Author Topic: Bolt mod or "Drop Free" bolt modification.  (Read 49626 times)

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czgunner

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Bolt mod or "Drop Free" bolt modification.
« on: January 16, 2007, 01:17:07 AM »
Anybody try to modify a bolt carrier so that mags can be inserted/removed w/out the bolt open? Is it possible.



 **Edit: There seems to be renewed interest in this mod since the advent of the Tapco 20rd mag,
             so I moved this to the top and made it a sticky .  :)

             Remember, All 922(r) laws apply. ;)

BB
« Last Edit: April 25, 2008, 08:50:49 PM by BillyBang »

cvasqu03

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #1 on: January 16, 2007, 03:17:44 AM »
There is no need to modify the bolt carrier at all.  You do, however need to modify the bolt itself by removing the extentions that slip under the feed lips of the mag and mechanically lock it into the magazine.  Basically, you have to make it match the bolt on an SKS-M, Many people have successfully done it. I'd recommend starting with a Dremel tool and finishing up with a file.

Heres' a picture of one I did.  The bolt to the left is an unmodified SKS bolt.  The middle is the one I modified, and the one to the right is the bolt from an SKS-M.  The one in the middle is kind of hard to see becasuse it was very shiny so it kept reflecting everything, but you should be able to get the idea from this picture. You don't have to go back as far as they did on the SKS-M either. 

This mod is relatively safe and will even allow you to continue using the standard fixed magazine.  Just don't damage the bolt face.

« Last Edit: January 16, 2007, 03:19:27 AM by cvasqu03 »
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Lollygagger

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #2 on: January 16, 2007, 06:11:32 AM »
Some more pics, bottom one is modified...





Lollygagger  :?

P.S -FWIW, this duplicates the bolts in the SKS "D"/"M" firearms.

Lollygagger

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #3 on: January 16, 2007, 06:32:32 AM »
Here is a pic thru the mag well ("cleaned up") of one modified...



Note that the modified bolt is narrowed in width for almost the full length of the mag well opening, just starting to "flare" towards the original wide width before it is covered at it's rear by the action.

This is what is required in order to gain a ability to use a detachable mag that CAN BE PLACED/REMOVED IN ANY CONDITION (loaded or unloaded) -as with anyother modern detachable magazine accepting weapon.

This is major SKS magic that I can't understand why anyone capable would not do, except the most dyed in the wool "purist" types. I would not use detachables without doing do, as w/o such, they are a PITA & have less reliability ('cause they get their flimsey selves bashed around too much in use).

Since it has no effect on use of the standard factory 10 round fixed box mag -it all come under the "Why not...duh!" catagory. Of course, screwing the bolt up if not done with care *is* not good.

Lollygagger  :?
« Last Edit: January 16, 2007, 06:44:26 AM by Lollygagger »

Lollygagger

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #4 on: January 16, 2007, 11:02:01 AM »
Damn Lollygagger, you really took a mill to that bolt.  I assume you used more than just a file right?

A file takes too long by itself...

I used a bench grinder with a fine wheel (with care!) to rough it out -and finish with a Dremel & stone, file & polish wheel on the Dremel with diamond grit (great stuff, but major danger to the eyes).

While maybe not required, I pretty well profile them to the ones in my SKS "D"/"M" firearms. I doubt that the "step" made on the bolts underside is actually needed for use in a standard SKS (does not hurt).

Lollygagger  :?


Lollygagger

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #5 on: February 28, 2007, 07:34:42 PM »
Ha! The SKS bolt mod EVILNESS grows!



Who will save you now, SKS "purists"?

Lollygagger  :lol:

Lollygagger

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #6 on: March 21, 2007, 03:31:53 AM »
One thing I'm wondering about this bolt mod. Do you need to reharden the bolt ?


No.

LG  :?

Trev

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #7 on: February 22, 2008, 07:59:04 PM »
I went ahead and did mine last night with a dermal tool.  Went slow and it only took me 20 minuets to finish.  I would definitely not hesitate to do this modification again.   

  Now, I have an unknown brand five round magazine and everywhere from 3 rounds to empty it works fantastically.  The forth and fifth rounds on the other hand are no goes with the bolt shut.  Has anyone tried this mod with the five round Tapco magazines?   People say the Tapco 20 rounders work fine butt I really prefer the looks of the smaller five round magazines.  I really donít want to relive the bottom of the bolt if I donít have to.


(Click on pic's to make bigger)
Before


After


The black bolt is the modified one
 

PS: If anyone wants more pics just let me know.

                                            Trev


                                       
« Last Edit: February 22, 2008, 08:05:52 PM by Trev »

milsurpcop

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #8 on: April 07, 2008, 11:38:09 PM »
Ok, I did it today.  Fortunately I have an M so I had a perfect template to go by.  I took my time and would remove a little, reassemble and test.  Remove a little more....ect. you get the picture.  I didn't remove as much as others have in the pics I've seen.  I used a dremmel with the conical stone & cutting oil.  I tried the sanding wheel as others used, but it didn't seem to work well for me.  I did try my bench grinder, but I didn't seem to have the control I wanted.  It took me about an hour, but I'm pleased with the results.  When I finished with the grinding, I used 600 grit sandpaper and polished it up.  I then used a polishing wheel w/compound with the dremmel and shined it up.  I didn't remove material from the bottom, but I did lightly polish it with the polishing wheel.  In the pics the M bolt is on top and the modified Chinese is on the bottom.  The last pic shows the bottom view, the modified bolt is more even than it looks, must be the camera angle.  I may take another look at it and see if it needs a little evening up. 



