Bergara pressure issues(?) with factory ammo

[H80Hunter]

I bought a Bergara B-14 Hunter, 7mm Rem Mag and have 32 rounds through it. I’ve had about 4-5 of those rounds result in a VERY tough to open bolt to eject the empty case.

I cleaned it before shooting, then again after 20 rounds. Have had it happen both in the first 20 and the second 12 rounds. I’ve ONLY tried Barnes 139gr LRX factory ammo. It shoots well. But on the problem rounds, I’m not talking about a tough to lift bolt, I’m talking it lifts and then won’t open when pulled back. After some fiddling I can get it to go. The empty looks totally fine otherwise.

The one other thing that maybe is helpful: if I save the problem rounds, they look the same as the ones that eject fine. I can remove the bolt and drop them into the chamber just fine, but if I put the bolt back in, the problem rounds are tough to close and tough to eject all over again, which I wouldn’t think was pressure. They seem to fall right into the chamber, so I wouldn’t think it’s overly tight.

I’m leaning toward trying different factory ammo but any other ideas?

 

[SDHNTR]

Let’s see pictures of the case heads. Do you have a caliper and comparator so that you can take measurements?

Take one of the problem pieces of brass, and color it all over with a sharpie. Chamber it again, and eject, take note of any rub marks.

 

[H80Hunter]

Somehow I’m not sure I have a caliper but I can grab one tomorrow.

 

[H80Hunter]

I’ll try to get measurements but here’s 2 “good” and 2 “bad” — what should I measure?

 

[SDHNTR]

Need to see square close ups of the case heads. Are there pressure marks?

To start, measure the diameter at web of the case just in front of the belt. Is there a difference between good and bad?

And again, take one of those bad ones, and completely color it with the sharpie. Chamber, close, bolt, and eject. Where is it rubbing?

 

[H80Hunter]

The sharpie trick painted a clear picture, I just don’t know what it means exactly. It left that rub all the way around. I did it twice to confirm.

 

[SDHNTR]

Yep, expansion at the web. Exactly what I thought. Now measure the rest of your rounds at that spot and see if some are bigger than others at that spot. If some are bigger than others, you’ll have your problem. Inconsistent brass sizing.

I hate to say it, but I shoot a lot of barnes ammo, and the quality control has been very inconsistent the last several years. It may be an issue with the ammo, and not the rifles chamber. Let’s hope. Try something else and see if you have the same issue.

 

[H80Hunter]

Will do, I’ll report back. Might be a few days or so but I’ll PM you if needed.

Thanks for your help.

 

[35WhelenAI]

Brass has a Barnes headstamp, anybody familiar with who supplies them with brass? I believe it is Remington.

 

[dieselchessy]

It’s interesting that of the two X cases one of them the primer looks well rounded like it was a soft load. The others look flattened a bit with one of the non-x and one of the X’s being the flattest.
None of them look bad. But primers aren’t always the best indicator.

 

[H80Hunter]

Good catch. I could be wrong but I think one of the primers looks weird because I tried working the bolt and eventually pulled the trigger again so that one the primer has been struck twice. Could be from that.

 

[SDHNTR]

It’s interesting that of the two X cases one of them the primer looks well rounded like it was a soft load. The others look flattened a bit with one of the non-x and one of the X’s being the flattest.
None of them look bad. But primers aren’t always the best indicator.

I bet the base to shoulder (headspace) measurements are all inconsistent too. Which might explain the primer flattening vs not.

 

[35WhelenAI]

With a belted magnum, base to shoulder measurement is a non-issue. The cartridge headspaces on the belt, and the belt dimension is the same on all belted magnums.

There can be enough space to house a small family of mice at the front of the chamber. As long as the belt is proper, it would simply fire form the case. I have personally seen 300 Win Mag ammo fired in a 300 Weatherby chamber, the case comes out with a Weatherby radius shoulder and very little neck. The knucklehead that did it I had no clue he was shooting the incorrect ammo, thought all 300 magnums were the same.

 

[SDHNTR]

With a belted magnum, base to shoulder measurement is a non-issue. The cartridge headspaces on the belt, and the belt dimension is the same on all belted magnums.

There can be enough space to house a small family of mice at the front of the chamber. As long as the belt is proper, it would simply fire form the case. I have personally seen 300 Win Mag ammo fired in a 300 Weatherby chamber, the case comes out with a Weatherby radius shoulder and very little neck. The knucklehead that did it I had no clue he was shooting the incorrect ammo, thought all 300 magnums were the same.

I know that. And you’re right, I didn’t say that well. I own several belted mags, including a 7 RM. I only made that point to say that I bet the brass is overall inconsistent. Front to back and diameter, making for an excessively sloppy fit. Excess space can cause some issues with bolt thrust and the brass being driven back into the bolt face, which can flatten primers, as can too little space and too tight a chamber.

 

[XLR]

One other thing to check is make sure you do not have any solvents in the chamber. This can give excessive bolt thrust that feels like pressure. Would have to bet its those cases by looking at your picture but its one that is very easy to check!

 

[35WhelenAI]

OP,

Sharpie the rounds that worked well, what do they look like?

 

[H80Hunter]

Just did that, the ones that cycle smoothly are not marked from the chamber

 

[35WhelenAI]

Thanks, good info. When the cases all drop in without an issue, I gather the bolt closes with the same level of resistance on all four of them, it's simply when you bring them out?

 

[H80Hunter]

It closes a little bit harder on the bad ones but not really enough to raise eyebrows. But it takes some fiddling to get it to eject at all after firing. Even now just placing the empties in there is tough.

 

[H80Hunter]

Also I bought a box of federal trophy copper which all chamber and eject smoothly, though I won’t be able to fire them until tomorrow.