Shoot the gun and learn things.

[ASH556]

I know a lot of guys that have a lot of nice guns that hang on their office walls or they sit in a safe, but they never shoot them. I'm talking VERY expensive setups that they've put together on theory with input from folks, but they've never shot them, or at best, they've shot them at the 25yd indoor range to get the optic "on paper."

You can't set something 80% of the way up, and then declare it "good to go." You need to shoot it and confirm. Zero distance, optic, irons, suppressed and not, with the ammo(s) you plan to use. When you do this, you learn things. One of the things folks quickly learn when they do this is that different guns respond differently to the same inputs.

Here's my story for the week:
I recently put together 2 new AR configurations as pictured below. Both of these are built with top notch components including Geissele triggers and rails, all Colt upper parts including SOCOM barrels (one shortened to 10.3), Nightforce and Aimpoint optics, etc. They look good, and the build lists are impressive, but do they work????

https://i.imgur.com/smCsOH9l.jpg

Well, the short one works well. Target is 100yds in an indoor range (I know, cool concept, right? but the lighting still isn't great). Red circled hits are without suppressor, un-circled hits are with suppressor using a 2MOA Aimpoint T1, bipod and rear bag with 64gr Gold Dots. I'll take that!

https://i.imgur.com/QWcvmksl.jpg

On to the long one. 5 shots at 100yds outdoors (from a couple weeks ago), 64gr Gold Dots, no suppressor. Grid squares are 1/2", so again, I'll take that all day!

https://i.imgur.com/MuoPRlil.jpg

So then I screwed the can on expecting to see the same negligible, if any, shift from the suppressor. I mean, after all I have a thick SOCOM barrel to mitigate droop, etc with the suppressor. WRONG! My rounds wouldn't even hit the IDPA silhouette I was using as a backer. Since this is a recently pinned-welded brake, I assumed it was a mount issue and took the gun back to the shop who did the work (no need to mention their name, but they're a well-known precision rifle shop). 2 hours later they called me to say the muzzle device checks out fine, but they found the problem:

https://i.imgur.com/m32Y1wGl.jpg
https://i.imgur.com/rQCpJXgl.jpg

You see, friends, it turns out that hanging a suppressor off even a heavyweight barrel can cause it to move and flex differently and what was enough clearance between gas block and handguard before, no longer is. Apparently having your barrel slap the side of your handguard will have negative impact on your accuracy. So off to home I ran and proceeded to further trim and then refinish the gas block. I then proceeded to the aforementioned 100yd indoor range to confirm correct zero.

100yds unsuppressed with 64gr Gold Dot:
https://i.imgur.com/aFnIYYCl.jpg

Then I put the suppressor on and was amazed by what I saw:

https://i.imgur.com/SZFJThel.jpg

That is the result of 3 rounds fired aiming at the top target, unmounting and remounting the suppressor, and firing 3 additional rounds aiming at the top target. At least it's repeatable I guess. So, when shooting suppressed with this rifle, I'll dial up 1.6mil (I'll probably make a mark on the turret) and for all other times it'll be zeroed.

Same POA with 1.6mil elevation dialed. I attribute the slighted opened group to the mirage I was seeing off the suppressor at this point.:

https://i.imgur.com/StwCjg0l.jpg

Don't assume anything and test all your gear in every condition possible.

[Backspin]

Thanks for this post. It’s a good example of doing the work. It can be tedious, but worth the knowledge and perspective it brings.

The unspoken cost of buying new gear is the vetting process. A new optic, new trigger, new bullets, etc. all cost time and ammo to verify performance and to explore nuances.

Back when life was simpler and I was just into pistols, my test as to whether or not to buy a new gun or piece of gear was this: “would I be better served by that new thing OR the equivalent money’s worth of ammo?” I almost always picked ammo and have never regretted that choice.

Since getting into rifles, I’ve been playing around with optics and gear so much more. When shooting for accuracy, every trigger press answers one question and produces two more it seems. There are many more variables to keep track of if one really wants to shoot the rifle to its potential.

[NH Shooter]

Good post! You don't know until you try...

