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How does a comp affect ejection


itchy
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Hi,

Looking for some knowledge here, since I mainly shoot production and revolvers. How does a compensator affect ejection patterns? Both weight and number of ports? I'm building a Bianchi gun (120-130 pf)and am trying to figure out what size comp to use.

I'm testing out a gun that had a 4 port aluminum comp that wouldn't eject. As soon as I pulled the comp off, it ejected like a champ. I should have paid more attention in physics class.

Thanks,

Seiichi

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Welcome to the wacky world of Open guns at minor PF.

A comp directs the gas upward and actually takes away the gas that normally works the slide as you noticed when you removed the comp. I use a 3 port aluminum comp from EGW.

The slide needs to be lightened. Recoil springs are 7 to 9 lbs. Mainsprings are 15 to 17 lbs.

Mag springs can also cause problems. A strong mag spring can push the top round up hard enough to slow down the slide.

If the barrel has a bushing then the barrel needs to be turned down so that the bushing is not dragging on the barrel. The bushing has a tight fit on the barrel where the slide is in battery. 1/2" back from that point on back is where the barrel needs to be turned down.

Is this by chance a 9mm?

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A comp directs the gas upward and actually takes away the gas that normally works the slide as you noticed when you removed the comp. I use a 3 port aluminum comp from EGW.

Yeah, not so much.

The reason for the difference with and without the comp is because the gas causes the comp to pull the barrel forward when the gas strikes the far side (muzzle side) of the first port, which delays the unlocking/slows the slide....hence the need for lighter recoil springs. The gas that goes out the comp didn't get taken away...it just got turned.

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Very interesting. I understood that the amount of gas would not change, but didn't think about the gas pushing forward on the comp.

My slide is just over 10 oz, using a cone instead of bushing. I have several comps on order...2 and 3 port aluminum from EGW and Gans and a 2 port steel from EGW.

Funny thing is that my steel gun runs great, commander length with 2 port steel comp.

Yup, 9mm. Trying an 8 pound recoil spring, not sure what my mainspring is. Maybe I should check that. I guess the combination of the mainspring and the angle of the firing pin retainer could determine how easily the slide begins moving. I need to learn more about 1911s.

Thanks for all the help,

Seiichi

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The reason for the difference with and without the comp is because the gas causes the comp to pull the barrel forward when the gas strikes the far side (muzzle side) of the first port, which delays the unlocking/slows the slide....hence the need for lighter recoil springs. The gas that goes out the comp didn't get taken away...it just got turned.

The comp does re-direct the gas but it has the effect of taking it away.

al503,

I believe you mean the firing pin stop.

Itchy,

I figured it was a 9. They seem to be more problematic.

Lighten the mainspring. Get a 7 and 8 lb varicoil spring. If you have a shroud on the gun, make sure the mounting screws are not dragging.

I have often considered using a commander slide in my action gun. After I went to a 6" barrel things started working so well that I abandoned the idea. What is the weight difference between the slide on this gun and the commander slide?

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The reason for the difference with and without the comp is because the gas causes the comp to pull the barrel forward when the gas strikes the far side (muzzle side) of the first port, which delays the unlocking/slows the slide....hence the need for lighter recoil springs. The gas that goes out the comp didn't get taken away...it just got turned.

The comp does re-direct the gas but it has the effect of taking it away.

Sorry, but that's a guess, at the very best, and likely incorrect. The gas column exits the muzzle in both cases. Whether they turn upwards while going through a comp, or go straight forward into open air really doesn't matter...the pressure has already been relieved from the barrel. In fact, since there is residual pressure in the comp, and some of that has to act back down the bore, along with the normal residual pressure that exists, your theory might actually be 100% opposite from reality.

The comp pulls the barrel forward, and down (as Al503 added)...those two things delay the unlocking of the barrel and slow down the slide, so you have to run a lighter spring to get the gun to cycle properly....it's not some magical dispersal of gas volume due to the comp.

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Why are comps so....complicated? ;)

4 port sluminum, out

3 port steel, out

2 port steel working. Waiting on 2 and 3 port aluminum from Gans and EGW. Gary at Gans made me 2 comps in one day. Now that's awesome. One day!

Might try taking a little more weight off the slide, getting a lighter mainspring, and tweaking the FP retainer.

Or add some more powder to those cases.

Can't wait to get more parts this week.

Seiichi

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