How to turn your 2 MOA tomato stake into a 1/2 MOA tack driver

[CMP70306]

Ok now that I have your attention I have a conundrum that I haven't figured out.

My dad recently bought an X-Bolt Pro LR in 6.5 PRC and to be frank it shoots inconsistent at best and terrible at worst. After chasing my tail with 3 shot load development groups I buckled down and shot 10 rounds of factory ammo to check the group size. One 4" group later I sent it back to Browning who shot a 3 rounds into .55" at 50 yards and was told it meets their 0.75" spec.

So I took it to the range to compare it to my 6.5 PRC and it continues to string shots along both horizontally and vertically with no rhyme or reason while my M7 shoots under 1/2" with the exact same ammo. So after shooting a group that was 1" vertical and 2.5" horizontal I was trying to determine how much the BC would be effected if I took the scope off before I javelined it into the woods when I got the bright idea to take the suppressor off mine and put it on the Browning.

That's where the title comes from, the next 4 rounds went into a ragged 0.4 MOA hole, the best group this gun has shot by an inch, and I'm utterly baffled as to what would cause the suppressor to have such a pronounced effect on the accuracy of the rifle. I even went back and shot my rifle unsuppressed to confirm that is wasn't just me pulling shots and proceeded to print the same size groups as it did suppressed.

So anyone have any ideas? None of my other rifles exhibit any noticeable change in accuracy so I have no idea what is wrong with this one that apparently weight can fix it?.

 

[ShtrRdy]

It sounds like you changed the harmonics of the barrel by hanging the weight of the suppressor on it.

Do you reload?

 

[Kamerad]

Did Browning inform you of the ammunition they used to get their results? Bullet weight, etc. I’m a novice, so I don’t have much technical advice to offer. However I’m interested to see what others have to say.

 

[BurnOut]

It sounds like you changed the harmonics of the barrel by hanging the weight of the suppressor on it.

Theeeeere it is. This is the same (basic) concept covered with a somewhat dated Browning feature, the BOSS.

 

[CMP70306]

I do, blew through a $114 box of Hammer bullets trying to get that damn thing to shoot with powder charges from 52gr to 58.5gr H4831 trying to find a load that works but no dice. Also tried H1000 and Superformance with the same results.

it could individually print ok 3 shot groups but it seemed to have a wandering zero as the groups would shift from target to target. However if you overlaid them on the same target you get a vastly larger group.

I would get a group like that but the next three shot group would be at the top of the target with a flier to the right. It was more random luck if the bullets landed close together.

Below is 10 rounds of factory 143gr ELD-X, the shots are pretty much in order right to left for the first 6 then 7&8 started back right while 9&10 hit 2&3.

That last group is why it went back to Browning.

Then the groups I shot yesterday unsuppressed then suppressed

Those two groups were shot a max of 10 minutes apart with the same batch of handloads with the only difference being the suppressor.

As for the test ammo Browning used it was the 143gr ELD-X Precision Hunter ammo, the same thing I shot the 4+” group with. It can print small groups if they happen to line up but the variability is far more than I’m comfortable with for a long range rifle.

 

[Romeo458]

Wedge some card stock or similar material about 1/2 to 1" behind the end of the stock forearm to add pressure to the barrel. You can add or subtract layers between groups to see if it helps.

It's an old trick that might work. Enfield had a spring and a plate to do this and if the spring was bad they would shoot shitty.

 

[CMP70306]

Theeeeere it is. This is the same (basic) concept covered with a somewhat dated Browning feature, the BOSS.

I figured it was related to the harmonics but was unsure of the underlying mechanical issue that would cause such a profound change.

 

[CMP70306]

Wedge some card stock or similar material about 1/2 to 1" behind the end of the stock forearm to add pressure to the barrel. You can add or subtract layers between groups to see if it helps.

It's an old trick that might work. Enfield had a spring and a plate to do this and if the spring was bad they would shoot shitty.

I had heard of that trick for old military rifles but hadn’t considered it on a modern rifle. I also noticed that it appears to be bedded 1” before the action as that’s where my dollar stops.

