I'm stumped...bolt won't close

[patriot07]

Defiance action with Bartlein barrel. 175-ish rounds on it. I bought it used (safe queen bought 10 years ago from customer maker and hardly used) and I have only put 15 rounds on it. Original buyer had 160 rounds on it.

All of a sudden the bolt won't close on factory 140 ELD-M ammo. If I really force it, it will barely go, but it takes an insane amount of force. When I extract the round, there are marks all over the bullet (see pic at end).

My handloads are all 140-ELD-M. I made one just for grins with the same results. It will chamber and extract new or fired brass no issue, so the binding is definitely at the bullet. Remainder of the action is smooth. It runs fine with nothing in it obviously, and it ran factory ammo last week no issue. But this week not so much. Can't see anything obvious with the bore camera.

This is a new box of ammo...maybe these bullets are slightly larger? It will cycle factory federal 6.5CM ammo and leave only a light mark...

Is the solution to have a gunsmith just run the reamer in on a clean-up pass?

Pic of new bullet (right) and chambered/extracted bullet (left).

 

[oldrifleman]

Defiance action with Bartlein barrel. 175-ish rounds on it. I bought it used (safe queen bought 10 years ago from customer maker and hardly used) and I have only put 15 rounds on it. Original buyer had 160 rounds on it.

All of a sudden the bolt won't close on factory 140 ELD-M ammo. If I really force it, it will barely go, but it takes an insane amount of force. When I extract the round, there are marks all over the bullet (see pic at end).

My handloads are all 140-ELD-M. I made one just for grins with the same results. It will chamber and extract new or fired brass no issue, so the binding is definitely at the bullet. Remainder of the action is smooth. It runs fine with nothing in it obviously, and it ran factory ammo last week no issue. But this week not so much. Can't see anything obvious with the bore camera.

This is a new box of ammo...maybe these bullets are slightly larger? It will cycle factory federal 6.5CM ammo and leave only a light mark...

Is the solution to have a gunsmith just run the reamer in on a clean-up pass?

Pic of new bullet (right) and chambered/extracted bullet (left).

View attachment 8744516

Have you measured the new round vs the extracted round? That is some serious engraving on the extracted round.

 

[ShtrRdy]

The Creedmoor chamber freebore diameter is spec'd at 0.2435". So, if the new bullet is 0.2435" or greater you could have interference fit.

Another possibility is the carbon ring buildup is aggravating the small-ish freebore diameter.

 

[FuhQ]

Possible carbon ring at the leade, if it didn't do that before. That would explain the marks being only on the bullet, and not the cases, and why it won't close on factory ammo anymore.

 

[JerkyFreak]

Carbon generally doesnt do that to copper. If it was a carbon ring I would expect some black particles to break off with that ammount of force.

Can you place some fotos taken with the borescope showing the neck-to-freebore transition and the lead?

 

[slodsm]

Do you have a modified case that you can drop a bullet in and just see where the lands engage at?

It’s nuts that it literally started from nowhere after shooting fine recently but I’d be interested to see where it touches the lands and what the CBTO measurement it compared to the factory loaded rounds.

 

[Kickin45]

Do you have go no-go gauge?

 

[Terry Cross]

Pull the bullet on a known "hard to close round" and try to chamber that empty case w/o a bullet. That would isolate the possibility of over size cases, which are not uncommon.

You could have more than one thing going on.....

Usually, jamming a bullet into a tight leader or throat that hard would result in a bullet staying stuck in the bore and powder all in the action when extracting the case. Rub marks on the bullet may only be a secondary issue. Maybe, maybe not...

Isolate and remove one thing at a time from the equation.

 

[patriot07]

Do you have a modified case that you can drop a bullet in and just see where the lands engage at?

It’s nuts that it literally started from nowhere after shooting fine recently but I’d be interested to see where it touches the lands and what the CBTO measurement it compared to the factory loaded rounds.

Yes I used my hornady oal length gauge and it was crazy short. Like 145 thousandths short of the factory round

 

[patriot07]

The Creedmoor chamber freebore diameter is spec'd at 0.2435". So, if the new bullet is 0.2435" or greater you could have interference fit.

Another possibility is the carbon ring buildup is aggravating the small-ish freebore diameter.

Do you mean .2635?

That may be it - the new bullets (before chambering) are around .2638-.2639 in the section where the marks are showing up

 

[patriot07]

Do you have go no-go gauge?

I do not. Tried to chamber both fired and unfired cases and no issues with either, although none of them chamber as easily as they do in my Tikka

 

[patriot07]

Carbon generally doesnt do that to copper. If it was a carbon ring I would expect some black particles to break off with that ammount of force.

Can you place some fotos taken with the borescope showing the neck-to-freebore transition and the lead?

Shoulder

End of case

freebore to lands

 

[patriot07]

Looking at the end of case picture, that seems like where the copper is catching. You can see flakes of it on that edge.

