What would you do with a supposed “1/2 MOA gun” that lost its mojo overnight?

[Iamero]

Hey guys, I bought a 260 remington off here a couple weeks ago and was told it was a solid sub 1/2 MOA shooter with FGMM ammo (which 40 rounds came with the rifle). It was a rebarrel with a bartlein (90 rounds on the barrel) sitting in a hogue stock.

Well I got it here and took it out to the range and it wouldnt stay consistently less than 1-1.25”. I thought maybe my scope or rings were loose so I grabbed a scope off another rifle that I knew had no problem shooting 3/4”. Same results. Thinking the flexible hogue stock was the issue I dumped it in a Manners that was free floating. Same results. I bought a box of hornady match ammo for kicks, worse results.

So at this point what am I missing? The only thing on this rifle that is different from the last owner is the brake on the rifle but that shouldn’t make any difference.

Should I bother hand loading to resolve the issue or just have my gunsmith rechamber it to 6.5 creed? I wanted to pick your brain before dropping the coin because I really didn’t feel like handloading for another cartridge when I already have everything for 6.5 creed.

 

[Gunfighter14e2]

Shoot it w/o the break, as a break made wrong or the tolerance stacking on the barrel can kill group size.

 

[lash]

Shoot it w/o the break, as a break made wrong or the tolerance stacking on the barrel can kill group size.

At least try this. Barrel harmonics absolutely matter.

 

[JMcBurn]

What break was on it before and what is on it now?

 

[savage_shooter]

Borescope it.

Also, are you capable of 1/2" groups? If the shooter cant do it, the rifle cant either.

 

[Rootshot]

Definitely try more brands of match grade ammo. Handloads can also make all the difference in the world. I had a friend with a Tikka T3 that wasn't grouping with factory 308. I threw him a couple of my handloads and it was a single ragged hole.

 

[Iamero]

I’ll pull the brake off and see what happens. That wouldn’t definitely be the first time I’ve seen a brake do that much but at this point I’m open to suggestions. It was a suppressor adapater brake before and a self timer Tuebor now.

Yea, groups aren’t an issue for me.

 

[theLBC]

did the prior owner claim 1/2" MOA with a clean barrel? some rifles will tighten up after a few dozen rounds.

 

[anotherwannabe]

Did you ask for proof of the supposed 1/2 inch groups all day with factory ammo?
Lots of guys say it, very few can demonstrate a single target with 5 groups in the .4's

I think the most likely suspect is that the gun simply doesn't shoot 1/2 inch groups with factory ammo.... I've -never- personally witnessed anyone shoot 1/2 groups repeatably with factory ammo.

 

[Ledzep]

Clean, remove muzzle devices, rule out optics, mounts, rings, etc... Rule out stock fit (looks like you have)...

If none of that shows improvement, inspect the chamber and bore condition-- recrown it if there's any evidence of being fuckered. From there... shoot closer distances or rechamber/rebarrel.

It's surprisingly easy to waste a few hundred bucks on ammo/components on a rifle that won't shoot when you could've just bought a $200-350 blank and had it spun up. Not necessarily money ahead, but time and frustration for sure.

 

[Iamero]

I’ll pick up another box or two of different amps and change/remove the brake and see what happens and report back tomorrow.

 

[Gunfighter14e2]

I think the most likely suspect is that the gun simply doesn't shoot 1/2 inch groups with factory ammo.... I've -never- personally witnessed anyone shoot 1/2 groups repeatably with factory ammo.

I had one of three 20" R 700 AAC-SD's (all bought at the same time) that will/would do less than 1/2moa with FGMM

 

[Clearlight]

Carbon clean it then check for copper with a good brand of copper cleaner. If it’s had 90 rounds on a
new barrel without any cleaning, it may be fouled badly. Some barrels run fine and don’t pick up
copper from the get go, others foul like crazy and need a ‘break in ‘ cleaning routine.

The last 300NM Bartlein barrel I had screwed on was excellent from the first few rounds. The current
Broughton barrel was a bitch for copper, and needed 1 shot and clean for quite a few rounds until
it stopped picking up copper like it was getting paid to do it.... As mentioned above check that the
brake is aligned correctly.

 

[Gunfighter14e2]

The last 300NM Bartlein barrel I had screwed on was excellent from the first few rounds. The currentBroughton barrel was a bitch for copper, and needed 1 shot and clean for quite a few rounds until
it stopped picking up copper like it was getting paid to do it.... As mentioned above check that the
brake is aligned correctly.

I'd put more money on the throat having a issue than the barrel. Never allow a house reamer to cut you a chamber on a custom barrel. Buy the reamer yourself an have the smith cut the chamber, an get it back. I learned this lesson long ago, an have never had a custom barrel foul there after.

 

[Clearlight]

^^Yup I should have elaborated. A shitty overused reamer will leave tool marks which will badly
foul, the actual unturned lands and grooves are probably fine. The current Broughton I have
picked up copper down the full length of the barrel : did notice it was very shiny inside straight
out of the box like it was lapped too much.

 

[TACC]

In fir the knowledge shared here, interested in the fix

 

[Rootshot]

^^Yup I should have elaborated. A shitty overused reamer will leave tool marks which will badly
foul, the actual unturned lands and grooves are probably fine. The current Broughton I have
picked up copper down the full length of the barrel : did notice it was very shiny inside straight
out of the box like it was lapped too much.

