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I have had my grendel a short time and fired about 200 rounds through it. I have yet to achieve a consistant group at 100yds. I've tried different powders and loads and the results are all similar, no tight groups, inch or better, and fliers. While cleaning the barrel after the last shoot I noticed two things: a couple of very small flecks of copper on the patch and when the jag went past the gas port there was a definite rough spot. You can feel the patch/jag pass over the gas port hole. Is this normal?
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It's an occasional problem in gas guns. It sounds like the projectile jackets are getting caught at a deformity in the gas port. I had this happen with an 18" select match Douglas barrel for an SPR. Bore scope analysis revealed a large chunk of metal protruding from the gas port, which had developed after about 200rds as well. The gun started out shooting 1/2" easy, then opened up noticeably, hence the bore scope analysis. Eventually, the metal bugger broke free and it returned to shooting well. -
Why not remove your gas block and measure your gas port size. Find the correct drill bit and redrill the gas port hole. Maybe that will remove the burr. Just make sure to NOT drill through the bore and hit the lands on the other side. Put a wood 1/4" dowel rod in the bore to keep from hitting the lands on the other side. You could send the barrel back to the manufacture and let them do it. If it were me, I'd do it myself.Comment
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I would have the manufacturer do it or have the pay to have a experienced gunsmith do it. You don't want to damage the barrel and be stuck with it. It is my understanding that if they try to drill the hole in one step that this can happen. Many barrel makers use several drill sizes to bring the hole to the final diameter.Comment
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