This was a new box of ammo last night. Maybe the bullets were just slightly larger in this box enough to catch? I looked up 6.5CM spec and the .2645 is correct diameter for the space past that lip, and if the bullets are .2638-.2639, they shouldn't be scraping around the entire diameter like that....wonder if it was a slightly worn reamer and we are paying the price a decade later?

ETA - I cleaned and cleaned and cleaned it and it appears maybe there was a light carbon ring. I took a few more new rounds and now the marks are still there, but lighter. The force to close is still there, but lighter. In the bore scope, the black by the end of the case is significantly lighter. Maybe @Terry Cross was correct that it's a couple things - a slightly tight freebore combined with a light carbon ring...

Of course I don't recall other rifles making any mark at all when I chamber a round so maybe there is still something else going on?

 

[DIBBS]

Is the profile the same on the two bullets, or is there more taper on the one that chambers easily without the engraving marks? Perhaps it's an optical illusion in the photo, but the bullets look slightly different. to my old eyes. What is the diameter of the bullet just ahead of the case mouths on each bullet in the photo where the problem is occurring?

 

[Schütze]

Hornady’s ammo is like a box of chocolates, you never know what you're gonna get….

 

[ShtrRdy]

Do you mean .2635?

That may be it - the new bullets (before chambering) are around .2638-.2639 in the section where the marks are showing up

Oh, yeah, brain fart. . For 6.5mm it would actually be 0.2645". Basically 0.0005" more than the ideal diameter on 0.264"

Thanks for pointing that out.

 

[ShtrRdy]

Hornady’s ammo is like a box of chocolates, you never know what you're gonna get….

Ain't that the truth! I use Hornady match ammo as well as my hand crafted loads and Hornady never fails to have a surprise .

 

[rustyinbend]

The Creedmoor chamber freebore diameter is spec'd at 0.2435". So, if the new bullet is 0.2435" or greater you could have interference fit.

Another possibility is the carbon ring buildup is aggravating the small-ish freebore diameter.

That's my vote ... a nasty carbon ring. Maybe there were a few more than 160 rounds through when you bought it.

 

[357Max]

Looking at the end of case picture, that seems like where the copper is catching. You can see flakes of it on that edge.

This was a new box of ammo last night. Maybe the bullets were just slightly larger in this box enough to catch? I looked up 6.5CM spec and the .2645 is correct diameter for the space past that lip, and if the bullets are .2638-.2639, they shouldn't be scraping around the entire diameter like that....wonder if it was a slightly worn reamer and we are paying the price a decade later?

ETA - I cleaned and cleaned and cleaned it and it appears maybe there was a light carbon ring. I took a few more new rounds and now the marks are still there, but lighter. The force to close is still there, but lighter. In the bore scope, the black by the end of the case is significantly lighter. Maybe @Terry Cross was correct that it's a couple things - a slightly tight freebore combined with a light carbon ring...

Of course I don't recall other rifles making any mark at all when I chamber a round so maybe there is still something else going on?

I've never had this particular issue. Problem is you have no idea if a custom tight reamer was used ect. In you pictures and from your description it seems the problem is the throat/freebore. I see no marks from the lands & no marks on the shoulder datum of the case.
I'd still pick up a go gauge & check but that doesn't look like the problem.

I have had a short reamed 6.5C that wouldn't close on go gauge. It was short enough that factory 130 prime ammo wouldn't close (AR barrel was Larue). My solution for that is the same I'd due in your shoes.

Clymer finish reamer off the shelf at Brownells with a few bushings cost about $200. I just turned by hand with a tap wrench & some tap magic cutting oil. Worked like a champ, gun hammers.
Just stop when you hit the shoulder and should be good to go.
If you don't have a barrel vise then pick up one of the PTG extensions from Midway & you wouldn't even need to remove the barrel.

 

[Emerson0311]

Just started happening with a new box of ammo? Did I read that correctly? Hornady? Compare bullet measurements, ogive location, and loaded round measurements. The rifle didn’t magically contract suddenly.

 

[patriot07]

Just started happening with a new box of ammo? Did I read that correctly? Hornady? Compare bullet measurements, ogive location, and loaded round measurements. The rifle didn’t magically contract suddenly.

Bullet measurements are identical between this new box of loaded ammo and my box of individual bullets for reloading.

I think it just so happened to occur when I went to a new box of ammo. Minor carbon ring combined with slightly tight freebore.

 

[patriot07]

I've never had this particular issue. Problem is you have no idea if a custom tight reamer was used ect. In you pictures and from your description it seems the problem is the throat/freebore. I see no marks from the lands & no marks on the shoulder datum of the case.
I'd still pick up a go gauge & check but that doesn't look like the problem.

I have had a short reamed 6.5C that wouldn't close on go gauge. It was short enough that factory 130 prime ammo wouldn't close (AR barrel was Larue). My solution for that is the same I'd due in your shoes.

