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Discussion Starter · #1 ·
Found a pretty decent accuracy 100 yard load that ejects too far. Anyone experienced a change in point of impact when changing gas bushings? I'm going from a .50 to a .40.
 

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I found that with my Mini, a smaller bushing forced more gas to stay in the barrel, and propel the bullet a little faster. This resulted in a very slight rise in the POI. IDK if your particular change will be noticeable or not.
 

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Like RIBob said there's a slight increase in velocity of the rounds exiting the barrel with the smaller bushes keeping more gas in the barrel. Most likely any noticeable POI change is a result of re-torqueing the gas block screws from the factory configuration. Each time you remove and reinstall the gas block it affects the operating rod's imparting of impact force around the barrel slightly (shear force on the gas bushing itself and the galling [friction] of the gas block halves on the barrel) differently affecting the barrel harmonics. Newer 580+ series with the flared shoulder on the barrel are less effected due to the heavier barrel design and a shoulder to receive any moment from the gas block, so there's less vertical whip from the shearing on the gas bushing and a more even distribution of forces around the entire round of the barrel reducing horizontal movement. But no matter what you do, if the gas block halves aren't exactly aligned and fastened to the exact torque measurement as the last time the gas block was installed, the POI will shift from the forces imparted on the barrel having changed slightly.
 

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Discussion Starter · #4 ·
Thanks RIBob and Waher, Good info.

Took it to the range this afternoon. There was a a slight rise in the POI and the group opened up from 1.7" to about 2.5 and about 2" right of where it was before There was a little wind, not enough to make any difference at a 100 but enough to make a difference further out.. I got it adjusted to where I was hitting a 12" plate at 220 yards pretty consistently and an 18" plate at 300 most of the time.

The main problem was it wouldn't eject so I cycled it by hand. Guess at around 250 rounds it's not broke in enough for the .40 bushing yet. I'll put the .50 back in tomorrow and give it another 250 or so before I try a smaller bushing again.
 

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The main problem was it wouldn't eject so I cycled it by hand. Guess at around 250 rounds it's not broke in enough for the .40 bushing yet. I'll put the .50 back in tomorrow and give it another 250 or so before I try a smaller bushing again.
The spring may not be worn in yet; temperature and ammo quality also play in a bit. I think most people run a .45 bushing or a .50 for reliability in extreme cold or with weak steel cased ammo. If you are using a front buffer bushing around the gas nozzle so that the operating rod doesn't fit tight to the gas block, that also results in less gas pushing the operating rod back from the poorer seal. I never run a front buffer, only a rear, because of the various issues a front buffer can cause in certain circumstances.
 

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Discussion Starter · #6 ·
The spring may not be worn in yet; temperature and ammo quality also play in a bit. I think most people run a .45 bushing or a .50 for reliability in extreme cold or with weak steel cased ammo. If you are using a front buffer bushing around the gas nozzle so that the operating rod doesn't fit tight to the gas block, that also results in less gas pushing the operating rod back from the poorer seal. I never run a front buffer, only a rear, because of the various issues a front buffer can cause in certain circumstances.
 

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Discussion Starter · #7 ·
Thanks. 70 degrees and brass case reloads but does have a front and rear buffer.

I put the .50 bushing back in and think I'll put another 250 rounds through it. before changing anything else. At that point, 500+ rounds, I'd think it should be broke in enough to remove that as a factor. Than I'll try the .40 again without the front buffer.
 

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0311,

Are you sure you did not install the recoil spring guide upside down. Going from "excessive ejection distance" to no ejection with that bushing change does not seem right.

Now, "too far" might mean more than 5 feet, in which case your rifle was on the verge of not ejecting already :)
 
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Discussion Starter · #9 ·
subscriber, Thanks for the input. Don't know if it was installed right or not. I'd think I would have noticed when I took it down to put the .50 bushing back in but can't say for sure. Your post did make me check to make sure it was installed right this morning.
 

