NM Super Blackhawk lockup - Pistolsmith
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Old 03-07-2011, 06:45 AM   #1
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NM Super Blackhawk lockup

I have a .44 Mag New Model Super Blackhawk (late 1980s vintage, I think)that has an annoying problem.

It appears machanically sound inside and out, and functions just fine when I'm not actually shooting it.

When I'm shooting, it's a tackdriver and plenty of fun -- until it gets heated up -- maybe two cylinders of .44 Special or Mag -- and then it gets very difficult to cock. It gets bad enough that I'm having to use significant effort to pull the hammer back to full cock.

I have checked the basepin and it's not moving under recoil.

Any ideas what's going on with my gun?

Thanks

JP
 
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Old 03-07-2011, 09:26 AM   #2
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The base pin may be moving just enough to cause a problem without you noticing it.
The spring-loaded rear tip of the pin keeps the transfer bar in position. If it moves forward...such as when the pin moves forward under recoil or when it's been removed from the gun...the transfer bar usually gets trapped under the firing pin and brings the whole works to a halt.

Or...Maybe the little spring that drives the tip gets hot and binds in the pin.

Try pressing on the base pin when it starts to bind up and see if it makes a difference. Check the spring loaded tip when it's hot. May be that a blast of carb cleaner will set it right.

Another possibility is that the base pin itself is bent slightly, and gets into a bind when the cylinder heats up. Remove it...clean it...dry it...and roll it on a piece of glass to see if it rolls true or goed clickety-click. If it's the latter...it's bent.

Last edited by JohnnyT; 03-07-2011 at 09:28 AM.
 
Old 03-07-2011, 01:58 PM   #3
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Thanks JohnnyT, let me take these in order

Base pin jump was my first thought, however when I experienced the binding I would reach forward and pull back on the base pin head to re-seat the pin -- but it wouldn't move, and nothing freed up. It appeared visually to be fully seated.

I took out the base pin and did a "roll test" to check for straightness -- I don't have a pane of glass handy but I tried some pretty flat surfaces and there is no noticeable bend or irregularity -- it rolls just like it's straight.

The plunger at the transfer-bar end of the base pin sounds interesting. I don't notice any binding in it, but have thoroughly cleaned and lightly relubricated. If the pin isn't jumping, then that plunger's length might be the source of the trouble. If it's too short it will cause binding.

Maybe when the gun heats up the original plunger isn't long enough to do its job anymore.

At this point, I'm thinking of installing a Belt Mountain pin just to take pin jump out of the equation. I've heard enough good things about Belt Mountain products that this should also take the out-of-spec plunger issue out of the equation, too.

Then we'll see.

Thanks for your input.

JP
 
 
Old 03-07-2011, 02:16 PM   #4
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One way to know if the transfer bar isn't clearing the firing pin is to get the gun to malfunction, and watch it as you try to cock the hammer. You should be able to see the transfer bar as it catches on the pin.

The Belt Mountain pins are top quality parts that are well worth the price. The possible issue is that it's a little larger in diameter and tightens up the cylinder side play...but if the hole in the cylinder or the frame isn't bored dead straight...it can cause things to bind up. You may find that you'll have to reduce the pin's diameter by a couple thousandths. The best way is to chuck it up in a lathe and spin it at 1500 rpms or so, and touch it lightly with a smooth mill file in the area that the cylinder rides on it.
 
Old 03-07-2011, 03:10 PM   #5
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Are you using reloads? If not mechanical, check for primer setback or headspace.
 
Old 03-07-2011, 04:38 PM   #6
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Thanks, Sarge

I am shooting reloads. I have been using .44 Special-level and low-.44 Mag level (1100 fps) loads, all loaded in .44 Mag brass. There's not a lot of power here. Primer setback is unlikely, I think. I also think I know that my reloads are in spec. There are no signs of excess pressure.

Basically, when this pistol gets hot, it's hard to index, whether the cylinder is loaded or not. Keep in mind that it starts fine, but begins to bind up after ~12 rounds.

FWIW, my feeling is it's some kind of lockwork problem.

I'm thinking of calling Ruger and finding out if they'll help me out with this by sending a replacement base pin. I'm also wondering about the spec on the transfer bar. I'm not the original buyer but maybe I can learn something by calling them...

Thanks Sarge and JohnnyT

JP
 
Old 03-09-2011, 03:34 AM   #7
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IS the flashgap normal when hot?
 
Old 03-09-2011, 07:23 AM   #8
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I think you found it

Thanks, retDAC

By "flashgap" do you mean the barrel-cylinder gap?

Interesting question!

I don't have feeler gauges but when I hold the barrel-cylinder gap up against a strong light I see 1) what looks like a VERY tight fit (it's kind of difficult to find the gap) and 2) the gap is not uniform, that is light shines through more toward the top of the gap, and not at all near the bottom.

I also note on the rear face of the barrel (the part closest to the front of the cylinder) there is some wear evident evident from 3:30 to 4:30 o'clock.

The front face of the cylinder shows wear below the horizontal midline of each chamber. Though the wear is uneven, it matches up with the wear on the rear face of the barrel.

So these two parts are making at least enough contact to scrape the bluing off, and score some of the surface slightly!

This looks like the culprit. Thanks for the steer, retDAC.

Any suggestions how I proceed to fix the problem? Send it back to Ruger?

JP
 
Old 03-09-2011, 07:46 AM   #9
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In other words the forcing cone is contacting the front cylinder face? Is that what your saying?
 
Old 03-09-2011, 08:24 AM   #10
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Yes. In a nutshell.

I didn't see the extent of the wear in that area until I worked on it for a while with a lead-away cloth...

Last edited by KellyHopkinsville; 03-09-2011 at 09:40 AM. Reason: follow-up
 
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