Bad Groups with Old Scope

[DustBuster]

Hello Shooters.

I have completed my 308 build in stages.

I have fairly good quality parts.

Good fitting Upper and Lower... 

Heavy Buffer/ Carbine length Extension

Faxon Match series heavy fluted rifle length barrel, thermally Tight and proper Barrel Nut torque.  

I had mixed success with cheap open sights, at 30 yards and 100.  I wanted then to see if my Barrel was any good.

So I replaced the milspec Trigger with a Larue MBT-2s and bought two Warne Mountain Tech Extra tall 1” rings.  I have an old Weaver K4 4 power scope.  I then went to sight it in.  I am not happy.  I think at 100 yards I shot better with my open sights.

Thirty yards yielded a few groups with bullet holes touching each other but always a spoiler an inch away.  I’m pretty sure I never flinched or moved as much as those spoilers. 

I have a few things I can work to determine what is bad( including my shooting technique). 

1) I could possibly be over gassed( maybe this takes away from bullet speed?)

2). My adjustable gas block is 1/16 or a bit less from touching the inside of the handgaurd. ( it is slightly tilted due to the orientation that Faxon drilled my hole) Maybe Barrel whip is making that make contact?

3) When I first installed my rings, I attached them to scope first, then arranged them to fit the Picantanny rail.  Upon tightening the rings down to the rail, it seemed that the rearward ring wanted to put slight torque downward on the system.  They have not been lapped at all.  Since then I’ve loosened the top halves of the rings and leveled the cross hairs, re tightening to what felt like adequate torque.  My front rings cross bolt is tight to the front of a picantanny rise and the rearward rings cross bolt is tight to the rear of a picantanny rise.  This makes those dual use Weaver/Picantanny rings fairly tight and snug with no slop, even before tighting the base bolts.  Could a non-lapped, slightly downward stressed scope cause shooting anomalies?  Is it worth it for me to buy a 40 dollar scope lapping kit for a 1” scope size?  I’m gonna be sad if I did buy it and later find out I just have a bad Barrel.

4). Bad Barrel maybe.  Many variables to rule out before I accept this fate.

Please pray for me 🙂

Good Day

[shooterrex]

If my gas port was not at 12 o'clock when it was installed in the upper it would be going back to the factory.

[Belt Fed]

9 minutes ago, shooterrex said:

If my gas port was not at 12 o'clock when it was installed in the upper it would be going back to the factory.

This^^^^^^^

[DustBuster]

I’d say it’s about at 12:15 or maybe 12:45 tops.  Too late for me to send it back.  What reason would you guys reject a barrel with a (slightly) rotated gas port?  Is it because it might require custom bending the gas tube to be exactly in line with the carrier gas key.  I have not altered the factory gas tube at all, it seems pretty straight with the gas key anyway.

 

[shooterrex]

If it's not @12 o'clock it shouldn't have left the factory. It shouldn't be to late to send back to the factory if it's not right. Faxon is good about fixing screwups.

If it works and you are happy with it then leave well enough alone.

Did the barrel extension come loose a little bit? Those are installed before the gas port is drilled SO the gas port is at 12 o'clock

[DustBuster]

The barrel extension on my first barrel ever purchased was loose, not this one.  I hope I can come to be happy with this barrel, I’ll try to trouble shoot the entire gun I guess till I’m out of ammo, about 350 more tries I guess 😞

Research on the Web here has brought to mind many different possibilities of trouble.  Ammo type.  Bullet size, some barrels like different loads I hear.  Not sure if the gas block clearance is a possible reason for my unhappy shot groups.

I might have dimpled the barrel slightly more off dead center of the off center gas port, exaggerating the tilt, I won’t know till I remove the gas block.  I have the gas screw cranked all the way out I believe, since because of my 4:30 o’clock brass ejection I thought it was undergased... I didn’t see or feel any remarkable change in gas from my first shot until the screws present location, mostly out.  

Im more interested I guess in the gas block clearance which can be resolved with my other non adjustable, and the possibility of a pinched or bent scope.  I made one adjustment sighting in at 30 yards, I shot two inches left so I clicked right 32 clicks, then back 5.  The POImpact   Tracked exactly.  Later in the day it almost seemed if I lost my lateral zero, however...but the wind was picking up some and I was starting to get frustrated.

Thanks for replying guys...

Here is a couple of pictures of:

Empty chamber open bolt gun

Top of muzzle view

Bottom of muzzle view

Gas tube which looks pretty parallel.

These might show relative gas port tilt.

Not sure if it is an issue

[shooterrex]

Ok you dimpled the barrel for the gas block. Did the gun run w/a fixed gas block? Bet if you take the gas block off the carbon pattern is to one side instead of centered. As long as the gas block doesn't touch the rails it shouldn't change your point of impact.

[DNP]

What ammo. You mentioned it could be an issue. What are you shooting for these tests?  Your scope mounting could play a large part in it. Why reject a barrel that isn’t right??...because I just paid fair money for a product that isn’t right. If I bought it as a blem, I could understand. 

