Fiddling around with my new RDB #409 I noticed an issue with unfired ammunition being extracted from the gun. There's a consistent and specific path of gouges running along the bullets. It's hard to see, but they are in an arc running in two separate directions.
(In the pic, they form an ellipse or "lens" shape side-by-side. The nick in the left case neck is part of those gouges.)
The culprit is the middle lug on the barrel extension. The machining creates a very sharp corner that gouges into the bullet as it rides past in a chattering motion. (If you look closely to the left side at the top of the bottm lug in the second picture, you should see a little white spec. That's actually the corner that's had the finish scraped off as it's been shaving copper.
Now I'm not telling everyone run out and start filing away, but. I do hope Kel-tec will examine this and see if there's a step that could be added to their machining to eliminate that. (AR's do this to a lesser extent, by the way.)
Auto-loaders are heck on ammunition, so there's only so much accuracy that you can wring out of one, but. Reducing or eliminating those gouges could increase accuracy an appreciable amount. Because of their two different paths, it's like shooting arrows with left and right-handed feathers. You basically have two points of impact for one point of aim. Even a small increase in accuracy makes your product that much better than the competitors.
The second issue is impacting of locking lugs. In the second picture you can see the rounding of the top edges of the 1:30 and 3:00 lugs. In the third picture I've changed the assembly of the gun and flipped it upside down to show you the impact point (now on the left side 9:00.) I believe the culprit this time is tolerance stacking issues.
You'll notice the bolt carrier in the foreground is shifted to the left (partially due to yaw from pulling the charging handle back.) Between the lateral clearance of the bolt carrier (BC) to the receiver, the BC vertical play in the receiver rails, and the bolt yawing starboard in the BC because it's pivoting against it's pivot pin any time the bolt face meets resistance (like loading a cartridge.)
I don't think it requires massive re-tooling to fix this problem. The only part that needs redesign is the block of the bolt carrier. Make the bore for the bolt a little smaller, mill the sides a little wider and the guide rail paths a little tighter and all should be well. (I'd save save the bolt's bore diameter for last. It doesn't have the advantage of the AR bolt's long tail to limit yawing.)
(In the pic, they form an ellipse or "lens" shape side-by-side. The nick in the left case neck is part of those gouges.)
The culprit is the middle lug on the barrel extension. The machining creates a very sharp corner that gouges into the bullet as it rides past in a chattering motion. (If you look closely to the left side at the top of the bottm lug in the second picture, you should see a little white spec. That's actually the corner that's had the finish scraped off as it's been shaving copper.
Now I'm not telling everyone run out and start filing away, but. I do hope Kel-tec will examine this and see if there's a step that could be added to their machining to eliminate that. (AR's do this to a lesser extent, by the way.)
Auto-loaders are heck on ammunition, so there's only so much accuracy that you can wring out of one, but. Reducing or eliminating those gouges could increase accuracy an appreciable amount. Because of their two different paths, it's like shooting arrows with left and right-handed feathers. You basically have two points of impact for one point of aim. Even a small increase in accuracy makes your product that much better than the competitors.
The second issue is impacting of locking lugs. In the second picture you can see the rounding of the top edges of the 1:30 and 3:00 lugs. In the third picture I've changed the assembly of the gun and flipped it upside down to show you the impact point (now on the left side 9:00.) I believe the culprit this time is tolerance stacking issues.
You'll notice the bolt carrier in the foreground is shifted to the left (partially due to yaw from pulling the charging handle back.) Between the lateral clearance of the bolt carrier (BC) to the receiver, the BC vertical play in the receiver rails, and the bolt yawing starboard in the BC because it's pivoting against it's pivot pin any time the bolt face meets resistance (like loading a cartridge.)
I don't think it requires massive re-tooling to fix this problem. The only part that needs redesign is the block of the bolt carrier. Make the bore for the bolt a little smaller, mill the sides a little wider and the guide rail paths a little tighter and all should be well. (I'd save save the bolt's bore diameter for last. It doesn't have the advantage of the AR bolt's long tail to limit yawing.)
