Gas release in a mag

[nippinout]

Why don't mag bolts have o-rings?

Perhaps the spring would eat them up? Would a harder material that is more resistant do abrasion be insufficient for sealing?

With all this talk of LVL10, I'm wondering about the mag bolts.

How about something similar to a slidecheck. The o-rings on these things are a PAIN in the arse to replace. But what if a mag barrel had an o-ring on the inner side of it that the bolt would seal with.

This would circumvent the problem of the bolt return spring eating the bolt.

Any thoughts?

[Top Secret]

Would probably make barrels cost more than they already are for the mag. The o-rings are probably unnecessary as it is.

[ts1spoc]

Barrel Seal

I like the idea of being able to seal the barrel with the ball as the shot is fired, but I'm not sure what would be gained. I shoot a Minimag with the standard quarter turn barrel. The thing I like about it is being able to take the barrel off to squeege it out if needed. With the internal O-ring I'm not sure a squeege wouldn't drag out the O-ring or allow the paint to build up on the back side of the ring. The least amount of paint in my barrel and my balls fly like a drunken bat. I think the spring would chew up the O-ring if it were installed on the bolt. In looking at my gun, as the bolt come out of the power tube it begins to discharge air before the bolt is fully extended into the chamber. An O-ring forward of the ball opening would not provide much benefit unless the discharge is delayed until the bolt fully seats. This would mean lengthening the rod in the back of the bolt and moving the O-ring in the power tube forward to the end.

[Cypres0099]

I remember something being said about the level 10 mod making the air discharge at the full forward position. So while it may not be practical to put an o-ring on the bolt or in the barrel, what if it was put in the body.

I'm not sure if it would work in the SS body but perhaps the extreme. You could place an o-ring in between the breach and the end of the barrel so, when the barrel is screwed in it kind of bulges out towards the center. This would provide the seal without the cleaning worries for the barrel and without the stress it would have on the bolt.

[athomas]

Why would you want the trouble of adding more o-rings?

It isn't the problem of gas escaping around the bolt and up the feed tube that cases a problem anyway. Any blowback problems (I assume thats the reasoning) are caused by the bolt cycling so fast that it returns to the valve before the ball has exited the end of the barrel. Pressurized gas behind the ball in the barrel continues to push the ball but also escapes up the feed tube. This gives the famous mag blowback problem which isn't a problem if you have a powerfeed anyway.

[ts1spoc]

The gas escaping is both blowing around the bolt as it travels forward and on the return, gas is coming back up the barrel. This is part of the yo-yo effect that AGD was talking about in another thread.

[athomas]

Originally posted by ts1spoc
The gas escaping is both blowing around the bolt as it travels forward and on the return, gas is coming back up the barrel. This is part of the yo-yo effect that AGD was talking about in another thread.

The gas escaping while the bolt is going forward is negligible because the area around the bolt stem and the power tube is small and the bolt is moving forward at the same speed as the air that is trying to push by it.

The gas pushing back does have an effect which is blowback.

[ts1spoc]

I disagree. If you insert your current bolt into the power tube (outside of the main body)you can feel when the bolt stem clears the internal O-ring. This is a very short distance. As the bolt comes forward and clears the O-ring any air behind it begins to escape and fill the chamber. Once the bolt clears the O-ring only momentum keeps it going forward not pressure.

[BlackVCG]

Originally posted by ts1spoc
I disagree. If you insert your current bolt into the power tube (outside of the main body)you can feel when the bolt stem clears the internal O-ring. This is a very short distance. As the bolt comes forward and clears the O-ring any air behind it begins to escape and fill the chamber. Once the bolt clears the O-ring only momentum keeps it going forward not pressure.

This is incorrect.

There is a slight amount of air that leaks out once the stem breaks from the o-ring, but the full pressure release doesn't come until the stem breaks away from the PT tip. If you place the PT tip on the stem and look for light inbetween the two parts, you'll notice that there isn't much light that comes through because it's such a tight fit. The PT tip is about .001-.002" over the O.D. of the small raised area on the bolt stem. This creates a seal between the two parts enough to hold the pressure back until the stem breaks away from the PT tip.

[aut911]

so chrome plating my mag bolt might be a bad idea?
the reason i wanted to chrome plate my mag bolt is to remove the machining marks so i would have two smooth surfaces running against each-other. the problem would be the main spring, but i could break out some polish for that.

is this a bad idea(chrome plating) ? would the chrome plating compromise the tolorences in the PT?

aut

[BlackVCG]

Aut- You're better off just using some fine grit aluminum oxide paper and polishing up your bolt to a mirror finish.

[aut911]

thats what ive been doing for a while now but those tool marks just wont come out, and i have been using chrome polish on a buffing wheel for a while, and it gives the bolt( and body) a nice shine. well ill just sand it down with a sand paper strip and then try again.

thanks

aut

[athomas]

Use a fine 600 grit sandpaper. It'll work better than polish for what you're doing. 600 grit won't alter the dimensions much but will smooth the surface.

[aut911]

ok i have some 600 and 800 grit aluminum oxide wet dry sand paper, so that should work. I used 120 sand strips to take my bolt down to where it no longer has the marks, and i may have lightened it up a little by drilling a hole down the center of the bolt, and making the face of the bolt more like a cup shape.

works just fine.

I wouldnt see any benefit by making the holes in my bolt about 1/16 of an inch bigger would i?


aut