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bolt hold open and improved grip mount ear

Ask your build questions here. Welding, assembly, etc.
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TOM R
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bolt hold open and improved grip mount ear

Postby TOM R » Wed Sep 06, 2006 7:57 am

here are the pics from fjruple, his bolt hold open in both designes and the improved mount ear for pirates grip systm to allow use of the dust cover for the ejection port :D
Attachments
P9050021.jpg
grip mount
P9050021.jpg (356.85 KiB) Viewed 7510 times
P9050023.jpg
handle forward
P9050023.jpg (369.28 KiB) Viewed 7470 times
P9050020.jpg
holding open
P9050020.jpg (340.27 KiB) Viewed 7464 times
P9050019.jpg
bolt hold extended
P9050019.jpg (352.66 KiB) Viewed 7456 times
P9050018.jpg
P9050018.jpg (371.38 KiB) Viewed 7456 times
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Postby propos » Wed Sep 06, 2006 10:08 am

Very clever design for the bolt hold open. What is attached to the receiver to engage the rod in the bolt hold open device. Is a tab welded onto the receiver. My receiver has the tab for the CH stop melted away when the receiver was torched. So far I haven't welded one onto the receiver yet. Right now I'm attempting to get to the "one pull of the trigger, one shot fired" mode.

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Postby TOM R » Wed Sep 06, 2006 12:35 pm

the bolt hold is a springloaded tube similar to the other 1 for sale here but made from available parts, firuple will have to explain it, its his baby,he has no time to make em for sale but i am sure he would have no problem tellin you how to make your own :D the one on the gun you can just kit it like a bolt hold on an ar or similar and the bolt runs forward, the one he made me has no big thumb pad so you just pull back the handle to unlock and let er rip, i had been thinkin bout these designes for a long time now just don't have that engineering mindset I guess :D
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Postby propos » Wed Sep 06, 2006 1:54 pm

Tom R, I know what you mean about the engineering thing. The BHOD looks like a fairly easy thing to make. And handy to have.

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Some details about the Bolt Hold Open Device for the SA 42

Postby fjruple » Wed Sep 06, 2006 3:52 pm

Again I would like to thank Tom R. for helping me on my SA42. He did give his blood for my SA42 having cut himself twice on a small spring Without his knowledge of the semi auto conversion I would still be in the dark about some of the easy fixs and problems with getting this gun together and working. Alot of stuff on the SA42 is still in the work in progress. Tom thanks for posting the pictures. I will put the design of this hold open device for everyone to use as long its for their private use.

Items on your SA42 that you must have:

Your SA42 must have the end tab on the SA42 receiver where your charging handle enters the receiver from the rear. If you may have the tab cut or torched away you must rebuild that section of the charging handle track.


Parts needed to built hold open device:

Complete hold device for a metric based FAL (7mm in diameter). This includes the thumb tab, spring, plunger, hold open housing and a small roll pin. I order one from DPMS new and it came assembled. You can use an inch patten FAL hold device (9/32 inch in diameter) but I found that the pin in the hold open device is press fitted into the hold device and if you want to remove hold open device from your SA42 you will have to be able to disassemble the hold open device. I believe the metric is better for conversion.

You will also need the hammer spring plunger housing for a FAL. You will have to make sure that you metric for metric and inch pattern for inch pattern. The inside diameter of the plunger housing for the metric is 7mm and for the inch pattern the inside diameter is 9/32 of an inch. If you get the hold open device for FAL and hammer spring plunger housing for the appropriate inch or metric FAL you will find that the FAL hold open device will easily slide into the hammer spring plunger housing back and forth.

You will also need a 1/8 inch diameter pin about 1/2 inch long. This pin will hold the hold open device in the housing (hammer spring plunger housing) that will be TIG welded to the back of the charging handle.