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I advise choosing reliability over the convenience of having spent brass land at your feet. Current model Mini-14s and Mini-30s come from the factory with a .085 inner diameter gas bushing last time I checked. Going to .050 is quite a drop. I wouldn't go any lower than .050 for a Mini-14 myself. Barrel length is a factor in how low you can go. a 16-inch model needs more gas than a 18.5-inch barrel.

I have an older Mini-30 that came from the factory with a .100 bushing. You could drive a truck through it. I replaced it with a .070 from ASI and that's as small as I'll go. Some have successfully gone lower than that.

The brass doesn't land at my feet, but it's not bad, landing a few feet away. Most importantly my Mini is getting a bit less battering while being 100% reliable in temperatures from below zero to 100+ F. In my part of the Midwest it can feel like Siberia in winter, then be as hot and humid as Bangkok in summer.

I guess it depends on the conditions where you live and where you plan to shoot, but having a Mini that's at the edge of functionality is asking for trouble if you ever have to employ it to save your life.

~ Beck
 

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The surest way to determine reliability vs/ gas port internal diameter is to test the cold ammo in a cold rifle, during winter time. The colder the better, for purposes of determining reliability.
Yep, agreed. If you have reliable functionality in cold temps, you're good to go.
 

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Discussion Starter · #13 ·
Thanks for the info. Took it back to the range for 50 rounds with the.50 bushing. Managed to get the far right bench. Ejected all about 15 feet at a 90 degree angle on average. which would have been hitting anyone three benches over if I hadn't been on the last bench.


























I advise choosing reliability over the convenience of having spent brass land at your feet. Current model Mini-14s and Mini-30s come from the factory with a .085 inner diameter gas bushing last time I checked. Going to .050 is quite a drop. I wouldn't go any lower than .050 for a Mini-14 myself. Barrel length is a factor in how low you can go. a 16-inch model needs more gas than a 18.5-inch barrel.

I have an older Mini-30 that came from the factory with a .100 bushing. You could drive a truck through it. I replaced it with a .070 from ASI and that's as small as I'll go. Some have successfully gone lower than that.

The brass doesn't land at my feet, but it's not bad, landing a few feet away. Most importantly my Mini is getting a bit less battering while being 100% reliable in temperatures from below zero to 100+ F. In my part of the Midwest it can feel like Siberia in winter, then be as hot and humid as Bangkok in summer.

I guess it depends on the conditions where you live and where you plan to shoot, but having a Mini that's at the edge of functionality is asking for trouble if you ever have to employ it to save your life.

~ Beck
The surest way to determine reliability vs/ gas port internal diameter is to test the cold ammo in a cold rifle, during winter time. The colder the better, for purposes of determining reliability.
 

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Discussion Starter · #14 ·
Tried it yesterday, 75 degrees, with a .045 bushing and per Waher's suggestion no front buffer. I was shooting a little warmer load, 24.5 gr of Ramshot X-Terminator, 4/10s under max and 55 gr Hornady FMJ BT. Decent, centered open sight accuracy at 100 yards and it threw the the brass about far as it had with the .050 bushing using a front buffer.. I'll probably try a .040 again pretty soon
 

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Discussion Starter · #15 ·
Tried it yesterday, 75 degrees, with a .045 bushing and per Waher's suggestion no front buffer. I was shooting a little warmer load, 24.5 gr of Ramshot X-Terminator, 4/10s under max and 55 gr Hornady FMJ BT. Decent, centered open sight accuracy at 100 yards and it threw the the brass about far as it had with the .050 bushing using a front buffer.. I'll probably try a .040 again pretty soon
 

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Discussion Starter · #16 ·
Back to the range today with a .040 bushing and no front buffer. Same load as used in above post. POI the same at 100 yards as with the .045 bushing. Perfect function and less than half the ejection distance than with the .045 bushing. Temp.was 60 degrees.
 
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