gm hydramatic > AR-15 / M-16 Retro Forum

Posted: 6/22/2013 5:18:49 PM EDT

Hello All:
I am trying to replicate the charging handle on a GM hydramatic M-16 A1 does anyone out there have measurements of the 6 little centerpunch marks on the back of the handle? I am looking for total length of all 6 dots, and maybe how far below the upper edge of the handle they are. Any info will help. Thanks in advance.

Posted: 6/23/2013 1:06:53 PM EDT

[#1]

LOL, "That's exactly what I,m talkin bout" OCD at its FINEST! Sorry, I just couldn't help myself, I don't have the answer, but I know one of our knowledgeable brothers will chime it quickly with the answer.

Posted: 6/23/2013 2:42:45 PM EDT

[#2]

Also interested

Posted: 6/23/2013 3:27:02 PM EDT

[#3]

Ill go measure the one i have.

Edit.
I swear i had one, I cant find it anywhere. Maybe im mistaken.

Posted: 6/23/2013 5:55:25 PM EDT

[#4]

I'm just holding calipers up to the dots / features and locking that measurement in for these pictures. The distance between dots is ~.100 apart when I put the tips of the caliper jaws in two adjacent holes, the holes get bigger depending on how deep they are. The grinding marks along the inner lower edge of the right hand "T" look like they are done with a dremel, but the right tip and back edge look like they are done with a belt sander with tool marks running up and down, some other "normal" charging handles (with no row of dots) look like they have sanding marks that go side to side. I don't know anyone that knows Hydra-Matic transmissions that well, but I wonder if the row of dots can be seen on some transmission parts, I've never tried to ask on an automotive forum.

ETA: The measurement I made in the 2nd photo is from the bottom edge to the bottom of the row of dots, I should have measured from the bottom edge to the center line of the dots. I will try to re-do that measurement this weekend.

Posted: 6/25/2013 9:53:32 PM EDT

[#5]

I'll re-measure the height of the (top) row of dots this weekend, I should have measured the height to the center line instead of the height to the lower edge. Here is a picture showing two rows of dots, I think it just comes down to the contour of each forging. I think my friend wound up with that charging handle so I'll have to measure both rows when I get a chance. Notice the vertical sanding marks along the back edge, I'm not sure other charging handles were sanded vertically but it could just come down to the worker's preference. (I know, I've lived through it!)

Here's a close-up of the grinding / dremel marks, look through the other pictures on the tacked GM / H&R thread for more examples.

Posted: 6/26/2013 7:29:37 AM EDT

[#6]

Dang somebob, I never realized until seeing the above pics that the dimples are actually square! Still learning something every day here......love this place.

Posted: 6/26/2013 3:45:11 PM EDT

[#7]

Mine for comparison. Hard to measure these buggers.

Posted: 6/26/2013 8:58:34 PM EDT

[#8]

Quoted:
Dang somebob, I never realized until seeing the above pics that the dimples are actually square! Still learning something every day here......love this place.

The close-ups / blow-ups from digital cameras show way more detail than I can see with my eyes, I'm starting to use my computer as a magnifying glass.

Quoted:
Mine for comparison. Hard to measure these buggers.

http://i271.photobucket.com/albums/jj149/halpark/DSC01636_zpsdccf49bf.jpg

http://i271.photobucket.com/albums/jj149/halpark/DSC01637_zps90ef4a62.jpg

That's a cool looking handle, have you tried paint stripper on it? It almost looks like there are a couple different colors of paint on that thing. Oh, do you have an upper receiver or any other gold parts to match it?

Posted: 6/27/2013 1:40:47 AM EDT

[#9]

Quoted:

Quoted:
Dang somebob, I never realized until seeing the above pics that the dimples are actually square! Still learning something every day here......love this place.

The close-ups / blow-ups from digital cameras show way more detail than I can see with my eyes, I'm starting to use my computer as a magnifying glass.

Quoted:
Mine for comparison. Hard to measure these buggers.

http://i271.photobucket.com/albums/jj149/halpark/DSC01636_zpsdccf49bf.jpg

http://i271.photobucket.com/albums/jj149/halpark/DSC01637_zps90ef4a62.jpg

That's a cool looking handle, have you tried paint stripper on it? It almost looks like there are a couple different colors of paint on that thing. Oh, do you have an upper receiver or any other gold parts to match it?

That's how I got it, I haven't tried to strip it or anything. The anodizing reminds of Dry Lube film that's on the early 20 rd. mags. It's very thin and light gray. It does appear to have gray anodizing and lighter gray dry lube on the latch. Only other gold parts I have are a slip ring. I hope I can find a gold or bronze upper, GM or not, to make a golden gun. Like yours.

Posted: 6/27/2013 2:00:22 AM EDT

[#10]

the marks you are seeing there are related to the fixture that they used to hold the part while machining. They sometimes use a fixture with little cleats on it to dig into (slightly) the forging or sand casting.

Posted: 6/27/2013 5:53:02 AM EDT

[#11]

Quoted:
the marks you are seeing there are related to the fixture that they used to hold the part while machining. They sometimes use a fixture with little cleats on it to dig into (slightly) the forging or sand casting.

I agree, I haven't spent enough time looking at Hydra-Matic transmission parts to know if those marks are common on them. I'm not as familiar with common fixtures either, do you know if a cleat that would leave a mark like that is still available? What do you think about the flat spot on the right hand side of the "T", I've never seen a raised burr / displacement swell around it.

Posted: 7/4/2013 3:59:51 PM EDT

[#12]

Here is the double row charging handle, my eyes aren't as good as they used to be. I stuck the tip(s) of the calipers in the holes and measured to the edge. For the flat spot on the side I tried measuring with the interior jaws but my eyeball-it measurement was about the same. I'll add these to the tacked thread later.

Distance from lower edge of CH to center of top row of dots is ~.291"
ETA:
Distance from the lower edge of CH to center of top row of dots is ~.291" on the 1st charging handle I measured. (I forgot to mention it was a the "other" charging handle) It looks like there are some variations in the distances, I didn't bother to measure them all, I'll do that before I add this to the tacked thread.

Posted: 7/5/2013 4:15:58 AM EDT

[#13]

Very cool. Fail on my part as I was unaware of these crazy details. So the dots were just GM identifiers then?

Posted: 7/5/2013 6:31:26 AM EDT

[#14]

Quoted:
Very cool. Fail on my part as I was unaware of these crazy details. So the dots were just GM identifiers then?

Not 100% sure, some recently upgraded Hydra-Matic rifles were all seen with them. See the tacked thread for more info.

Posted: 7/5/2013 6:58:10 AM EDT

[#15]

Quoted:
the marks you are seeing there are related to the fixture that they used to hold the part while machining. They sometimes use a fixture with little cleats on it to dig into (slightly) the forging or sand casting.

Tom, that's what comes to mind when I look at these too. I'm guessing that the clamp detail had tapered "spikes", or grippers, on it, and if they clamped square to the part it left uniform holes like what are shown on the top handle in the stack of handles. More likely, the grippers clamped up at a slight angle, leaving non-uniform holes, like most of the pictured handles show.

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