 

[BurnOut]

I figured it was related to the harmonics but was unsure of the underlying mechanical issue that would cause such a profound change.

Barrel harmonics is one of those discussions that can get into heavy math pretty quickly, and there seems to be just as much art as there is science in it.

I admit to not knowing much about it, but know that it's one of the major players in regard to the ultimate accuracy potential of a long gun.

 

[Steel+Killer]

Just a thought what if you installed a muzzle brake on it to see if you get lucky that it corrects the barrel harmonics could be a cheap fix...... other thought is to cut a little off the barrel and have it re crowned and or threaded.

 

[hlee]

Shoot a 10 shot group and if the results are acceptable, stop worrying about it. Shoot it with the can. Or, as you brought up the wandering zero, shoot 5x5 shot groups and if the groups are good and the zero stays put, stop worrying about it.

That said, it's hard to shoot good groups when frustrated. And, it's hard to shoot good groups when your not confident in the gear. I am reminded of the scene from the movie Tin Cup, where Roy is taking swing practice before the US Open and can't hit straight. "Your brain was getting in the way..." Your suppressor could be your psychological "tee behind the ear."

 

[ShtrRdy]

The groups from suppressor off to suppressor on are dramatically different. Have you been able to shoot more than one nice group with the suppressor on? If so that would say the scope/rings/base and bedding are likely okay.

Since you were able to attach a suppressor could you try different muzzle brakes or even hang a weight on there?

 

[CMP70306]

Shoot a 10 shot group and if the results are acceptable, stop worrying about it. Shoot it with the can. Or, as you brought up the wandering zero, shoot 5x5 shot groups and if the groups are good and the zero stays put, stop worrying about it.

That said, it's hard to shoot good groups when frustrated. And, it's hard to shoot good groups when your not confident in the gear. I am reminded of the scene from the movie Tin Cup, where Roy is taking swing practice before the US Open and can't hit straight. "Your brain was getting in the way..." Your suppressor could be your psychological "tee behind the ear."

This is what I get when I shoot 5 shot and 10 shot groups. This has been on going since the first time I fired the rifle as I was doing load work ups and was expecting large groups moving around. The problem is that no matter what I shot through it it never got better. Some would group good one trip then fall apart the next for no apparent reason.

As you can see it is consistently inconsistent, sometimes they are all over and sometimes they happen to fall into a tight group. The first two pictures are the same loads shot at different targets with no scope adjustment, as you can see one group is to the left while the other is right above. Also I will note that the stringing is not sequential and it follows no real pattern, the 10 shot group went to the left for shots 1-6 but then doubled back on itself for 7-10.

Additionally just to check when I built my new rifle with a proof prefit CF barrel I fired some of the left over reloads that I had made for the Browning, this was my result with several different charge weights. The two in the top middle were my first two shots at 100 after zeroing at 50, all the rest are 3 shot groups with mostly different charge weights and a couple dulicates.

As you can see the same reloads in a different rifle are night and day different so clearly it isn’t an issue with my handloading either or the scope that I took directly off the rail of the Browning and put on my M7.

As you said I thought the concussion reduction with the suppressor could be the contributing factor but I shot my rifle without it and it groups the same as it does suppressed. Unfortunately I ran out of ammo before I could test the suppressor again but was able to test with the protector on, the suppressor on and the ff waiting 5 to 10 minutes between groups.

The normal one went horizontal

The suppressor shot a tight group

Then the bare muzzle without protector shot the same ammo stringing vertically and a similar bullet with the same charge horizontally.


At this point I’m not really sure what to do with it, it’s my Dad’s rifle but I’m the one who convinced him to go with the LR model in 6.5 PRC because of how accurate it was supposed to be. Now I feel bad because he spent $1800 on a gun that shoots way worse than his $300 7600 and deer season is in less than a month. If it was mine I’d just leave it suppressed but he doesn’t want to deal with the extra length or weight of the suppressor when he spends a lot of his time walking through thick brush.

 

[CMP70306]

Just a thought what if you installed a muzzle brake on it to see if you get lucky that it corrects the barrel harmonics could be a cheap fix...... other thought is to cut a little off the barrel and have it re crowned and or threaded.

