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Discussion Starter · #1 ·
I am having huge problems with pinning my barrel on my k-var krink kit. I drilled a beautiful hole with a letter H drill that gave me a hole of .270 and my pin with the kit was .276. So I tried hammering it in...needless to say I F*#ked everything up. The pin is about 3/4 of the way through and It will not move. I hate to order more drills...Has anyone ever used a roll pin for the barrel pin??? WHAT DO I DO!!!!!!!!
 

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Happy Camper
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Roll pins will work - Mcmaster-Carr.

I think that you'll be best served by sacrificing an "I" drill bit, 0.2720", and use a dremel to cut off the fluted section. That can be replaced for a few bucks.

You can also order drill rod in the appropriate size if you want to have more than one pin. ;) Again, from mcmaster-carr or other project-supply places. The I drill bit may be easiest/cheapest. That's what I would try first (no pun intended) if it were me.

hth,
- Jerry
 

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Discussion Starter · #3 ·
Thanks Jerry, I bought an "I" drill today and the bastard was too small!! It mic'ed in at the same size as the hole!! I bought it from a machine shop, but its tolerances must just not be tight enought....Will a spring pin work??? You know, the ones have a slit down one side??
 

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I have sacrificed a few drill bits for barrel pins to achieve the proper headspace, they work great.
I don't think I would trust a hollow, split roll pin for a barrel pin.
Maybe you could devise a way to knurl the "I" bit to tighten it up a bit.
Or possibly find a metric bit that would work.
You could always have somebody turn one on a lathe for You.
 

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7.62x39 said:
I have sacrificed a few drill bits for barrel pins to achieve the proper headspace, they work great.
I don't think I would trust a hollow, split roll pin for a barrel pin.
Maybe you could devise a way to knurl the "I" bit to tighten it up a bit.
Or possibly find a metric bit that would work.
You could always have somebody turn one on a lathe for You.
Do you set the headspace, drill the hole, then unchuck the bit and drive it through? I mean cut off both ends of the drill bit while the drill is still in place and use the shank as the pin. Sounds like a great idea! You wouldn't have to drive it in and it would be a perfect fit. Some of the solutions you guys come up with amaze me! LOL!!!
 

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The barrel pin is nothing to be cavalier about. It keeps your headspace from changing. The barrel pin should be a .001" press fit or so. That means the hole should be just slightly smaller than the pin. With a .270" hole and a .276" pin you have a .006" press. Way too much. You can use the drill trick, but just be aware that the way it works is you really don't have a press fit until you fire a few rounds and the barrel moves that couple of thousandths to "capture" the pin. No hole is smaller than the drill that made it. I suspect that when you pound out the pin, you will find it galled the hole somewhat. My suggestion is to order a .275" reamer from MSC and run it through the hole, preferably with a decent drill press and then reinstall the pin. Here is a link:

http://www1.mscdirect.com/CGI/NNSRIT?PARTPG=NNSRAR2&PMPXNO=1697494
 

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Did you tried to press in the pin you now have stuck, or were you just hammering on it?

Pookie has a little tutorial on his server from me. I use a medium size vise to press in the pins. It works slick and doesn't take much to do.

If not then disregard my post.
 

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Discussion Starter · #8 ·
Build steps...riveted in front trunnion, drove in barrel, headspaced, drilled barrel pin hole, attempted to hammer in pin.

Okay, I hammered the pin out and yes the hole is galled, so I have to go bigger. It is measuring somewhere around 0.274-0.275, So I think I will drill with a "J" or should I go with a 0.280 reamer??? that's the next size up, I have never used a reamer...Is it just that it is more accurate???? Do I just use the reamer or do I have to drill it first, my quess just the reamer, right???

Sang, I was just hammering it, I don't have a press and my brother has my large vise. I was just using the technique I had used in the past BFH.

Also, is this correct about the press fit-it should be loose????? I have always been told that the press fit is from .002-.005??? It shouldn't move when you first shoot it should it???
 

