Firing pin bushing options and bolt truing questions

[Rich S]

I plan to bush the bolt head for the 0.062 firing pin and a couple of bolts - Remington 223 and 308. I looked at some of the post on the subject and the Jim Borden method. For the most part is looks fairly straight forward. The one thing I was wondering is if the bushing could be made a smaller diameter to avoid the ejector hole? Instead of using a 1/4 - 28 with a 0.480 head bushing that is in Jim's write up, I was thinking about a 10-32 with a head diameter that just reached the ejector hole. Other than that I figured follow Jim's method for depth of cuts, tapping, etc... Using the smaller screw you would end up with ~0.045 - 0.047 wall thickness from the the 0.062 ID to root of the threads and only 0.025 -0.030" shoulder on the head. I haven't taken an exact measurement of the ejector location yet, just roughed it out with a caliper. Does this seam reasonable or should I just plan to take the extra step to re-establish the ejector hole?

When re-establishing the ejector hole is it best to do this by hand with a dremel or set it up in a mill?

I plan to do this while I have the bolt set up to true the lugs and face. It looks like most folks leave the extractor in place. Is there any reason not to remove a non-riveted extractor during machining?

The bolt on the 223 has 0.019" float as it came from Remington. I'm assuming it will be 0.022 - 0.025 by the time I clean up the lugs and receiver. Is there standard on the max allowable before the handle needs relocated for timing?

I appreciate all the help offered on this forum. This is my first project truing Remington receiver. I'm mainly just doing it as a winter project and am collecting the parts, information and building the tooling needed. I hope to start the actual work in the next couple of weeks.

 

[RWO]

Frank DeHaas advocated bushing the hole with a 6-48 cheese head scope mount screw. Simply tap drill the hole, thread and counterbore to match the head dia. but not deep enough for the screw slot to enter the counterbore. He used a hot screw, tinned with soft solder and ran it into the hole. Red Loctite works just as well. Machine off the extra head height to remove the slot. Locate the new hole by whatever means you like. One good one is to make a center punch tip for your cleaning rod that fits the flash hole of a case well. Chamber a good de-primed case and feed the tip down to the flash hole and tap for a mark. Drill new hole. I have done it and it works perfectly well. Scope mount screws used to be made from good steel. Don't know about the Chinese crap.

RWO

 

[chuckshooter]

I have done 4 martini bolts so far, two with the screw method and two with the weld method. on the screw method, I do everything that has all ready been talked about with one additional step. I carefully hold the bolt and hit the newly placed screw with an rotor hammer set on impact only in order take up any possible slack. then I mill it off. re drill hole. my opinion on the weld method is still not in. I don't have enough rounds down the barrel yet. it is easier, countersink the bolt, weld, face off, re drill hole. I have one more martini to do, we'll see, after all, I am just a you tube video trained wannabe gunsmith

 

[Rich S]

Thanks for the replies. I think I will stick with the larger bushing head and re-establish the ejector hole as chuckshooter suggested. Shouldn't take much extra time since I'm only doing a couple. I will likely drill with a #21 first just to verify if a 10 - 32 bushing would have engagement for the length of the Borden style bushing. Im not familiar enough to know at what depth the firing pin hole opens up. At that point I can always drill a larger hole and use the Borden dimensions. The only down side I see is the extra set up time since I'll likely make the bushing after the bolt face is machined.

 

[Alex Wheeler]

I use an 8-40 slotted head screw. Drill and tap the firing pin hole and recess the head .050". I use a 3/8" long screw. Then center drill, drill and ream a .062" hole. Use carbide. With the tap, use a spiral point, moly D, and do it under power. You wont tap it by hand, you'll break taps like crazy. This method does not effect the ejector hole. Its right on the edge, but not into the hole. Screw heads are .233" diameter I believe. Use a mini carbide boring bar to make the countersink. I usually shoot for .001" under head diameter so there is a slight interference fit and you cant see where the bolt face a screw head meet. Red locktite on the threads. The gap in front of the bolt handle is part of it, but the clocking on the handle is more important. Measure the gap closed and open, thats how much primary extraction you have. Factor in how much slop is between the extractor claw and rim of the case to see how much its actually going to pull the case.

 

[carlsbad]

IhuntIl,
How are you planing to hold your bolt? That is the biggest challenge unless you're planning to take the handle off. I'll add to Alex's great directions that I chuck the screws in a collet and machine the outside of the head a skim cut to make sure it is round, concentric with the axis, and has no dings.

--Jerry

 

[Rich S]

Jerry

I plan to hold the bolt in a pipe (2 3/4" OD, 0.375 wall DOM) with two spiders and a cut out for the handle chucked up in a 4 jaw chuck. Pretty much copying what I have seen others post. I made one to hold the reciever from 4" aluminum. Still need to finish the one for the bolt. I contemplated using a mandrel threaded into the bolt body to hold it in the 4 jaw and a steady rest closer to the lugs. I like that method allows more access to indicate off the bolt body. The spiders seem a little more flexible and easier to set up. I will check runnout of the nose of the bolt in a V block before I take it to the lathe.
Rich

 

[DickE]

How do you get the firing pin down to .062"?

 

[carlsbad]

tool post grinder or sometimes you can buy one from PTG. Lots of guys here, including me, are glad to bush your bolt and grind your pin for a reasonable fee. --Jerry

 

[Alex Wheeler]

I use a very sharp tool, spin as fast as the lathe will go and turn the pin down. Light cuts and a little paper after.

 

[carlsbad]

I use a very sharp tool, spin as fast as the lathe will go and turn the pin down. Light cuts and a little paper after.