The groups from suppressor off to suppressor on are dramatically different. Have you been able to shoot more than one nice group with the suppressor on? If so that would say the scope/rings/base and bedding are likely okay.

Since you were able to attach a suppressor could you try different muzzle brakes or even hang a weight on there?

I have not shot it with the radial break that it came with and we don’t use muzzle breaks so I don’t have any others to try. Next time I’ma the range I’ll test it with the brake and the suppressor to see if that fixes it.

Out of curiosity would the suppressor fix an issue with the crown?

 

[Milf Dots]

Because you've thoroughly troubleshot the issue, if it were me, I'd find an expert riflesmith to handle it. Because the can changed the harmonics and made it shoot better, a simple cut and recrown by an expert may do wonders. Perhaps it has a bit too much muzzle run out that, when combined with its barrel length and barrel contour- make it shoot poorly.

ETA: Shoot it with the factory brake before spending any money.

 

[ShtrRdy]

Out of curiosity would the suppressor fix an issue with the crown?

I don't see how a suppressor would fix a problem with the crown. But I'm still learning.

Next time out try the "card" trick that was suggested.

 

[Ranger Bob]

I've been away from precision rifle shooting for a while so I don't know if these still exist but, there was a company that made harmonic dampers. They were basically rubber donuts that you shoved onto your barrel and they interrupted the harmonics. I never used them and I never got the impression they were a fix but they seemed good at identifying/isolating a harmonics problem.

Bob

 

[Kadams1563]

What stock is it in? Have you tried taking it completely apart and then putting it back together ensuring that your torquing everything to spec.

I don’t believe this is a suppressor issue.

 

[myronman3]

i am curious as to why your dollar stops. the xbolts are supposed to be free floated. Both of mine are.

The only issue i have seen with them was an elderly couple out last fall sighting in their matching 7mm08s. Both rifles had incorrect headspace. Saw them the next day at the range, they had went back to the store, and showed up with two more identical rifles that the store exchanged. BOTH of those rifles had incorrect headspace as well. I told the guy to take the rifles back, AND to take his headspace gauge with him to check it before he accepted another gun from them as a replacement.

Im not slamming on the xbolts....just stating what i saw. I still like them enough to have two of them.

 

[CMP70306]

What stock is it in? Have you tried taking it completely apart and then putting it back together ensuring that your torquing everything to spec.

I don’t believe this is a suppressor issue.

It is the factory carbon fiber stock, I did have it apart and torqued it back down thinking that might be the issue though It does not appear to have changed anything. That being said I might swap it with the McMillan off one of the other X-Bolts to see if that fixes the issue.

 

[ALShooter]

I've been away from precision rifle shooting for a while so I don't know if these still exist but, there was a company that made harmonic dampers. They were basically rubber donuts that you shoved onto your barrel and they interrupted the harmonics. I never used them and I never got the impression they were a fix but they seemed good at identifying/isolating a harmonics problem.

Bob

limbsaver

 

[chevy_man]

Every rifle but 1 that I've screwed a can on (direct thread, adapters only seem to cause problems) has gotten more accurate. It dramatically alters harmonics and changes the way it whips.


I would guess the barrel has some internal stressors which are causing it to walk around as it heats. Try shooting all shots 10 minutes apart. Don't let it even get remotely warm and see what it does.


The thing about their accuracy guarantee is that 55 yards is nothing to have any issues show up.
My BIL bought an a-bolt that is the same way. However it shoots 129 interlocks just fantastic. Only bullet he's found that will shoot sub-moa, everything else he tried was 2 moa.

 

[Precision Underground]

Isn’t this bad target showing the suppressed group you zoomed in on? (Top right target)

The suppressed group looks exactly like the top right group on the bad target. You can see the very edge of the hole that is out of frame after the zoom.

Either way what you are describing would suggests some kind of harmonic issue. I’m guessing you have a thread protector on when the can isn’t on. Did you try without that? Have you checked/retorqued action screws?

