AR Barrel Bore Pin Guage

[tangolima]

The tolerance is in the plus dimension. . .

True. But OP has tight spots in his barrels. The point I was trying to make is groove diameter is bigger. A pin gauge can't get to it, either .223" or .224".

Anyway, I have slugged barrels with lead balls from shot shells or even lead sinker. Didn't think of pellet. A .22 pellet can be squashed fatter to fit.

-TL

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[markm]

My assumption is that the land and groove relationship is parallel even in the tight spot. In other words, the groove is the same depth, but there's a narrow spot in both land and groove at the tight spots. But I could be wrong.

[tangolima]

My assumption is that the land and groove relationship is parallel even in the tight spot. In other words, the groove is the same depth, but there's a narrow spot in both land and groove at the tight spots. But I could be wrong.

Hard to say, depending on how the barrel is made. I can only say the depth is not necessarily constant. Slugging will tell you both diameters. And of course everything is hunky dory if you just read the specs.

Traditionally riflings are cut. The bore is predrilled, and cutter is pulled through the bore to cut the grooves in multiple passes. Now there are many different ways to manufacture. But for handloading, with cast bullets especially, and gunsmithing, slugging and chamber cast are the standard methods.

-TL

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[lysander]

Not really a good assumption, especially if it was single point cut, broached or button rifled.

Generally, the pilot for these methods is at or just under the minimum bore diameter, so when it passes through the bore the grooves get cut or cold formed fairly uniformly, but the reamed bore keeps its irregularities.

[bobcatdriver]

My assumption is that the land and groove relationship is parallel even in the tight spot. In other words, the groove is the same depth, but there's a narrow spot in both land and groove at the tight spots. But I could be wrong.

Did you bore scope them? Sorry if I missed it. Just curious if there are any anomalies that can be seen. Not that they would necessarily cause a tight spot.

[markm]

No. We don't have a scope.