[MG34_Dan]

I just tried to mount my 1928 Colt, Group Industries side plate, MG on a restored 1928/M35 tripod and the front cross pin won't go through the MG front mounting hole. But the rear cross pin fits nicely. The front cross pin is mirror smooth with no burrs and fits the tripod perfectly. I ran a caliper down its entire length and the diameter never wavers. My MG will mount correctly on a 1917A1 tripod. A 9/16" drill bit fits the M35 tripod holes and the MG front mounting hole. The cross pin can be inserted about 1/4" and then it jams. The same jam position occurs on both the right and left sides. The jam seems to be within the trunion area. Has anyone else encountered this problem? How do I polish out/ream front mounting hole? Any other suggestions would be appreciated.

 

[PKw VI Tiger1]

My guess would be that either the hole through the trunnion is not straight or the pin is bent. I'd first try inserting the front pin before the back in case it has anything to do with alignment.

 

[dghattierdc]

Could the trunnion be sleeved? I have that issue with a 1917 repro and have not drilled it out yet.

 

[MG34_Dan]

I already checked the front pin to make sure it is straight.

It is perfectly straight. I cannot insert the pin even when the gun is not on the mount. It is just sitting on the floor next to the collapsed mount. What confuses me is that the trunion forward is from an Argentina 1928 Colt and the M35 tripod is a restored one from Argentina too. How one earth did it ever fit? Maybe the trunion was squashed slightly when the MG was rebuilt with the Group Indistries side plate.

 

[MG34_Dan]

The trunion doesn't appear to be sleaved.

All I see is brass.

 

[MG34_Dan]

I just bought a small engine cylinder hone on eBay.

I think it should work as it will handle bores of between 1/2" and 2 3/4." The total with shipping for it was $20. Not too bad. The diameter of the front pin is exactly .568" which works to between 36/64" and 37/64". What a PIA this is problem is! It just goes to show how the smallest thing can shut things down. Who would have ever thought?

 

[Lucky#13]

9/16 is .5625, and bear in mind that most drills are a bit undersized. With your pin measuring .568, I think it is indeed a clearance issue through the trunnion. If you have access to a 9/16 reamer, that might make the difference, but you can do the same with that hone I expect. Just go carefully.

 

[MG34_Dan]

I'll go verrrrrrrrrrrrrrrrry slow.

I'll post the results after I finish.

 

[jmann]

Dan, I got my ends mixed up when we were talking earlier, I thought it was the rear pin you were referring to. I have had this happen before after guns were rebuilt. Often a 9/16 drill bit run through thr hole will fix the problem. Usgi uses bolts instead of finely machined pieces of steel (notice the intentional colt snobbery) so the gi pintle bolt will pass through a gun that a true pin will not. I did a post sample at last creek when I left my bolt at home, I bought one of the quick release pins numrich had and to get it to go through the gun I had to run a 9/16 bit through it. I turned the bit with vice grips, so it doesnt take much.
Good Luck

 

[ohioblacksheep]

Dan,

From what I'm reading here, you have a PIN problem, not a tripod or trunion problem..If you have a 9/16 bolt or pin, try that and see if it works before you open up your trunion and tripod to an out of spec pin....

Remember, not all those 28 tripods were made by Colt, Arg built them also, and of course they probibly made the replacement pins too....Lou

 

[oprod]

pin prob

I too lean toward pin prob or slightly undersized / offset pintal pad. Put a straight edge along side your pin. If straight then run the correct size drill through the front hole.

 

[MG34_Dan]

I already tried a 9/16" drill bit and it goes through just fine.

As I said before, my MG mounts just fine on a 1917A1 tripod. The USGI 9/16" pintel bolt goes through nicely.
As for the M35 tripod setup, if I turn the cross pin down then I will need to install bushings in the tripod for the thinner pin.
Can anyone out there with an M35 tripod take some measurements of the front cross pin? I do not think my cross pin is out of spec, but who knows?

 

[ohioblacksheep]

Dan,

I had a cross pin out of a 28 pod laying on a table at the shop and gave it a quick measure, and it was .562....Lou

 

[amish-bob]

From my experience rebuilding nearly 200 of those tripods, I have run into pins that would NOT interchange between tripods. That leads me to believe that some pins were a larger diameter than others. I'm not a machinist but I believe the machinists technical term was "snowflakes". If it were my tripod, I'd alter the pin to fit the trunnion. I feel that the smartest move is to modify the cheapest part.

Also, you might be able to get another front pin from Ordnance Research. I know we have some....I just don't know Curt's views on selling them. These were newly manufactured pins for these tripods. You can call Curt at 717.738.6941 roughly 9-5 eastern time.

amish-bob

 

[MG34_Dan]

Success! And it only cost me 20 bucks.

The small cylinder hone worked perfectly. The inside of the front mounting hole is now perfectly straight and mirror smooth. The stones on the hone were very soft and extra fine. The residue was like talcum powder. After watching the hone do its thing you could see exactly where the tight spots were. The exact center of the brass trunion and the inside edges of the bottom plate mounting holes were the problem areas.

 

[jmann]

Glad it worked out Dan. Sometimes the brass trunions get squeezed slightly when bucking the big front rivets. So I assume she mounts up good and tight now?

 

[MG34_Dan]

Yes, everything locks up tight.

And the whole setup looks correct on the M35 tripod and connected to a commercial water chest. On another note, it doesn't appear that the MG has ever been fired. The inside of the flash hider is clean as a whistle. and there is no carbon residue anywhere.