Very talented and experienced manoeuvre. Not for the beginner. --Jerry

 

[Rich S]

IhuntIl,
How are you planing to hold your bolt? That is the biggest challenge unless you're planning to take the handle off. I'll add to Alex's great directions that I chuck the screws in a collet and machine the outside of the head a skim cut to make sure it is round, concentric with the axis, and has no dings.

--Jerry

Jerry,

My description was probably poor. I finished making a jig to hold the bolt last night. Kind of wish I'd have made it a bit longer. The bolt in it is for a SA. I'll likely make up some shorter bolts for the OB end and give it a try. Have to get some screws and a tap on order for the bushing.

Rich

 

[carlsbad]

Rich,
I knew what you meant. What I don't like about that type of setup is that you can't indicate the rear of the bolt. I made a LaBounty style holder for working on bolts. By making rear indicating surface concentric and coaxial with the bolt channel, I can indicate on the back of the jig to confirm the alignment of the back of the bolt.

 

[Alex Wheeler]

Rich,
I knew what you meant. What I don't like about that type of setup is that you can't indicate the rear of the bolt. I made a LaBounty style holder for working on bolts. By making rear indicating surface concentric and coaxial with the bolt channel, I can indicate on the back of the jig to confirm the alignment of the back of the bolt.

That would work for one bolt diameter, a bolt .001" lager is now off center .0005". How are you adjusting this in the chuck? indicating the back, then the nose and tapping it around? I use one similar to the one up the page but the jacking screws are only an inch apart, I can indicate about 4" of the bolt. Lots of overhang so cuts need to be light. Id like to have a little handinge collet lathe, then Id just knock the bolt handles off everyone and put them in the collet.

 

[carlsbad]

Alex,
Indeed oversize bolts are not easily accomodated.

I considered making just what you describe with the close jacking bolts and lots of bolt exposed and decided to try this first instead. I've had good luck with stock remington bolts which is 90% of my work.

The close jacking screws bothered my sense of "How rigid can I make it" but 8 heavy screws should be good enough, even if close together. I have a good supply of long brass tipped set screws.
thanks,
--Jerry

 

[boltfluter]

Some very nice fixturing guy's. Fixturing is the name of the game in machining. Keep the pics coming.

Regards, Paul

www.boltfluting.com

 

[Rich S]

I use an 8-40 slotted head screw. Drill and tap the firing pin hole and recess the head .050". I use a 3/8" long screw. Then center drill, drill and ream a .062" hole. Use carbide. With the tap, use a spiral point, moly D, and do it under power. You wont tap it by hand, you'll break taps like crazy. This method does not effect the ejector hole. Its right on the edge, but not into the hole. Screw heads are .233" diameter I believe. Use a mini carbide boring bar to make the countersink. I usually shoot for .001" under head diameter so there is a slight interference fit and you cant see where the bolt face a screw head meet. Red locktite on the threads. The gap in front of the bolt handle is part of it, but the clocking on the handle is more important. Measure the gap closed and open, thats how much primary extraction you have. Factor in how much slop is between the extractor claw and rim of the case to see how much its actually going to pull the case.

Could a person get by with a HSS reamer? I'm only doing a couple and would like to limit the extra cost of carbide reamers.

Is there any down side to using a 9/64th carbide endmill instead of a #28 carbide drill for the tap hole? There is only a tenth difference in size. I figured this may be a better tool when I oversize the scope mounting holes to 8-40 as I could ensure proper location and not rely on following the existing holes.

 

[Rich S]

That would work for one bolt diameter, a bolt .001" lager is now off center .0005". How are you adjusting this in the chuck? indicating the back, then the nose and tapping it around? I use one similar to the one up the page but the jacking screws are only an inch apart, I can indicate about 4" of the bolt. Lots of overhang so cuts need to be light. Id like to have a little handinge collet lathe, then Id just knock the bolt handles off everyone and put them in the collet.

Thanks for the additional information. I was concerned about the rigidity with that much overhang and was shooting to keep it minimal. I think I will make a mandrel to add to the back of the bolt. That will allow ~3.25" overhang with my current setup and provide a longer span between supports. If I increase the slot length I could get more overhang as well. The down side is I will need to screw it on after it is in the fixture. My bolts are currently 2.5" BTCs. The other option is to just add another set of holes.

One thing about making my own tooling is I'm getting lots of practice and it keeps me off the couch. May have to stop before too long and add some heat to the garage though.

 

[Alex Wheeler]

Could a person get by with a HSS reamer? I'm only doing a couple and would like to limit the extra cost of carbide reamers.

Is there any down side to using a 9/64th carbide endmill instead of a #28 carbide drill for the tap hole? There is only a tenth difference in size. I figured this may be a better tool when I oversize the scope mounting holes to 8-40 as I could ensure proper location and not rely on following the existing holes.

The end mill will be fine . I have broken hss off doing this job. if its new and sharp you should be okay

 

[Alex Wheeler]

Thanks for the additional information. I was concerned about the rigidity with that much overhang and was shooting to keep it minimal. I think I will make a mandrel to add to the back of the bolt. That will allow ~3.25" overhang with my current setup and provide a longer span between supports. If I increase the slot length I could get more overhang as well. The down side is I will need to screw it on after it is in the fixture. My bolts are currently 2.5" BTCs. The other option is to just add another set of holes.

One thing about making my own tooling is I'm getting lots of practice and it keeps me off the couch. May have to stop before too long and add some heat to the garage though.

The work we are doing to the bolt doesn't need much rigidity , I'd worry less about that and more about being sure the bolt can be indicated in as best as possible