Tools

1/8 drill bit
TIG welder
Dremel Motor Tools with cut off wheels

Step 1 - Modification to hammer spring plunger housing-- With a cut off wheel remove 1 1/4 inch of the hammer spring plunger housing from the OPEN end. You should have a round tube of 1 1/4 inch long with both ends open. Next drill a 1/8 inch diameter hole through the tube 1/2 inch from one of the ends of the tube. This end of the tube will be nearest to the thumb pad when assembled to the charging handle. Your hold open device housing is finished and ready for welding to the charging handle. When you weld this tube to the charging handle it pretty thin and you will have to watch for warping when you weld.

Step 2-- Modifications to FAL Hold Open Device- with a cut off wheel or grinder from the bolt notch at the top end of the FAL hold open device shorten the hold open device to 1 1/2 inches in length. Now this is IMPORTANT!! If you are using 8mm Mauser DO NOT I repeat DO NOT renotch the end of the hold open device. If you renotch the end of the hold open device as illustrated in the pictures that TOM R. posted the rear of the bolt will be inside of the 8mm Mauser feed tray. If you are shooting 7.62 NATO it does not make a difference since the front of the bolt is well behind the feed tray with the notched hold open device. If you have to assemble all of the internal parts for your new hold open device. Assemble the internal parts your hold open device.

Step 3-- Before welding may sure there is proper clearance between the new housing so that the handle on the charging handle will move and operate freely. After you have welded the hold open device housing to the charging handle make sure the hold open device moves freely through the housing. Take the 1/8 1/2 inch long drift pin and cut a notch in the middle of the pin. This pin will keep the entire hold open device in the housing and provide spring tension on the hold open device. Once assembled to the welded housing on the charging handle you should easily push in on the hold device and it should stop on the track on the charging handle.


If for any reason you have to disassemble the hold open device you will have to push the small roll in the hold open device assembly out to take off the spring tension off of the spring plunger in the hold open device which is retaining the 1/8 inch drift pin in the housing. Do not try to punch out the 1/8 drift pin with the hold open device assembled you will damage the spring plunger inside of the hold open device. Then you can remove the hold open device from the housing on the charging handle.

Total cost of parts about $20.00 Time: about one hours work not including welding.

Well that's it!! If you should have any questions please let me know.

fjruple

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Forgot Item in Step 2 of Hold Open Device

Postby fjruple » Sat Sep 09, 2006 2:32 am

All--

I was reviewing my post and realize that I forgot one small detail in Step 2 of the build process for the Hold Open Device. On the FAL Hold Open Device there is a small stud which engages the magazine follower that pushes the FAL Hold Open Device up to engage the FAL bolt to keep it open. This stud is either press fitted or sweated into the hold open device itself. Do not remove the stud itself. With a cut off just simply grind the stub that is protuding from the hold open device to being flush with the rest of the hold open device. The assembled new SA42 hold open device should easily move inside of new hold open device housing which is attached the charging handle.

Sorry, for forgeting that detail.

-fjruple

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Postby FAL_specialist » Mon Dec 11, 2006 3:03 pm

thanks for the info.
I do have a ? though.

In your instructions, you state:
Now this is IMPORTANT!! If you are using 8mm Mauser DO NOT I repeat DO NOT renotch the end of the hold open device. If you renotch the end of the hold open device as illustrated in the pictures that TOM R. posted the rear of the bolt will be inside of the 8mm Mauser feed tray. If you are shooting 7.62 NATO it does not make a difference since the front of the bolt is well behind the feed tray with the notched hold open device.

It seems this would only be true if you are using a MG2 or MG3 feed tray. The FT that came on the IO 42 kits (MG1?) is set up for 7.62, but still has the same length as a std 8mm FT. The 7.62 gate spacer is at the front which forces the belt to the rear of the FT.

Thought I should ask?
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Postby fjruple » Mon Dec 11, 2006 4:16 pm

Larry--

You are quite right about the early 7.62mm NATO feed trays (MG1?) which were of the 8mm Mauser cartridge length. The SA42 that I have has the short 7.62mm NATO (MG2?) feed tray which was converted from a regular MG42. If you have the longer 8mm Mauser length feed tray in 7.62 do not notch the shaft of the hold device as illustrate in this sticky as it will not work properly.

