I had the 419 knob and didn't like the way if felt. Doesn't mean it's bad of course, just that it didn't work with my method if working the bolt.
I have tried a little bit of everything. My current and favorite knob is the one from my B-14R. I tried it, then tried some others then come back to it and will probably never take it off again.
Lumley Arms makes a very nice adapter that I have used to try several bolt knobs on my 457. I'd highly recommend one so you can put just about any bolt knob you want on the 457.
Metric M6 bolt knob adapter
lumleyarms.us
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This is the Acorn style from Anarchy Outdoors. This is a great knob but its too long for some applications. The shorter version is ideal, I have the short version on my PB-14R. You have to use the above adapter to use this knob.
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Area 419 knob. The design didn't work for me.
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This is the Bergara B-14R knob. It's the same thread pattern as the 457, no adapter needed. This is the one I currently use and will probably never change. In this photo I have the knob screwed completely in. You can put something inside the hole and extend the length.
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Here is the short Acorn knob from Anarchy. This is my PB-14R. The shorter size works best for this rifle.
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This is the Long Acorn knob. I use this on the Tikka T3x CTR. It's still long and I may talk with Anarchy and see if they will swap it out for the shorter one.
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This is the Grenade knob and it was too rough for my skin. Sent it back for a refund.
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This is a good simple pear shaped knob that cost $10. Doesn't mate up to the handle as good as other but it highly functional.
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Hope this helps or answers some questions. I'd highly recommend the Lumley adapter, I have one. It opens the door to a much larger variety of knobs.