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Robert's 17HMR Magnum Build

16K views 147 replies 14 participants last post by  tanakasan 
#1 · (Edited)
Robert's 17HMR Razor Magnum Build

Well, I got the chance to machine my Razor receiver and bolt today!

Also, I was surprised at how light the recoil spring is!:eek: I have found a like sized replacement but with twice the rating. The SF spring is around 62# rating, the possible replacement is 124#.

Also going to machine a long brass follower. The SF follower is 5g, the joiner (not really coupled mass) is 3g. I am thinking that a 3" long follower should add a few grams to the bolt mass. SF charging handle by itself is 22g. Going to see how much mass I can add...can't hurt, right? I was surprised that brass is slightly more dense that stainless steel! Learn something every day!

I did not install my KID +10% spring. If these mods are successful, I would rather anyone else not *have* to add another item.

Will keep adding to this post as I go along, any comments or suggestions welcome!

Robert

Here we go again!


Indicated within .0005 over 4~5"


Barrel hole location within .001


Final drill operation, stepped up over a few sizes


.6875 reamer ready


Done


Looks good!


.1875 ream for TG holes


Numbers look familiar?


V-block threads


5/16" magazine hole @ 3 degrees


Milling the bolt shelf (about .050~.060) so the bolt will drop in easy


Enlarging the pocket on the bolt face


Fits a lot better now

Not much came out


Fits and stays great
 
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#148 ·
Hey Brian, sorry for the late reply!

BigNick73's McM numbers are correct. The.047 is very heavy and too stiff IMO and trial experience.

Be sure to pre assemble your longer test piece of spring and pull the bolt back w/o the buffer installed. Look throughout the buffer hole and check to see that it actually will hit the buffer. One of my tests was with a longer .041 and I did not check this. It was stacking the spring before hitting the buffer.

I am wondering now if the standard/short brass SelectFire guide and a longer/max length .041 spring would perform better than the additional mass provided by our extended guides and a shorter spring length?

Anyways...

Robert
 
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