My Day At Belmont

Improving and repairing firearms. Rifle bedding, barrel work, stock replacement and other ways to improve your firearms.

My Day At Belmont

Post by Wm.Traynor » 09 Nov 2019, 8:37 pm

I had high hopes for two rifles today after having done quite a bit of work on them.
Firstly, the Mossberg 464.
This thing has had terrible vertical dispersion apart from the first few shots. I put this down to the bedding of the fore end and the way the mag tube would slide forward, waaay out past the muzzle, during firing. Finally, I got the chance to try in2anity's method, Many different approaches had been made in the past but this worked on his rifle. Then I tackled the mag-tube for the second time, during the week, in the location of the front barrel band (FBB), where there is a lot of vertical free play, which I assumed was allowing forward movement. There are grooves in the tube and the barrel to accommodate the FBB screw. Trouble is, thought I, that the screw was not a tight-enough fit in those grooves, to "catch" the tube in its forward travel. To make better contact, between screw and tube, some shims were inserted between the bottom of the band and the underside of the tube. The first few shots at 50 yards grouped under 1.5", heaps better than the usual 6"" of vertical spread. The previous week a thinner shim performed dismally and the tube shifted. This time, I thought I was home free and when the barrel cooled, a further 3 shots were fired. Hmmm. A 2" group. Later in the afternoon, another attempt was made and the tube shifted.
To be clear, I don't know what I'm doing but there was no slop/freeplay at the FBB, this pm. There was last week and the tube moved almost straight away. Not today though. However, I think you will agree that there are no more options where that kind of shimming is concerned.
This brings me to the question, "What is supposed to stop the tube sliding forward in a properly assembled rifle?" I am not out of answers yet and had the solution quite a while back but while not revoltingly ugly, it did stick out like a sore thumb, which now that I recall, it closely resembled. That is why shims were tried; it looked a lot more standard.
But back to the question: "Is the tube held in place by the clamping force of the FBB?" That is, should the tube be held in place by the tightness of the fit, between it and the FBB? Surely that would involve such tightness, (when the screw is torqued), that assembly/ disassembly would be a nightmare?
On the other hand, could shims be placed around the tube during assembly, so that tightening the screw in the FBB, exerted enough grip to prevent tube movement? And now that I've thought about it, that's a suck it and see thing, isn't it :)

I was going to talk about my CZ455 but I have to wash up and have a shower. So that might do me.
Thank you for your patience and above all, don't buy a Mossberg 464.
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