I will also state that the more variability you introduce, the more complex the vetting process becomes in verifying POI. A few that come to mind;


suppressed vs. unsuppressed
optics and parallax (how does a shift in my cheek weld affect POI?)
POI change as barrel heats up
variable power scopes at different power settings
forward sling mount tension placed on free-float rail with front sight attached to it



Not to mention function variability and all the factors involved with that, as well as ergonomic issues (rifle balance, ease of portability, etc.).

This is why I've grown extraordinarily fond of KISS rifles - keeping the variabilities as low as possible. The easy trap to fall into is the justification of why one thinks they need a certain accessory, where is might be wiser to honestly access why the accessory is not needed for the role the rifle is intended to fill.

In any case, my KISS rifle is irons-only and I am currently experimenting with a different set that I think will improve speed and accuracy. I'll be putting that theory to the test soon because as ASH556 stated, it's the only way to know for sure.

Improving the function and usability of a modern sporting musket is very gratifying, especially when it does not involve adding more stuff to it.

[hufnagel]

I've heard many stories about how putting on a can shifts POI, and being of engineering background I understand the concepts of mechanical droop and altering harmonics, but I've NEVER heard of a case of the inside of the hand guard getting bitch slapped by the gas block like that. I know it sucks it happened to you, and you have to sort out the issue now, but that's FREAKING COOL! :cool:

[TCinVA]

With some of these setups and some of the newer generation lightweight compact "rails" there isn't much room for error. I'm not shocked hanging a can off the end of it produced that result.

The point of the original post is, of course, correct. I can't tell you how many times I've heard "It works for me!" from people who have not taken even basic steps to pressure test what they are yakking about. You don't know if it works until you prove it does.

And I'll stop there before I start ranting about the staggering percentage of people out there who cannot effectively zero a carbine in the first place...

[HCM]

And I'll stop there before I start ranting about the staggering percentage of people out there who cannot effectively zero a carbine in the first place...

Preach it !

[Jay Cunningham]

With some of these setups and some of the newer generation lightweight compact "rails" there isn't much room for error. I'm not shocked hanging a can off the end of it produced that result.

The point of the original post is, of course, correct. I can't tell you how many times I've heard "It works for me!" from people who have not taken even basic steps to pressure test what they are yakking about. You don't know if it works until you prove it does.

And I'll stop there before I start ranting about the staggering percentage of people out there who cannot effectively zero a carbine in the first place...


But that's what the first five hours of class are for.

[Duelist]

But that's what the first five hours of class are for.

That’s what BRM was for. 9 rounds or less. Zeroed.

I’ll confess to having had some trouble getting a good scope zero on an AR, however.

[rob_s]

A long time ago, on a forum far, far away. (https://www.m4carbine.net/archive/index.php/t-28658.html)

[Jay Cunningham]

Reminds me of something G.K. Chesterton wrote:

“...she [Joan of Arc] did not praise fighting - but fought!”

“She [Joan] was a perfectly practical person who *did* something. While they [Nietzsche and Tolstoy] are wild speculators who *do* nothing.” - Chesterton, Orthodoxy

[El Cid]

Sounds about right Ash. I learned that despite the marketing we must choose... zero with can or without.

https://i.imgur.com/iswsTQT_d.jpg?maxwidth=640&shape=thumb&fidelity=medium

[MistWolf]

A long time ago, on a forum far, far away. (https://www.m4carbine.net/archive/index.php/t-28658.html)

That was a good thread. "Go Shoot the Gun" is some of the best advice to be given.

[ASH556]

I thought I'd gotten this thing all sorted out. I even un-mounted and re-mounted the can in my previous range session (as posted earlier in this thread) to confirm. Apparently, though, something is still off with the mount and now I'm beginning to question whether it was the culprit all along. Yes, there were marks inside the rail, but I think that may have been from the round hitting the suppressor endcap and popping the barrel around rather than just the harmonics of the shot.

I hit the range with Karmapolice last Saturday AM and he ran me through a new rifle exercise he's working on. Should've been pretty straight forward, but I had some random misses just winged out there like "WTF?" Figured it was me just having a bad day until I went to re-shoot the 25yd portion and couldn't hit shit. Took the can off the gun and had zero additional problems getting the hits.