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Sabre

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #9 on: April 08, 2008, 08:56:37 AM »
Thanks to LG I did mine. It was no problem and works great with the TAPCO mag.

{broken pic links removed BB/Mod}
« Last Edit: January 16, 2009, 06:01:17 PM by BillyBang »

BillyBang

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Re: Bolt mod or "Drop Free" bolt modification.
« Reply #10 on: January 30, 2009, 01:23:37 PM »
I'll post this pic up here for a while (best my cam can do).
Hope it helps to explain what is done to make a standard bolt "Drop Free".

Note on the extractor side (left pic), the ledge ground flush to the bottom of the "slot" (slight trace of ledge left on mine).
The other side is ground down an equal amount but the slot is deeper so you still have some slot/ledge left.
Only the side ledges are ground on this one, none is taken off the bottom of the bolt.
If you want clearance for that "last round" for a detachable,
I would look at trimming the follower, not the bolt. IMHO.

{pic removed}


BB
« Last Edit: April 07, 2010, 07:40:27 PM by BillyBang »

Midknightrider1

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Drop Free Bolt Mod Tutorial In Detail
« Reply #11 on: August 16, 2013, 02:29:05 PM »
This tutorial will explain step by step how modify your stock SKS bolt and allow you to insert and remove a detachable magazine without having the gun out of battery (bolt and carrier in the rear position). This modification will not have any negative effects on your rifle except diminishing the value of a matching numbers gun. If your numbers match or you want this done professionally just buy a Tapco replacement bolt without the steps and be sure to have it head-spaced before you shoot. The SKS D/M models were manufactured with these modified bolts. If your unsure on how much to take off on the side of the bolt with the chamfer, I posted a pic down below.

First step is to break down your gun to remove the bolt. Take the top cover off, remove spring and pull the bolt carrier backwards and up. With the gun pointing downward  the bolt should be hanging under the carrier. Now that you have your bolt removed go ahead and remove the firing pin by punching out the retaining pin, then remove the extractor. I left my extractor spring in because it was stuck but if you can remove yours then go ahead. Removing these parts off the bolt will save you money if you happen to slip and hit them. Now's a good time to clean your firing pin and it's home, the hole it resides in. Cleaning this will prevent slam fires. There's really no need to buy a spring loaded firing pin if you keep yours clean.

Now here's where you have several options as to how you remove the lips or ledges on the bolt. You can use either a angle grinder secured with clamps to your work table or a dremel with the bolt secured. If you use the angle grinder, have the side handle installed so you can rest your hands on it while removing the material. Also I would buy a new ľin. wide fine and course grinding wheel or stone so you have a nice flat edge on it. If you use a dremel, set up something to rest your hands on so you can be comfortable and not shaky. If your going with a grinder use the 1/4in edge of the wheel.

Start with the course wheel or stone and remove the ledges at the bolt face end first. Make sure you keep an eye on the angle of the material left over. You'll be surprised how easy it is to get a bad angle going on your cut. Also don't get the bolt too hot when grinding. This will change the properties of the metal and possibly weaken it. If it gets hot then just take a break and come back to it in about 5 minutes.  Work your way back leaving about 1/32in. of material for you to finish with the fine wheel. A easy way to get a straight line when grinding is to move the bolt left to right or the dremel and keep going back and forth instead of grinding one area at a time. When you get to the rear of the bolt where the lip disappears you'll want to make sure you remove the ledge entirely but don't cut to far  into the area without a lip. If you don't remove that lip entirely at the back your mags are going to catch on it.

Switch over to a fine wheel or stone when your done removing the majority of the lips. Once you have a nice flat smooth surface that's flush with the unaltered area you'll need to bevel the bottom edge with the fine wheel or file at a 45 degree angle just enough to remove that sharp edge. Don't worry about removing too much as long as that beveled surface is no wider than 3/32in. After that take the fine file and round the new edges you just created. And then run the file along the bottom of the bolt to be sure there is no burrs left over. You now have completed the mod. Just oil everything (don't forget the firing pins home) the way you like it and reinstall everything. You can polish the bolt up if you want but it's not necessary. A unpolished surface holds oil better than a polished one.  Enjoy removing your mags without the hassle.


« Last Edit: August 22, 2013, 08:13:07 PM by Midknightrider1 »
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dalaitom

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Re: Drop Free Bolt Mod Tutorial In Detail
« Reply #12 on: August 16, 2013, 02:51:54 PM »
I think it would be good to point out to not try and remove material too fast .  The bolt could get so hot it would remove the temper.

I've done a couple of these and always had trouble with controlling the angle grinder. I like your idea of securing the angle grinder to the bench.
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Midknightrider1

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Re: Drop Free Bolt Mod Tutorial In Detail
« Reply #13 on: August 16, 2013, 03:07:32 PM »
Thanks your absolutely correct. I thought I was forgetting something and that was it. :doh:
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