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snazi said:
Do you set the headspace, drill the hole, then unchuck the bit and drive it through? I mean cut off both ends of the drill bit while the drill is still in place and use the shank as the pin. Sounds like a great idea! You wouldn't have to drive it in and it would be a perfect fit. Some of the solutions you guys come up with amaze me! LOL!!!
I did not use the same drill bit.

I don't recall the exact sizes I used, but I drilled it with a fractional bit and found a letter drill that was a couple of thou larger and pinned it with that, or vice versa. I honestly don't remember.
 

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Make sure you use some weiner slider on that pin. I have cracked a trunion because I forgot to grease it up.That really sucks when its already in the receiver.
 

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Happy Camper
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magicald_223 said:
It is measuring somewhere around 0.274-0.275, So I think I will drill with a "J" or should I go with a 0.280 reamer??? that's the next size up, I have never used a reamer...Is it just that it is more accurate???? Do I just use the reamer or do I have to drill it first, my quess just the reamer, right???
Go with the J bit. Use a drill press if you can.

Also, is this correct about the press fit-it should be loose????? I have always been told that the press fit is from .002-.005??? It shouldn't move when you first shoot it should it???
No, should not be loose. Guessing here, but press fit should be .001-.003 difference. The smaller the hole in comparison to the pin, the tighter the fit. You obviously learned this the first time. Now we are aiming for a slightly less press fit. So if your hole drills to let's say .276", you would want to use a .277"-.279" pin. That would give you a .001-.003" press fit. Again, the bigger the pin the harder it will be to seat. I would think that would work.

I have no time to look at it now, but this evening I could measure the difference on my disassembled kits and get the exact measurements for comparison. Not sure if I have recorded those on my website because I've yet to need to re-drill a pin.

- Jerry
 

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What's all the talk about "H" and "I" drill bits guys? How is this determined? The only form of measurement that I know of is the standard sizes 9/64",7/16",9/32" and so forth and so on. fill me in.
If you go to a hardware store around here and ask for a "letter "C" drillbit, they look at you like your an idiot. Just inquiring.
Thanks,
-shadow-
 

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BARREL PIN?

I to have a simliar question.
On my build the trunion happend to be a new one and the hole wasn't drilled so I drilled the hole. Well, the hole looks to be a little low and also kicked to the side a tad. Any suggestions. Should I tack weld the hole or what? The barrel is already pressed.
This specific build is a pain.
Thanks,
-Shadow-
 

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shadow29483 said:
What's all the talk about "H" and "I" drill bits guys? How is this determined? The only form of measurement that I know of is the standard sizes 9/64",7/16",9/32" and so forth and so on. fill me in.
If you go to a hardware store around here and ask for a "letter "C" drillbit, they look at you like your an idiot. Just inquiring.
Thanks,
-shadow-
There are 3 major bit sizing formats.
Fractional 1/8" 1/4" etc
Letter A-Z
number or wire 1-60

A complete drill index includes all of these. 115 bits total.
If you are using a hardware store, that doesn't know what a "C" bit is, time to find a new one.
 

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I've got a similiar problem myself. On this specific build The trunion has already been riveted to the receiver. Well since it was a new trunion, the barrel pin hole has not been drilled. I did not have a drill press at the time so I took the liberty of drilling it with a regular drill. The hole is a little off. It actually about an 8th to low. Should I have someone tack up the hole and re drill or do you guys have a better alternitive? The barrel has already been pressed. Boy this one is really has been giving me problems from the get go. It's the "Global Trades" 1.6 receiver.
Thanks,
-Shadow-
Thanks,
 

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M223...sounds like you were heading in the right direction in the first place. Since your pin was already 3/4 of the way through you should have just had someone press it the rest of the way. Get a good drill chart with all sizes of drills (ie;inch,metric,letter,and numbered. What a bit measures and what size hole it drills depends on the quality of your drill. The more slop in your equipment the bigger the hole. Generally if a pin will start in a hole at all a press will finish the job. If you don't have a press most machine shop/auto shops will do it for next to nothing.
 
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