@@veracitysolutionsllc I did not. I said the forces imposed on the rail cause RECEIVER flex because of where the forces are transferred to the receiver (at the barrel nut). I think you accidentally contraindicted yourself at the end of your reply. The reason Im trying to differentiate between rail and receiver flex is in offering a partial solution. Find a stiffer receiver to minimize the effect?

[@veracitysolutionsllc]

@@jamesdrakcip9276it’s still rail flex. But yes.

[@jamesdrakcip9276]

@@veracitysolutionsllc the rail does flex, but the rail flexing isn't what directly causes the issue. Its like saying that bipod flex causes poi shift. The force put on a bipod transfers force to the rail, which transfers force to the receiver, which flexes the receiver. What causes the poi shift? The receiver flex.

[@veracitysolutionsllc]

@@jamesdrakcip9276 👍

[@Travis-y9k]

Have you been playing buffer springs or weights or the A5 system to smooth out the recoil impulse

[@jatollar]

Those things affect reliability so should only be tuned to get the rifle working properly ie. brass flying back instead of bouncing forward. Heavier springs and weights do reduce the feel of recoil slightly, but the only good way to do it and stay in a reliable operating window is a muzzle brake, but then its really loud. To be honest, learning proper recoil control is the best way. Try firing the rifle with a loose grip and watch what your sights do, make an adjustment that you think will reduce that sight lift and see if it works.

[@jatollar]

This guy worked for Colt and this may help explain what I was saying about operating window: kzbin.info/www/bejne/eorJXoCCgrR3nqM

[@brandonRMS]

What bag is that?

[@masoverse1]

Well, if it were a sales pitch for the Broadsword, it’s wasted. Last I checked, they don’t have any on their site. So wouldn’t be able to get one if I wanted. Guess I’ll stick with my DD’s and Wilson Combat AR.

[@jimdavis303]

That’s because they’re selling faster than we can produce them still.

[@Buck762]

I thought the whole point of free floated barrels is that pressure on the handgaurd doesn't impact POI

[@andrewwilkey6195]

In normal shooting from a bipod or resting on a wall/bag etc.. with a free float hand guard there would be no noticeable zero shift, but he’s hanging a sandbag off the end to overload the rail. Free float rails do still touch the barrel through the barrel nut so technically they can still affect the zero it just takes way more force.

[@jatollar]

It helps a ton, but the platform is still somewhat flexible because it's originally designed to be as light as possible.

[@mavrikmavrik3032]

I think the term is “free float” in quotes meaning that there is typically nothing connected/fixed to the barrel down its length. If there is you can have all kinds of issues like differences in thermal expansion between components that can cause forces on the barrel and contribute to shifts in bullet impacts. In the ARs that are “free floated” they typically don’t have the connection to the barrel out towards the muzzle. However handguards that use the barrel nut as the connection point to the rifle are connected to the barrel through the nut. The flex impact is much lower because it’s so close to the chamber but there is still a connection to the barrel. In this case it’s nearly free floated but not 100%.

[@seanoneil277]

The main point is to reduce and not eliminate POI shift. To let the barrel be as independent as possible from whatever the rifleman may rest his rifle against while shooting. If the handguard isn't free floated then any pressure on the handguard pushes the barrel immediately. If the handguard IS free floated then eventually, some pressure on the handguard will make a POI shift because the handguard does connect to the upper receiver at the barrel nut, and the barrel nut holds the barrel to the upper receiver. It's really more about the length of "free float" rather than the bare existence of any "free float."

[@JohnSmith-yx8kf]

Yeah but most AR15 handguards aren't technically free floating because they attach to the barrel nut. You could argue that the gas tube makes it a non-free float system, but i think that flexes enough with the barrel for the impact to be negligable. It's not like a bolt action where the only thing touching the barrel is where it's screwed into the action.

[@wood-wheel-wizard]

If the rail was shorter would the system whip less?

[@macalvand]

Yeah, shorter = less leverage you can apply to the end that isn't attached to your barrel nut

[@mavrikmavrik3032]

Has anyone done this on an Aero M4E1 with the Enhanced rail that screws directly into the upper?

[@veracitysolutionsllc]

Yes. The shift mechanical shift is imperceivable in my testing. Not the M4 enhanced and M5 enhanced that I tried.

[@ulisessalas6420]

Huh… interesting results.

[@boygonewhoopdataZZ]

I was wondering who this jimmy was and why he keeps popping up in my feed 🤣

[@okienightstalker3145]

POF has the rail that mounts to the barrel nut and the top of the receiver and keeps thing really stiff. LWRC aslo has a great rail mounting solution. SOLGW seems to rebrand a lot of their stuff maybe they should just rebrand a POF or LWRC rifle...lol

[@MichaelLeopold1]

Score

[@mitch511]

Goofs with that string on the bipod lol.... still haven't clued in that using shock chord and stretching it back over the bipod would eliminate the snag hazard and be faster to deploy and closer to the hand of the shooter.

[@seanoneil277]

It's lonely out there in the vanguard.

[@veracitysolutionsllc]

By all means. Make a video.

[@NATHANBROWN80]

If you're wanting to work on your mental side of shooting.... Hands down, go talk to Joel Turner from "Shot IQ". He is absolutely amazing and has the background to prove it. Retired SWAT Sniper Instructor and has coached thousands of people. He's a humble guy and fun to talk to. Oh, and his son has won numerous world level events archery events while shooting in the adult pro division and he's only 15 and has been winning since 12 or 13. Go talk to Joel!!!