Gas Port bushings, making your own

[handirifle]

OK I've figured out I need a 3/16" stainless rod (.185" dia) cut in pieces .300" long, but what drill size is .042"?

My drill set is very small and I know it's about 3/64 but 3/64 = .047 roughly, so what for .040, 042, 045 etc?

Lastly WHERE do you get them? I know ASI sells them for about $16 but if I can I like making my own. Plus I have the material and tools.

[Philipp2]

For those sizes, you will need some number drill bits.
0.040" = #60
0.042" = #58
0.0465" = #56

http://bobmay.astronomy.net/misc/drillchart.htm

[Calif Mini]

Handirifle: This may make things easier for you and shed some light on the "bushing and material" chat and where to look for small drill bits without a specialty store handi(a little pun intended)

At the local hardware store, (actually found it at the only two I looked in) I found a Oxy-Acetelyne drill cleaner kit. It is about the size of an X-ACTO knife handle and has 12 tiny drill bits inside it's handle. Similar to a pin vise. The sizes were (+ or - .0005)
.022, .024, .027, .030, .037, .039, .042, .046, .054, .063. I don't know how tough these are but I was able to carefully use a couple with success. The small ones would be easy to destroy without trying. Also a .042 drill is a number 58. Find a chart of decimal equivalents for number, letter and fractional drills. (on line?) You will use it often.

The material I used was drill rod from the same hardware store. Not cold rolled or hot rolled but "Drill Rod". This can be machined and drilled then heated and quenched in either oil or water depending on the type or rod you found. Easier than you think. This produces an extremely hard part if you don't soften it by reheating to make it less brittle or more malleable. I made the gas bushing and a gas pipe too. For a gas bushing, in my opinion, there is no need to soften it. Both parts show no wear or deformation after a couple hundred rounds. You still can use stainless but I do not know anything about heat treating it. It won't rust as mine may. That is if I ever stop shooting.

On my first go round, I pulled my bushing out, heated it red hot, and slowly retracted the heat to slowly let the bushing soften. After it cooled, I simply drilled it out and tapped it to 6/32 if I remember correctly. Still was tough stuff. Then I put in a short allen set screw and drilled it to the size that you want to try. I did several with various sizes for easy adjusting as needed. I found that my bushing hole size needed to be smaller than others who were plugging the gas pipe and using .042 to .055 ? Mine was .030 - .035. Closer to the pressure??

This gets long winded, so keep your refreshments handy.

Next I made my gas block an adjustable one by using the gas pipe as a drill jig, found a drill bit that fit perfectly, drilled through the gas block and tapped it for a long set screw. 8/32. The end of the set screw needed to be ground down to fit into the gas pipe without the threads. Now moving the set screw adjusts the gas available to the port and op rod etc. Actually what I am not saying is the end where the threads were removed, needs to be tapered like a needle valve in a carburetor. Very gradual taper is a must or a half turn will close off all the gas. Get it?

This is more than you asked but I hope you followed along as it all will help you in future tinkering.

I have more as I ended up making a gas block out of 304 stainless and installed a Krieger barrel, altered........................................Sor ry, I got started again......

Good luck, Ed

[handirifle]

Handirifle: This may make things easier for you and shed some light on the "bushing and material" chat and where to look for small drill bits without a specialty store handi(a little pun intended)

At the local hardware store, (actually found it at the only two I looked in) I found a Oxy-Acetelyne drill cleaner kit. It is about the size of an X-ACTO knife handle and has 12 tiny drill bits inside it's handle. Similar to a pin vise. The sizes were (+ or - .0005)
.022, .024, .027, .030, .037, .039, .042, .046, .054, .063. I don't know how tough these are but I was able to carefully use a couple with success. The small ones would be easy to destroy without trying. Also a .042 drill is a number 58. Find a chart of decimal equivalents for number, letter and fractional drills. (on line?) You will use it often.

The material I used was drill rod from the same hardware store. Not cold rolled or hot rolled but "Drill Rod". This can be machined and drilled then heated and quenched in either oil or water depending on the type or rod you found. Easier than you think. This produces an extremely hard part if you don't soften it by reheating to make it less brittle or more malleable. I made the gas bushing and a gas pipe too. For a gas bushing, in my opinion, there is no need to soften it. Both parts show no wear or deformation after a couple hundred rounds. You still can use stainless but I do not know anything about heat treating it. It won't rust as mine may. That is if I ever stop shooting.

On my first go round, I pulled my bushing out, heated it red hot, and slowly retracted the heat to slowly let the bushing soften. After it cooled, I simply drilled it out and tapped it to 6/32 if I remember correctly. Still was tough stuff. Then I put in a short allen set screw and drilled it to the size that you want to try. I did several with various sizes for easy adjusting as needed. I found that my bushing hole size needed to be smaller than others who were plugging the gas pipe and using .042 to .055 ? Mine was .030 - .035. Closer to the pressure??