[Magwa]

ok lets break this down from a shooting point,

1. did you or are you breaking the barrel in?

2. what kind of ammo all details if you want 1/2 or 1/4 MOA groups you have to shoot quality ammo match ammo like sierra Match king 168

3 you have to break the gun in is it well lubed on the bolt carrier group, inside of upper all moving parts just about dripping wet till surfaces mate....

 4.  does the upper have 20 MOA added to it? your scope is how old? 4 power is really not suffecient to shoot groups like you want unless you have 20 year old eyes a one piece scope mount is what you want again Larue is your friend....

5. under what conditions are you firing the rifle ? slow fire? (which it should be to break barrel in ) or are you just banging away? are you shooting from prone? bench with what kind of rest ? Bipod? how is the rear of the gun supported when shooting? do not! heat up the barrel while breaking in... or really ever unless you are in combat then the group is not so important you are...

6.  pictures of groups tell a awesome story are they stringing shots horizontally? vertically?  cloverleaf ?

7.a carbine stock is not a great choice for precision shooting to much movement internally just as lead tipped bullets are not good for accurate shooting they are for hunting lets work this out give me data..... 

P.S. if you fire prone with a Bipod you will hate that comp on the front with holes all around you will be kicking dirt up in your face constantly...

 

Edited May 27, 2021 by Magwa

[DustBuster]

I will send a picture of the groups... and fill in more details later today... yep, lots of stuff.   Ammo is cheap pmc gold 147gr,

also I had a tiny bit better results with my Hand loads, which I carefully trickle charged to very close amounts.  Not big improvement over pmc though.  I’ll give more details later, thanks, gotta go

 

[edgecrusher]

1 hour ago, DustBuster said:

I will send a picture of the groups... and fill in more details later today... yep, lots of stuff.   Ammo is cheap pmc gold 147gr,

also I had a tiny bit better results with my Hand loads, which I carefully trickle charged to very close amounts.  Not big improvement over pmc though.  I’ll give more details later, thanks, gotta go

 

You gas block clearance is fine. I don’t believe you slightly off center issue will affect accuracy but is more of a cosmetic concern if functionally the rifle is ok. Scope and mount? Possibly, but….
 

I’m going straight to ammo. Pms is fine ammo, but…

1. what’s the twist rate of your rifles barrel? 
2. have you tried any other factory ammo? 
3. what are the projectiles in your hand loads? 
4. shooting position? This also can affect groups- we are often the weak link

[DustBuster]

8 hours ago, edgecrusher said:

Scope and mount? Possibly, but….
 

I’m going straight to ammo. Pms is fine ammo, but…

1. what’s the twist rate of your rifles barrel? 
2. have you tried any other factory ammo? 
3. what are the projectiles in your hand loads? 
4. shooting position? This also can affect groups- we are often the weak link

1) Twist Rate 1:10 

2) Norma tactical FMJ 150gr and PMC bronze FMJ 147gr

my Handloads are 150gr Hornady FMJ 42.5 grains IMR 4895

3) FMJ, the seating depth for the Norma is seems quite deep But they seem to shoot same

4) I was prone using a bipod on a bumpy wool blanket with millions of shotgun hulls and brass underneath.. not comfy.  Had a carhart coat and sweatshirt jammed up as a rear bag.  I could get reasonably steady after adjusting for a while, but Neck had to kink upward awkwardly to see through the scope at that angle with my higher rings.  I could feel cheek pressure shaking the situation.  I’m sure I was the Weakest Link!

After closer inspection of my targets, I won’t draw any conclusions just yet.. I just felt I was steady enough when I pulled the trigger to have better groups.. The thirty yarders would be nice to be 100 Yard groups.  Here is a picture of the groups.  I ran out of space and some shots got mixed up... two must have gone into other holes.  I always shot groups of 3.  Anyway... thanks for advice and interest... I think I’ll buy the 1” lapping kit from midway even though I probably will never use it again... 30mm scopes are probably the next thing to go to in my future.

 

 

 

[Matt.Cross]

1. In the decade or so that I've been here, it's been extremely rare to see a 1:10 twist barrel to perform well below the 168gr bullet weight. Go heavier with your bullets.

2. GIGO - Garbage in, garbage out. Match ammo is going to be the best indicator of your true accuracy potential.

3. If you aren't confident in your gear, your fundamentals will tend to be executed poorly. Get an optic and rings combination that's unimpeachable in quality, this eliminates your kit as the weak link and leaves you with a much clearer idea of the accuracy potential of you and your rifle combined.

4. A 3-shot group won't tell you very much about how accurate your rifle is, I'd shoot at least 5-shot groups, if not 10-shot groups.

[DustBuster]

I will look at getting heavier bullets for sure... a sand bag, and will search for a good scope.  I’d like to be able to hit the steel turkey at 500 yards some day in my lifetime... 

[edgecrusher]

30 minutes ago, Matt.Cross said:

1. In the decade or so that I've been here, it's been extremely rare to see a 1:10 twist barrel to perform well below the 168gr bullet weight. Go heavier with your bullets.