I have observed at least three different 7.62mm feed tray for the MG42/SA42/MG3 series of guns. I have listed them below for quick reference.

1. 7.62mm NATO feed tray which is the same length as the 8mm Mauser cartridge. The feed tray is blocked for the 7.62mm NATO cartridge. The lips for the drum have been deleted or removed. I believe the standard 8mm Mauser top cover is used. Is this a MG1 or MG42/59?

2. 7.62mm NATO feed tray which shorten for the 7.62mm NATO cartridge. The feed tray has the same lips for a drum as the 8mm mauser but the 8mm mauser drum will not fit as it is too large. Has anyone seen one of these drums for this 7.62mm NATO feed tray? This feed tray takes the same top cover as the MG3.

3. 7.62mm NATO feed tray which is designed to take the M13 Links as well as the belts. A special MG3 type drum is designed for this feed tray and is not interchangeable with the other drums or feed trays. This feed tray uses the MG3 top cover.

--fjruple

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Postby drooling idiot » Mon Dec 11, 2006 7:03 pm

MG59 is a yugo copy of the MG42 also in 8MM with minor changes, but no changes to the feedtray.
feedtray info found at this link
and a picture of a MG2 drum can be found here
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Postby fjruple » Tue Dec 12, 2006 3:27 am

drooling idiot--

Thanks. That helps clarify a lot of interests for me.

--fjruple

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Re: bolt hold open and improved grip mount ear

Postby reb62 » Sun Oct 21, 2007 11:37 pm

Do these pics still exist of the bolt hold open design somewhere here in the site? I can't seem to view the pics that were on this topic. Perhaps the age of the topic has expired. Don't know.

Thanks.

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Re: bolt hold open and improved grip mount ear

Postby Orion Arms » Mon Oct 22, 2007 12:52 pm

having trouble viewing the pics as well.
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Re: bolt hold open and improved grip mount ear

Postby Bil » Mon Oct 22, 2007 2:25 pm

A lot of the pictures went away when we changed servers recently-some computer thing I know nothing about.If anyone saved the pics on their home computer or if you are the original poster,let us know and we can get them back up. Thanks. ---bil
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Re: bolt hold open and improved grip mount ear

Postby fjruple » Mon Oct 22, 2007 2:46 pm

Tom R took the pictures with his digital camera I don't know if he still has them. Unfortunately, I have my SA Receiver out being engraved and should have it back shortly. Once I get it back I will take new pics and send the new pics to the moderator for reposting.

--fjruple

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Re: bolt hold open and improved grip mount ear

Postby fjruple » Tue Oct 23, 2007 4:09 pm

All--

Attached are the photos that were lost for this sticky

Enjoy

--fjruple
Attachments
p9050023_351.jpg
p9050021_326.jpg
p9050020_118.jpg
p9050019_799.jpg
p9050018_418.jpg

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Re: bolt hold open and improved grip mount ear

Postby reb62 » Tue Oct 23, 2007 11:23 pm

Thanks fjruple,

Sometimes you just feel a little lazy and like picture books.......lol.....I now have new food for thought. :D

reb

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Re: bolt hold open and improved grip mount ear

Postby Blademaster » Mon Nov 19, 2007 9:30 am

Here is how I did it.
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Re: bolt hold open and improved grip mount ear

Postby fjruple » Mon Nov 19, 2007 3:55 pm

Blademaster--

Looks good and it works!!

--fjruple

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Re: bolt hold open and improved grip mount ear

Postby Blademaster » Mon Nov 19, 2007 5:05 pm

I later went back and added a small tab on the back of the charging handle to help release it. It is very easy to operate with the thumb. So the way it is set up it holds the bolt back with alot on tension. When you release it there is no problem getting a round out of the belt. Just like the orginal. Plus I like the fact that you can just pull it back and it will hold the bolt back for barrel changes. Some thing that the BRP is missing. Along with a working dustcover.
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Re: bolt hold open and improved grip mount ear

Postby usmc8488 » Mon Jun 16, 2014 12:35 pm

Can someone please re-post these photos..

Thanks


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