Clymer finish reamer off the shelf at Brownells with a few bushings cost about $200. I just turned by hand with a tap wrench & some tap magic cutting oil. Worked like a champ, gun hammers.
Just stop when you hit the shoulder and should be good to go.
If you don't have a barrel vise then pick up one of the PTG extensions from Midway & you wouldn't even need to remove the barrel.

View attachment 8744714


View attachment 8744709

I have a barrel vise but no action wrench for the Defiant and I have no idea how much it was tightened and would rather not mar up the gun-kote finish. Do you have any interest renting out the tools?

 

[patriot07]

That's my vote ... a nasty carbon ring. Maybe there were a few more than 160 rounds through when you bought it.

Perhaps, but he is a guy with a good reputation on the local forum and like 20k posts with nothing but positive reviews, and he had a log book showing the rounds. So I don't suspect that to be the case, but obviously I have no way of knowing for certain.

I do know he was reloading for it and can't remember the powder, so it's possible he was using a powder more prone to carbon deposits? I don't know specifically what causes the carbon ring honestly, although I did have a carbon ring show up on my Tikka around the 500 round mark if I recall. No bullet interference or bolt issues - just crap accuracy

 

[patriot07]

Ain't that the truth! I use Hornady match ammo as well as my hand crafted loads and Hornady never fails to have a surprise .

This would be a first for me - I trust Hornady's loads to be very high quality and it's never been an issue before.

 

[patriot07]

Is the profile the same on the two bullets, or is there more taper on the one that chambers easily without the engraving marks? Perhaps it's an optical illusion in the photo, but the bullets look slightly different. to my old eyes. What is the diameter of the bullet just ahead of the case mouths on each bullet in the photo where the problem is occurring?

Same profile

 

[Schütze]

If one of the two chambers fine and the other does not, it isn’t possible for both having the exact same measurements.

 

[Mulepackhunter]

The new bullets are just slightly larger Im guessing. The reamer was probably tight in the throat to start with. I have sent back a few reamers with undersized throats. A good smith can tell you the actual diameter for free and fix it for pretty cheap. Guage pin on a magnet works, I use an aluminum rod with bore and set screw to hold pins to check that.

 

[patriot07]

If one of the two chambers fine and the other does not, it isn’t possible for both having the exact same measurements.

At this point, nothing is chambering fine except completely different ammo which yes, is a different profile.

Sorry, I realize now my wording was unclear.

 

[wchartz]

I am going to take a shot in the dark on this one. If you are shooting with a suppressor, check to see if there are any carbon deposits on the bolt face. I had a similar incident a couple of years ago. If you have loose carbon in the suppressor and set the gun down on the butt the loose carbon lands on the bolt face and effectively decreases the headspace. A small speck of hard carbon prevented me from closing the bolt no matter how hard I tried. This has happened to me at least three times. I full lenght size my ammo with about .002" shoulder setback. I now clean my suppressor regularly.

 

[JAS-SH]

I had exactly the same marks on a new 6mm barrel - 6mm GT. Turns out the barrel was reamed not with a SAMMI 6GT spec reamer but more like an older .243 reamer. My guess is that they didn't have the newer SAMMI reamer for the 6 GT. Get a new reamer (SAMMI spec) and have it redone on the same barrel. Make sure your gunsmith is aware of the issue.

Image below:

 

[patriot07]

I had exactly the same marks on a new 6mm barrel - 6mm GT. Turns out the barrel was reamed not with a SAMMI 6GT spec reamer but more like an older .243 reamer. My guess is that they didn't have the newer SAMMI reamer for the 6 GT. Get a new reamer (SAMMI spec) and have it redone on the same barrel. Make sure your gunsmith is aware of the issue.

Image below:

View attachment 8745234

Looks very similar to the issue I'm having. Thanks for the info

 

[JerkyFreak]

I don't know if you have a bronze brush. If you do, see if you can brush out the transition (end of case area). If not, you are going to need a lot of Boretech Cu2+ applications to remove that ammount of copper.

Doesn’t look like much of a carbon ring, if any, but you can see a lot of copper at the edge that will just get worse the more you try to chamber a cartridge.

If you can get ahold of the reamer drawing from the previous owner, I think that you will find that the freebore is very close to bullet diameter. I suspect that any secant ogive bullet with a long bearing surface, loaded long, will be scratched by that transition.

 

[ShtrRdy]

I don't know if you have a bronze brush. If you do, see if you can brush out the transition (end of case area). If not, you are going to need a lot of Boretech Cu2+ applications to remove that ammount of copper.

Doesn’t look like much of a carbon ring, if any, but you can see a lot of copper at the edge that will just get worse the more you try to chamber a cartridge.

If you can get ahold of the reamer drawing from the previous owner, I think that you will find that the freebore is very close to bullet diameter. I suspect that any secant ogive bullet with a long bearing surface, loaded long, will be scratched by that transition.

When I saw that my thought was the copper from the bullet jacket is getting scraped off by the carbon.