When the Brake doesn't line up?

[Bhamm]

This is my first question for the forum. I recently assembled my Mini using the BM59 brake to go with the gas cylinder. I seated the gas cylinder on the barrel and screwed the brake on the barrel. The brake passed the gas cylinder opening before stopping, so I backed it off to line up the hole for the gas plug.

My issue is the gap between the brake and gas cylinder after backing it off to line up, and it appears when I tighten the gas plug it pulls the brake down a little on the gas plug side making it not line up with the barrel slightly. Is this normal and can it be corrected?

I could try taking a little material off the bottom of the brake, but it may need machining to do it correctly.

[Bhamm]

Well, I'll answer my own question. The muzzle brake would almost tighten up over the gas plug opening, but not quite. That meant backing it off almost a full turn which was unacceptable. So, I used an orbital sander on low and removed just a little material from the end. Now it tightens up perfectly over the gas plug hole. This is now my favorite rifle.

Bhamm

[timshufflin]

Sir, it was actually acceptable to back off that brake. Your fix may also be acceptable. Let us know if it worked or not. Long family week and a half for me and I know others have been 4th of July'n. Peace.

[Bhamm]

I do get impatient sometimes, and I've paid for it, but it worked out this time. I hope to shoot it this week. I'm not really fond of the brake and will be looking to swap it out.

[timshufflin]

Yah, all you need to do is make sure the gas port in the barrel is lined up with the gas hole in the gas cylinder. You can turn the brake back and forth until it is positioned straight up and down and then move the gas cylinder either to it or away from it so that the hole is still lined up. These things always have one full turn of play.

[Old Guard]

Neither of my BM59 type 2 Gasbreaks lined up perfectly but the play was way less than a turn..on either of the rifles. They fired fine, and seem to control the muzzel better on firing, so I like them...I still need to buy the proper allen headed lock, I'm just using a Gi key..

[Bhamm]

When I converted my Mini-G to the BM59 gas cylinder, I used the Standard Parts BM59 builder lower band. It is to thick for the Mini-G so I had it machined to fit. After measuring the gas cylinder port to barrel port alignment, I had the machinist leave .060 material on the lower band (my Standard Parts BM59 gas cylinder had a much smaller gas port compared to the M1's gas cylinder). After installing the lower band to the barrel with the pin, I slipped the gas cylinder on and seated it against the face of the lower band. The gas ports match up perfectly, although now I cannot move the gas cylinder to help align the gas cylinder lock or brake. Had I just had the lower band machined to the same thickness as a Garand lower band, I could have moved the gas cylinder accordingly to help align the brake. Long and un-needed explanation, I know.

BHamm

[timshufflin]

When I converted my Mini-G to the BM59 gas cylinder, I used the Standard Parts BM59 builder lower band. It is to thick for the Mini-G so I had it machined to fit. After measuring the gas cylinder port to barrel port alignment, I had the machinist leave .060 material on the lower band (my Standard Parts BM59 gas cylinder had a much smaller gas port compared to the M1's gas cylinder). After installing the lower band to the barrel with the pin, I slipped the gas cylinder on and seated it against the face of the lower band. The gas ports match up perfectly, although now I cannot move the gas cylinder to help align the gas cylinder lock or brake. Had I just had the lower band machined to the same thickness as a Garand lower band, I could have moved the gas cylinder accordingly to help align the brake. Long and un-needed explanation, I know.

BHamm


I see, I thought you had heeded my advice on the phone and made the lower band standard thickness. Alas, no you didn't, you went your own way :) It's fun to try things on your own though and find out the "why" in your own way. Good on you for doing it your way.

[Bhamm]

If I do it again it will be Tim's way :cool:

[Punch The Clown]

You can open up the gas port hole in the gas cylinder. Just drill straight down through the existing hole under the front sight. Not to take a dump in your Wheaties but where the op-rod tip ends up is critical in this whole thing too. It has to end up in exactly the correct spot in the gas cylinder,so moving the gas cylinder can throw off the whole geometry of the system. If you ever go to Tim's shop you'll see he has diagrams and models all over the place. Although there is a little tweaking for the most part all his stuff is plug and play because he sticks to the plans-fanatically I might add.

[Bhamm]

Thanks P the C, good to know. I did measure the op rods before and after straightening, and they measured the same length. Tim deduced I have a 1st generation Mini. I think I'm lucky it came out good since it was done over the phone, and Tim did not have the rifle to look at. Also, a testament it can be converted so easily. Once I get the trigger group back and no more double-taps all will be good. Heck, I've had new rifles with more teething problems than my Mini.

Bhamm