2. GIGO - Garbage in, garbage out. Match ammo is going to be the best indicator of your true accuracy potential.

3. If you aren't confident in your gear, your fundamentals will tend to be executed poorly. Get an optic and rings combination that's unimpeachable in quality, this eliminates your kit as the weak link and leaves you with a much clearer idea of the accuracy potential of you and your rifle combined.

4. A 3-shot group won't tell you very much about how accurate your rifle is, I'd shoot at least 5-shot groups, if not 10-shot groups.

I totally agree. With all of this (don’t tell Matt, plus, what the hell is unimpeachable?!)

 

ive been shooting ten round groups, off a mat and prone loading the bipod. At 100 yds I’m usually getting just under 1.25” That’s me being the weak link.

 

if you’re truly concerned the only true way to know is shoot off a bench with the gun in a sled or vise. Take the human out of the machine. If you know you pull a shot or two (or more) but are generally happy then forget it and practice those fundamentals.

 

also, 1:10 should be shooting 168-175 gr match stuff for accuracy for best results. Nothing wrong with m80 for steel and practice but if you want pretty paper targets then go heavier and test out some different stuff. I haven’t got a load for .308 yet but an example of 5.56:

Mk12 mod 0 rifle

1-7 18” SPR profile with rifle gas, likes heavies, mk262 shoots amazing. I cloned it with 77gr SMK, LC brass, 23.8 gr of Varget. It’s very close, maybe only 1/4 more for group size but costs a fraction to produce. The gun shoots my hand loads around 1” prone on the bipod with 10 shot groups. 
 

you just got to find out what she likes

[98Z5V]

3 minutes ago, edgecrusher said:

I totally agree. With all of this (don’t tell Matt, plus, what the hell is unimpeachable?!)

Unimpeachable?   That's easy, brother.  See below.    

[DustBuster]

21 hours ago, shooterrex said:

If it's not @12 o'clock it shouldn't have left the factory. It shouldn't be to late to send back to the factory if it's not right. Faxon is good about fixing screwups.

If it works and you are happy with it then leave well enough alone.

Did the barrel extension come loose a little bit? Those are installed before the gas port is drilled SO the gas port is at 12 o'clock

Geez, Shooter Rex, I was rereading your reply here and it finally clicked what you were asking.... I sure hope the barrel extension didn’t  loosen from factory to my place.... It didn’t feel loose, maybe a bore scope would see a gap inside if it did?  I’d be the most unluckiest barrel buyer in the world if my first two barrels both had loose extensions... I’m gonna have to study more about their process and look at a cross section of how the extension and barrel meet up inside... I’ve read a quick explanation from 98 of the process... but I could learn more in depth about it.

[DustBuster]

Unimpeachable, I was impressed with the term but I didn’t even see the Trump connection, haha

[Matt.Cross]

Suit yourselves, ya want me to hold your hands and spoon feed you, fine with me.... 

[DNP]

Your smarts are showing again...quick, Say something about meal dots. 

[DNP]

14 minutes ago, DustBuster said:

Geez, Shooter Rex, I was rereading your reply here and it finally clicked what you were asking.... I sure hope the barrel extension didn’t  loosen from factory to my place.... It didn’t feel loose, maybe a bore scope would see a gap inside if it did?  I’d be the most unluckiest barrel buyer in the world if my first two barrels both had loose extensions... I’m gonna have to study more about their process and look at a cross section of how the extension and barrel meet up inside... I’ve read a quick explanation from 98 of the process... but I could learn more in depth about it.

You didn’t put the compensator on with a cheater bar and work it open and closed to achieve index...did you?

[Matt.Cross]

3 minutes ago, DNP said:

Your smarts are showing again...quick, Say something about meal dots. 

[98Z5V]

6 minutes ago, DNP said:

quick, Say something about meal dots. 

 

1 minute ago, Matt.Cross said:

I encountered this mentality last weekend, at the shoot.  I smoked two 500+ targets out of the gate, from one of the stable shooting platforms, then everything went downhill after that for me.  One dude comes over and asks "What was your hold on thise first two?..."   My reply was "held 4.6..."  

After a short pause, and a little misunderstanding, then a dawning of light, he says, "Oh, you're mils..."   

He walks away, turns around a few times, and pokes his smartphone a bunch, and comes back and says, "I was holding 5.0 mils..."  

[DustBuster]

14 minutes ago, DNP said:

You didn’t put the compensator on with a cheater bar and work it open and closed to achieve index...did you?

No, I saw someone else here did that...No I clamped the barrel wrapped in thick leather near the muzzle and turned it I hope less than a turn and a half past tight on a crush washer, just till a nail I had going through the bottom holes of the compensator eyeballed level...Armorers wrench at 90 degrees to a torque wrench an I got near to 30 fr lbs when it stopped correct.  I’ve heard how an overtightened compensator could squish the barrel tip, hope they didn’t happen to me...Geez these things are not simple to put together right 

Edited May 28, 2021 by DustBuster

[DNP]

Sometimes we get lucky and they aren’t too bad.