tuning for a lighter load

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tuning for a lighter load

Post by Lightfoot on Wed Feb 08, 2017 4:01 pm

Howdy!

I'm helping my brother in law get started in Bullseye.  I took his new Colt G.I. gun at Christmas and had my local Smith add a rail and do a trigger job. (Factory Colt is about as bad as I've ever felt, but that is another topic)  I dropped in a 10 lb spring and added an Ultradot and took it to the range today.  The load I use for practice is a 185 coated swc with 4.1 gr of Bullseye.  This load works well in any other gun I've tried so far and my gun will function as low as 3.5.  His gun won't eject reliably and when it does it stovepipes and jams.  

I'm thinking about going to a 19 lb mainspring.  Also wondering about the firing pin stop.  It has a well radiused stop now, I'm wondering if a tighter radius would help or hurt.  I don't like the idea of going to a 8 lb spring, it seems to cause the slide to lag and not go into battery so well in my previous experiments on another gun.

Thanks for the help!

Lightfoot

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Re: tuning for a lighter load

Post by Jon Eulette on Wed Feb 08, 2017 6:47 pm

10# spring is more than likely too light for 4.1 gr charge. Probably issues with ejector/extractor or magazine. Squared firing pin stop will make it worse. 
Jon

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Re: tuning for a lighter load

Post by Lightfoot on Wed Feb 08, 2017 6:52 pm

Thanks Jon!

It feels in the hand like the slide is not fully retracting.  That's my thought on the light spring.  What about the main spring?  Would that be the solution?  My son's R/O is set up just like this Colt but with a 19 b m.s. and it runs with the 4.1. Both have the same Ultradot.

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Re: tuning for a lighter load

Post by DavidR on Wed Feb 08, 2017 7:01 pm

10# or even a 11 should be fine, load should function fine too, i would change out the mspring to a 19#, then id make sure the slide is well oiled, fps wont make any difference. It should funtion fine if set up like this mine do, unless there is issues with extractor or ejector.

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Re: tuning for a lighter load

Post by Ghillieman on Wed Feb 08, 2017 7:04 pm

If the Colt G.I. gun has a larger chamber as compared to your other match (tighter) chambers, you could be witnessing the effect of Boyle's law. Boyle's law- The pressure of a gas, while at the same temperature, will act inversely to the volume of which its contained.
So larger chamber equates to a lower gas pressure, and a smaller chamber equates to a higher gas pressure.
The easiest fix would be to up the charge on the loads for the Colt G.I., or you could install a Kart with a tighter chamber and hopefully all use the same load.

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Re: tuning for a lighter load

Post by jglenn21 on Wed Feb 08, 2017 7:07 pm

19 lb mainspring should help a bit
 All I run in any std 1911

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Re: tuning for a lighter load

Post by Lightfoot on Wed Feb 08, 2017 7:28 pm

Ghillieman wrote:If the Colt G.I. gun has a larger chamber as compared to your other match (tighter) chambers, you could be witnessing the effect of Boyle's law. Boyle's law- The pressure of a gas, while at the same temperature, will act inversely to the volume of which its contained.
So larger chamber equates to a lower gas pressure, and a smaller chamber equates to a higher gas pressure.
The easiest fix would be to up the charge on the loads for the Colt G.I., or you could install a Kart with a tighter chamber and hopefully all use the same load.

Boyle's law....Dan, I didn't pick you as a scientist!  Lol  See you in Terrell in a couple of weeks.  I'm bringing my dad, son, bro in law, and an employee too.  At least that's the plan.

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Re: tuning for a lighter load

Post by bmize1 on Wed Feb 08, 2017 8:20 pm

After fooling with one for a friend for a few days, I decided the ejector was the culprit. 
I changed springs(both), OAL, crimp, mags.
I got it to finally function 95% of the time, but would usually leave the last case laying on top of the mag with the slide locked back. 
Told him to sell it and buy a RO. He's much happier now

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Re: tuning for a lighter load

Post by BE Mike on Thu Feb 09, 2017 10:02 am

I'll just reiterate what others have said. It could be that the extractor needs tuning. That was a problem I had when going from a BoMar rib to a slide mounted Ultra Dot.

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Re: tuning for a lighter load

Post by Lightfoot on Wed Feb 15, 2017 1:28 pm

Quick update.  Extractor was very loose.  I tightened it.  Borrowed a 19 lb ms to go along with the 10lb recoil spring.  Loaded 4.8 gr B.E. under 185 swc.  Got about 90% function.  Brass landed on my hand once.  Last casing left laying on the top of magazine.  Funny thing though, the 4.8 load should have felt snappy.  It didn't, it was soft.   I'm going to try 5.0 next and see if that runs better.

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Re: tuning for a lighter load

Post by JKR on Wed Feb 15, 2017 1:55 pm

Being a GI model, does it have the short GI type ejector?

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Re: tuning for a lighter load

Post by Lightfoot on Wed Feb 15, 2017 3:48 pm

Yes I do believe its a short ejector.  Maybe this is the problem?

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