Cocking Piece Question

02 October 2007, 19:27

Here's something odd I'd like to have the collective take a stab at.

On my Mark X, when the cocking piece runs dry of oil or grease it locks the bolt up tight enough that you have to hammer it open. This happens regardless of a cartridge being chambered or just dry-firing.

Put a dab of grease, a drop of oil, or even just put a coat of cold-blue on the cocking piece and cam and it'll work, heavy as sin, but it works.

Any ideas what might be causing it, and any other solutions than keep it greased?

02 October 2007, 20:04

Westpac

Sounds like the tolerances could be a little tight between the bolt shroud and cocking piece. Could also be a problem associated with the firing pin and how it and the cocking piece are aligned with the shroud. Pull it down and have a look.

Look also at the nose of the cocking piece and the cocking notch itself to make sure they are smooth so as to avoid dragging as the cocking piece rides up the notch. There is a lot of metal moving in contact with each other when you lift the bolt handle after dropping the firing pin, so look every piece of the puzzle over really good and pay particular attention to those areas where there are heavy rub marks present. Grease makes things move easier and with less friction so when you find the problem and make it smooth, use a little grease to keep it moving.

02 October 2007, 20:13

jeffeosso

did you adjust the trigger? sounds like you might have adjusted the sear travel

opinions vary band of bubbas and STC hunting Club

Information on Ammoguide about
the416AR, 458AR, 470AR, 500AR
What is an AR round? Case Drawings 416-458-470AR and 500AR.
476AR,
http://www.weaponsmith.com

02 October 2007, 20:58

tsturm

quote:
Originally posted by jeffeosso:
did you adjust the trigger? sounds like you might have adjusted the sear travel

02 October 2007, 20:58

SuperMidget

Jeffe,

The problem exists with the factory trigger/factory sleeve, factory trigger/military sleeve, new timney trigger/factory sleeve, new timney trigger/military sleeve.

Now this is not to say that either the new timney trigger or the original factory trigger are in fact adjusted correctly, so maybe that is an avenue to try. With the new trigger I've adjusted it to reduce overtravel and that's about it for the moment.

Keep the ideas coming, I really appreciate it.

02 October 2007, 21:14

jeffeosso

here's the instructions for a timney trigger
http://www.timneytriggers.com/InstallInstructions/F%20&%20FD%20Mauser.pdf

02 October 2007, 21:31

SuperMidget

I'll give that a shot when I get home from work this evening.

03 October 2007, 02:56

MKane160

Have you had a bolt handle welded on? If so, the cocking cam may have gotten annealed and the cocking piece is trying to gall the cam. Jack Belk described this several years ago...

MKane160

03 October 2007, 05:19

1 Shot Hunter

Is the bottom surface of the cocking piece perfectly flat, behind where it contacts the sear?

I swapped mine for a Mod 98 cocking piece and had to fill the "98 notch" with epoxy. With the notch, it sort of did what you're describing and I had to squeeze the trigger to open the bolt.

03 October 2007, 05:25

Rojelio

Take the trigger completely out and then see if the bolt handle is still hard to raise. If it is, you know it is not the cocking piece/trigger relationship. It would then be the cocking piece/bolt relationship. Process of elimination.

Rojelio

03 October 2007, 05:49

D Humbarger

There is something else to look at that no one has mentioned. The surface of the nose of the cocking piece & the surface of the angled mating surface at the rear of the bolt both need to be as smooth & as hard as glass.

03 October 2007, 06:12

rem721

quote:
Originally posted by D Humbarger:
There is something else to look at that no one has mentioned. The surface of the nose of the cocking piece & the surface of the angled mating surface at the rear of the bolt both need to be as smooth & as hard as glass.

If they are not, how do you fix them Doug?

03 October 2007, 07:32

Westpac

quote:
Originally posted by D Humbarger:
There is something else to look at that no one has mentioned. The surface of the nose of the cocking piece & the surface of the angled mating surface at the rear of the bolt both need to be as smooth & as hard as glass.

quote:
Originally posted by Westpac:
Look also at the nose of the cocking piece and the cocking notch itself to make sure they are smooth so as to avoid dragging as the cocking piece rides up the notch.

03 October 2007, 07:32

D Humbarger

Heat cherry red then quinch in oil.

03 October 2007, 08:12

rem721

quote:
Originally posted by D Humbarger:
Heat cherry red then quinch in oil.

Thanks Doug but what I should have asked was if the surfaces aren't smooth, how do you correct them. The surfaces are helixes.

03 October 2007, 19:29

SuperMidget

Ok, quick update. Before I started monkeying with the trigger, I took the trigger out and let the cocking piece fall when I dropped the safety. Lo and behold, same problem.

I did take a bit of 600 grit wet/dry sandpaper to it to remove some machine marks, now it looks slick and shiny, but it's still hard to lift.

Another thought I had was to find a weaker spring, and put some lapping compound on the two pieces and lap them together a bit.

As for hardening, can that be done with a blue-bottle propane torch or do I have to try and find some form of real torch? Also the oil used, that is a vegetable type oil, yes?

Keep the help coming, I'm learning a huge amount just buggering this whole thing up. =)

03 October 2007, 19:43

Westpac

quote:
Originally posted by SuperMidget:

As for hardening, can that be done with a blue-bottle propane torch or do I have to try and find some form of real torch?

No you need real heat, Oxy Acetylene at least. You need "control" when spot hardening the ramp of the notch. If you can't concentrate the heat to one spot then you risk damaging the surrounding areas.

You need to carefully play the tip of a neutral flame on the ramp of the notch until it begins to turn red and then immediately quench it in a light to medium weight oil. I use machine oil like Mobile Vactra, but some folks use a low viscosity engine oil. The important thing is how you quench it. For a thorough quench, you should move the part through the quench in a figure 8 pattern. This steady movement keeps bubbles from clinging to the surface. Merely dunking the piece won't do much in the way of cooling because the bubbles that form on the hot surface tends to hold heat. You shouldn't need to draw the part beyond this.

03 October 2007, 22:09

Atkinson

Pull the cocking piece and firing pin etc. out of the bolt body...you will see a rather large notch in the end of it by the bolt handle. It is the camming notch..polish this, then heat it cherry red and quinch it in water or quinch liquid then polish again..

That should fix the problem. If your not so inclined then better to have a gunsmith do the work. It is not an expensive operation.

Westpaks description above is a better scenario than mine. I did not read his post until after I had posted..