This gets long winded, so keep your refreshments handy.

Next I made my gas block an adjustable one by using the gas pipe as a drill jig, found a drill bit that fit perfectly, drilled through the gas block and tapped it for a long set screw. 8/32. The end of the set screw needed to be ground down to fit into the gas pipe without the threads. Now moving the set screw adjusts the gas available to the port and op rod etc. Actually what I am not saying is the end where the threads were removed, needs to be tapered like a needle valve in a carburetor. Very gradual taper is a must or a half turn will close off all the gas. Get it?

This is more than you asked but I hope you followed along as it all will help you in future tinkering.

I have more as I ended up making a gas block out of 304 stainless and installed a Krieger barrel, altered........................................Sor ry, I got started again......

Good luck, Ed


Thanks for a TON of info, I really appreciate this.

OK NOW you got me curious. I really appreciate the info, not sure, yet, I understand it all, but I'll work on that part.

Did you use a lathe with those tiny bits? What speed?

You are moving on things I think about, ie your barrel, your gas block. They don't seem like complicated devices, but are almost treated like Voodoo by some.

How many times did you "treat" the drill rod to harden it?

[Calif Mini]

Handirifle:

Used the smallest thing I had which was a small battery drill. I could feel and see the results better. A dremel with a drill chuck might be the ticket. Don't bend the bits or use excessive pressure or you may end up with a two piece bit. Cutting fluid may help. Speed was limited to the Battery drill speed. In my example, I was drilling out the set screws which are tough enough but the Ruger SS is in a league of its own.

I needed to only heat the bushing one time (gas pipe also)--kept it heated for a few extra seconds, then dropped it into automatic transmission fluid. I balanced the bushing on top of a larger (2" wide & 12" long) flat piece of steel in order to indirectly heat the small bushing. Heat the large piece from the bottom and this will indirectly heat the bushing above. This keeps the bushing from prematurely deteriorating due to to much heat or an irregular heating pattern. Then tilt the base over a can with a couple inches of fluid and drop it in. It is over in a fraction of a second. A larger part being quenched can result in a small fire in the fluid (which will subside shortly) so always use a metal can and if holding the part with a coat hanger or tie wire, swish it around for a couple seconds. Always have a way to extinguish a fire handy whenever heating parts with an open flame. Holding the heat a few seconds after it is bright red or orange will assure enough heat and this will produce a part that will be to tough to file. Test it and if you want it softer just use the same method of heating (with a larger base material) after wire brushing the part back to a silver look, then heat it slowly until it is evenly light to medium blue. Be careful not to overdue it here as a little heat goes a long way.

One note: The water harden-able drill rod usually can be quenched in oil and if it does not harden, heat it again then use water, but oil harden-able cannot be quenched in water as it will fracture and cause it to not be very strong. I hope I didn't get this backwards. This is a handy trick but is not an area I am strong in.

In our endeavors some will shoot themselves in the foot, but the trick is to avoid aiming at it.

Ed

[handirifle]

calif mini
Thanks will update my progress as it happens. So much to learn and a LOT of info from this site, from folks like yourself. Nothing ventured, nothing gained as they say.

"Keep the toes out of the way":)

[gundoc]

Since I have a shop full of tools I make mine this way -

I start with 3/16th W-1 (water hardening) drill rod in lengths from 18 inches to 36 inches. I chuck them in the lathe and use a cut off tool to cut them a bit over sized. Using a Dremel tool and cut off wheel generates too much heat. Once I have a batch of them cut to about .310" I size them to proper length by face cutting both sides and cutting a bevel on both ends.

Once they are all to proper size, I center drill at least one side to start the small drills in straight. I drill them in the lathe by turning the headstock at a high RPM and use the dills in the tail stock.

After they are all drilled I can then harden them. The steel manufacturer I use recommends 1350 degrees F and quenching in brine. Proper heat and quench are essential if you're going to harden them. I place a batch of them in a V created by a piece of L shaped steel and apply the heat from an oxy-aceylene torch to the underside of the V. I place a few drops of Tempilaq to the bushings to guage heat, as it melts at a secific temp. Once the Tempilaq melts I hold the heat for a few seconds and them quench in a deep steel cup full of brine. The manufacturer will tell you how much salt to add to a specific amount of water for proper quenching.

The parts are now hard and nasty looking. They can be polished in a tumbler, or chucked in a drill chuck and polished. I use a drill chuck on a handle and polish with a Cratex wheel for small batches. I allow them then to soak in a good penetrating oil until all of them are done, and then use the same drills I used previously to clean the holes and sort them by size.