I can see a shitty reamer messing up the freebore & throat and could see how a rough surface could support carbon fouling but I don't understand how this could lead to copper fouling in the barrel...

FWIW - I did have one rifle from a well known custom gunsmith where the ejected brass showed two rings behind the shoulder. The reamer was fuxored and scratched the inside of the chamber which the brass flowed into. Luckily this didn't impact accuracy at all.

 

[Ledzep]

60,000 PSI and something like 3000 degrees if memory serves. The rough surface in the throat engraving copper basically turns it into a vapor and that's what coats down the bore.

Also, @Rootshot your rings were most likely caused by chips that either rolled between the reamer and the barrel and/or got stuck to the reamer, not the reamer itself.

 

[JMcBurn]

Did you ask for proof of the supposed 1/2 inch groups all day with factory ammo?
Lots of guys say it, very few can demonstrate a single target with 5 groups in the .4's

I think the most likely suspect is that the gun simply doesn't shoot 1/2 inch groups with factory ammo.... I've -never- personally witnessed anyone shoot 1/2 groups repeatably with factory ammo.

I myself am not much of a group shooter but I will typically shoot 5rds for zero confirmation and the last 3 times ive checked zero on my new 6.5 Creedmoor barrel shooting the factory berger ammo it has shot in the .5moa range every time.

That being said all of those are from the same lot of ammo, might change if i change lots.

 

[savage_shooter]

That being said all of those are from the same lot of ammo, might change if i change lots.

I'll fully agree that different lots of powder, bullets, etc can have an impact on accuracy. However, with the OP going from a supposed .5" gun to over double that I can't see how a different lot of the same ammo is going to be impacted that much.

Not knowing anything about the OP's rifle, I have questions on if this was in fact a Bartlein barrel. Who chambered and installed it? Did the seller have any receipts or documentation for it?

He's already swapped scopes/rings so that should be ruled out. He's tried different ammo that in a premium barrel should certainly perform better than it did. Was the scope base tightened down properly? How is the headspace? Did he take a look at the throat as has been mentioned a couple times?

There aren't that many potential root causes left...

 

[Iamero]

Yea, trying to slowly chip away at each of these one at a time.

Scopes have been swapped and I checked that rings and base were properly torqued (as well as the action screws while I was at it). I swapped brakes out this morning to an APA Lil Bastard and it seemed like it might have had slight impact on the groups, but overall nothing too impressive. I thought I was getting somewhere when it stacked those 3 shots left of center, but unfortunately those were shots 1, 3, and 5...not 1, 2, 3. The first two groups appeared to consist of some horizontal stringing, but then the 3rd group just completely opened up.

I'm going to load some scenars and ELDs to mag length and give those a try. If that performs similar results to what it has been doing, I'm going to drop it off at the smith for a bore scope and most likely a rechamber into 6.5 creed with a new reamer.

PS: POI shift on the second group was intentional dialing so the impacts wouldn't cover my point of aim.

 

[jdodd]

Shoot it w/o the break, as a break made wrong or the tolerance stacking on the barrel can kill group size.

+1

I threw a flash hider on my 6.5 grendel hunting rifle and the groups grew by about an inch. As soon as I took it off and put the thread protector on it went back to normal. Sometimes kit just doesn't play well together.

If shooting it without anything on the barrel and it still wont group I would think you got screwed...

 

[jdodd]

Try it without ANYTHING on the barrel for a group of two and observe the changes.

I threw a flash hider on my 6.5 grendel hunting rifle and the groups grew by about an inch. As soon as I took it off and put the thread protector on it went back to normal. Sometimes kit just doesn't play well together.

If shooting it without anything on the barrel and it still wont group I would think you got screwed...

 

[Gunfighter14e2]

If shooting it without anything on the barrel and it still wont group I would think you got screwed...

unless he really cranked on the break to get it timed, I've seen that a time or two as well.

 

[Iamero]

Just has the self timer brake on there just it's just beyond handtight with a wrench so I wouldn't think that is it. I'm going to test it a bit more later today and I'll shoot a few groups without a brake on there and see what that does.

 

[6brshooter]

I see definite stringing of groups, I'd look at bedding or action stress. I always bed aics and manners gen1 mini chassis at the tang. Both do not support tang at rear screw or behind, anything over 10"/lb on rear screw and it starts bending the action. Some action/barrels dont mind it and others shoot like this.

 

[keystoneshooter]

I was told by well a well respected smith from the hide if it won’t shoot 139 scenars 20 thou off the lands send it back. But not until you try that bullet!

Mine was a 6.5 creedmoor but was talking 260/creed debate and said he felt the same either way

 

[Iamero]

I really wanted factory ammo to shoot since I bought the rest of the ammo that SWFA had on their sale, haha. Seems that’s a no go so I’ll have to see if my buddy’s rifle will shoot them.

I loaded 136 scenars and 140 ELDs to mag length and let them rip. To my relief they finally pinched together.

 

[savage_shooter]

That's definitely better than before, but still not the accuracy you expected.

 

[Iamero]

Yea, I’ll toy around with powder charge and seat depth. Bummed it won’t shoot factory ammo, but at least the entire barrel isn’t a lemon.

 

[kingston]

Have you checked the scope rail for flatness ensuring that it’s straight and not twisted. If the scope rail is twisted or not straight it, it will stress any scope mounted to it. Often on 700’s you’ll see a rail dip down toward the front, if not bedded to the top of the action.