tuning for a lighter load

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!

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

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.

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.

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.

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

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.

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

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.

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.

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

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

that's a way too light of a spring for that load. I have a long slide Clark with a slide mounted UltraDot. On the long line I shoot 180 jacketed with 4.6 of Bullseye and I'm using a 16lb spring. No ejection probs at all. It does sound like u need an extended ejector. Short line 4.0 Bullseye with a lead 200gr 68 bullet. Something not right

Update:  I had my local smith work it over.  He filed the extractor and polished the hook to give it a fuller bite, added an extended ejector, and lowered the port.  Now with 10lb spring it functions well with 3.8 B.E./200 gr swc.   Charged me $81.00 which I thought was more than fair.

Still a bit light on the spring. I feel you might be hammering the barrel link and frame. Use a shock buff if you don't want to damage anything. Try a Wolf 12lb. Recoil wont be as whippy

tenx9 wrote:Still a bit light on the spring. I feel you might be hammering the barrel link and frame. Use a shock buff if you don't want to damage anything. Try a Wolf 12lb. Recoil wont be as whippy

Not to argue with you, but I think a lot of folks use 10 lb with slide mount dots at similar loads.   I'd be interested to hear from others.   It  might sure work with a 12lb, maybe I'll try it.

 I couldn't get my son's gun to run well until we got down to 10 lbs, it would stove pipe.  I might look at tightening the extractor though.  It's tight enough to hold a round, but not nearly as tight as the Colt came back from the smith with.  He has to run higher loads currently.  Maybe that would fix it and we could up the spring.  Currently the slide is slow, I can almost feel it move back into battery in slow motion.

My stainless RO with slide mounted dot functions very well with 10lb recoil, 19lb hammer, and 6lb mag springs shooting 3.8 BE/185 LSWC.  You do need to keep it clean and oiled, but not obsessively so.

It initially did not perform with a 10lb spring and needed a slightly heavier recoil spring.  You know why it functions well with that spring set now?  I took out that damn shock-buff that was causing the slide to lose too much energy when cycling.   The gun feels great when shooting and cycling now, and simply functions better with the buffer out.

The lighter mag and hammer springs were a key ingredient too, but removing the buffer took me to 100% function.  I don't think one is needed for light target loads and may do more harm than good.

As Lightfoot says, in my own researching for my powder load/spring/pistol/dot combo the postings I saw point to something close to a 10-lb recoil spring when everything else about the gun is functioning well and the other springs are lightened to match.  My actual experience has been in line with those postings.

Shock buffer = alibi generator. 

Probably right about shock buffer. But, I think 10lbs is way too light. Especially for a .45. That's lighter than .38 spec wad territory. I think Jon E should way in. He just rebuilt my .38 and with an 11 lb spring its breaking in and whacking pretty good. Jon makes a very tight gun.

Every gun is different but on average I see 10-12 for slide mount optics w/ target loads

It's not just the recoil spring that will determine the weight.  It's a combination of a load, firing pin stop, mainspring AND recoil spring.  For the combination you specified I would have started out with a 12 lb spring.  But there are many other things contributing to what recoil spring allows the best function.

And at a high of 40f, even a 10 may be questionable depending on the ammo temp. I run an 11lb recoil, not sure of the main spring (whatever Curtis installed in 1998). But ejection is iffy with my Summer loads in winter. This was true for the previous owner as well.