Today I took 2 rifles and 2 cans to the range to try and figure this out once and for all. Rifles consist of Colt uppers with Colt SOCOM barrels, one cut to 10.3, the other is the problem gun pinned/welded on 14.5". Suppressors are AAC M4-2000 and AAC SDN-6.

My hypothesis was that the mount on the pinned gun is compromised such that it's causing slight tilt of the can such that it sometimes creates minor impact of the bullet into the endcap and slings the wild round. I further hypothesized that using the SDN-6 with it's larger .30 cal bore would negate these issues. It seems I was right. I further confirmed this by firing the 10.3" gun with both cans as well as sans can to remove the M4-2000 can itself as being the issue.

Path forward: since I've already taken the pinned gun back to the shop who did the work and they claimed the mount was fine; I'm done with them. I've emailed Steve @ ADCO and expect that having him cut off the existing mount and pin/weld a new mount properly will solve the issue.

Endcap strike:
https://i.imgur.com/xniPtTfl.jpg

Mount (see that material missing between the shoulder and the last thread? My guess is that's the issue.

https://i.imgur.com/xyJUzXOl.jpg

Shiny spot on back of the thread is interesting:

https://i.imgur.com/2GbT16Sl.jpg

Targets these are 10-shot groups standing at 25yds with AE 55gr. I know benching would be more precise, but I'm looking for a trend, not zeroing the gun. The problem is still plenty evident:

https://i.imgur.com/AxWr42bl.jpg
https://i.imgur.com/4IkFc00l.jpg
https://i.imgur.com/MqXmNiSl.jpg
https://i.imgur.com/1iCPH0Pl.jpg
https://i.imgur.com/0N5rYM0l.jpg
https://i.imgur.com/iiXTvILl.jpg

[ASH556]

Just as a bit of follow up, I pulled the barrel this morning to send to ADCO to have the brake cut off and replaced with a 51T FH, and observed no marks of interference with gas block and rail. I'm convinced this is and always was 100% a mount issue.

[ASH556]

I received the barrel with newly-pinned brake from ADCO yesterday and slapped it together (I mean, properly assembled, torqued and re-torqued 3X to 40 ft/lb, even used a fresh gas tube roll pin ;) )this morning. I hit the range over lunch today and confirmed that all is good to go.

10 rds, 25yds standing, NX8 on 1X illuminated, rapid fire aiming at top of 2" dot (noted by red mark).

https://i.imgur.com/NniFMN1l.jpg

5 rds, 25yds, standing, NX8 on 4X, no illumination, slow fire aiming center of 2" dot (noted by red mark).

https://i.imgur.com/eNzsCQ2l.jpg

I'm pleased that the gun is now GTG. I'll get it out to 100yds and re-zeroed with Gold Dots, then confirm suppressor shift; if any.

[ASH556]

Zeroed at 100, no can
35137

SDN-6 shift 3” (.8mil) straight down:
35138

M4-2000 shift 2.5” down, 2” left:
35139

SDN-6 with .8 mil elevation dialed (mirage getting to me by this point, but basically there.)
35140

I’m good with this. The elevation correction is simple and not that much with the N6. That lets me keep the M42K on the 10.3, where I like it better anyway, but if I had to use the M42k on this gun it would work. Bottom line the mount and endcap strike issues are solved!

[StraitR]

Good stuff Ash. Glad you got it worked out.

Curious that the contact between the cut FSB and rail is at the top. This problem is more often seen on the bottom, when barrel droop is introduced due to adding a heavy can. I have no doubt that you had a mount issue, but could the upper contact have been caused by preloading a bipod?

[ASH556]

Good stuff Ash. Glad you got it worked out.

Curious that the contact between the cut FSB and rail is at the top. This problem is more often seen on the bottom, when barrel droop is introduced due to adding a heavy can. I have no doubt that you had a mount issue, but could the upper contact have been caused by preloading a bipod?

Yep! Absolutely and that's probably what caused it. At the time the shop showed me the rail contact I was baffled because I've shaved literally dozens of gas blocks for myself and others and never had a problem. Bipod load makes sense.

[ASH556]

Also, for the CDO among us, I was a little rushed at the range yesterday evening, but when I got home and looked at the pics some more I decided to add 1 click (.2 mil) rightward windage and re-zeroed the turret. That should take care of the left bias you see in the groups! :cool: