Well, I got the chance to machine my Razor receiver and bolt today!
Also, I was surprised at how light the recoil spring is! 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
Looks great so far! Don't forget to contour the bottom middle ridge of the bolt to avoid mag strikes and possible OOB detonations. Keep us posted! Still very interested in the one-piece spring replacement.
Looks great so far! Don't forget to contour the bottom middle ridge of the bolt to avoid mag strikes and possible OOB detonations. Keep us posted! Still very interested in the one-piece spring replacement.
I test fitted the mags into the receiver assy. and it does nick the feed ramp.
I will purchase the heavier spring this week and machine a 3" long front spring follower to add mass. Looks like it will clear a fully retracted bolt to me. Spring only comes in a 5-pack so if it works, there will be extras.
Also going to look at a hammer spring spacer to increase the force...not to fire, but to help resist the bolt. Trying to solve the issues so that others will not have to buy so many more parts!
Got my mags in Friday, waiting for the stock and barrel to arrive.
Build so far:
Razor Magnum 80% receiver kit
Butler Creek 17HMR 20" blue .920 target barrel
Hogue OM black magnum stock
Clark Customs complete TG-only silver piece, but was a good deal!
Ruger JMX-1 factory mags
Mueller APV 4.5~14 AO scope
Lots of DIY mods and tweaks!
Mine needed a secondary cut on the tip of the opposite side. Both new mags were not the same! One cleared, the other *just* touched. Now has no contact even when squeezing the mag to the receiver. Should be fine.
Tried a roll pin for a charging handle spring spacer, but no go. Must be very thin walled-not much thicker than the spring-to clear in the receiver. Guess I have to fabricate one.
Did manage to make a hammer spring spacer and a long follower for the main spring. Got the heavier rate main springs on order too!
Robert
Spacer for hammer spring. 1/8" long, tried 3/16" but too long. 5/32" might work, but this should work for any hammer spring.
McMaster Carr for the spring, I machined the SST follower today.
Springs come in a 5-pack...if it works, there will be extras. If not, there is also a twice again stronger one available.
I hope no one goes this route until I get to shoot this combination of tweaks. I want to try it before anyone follows my path. Would be a shame if I wasted someone else's money!
I ordered some mallory metal for my build today, the plan is to cut a 3/4"x3/8" channel on the bottom of the bolt ( just in front of the buffer relief ), replace that with a 3/4" x 3/8" piece of mallory metal, then tig weld it, and surface grind it flush. We calculated a gain of about 40 grams (or so). That in combination with a 2" addition to the top spring should get me there...I hope. If not, adding mass this way is a great Idea. I still might do this just to add more mass. I don't think we will be able to create too much mass, but we may be able to create enough so the springs will control it properly.
2x denser than steel! And the addition of this heavier spring I found (which is also 2" longer than stock!) just might do the trick! Definitely keep us posted! :bthumb:
My goal is a drop in kit for a standard SureFire factory Magnum kit that will shoot the 17HMR reliably and safely w/o all the R&D and tweaking. That's why I am trying to fab parts that work with the factory pieces. Maybe Phil could incorporate it into his offering.
A mallory metal follower would be cool, but...cost is the issue. I bought a piece from Ebay that was 1" diameter by 1.25" long, that was $30 + $6 shipping. Finding a piece longer than that would be difficult and expensive.
Feels...well...twice as strong as the SF piece. Cut a 9" piece (7" stock + 2" additional per Guitdolin) and tossed it in with my extended follower.
First thing I notice is that the bolt does not go all the way back to the buffer. Makes sense since the new spring is .005 thicker wire. Gradually cut it down to the bare minimum. Ended up 8" to consistently reach the buffer.
I think that if I need to go to the next heavier spring, it would probably stack at an OAL of 7". Same OAL as stock, but with heavier wire again.
Hogue OM stock arrived today, just waiting on the barrel now!
Robert
Here's the pics...P/N 666 the mark of the beast!
Wound the other direction...think the rifle will know?!?
Close up showing the larger diameter wire; .035 vs .040
You know, I was thinking...If you made the head of your follower longer, say .5-.75" long, that would add more mass and provide more pre-load on the spring. Again, another tuning aid if need be.
I thought of a longer/heavier follower as you suggested. Say 1" of full diameter followed by 2" of turned down shank. It might require the thickest spring in order not to stack. I know that the .140-ish long tip on the SF and my custom one would stack the spring at anything over 8".
I have the thicker (middle weight custom) spring cut to 8" right now with the long follower I made. Started at 9" and the bolt would not touch the buffer. Cut it back gradually from 9" until it touched consistently. Its still 1" longer than stock SF which is 7".
Well, today was machine the hammer and sand the mag well in the Hogue stock. The mags drop out w/o help now! Also removed the extractor and polished the slot and nose.:bthumb:
The action is complete and functioning. Have to wait and see if it fires reliably. I compared the amount of pull needed vs the SF spring, custom spring, 22LR Razor and my stock 10/22. What a difference! Hope it is enough to handle the 17HMR.
Another thing we could try would be to lengthen the head of the follower, and shorten the spring. I think it would probably be better to have more spring controlling less weight, than less spring controlling more weight. But I would only experiment with that if this round of modifications doesn't work.
Also, you may be @ coil bind @ 8". You may be able to touch the buffer, but the spring may be coil binding then deforming inside the tube, allowing enough movement to touch the buffer. I'm not saying it is, but you may want to check. Scrunch your spring together and see what the total height is compressed (coil bind), then measure the distance from the top of the charging handle nub to the end of the reciever, subtracting the height of the set screw, the stroke of the bolt, and the compressed height of the spring. Keep in mind that the charging handle doesn't sit all the way forward with the bolt installed. It may be easier to measure with the bolt installed, and using a long skinny screwdriver down the set screw hole to the bolt nub, mark it with a fingernail, then measure. Then subtract, if the remainder is a positive number, then no coil bind.
You can feel the coils stack up hard when the spring is too long. Feels like it hits a solid metal stop. I cut one or two coils at a time to reach the 8" length. Probably would work with one additional coil, but wanted to be well within the clear zone. I think the longer shank of the extended follower helps guide and control the spring at compression.
BTW, I will mail your spring out tomorrow! :bthumb:
Today was deburr and polish the bolt and inside of the receiver. Lots of sharp edges and burrs. Too bad about the bolt...the black finish is gone along all the edges and where the hammer slides on the bolt. Can't see it from the bolt side so not unpleasant at all.
Hand cycled the action and it feeds relatively well. A lot smoother than before. The opening of the chamber is sharp and very slightly chaffs the cartridge going in. Phil suggested a .020 feed ramp be put on the chamber entry. That is tomorrow's task along with polishing the bolt handle rod.
A note on the BC 20" blued 17HMR barrel; the shank is slightly under ideal/nominal size. Went a bit looser in my receiver than the GM did in my 22LR build. The GM was a snug, twist to fit line to line assembly. No wiggle, no rocking. It would stay in w/o the v-block.
Kind of liking the assembled rifle. All black except the TG. Looks simple, mean and all business. Hope it shoots half as good as my 22LR Razor!
A cone-shaped felt/fiber polishing bit in a Dremel with some polishing compound on it will take care of that sharp edge around the chamber entry. That was Phil's suggestion to me, and it worked great.
I got a package of the thickest springs in today. Wow, .047 wire! Its stout!
I now have cut and ready for testing:
Stock SF .035 x 7" lg...I believe is way too light for 17HMR, even with extra length added
Medium weight .040 x 7" lg
Medium weight .040 x 8" lg
Heavy weight .047 x 7" lg
Heavy weight .047 x 8" lg
Trial fitting all of them, I am leaning towards the heavy spring @ 7" lg. Just feels right. But who knows? Maybe 6"...maybe 6-1/2"...we will see!
I am using the long SST follower unless it ends up a problem.
Did the .020 feed ramp to the barrel, manually cycling feeds a lot smoother and consistently now. Under fire, who knows?!?
Bruce, your spring on its way...Shane, yours will go out in tomorrow's post. G/L!
Super. Thank you, sir! Let us know what spring and length you settle on.
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