Anyone else had this problem? I have a Mossberg Patriot in .308, the walnut stocked version. I love it. It's accurate as all get out with my handloads and a joy to shoot. I do have one thing that gives me pause. All of the brass fired out of that rifle have a carbon fouled neck, and I mean all of them. To me, that indicates an oversized chamber that doesn't allow the neck to seal properly and is permitting gasses to flow back. It doesn't reach the shoulders, just the neck. Thoughts?
Mossberg Patriot over-bored chamber?
- Thread starter LawrenceN
- Start date
That's the thing. It's not just one loading. Every round, irrespective of brass, bullet weight or style, or powder, exhibits the fouling. I usually load maybe a grain below max according to my Lyman manual so nothing too hot but nothing too anemic either. I plan to load some 150 gr. and 165 gr. with max loads (different powders and brass) when the ranges reopen and spend a day trying out different recipes.
Have you fired any factory ammunition in this rifle? If so, does it also foul the necks?
I suspect that your loads are still not up to "working" pressure. I always give the
necks on my fired brass a twist with very fine steel wool to remove even light fouling
on the neck. Dave.
I suspect that your loads are still not up to "working" pressure. I always give the
necks on my fired brass a twist with very fine steel wool to remove even light fouling
on the neck. Dave.
Like you, I give the necks a little polish with steel wool if there's any sign of fouling. I have a .308 Ruger M77 HBar, and .308 Mod. 100 Winchester and I don't get the dirty necks off those with the same loads. As to being not "up to working pressure", do you really think 1 gr. below recommended max would be insufficient "working pressure"? I've be reloading for a long time both for myself and for friends being as how I'm very meticulous and precise. I love the Mossberg, but I have to ask myself why the fouling and only out of the one rifle.
fade2black
CGN Regular
- Location
- Central Ontario
Have you tried a mild crimp to see if it makes a difference?
No, I haven't, but I can't see where it would make a difference. One would think that the pressure of firing would seal the neck against the walls of the chamber, crimped or not.
Take a cast of your chamber, then you'll know the dimensions for sure. - dan
fade2black
CGN Regular
- Location
- Central Ontario
Excessive crimping and neck tension can increase chamber pressures. A crimp might give it the time to build pressure and seal before the gasses escape past the case mouth back towards the neck. I had a similar issue with a Tikka T3 and a light crimp took care if the issue.
If the pressures were enough to seal it, not matter how over bore it was it would still seal. The case would fireform to the overbore chamber or neck area.
Well, all I am suggesting is that, for one reason or other, your Mossberg is not building as much pressure with a
given load as your other rifles. I started reloading in 1964, and I have seen identical loads give 200 FPS different
muzzle velocity in two different rifles. The only possible reason for this discrepancy would be different pressures.
[Pressure differences can come from bore/groove differences, chamber dimensions, interior bore finish, etc.]
If it were me, I would move up with your load in that Mossberg in ½ grain increments, and see if your smoky necks
diminish or even go away. A chronograph might also give an indication of pressures. Dave.
I now remember it was EagleEye giving me the same advice. It worked.
As mentioned several times your loads in that particular rifle are not hot enough to fully expand the necks before the carbon fouling eases back along the neck. If your cases weren't expanding to full chamber diameter at the neck you would have case shoulders blown in.
- Location
- Edmonton Area Ab, Candle Lake Sk
I'd wipe the necks off, if the look bothers you. I wouldn't change a thing on an accurate load.