 

[feelinducky]

Cheap possible fix would be to try the Limbsaver Sharpshooter X ring barrel dampener. Amazon $9.99

 

[Kadams1563]

Isn’t this bad target showing the suppressed group you zoomed in on? (Top right target)

View attachment 7177177


The suppressed group looks exactly like the top right group on the bad target. You can see the very edge of the hole that is out of frame after the zoom.



View attachment 7177179

Either way what you are describing would suggests some kind of harmonic issue. I’m guessing you have a thread protector on when the can isn’t on. Did you try without that? Have you checked/retorqued action screws?

Lol damn man your good! BUSTED

 

[CMP70306]

Isn’t this bad target showing the suppressed group you zoomed in on? (Top right target)

View attachment 7177177


The suppressed group looks exactly like the top right group on the bad target. You can see the very edge of the hole that is out of frame after the zoom.



View attachment 7177179

Either way what you are describing would suggests some kind of harmonic issue. I’m guessing you have a thread protector on when the can isn’t on. Did you try without that? Have you checked/retorqued action screws?

You are correct that was the target I shot yesterday after getting the rifle back from Browning. The groups on that target were thread protector on in the top left, suppressed in the top right and thread protector off in the bottom right. You can clearly see how much of a difference the suppressor makes.

The hole to the left of the suppressed group is actually my first shot on paper after remounting the scope, I was aiming at the center bullseye and then used bottom left to work on getting the rifle mostly dialed back in. As you can see my first group was pretty good at roughly 3/4 MOA. I them waited 10 minutes and shot my other rifle to let it cool before shooting the main group.

The main group in the center was 6 rounds of a load that shoots 1/2 MOA in my PRC but clearly does not work in this rifle. Each group was shot over a period of a minute or two then the rifle was set aside to cool while I shot the other one with roughly 10 minutes between groups.

 

[Milf Dots]

When you did the dollar test, where did it stop, at the recoil lug?

 

[CMP70306]

When you did the dollar test, where did it stop, at the recoil lug?

About an inch before that.

 

[myronman3]

First thing i’d do is chase that down.

 

[408w]

My friend had an issue finding a load on this same model gun. He ended up after calling browning was a Barnes 130g bullet way off the lands. Went from like 2 inch groups to .5” groups. He tried many bullets and loads. I can get the load data if you want.

 

[candyx]

It looks a little better but some barrels are just destine to hold up tomatoes, so unscrew that tomato stake and bang it back in the ground.

 

[Milf Dots]

About an inch before that.

Hmm. I searched the 'net and found a couple of photos of X-Bolt action bedding where the bedding was just a bit forward of the recoil lug, but an inch seems too far. You may want to take a look at the bedding in front of the lug, and perhaps trim it back a bit.

 

[chevy_man]

My friend had an issue finding a load on this same model gun. He ended up after calling browning was a Barnes 130g bullet way off the lands. Went from like 2 inch groups to .5” groups. He tried many bullets and loads. I can get the load data if you want.

I've seen Berger's shoot at .120-130 off the lands. Haven't played with Barnes in years though.

 

[Milf Dots]

Any updates on this?

 

[CMP70306]

Yup, turns out the suppressed group was a fluke and a pretty good representation of how this rifle behaves, just when I think I get it shooting good the next trip it goes to shit again.

In the interest of testing I decided to see if the bedding was the issue, we have a spare laminate thumb hole stock off another X-Bolt that was swapped for a McMillan stock. That rifle had a bull contour vs the heavy sporter on the PRC and would put the 140gr American Gunner 6.5 Creedmoor ammo under 1/2 MOA. In the laminate stock the PRC shot a bit better than in the carbon fiber stock but was still pushing 1.5 MOA. The one to the right is the muzzle break while the low group is suppressed.

So I packed it back up and it is heading back to Browning today with a request for them to see if a 5 or 10 shot group still falls within their 0.75” at 50 yard spec.

On the plus side when it does get back fixed I should have a good load for it, 58.8gr of Superformance is putting a 119 to 125gr copper bullet around 3250 fps out of a 24” proof barrel with a suppressor. Should be devastating on PA whitetails but I’ll find out in 2.5 weeks when deer season opens.