The proper lengths are:
Mini 14, old style and 580 style - .295" long
Mini 30, old style and 580 style - .265" long
Heavy barrel styles and Target mini's - .263" long
You can allow a thousandth or two for tolerance, but too short or too long will not allow the gas block and barel to properly mate and will lead to problems. I have measured hundreds of factory bushings and these are the average lengths.

I found the stainless steel in the right size to be unsatisfactory to way I make the bushings, so I don't use it. I experimented with stainless, brass, bronze, and finally settled on W-1 rod.

The bushings don't have to be hardened if you use good drill rod, but they will be subject to gas cutting more than hardened steel. It'll take thousands of rounds to wear them out, as the hole will just get a little bigger over time. The bushing won't break, it'll just allow more gas through and then you can replace it with another one. That's important to note, because the gas pressure and heat will eventually pen up even the hardened ones, just like it will wear the barrel.

Lastly, I purchase my drills at a tool store or tool supplier, not the hardware store. Buy good US made drills and they will resist breaking and be sharper for longer. You'll also need to make sure your drill chuck closes to zero. Many larger chucks won't close less than 1/16th or so, and won't support the smaller drills. Buy short wire sizes as they will be stouter and less prone to break. 135 degree points seem to work better than 118 degree points. Use a drop of cutting oil on the bits and back them out often to clean the flutes. Break a small dril off in the bushing and you'll pretty much have to start from scratch as they're difficult, if not impossible, to shatter with a small enough punch, and the small drills lack the strength to drill out the broken part.

Sorry for the length of post, but I wanted to be thorough.

[Philipp2]

And now we have heard from the pro.

Thanks Doc.

[Jaybird]

Yep, Everything The Gundoc Does/makes/repairs Is Great! That's Why I Bought Mine From Him. What Sold Me, First Time, Was His Trigger Job. AND OF COURSE ALL THE OTHER STUFF HE DID FOR MY MINI'S.

[handirifle]

Yep, Everything The Gundoc Does/makes/repairs Is Great! That's Why I Bought Mine From Him. What Sold Me, First Time, Was His Trigger Job. AND OF COURSE ALL THE OTHER STUFF HE DID FOR MY MINI'S.

Gundoc
You are a class act. Here I am looking into making my own, cause I'm cheap:), and you go and give me all the details in making them, potentially shooting yourself in the foot.

Since you have been so generous with your knowledge, the least I can do is order the first set from you, I owe you that much.

Now how do I order from you. I cannot find an order page.

Oh, yes, the info is appreciated.

[planeoldguy]

Gundoc
You are a class act. Here I am looking into making my own, cause I'm cheap:), and you go and give me all the details in making them, potentially shooting yourself in the foot.

Since you have been so generous with your knowledge, the least I can do is order the first set from you, I owe you that much.

Now how do I order from you. I cannot find an order page.

Oh, yes, the info is appreciated.

Same here, where do i send it?

[Philipp2]

I think that I just sent him an email and a PayPal payment. He shipped them back to me in the box with my newly reworked trigger. Great service!!

[handirifle]

OK email and payment sent.

[handirifle]

Gundoc
I have a question for you from your site. I noticed you offer the service to rechamber from 5.56 to 223. Why is that? Is it to clean up a sloppy chamber in the 5.56 version?

I've seen some AR's, purpose built for accuracy, that were also 5.56 chambered, can't you have the best of both worlds?

[gundoc]

I don't mind a bit to help out with the things Ive learned. Only a small part of what I do is VooDoo magic, the rest I'll freely share with folks who want to learn their rifles better and try their hand at improving them. I offer to rechamber to .223 because there really are differences between the two chambers and if you want to shoot .223 exclusively you might as well have the best chamber for it. 5.56mm is a little sloppy for .223 and might be that final touch a rifle needs to really shine. It requires setting the barrel back 1 turn only, rechambering, and refitting a few parts.

If you haven't checked it out, I have been producing some amatuer videos of the services I offer so that DIYers can see how I do it. It's not the only way many times, but it's the way I do it when hired for the job. They're on my website under videos. Once I get better at it I may release them on DVD in their original many-megs format. :)

It's actually on purpose that nothing can be ordered from my website. If you want to order bushings just send me an email requesting them and I'll reply with my ordering info. Everytime I make a batch I go through them pretty quickly, and a batch of 50 sets (150 pieces) takes about 2 days to make. So by ordering through email I can give real-time stock information as to when to expect your bushings.

For all of you guys that I have done work for, I really appreciate the kind words and your support of my services. The Perfect Union family is the best bunch of folks on the net!