MEGA ARM's SBU Upper

[Tedward]

I bought a MEGA ARM's SBU upper last week and went to put the barrel on it today. When I tried to slip it on it wouldn't fit. I was feaking out. I tried my new barrel on my other upper and the barrel fit fine. I was thinking UNBELIEVABLE, What QC from Mega.

I called MEGA and the guy said, yup it sure doesn't. I was baffled... He said the upper needs heated up but grease the inside of the upper and the barrel extension first. I said WHATTTT? He said they are a tight fit so you need ot heat it up, alighn the pin and use a dead blow hammer and tap it into place. I used my heat gun as he suggested, not a torch, And it tapped right together. I have never heard of such a thing. Well I guess I just haven't had this type of upper.

Anyhow, the MEGA SBU Uppers are tighter fit than a slip on system and the guy said they are way more accurate than any other upper out there. SO, do any of you have any idea about this and do any other manufactures do this? I never saw anything on there website about this so was totally amazed but again happy when it all came together.

Just wanted to share and if anyone buy's one, no instructions and don't sand down the inside to make it fit. I thought of that so I'm VERY happy I called.

[LRRPF52]

Yup. Seems standard on many Mega uppers, unless you have a slightly undersized barrel extension.

[Spurrious]

I had to grease my extension to get it in a Mega billet upper ....they do fit tight....but I feel that is a good thing.

[stokesrj]

Tight fitting gear sounds cool and I like it that way but it has no bearing on accuracy. Carl Bernowsky uses a plain old RRA A4 upper for his 6mm Hagar and won the national championship with it again this year.
Bob

[Y85]

Had the same experience and reaction with mine - great upper but I wish they included this info when you got the upper

[Keep The Change]

I'm curious what the interference.was prior to install. You definitely just want to get it warm and not hot. You could heat treat or annel the 7075 if getting too hot.

I think being snug or tight is good though. I dont see how it could be more accurate when it is the nut clamping yhe extension flange to the uppers flange that holds the barrel in place.

However I think tight extension helps with whip of the barrel. I think lrrpf52 made a comment about barrel whip before. Seeing an AR in slow motion. It definjtely whips around and Grendel even more so. But whipping action is reacted at flange and nut and threads. I think a tight.extensiin would help in distributing the load.

To aid in even distribution of barrel whip I think lapping or squaring the upper is a good idea. The barrel extension will sit flush to the upper and distribute the barrel loads evenly.

[Keep The Change]

Tedward is that a MFT grip?
I really like their stocks. Unfortunately I couldnt find a mil spec one in stock on a build. Once they get caught up ill swap my magpul out with one.

[Spurrious]

It may have started life as a "plain old RRA upper" but that is not the whole story. According to 6mmBR.com: "Carl Bernosky's rifle features a custom upper built by John Holliger". I will bet pay checks with you that upper is speced out tighter than most people can accurately measure. You don't really think Carl uses off the shelf stock parts in his competition guns ...do you?

Also at least one of his championships was won with a build featuring a White Oak Precision upper.

In any case Carl is obviously is not human like the rest of us.

Tight fitting gear sounds cool and I like it that way but it has no bearing on accuracy. Carl Bernowsky uses a plain old RRA A4 upper for his 6mm Hagar and won the national championship with it again this year.
Bob

[Tedward]

It may have started life as a "plain old RRA upper" but that is not the whole story. According to 6mmBR.com: "Carl Bernosky's rifle features a custom upper built by John Holliger". I will bet pay checks with you that upper is speced out tighter than most people can accurately measure. You don't really think Carl uses off the shelf stock parts in his competition guns ...do you?

Also at least one of his championships was won with a build featuring a White Oak Precision upper.

In any case Carl is obviously is not human like the rest of us.

I don't know who Carl is, don't follow the competition to close yet, but like you said, not off the shelf for $1,000 Rifle paycheck bet +1....

What the guy at MEGA said is it reduces the harmonics and that is the vibration that JP Rifles Tech Support told me about months ago. I'm going to call them Monday and discuss this with them to see if this is required with there billet uppers, CRT-02, SCR-11 and PSC-11 too. The tight fit like the MEGA needs heated for the metal to expand and then when it cools it shrinks around the barrel extension which I never would have thought of.... I also heated mine with a heat gun, super duper hair dryer, on medium which is around 500 degrees. I didn't hold it directly on it and kept it moving around as I blew air thru it from the front at the threads thru the upper. The barrel then slid on with the surfaces greased as recommended by T.S. along with slight tapping with a dead blow hammer. T.S. knew what they were talking about and that is also a great thing for MEGA's support team. Again +1 there too....

Yes I also wish they included this information with the part or even some kind of instructions would be nice so I didn't feel so stupid. Maybe they expect knowledgeable Gunsmiths to be installing barrels and they would already know this. Looks like anyone of us reading this is more knowledgeable.... Great thing to pass along these helpful tips to one another... Forums rock, at least this one....

Anyhow keep the info coming....

[Tedward]

Tedward is that a MFT grip?
I really like their stocks. Unfortunately I couldnt find a mil spec one in stock on a build. Once they get caught up ill swap my magpul out with one.

Just looked it and Yup, MTF and it has G-27 on the other side. I didn't even know that so good eye...I like the finger groves and it does feel good, better than the stock hard plastic one I had. I have held the mushy "shock proof" ones and they are to mushy. I didn't care for those.

[Spurrious]

What the guy at MEGA said is it reduces the harmonics and that is the vibration that JP Rifles Tech Support told me about months ago. I'm going to call them Monday and discuss this with them to see if this is required with there billet uppers, CRT-02, SCR-11 and PSC-11 too.

I have a CTR-02 set and it's very tight as well. I didn't have to use heat on it or my Mega....a little grease and a rubber mallet did the trick.

BTW: On the subject of grease ...I was advised not use a metal bearing anti-seize lube because of some kind of corrosive reaction it can cause with the dissimilar metals of the extension and receiver. Silicon grease was specifically recommended.

[Keep The Change]

Aeroshell 33ms is the mil spec recommended grease for barrel nut and should be fine for barrel extensions.

https://www.ucwrg.com/materiel/weapon-lubrication/18/aeroshell-33ms-grease/

[Spurrious]

Aeroshell 33ms is the mil spec recommended grease for barrel nut and should be fine for barrel extensions.

You DO know you sent me off on a google search. LOL. Seems any good axle grease with 4.5~5.5% moly and specifically NO graphite is good to go. Graphite causes galvanic corrosion on aluminum. Every anti-seize I came across has graphite...so I assume that is why it is a no go.

[Tedward]

Aeroshell 33ms is the mil spec recommended grease for barrel nut and should be fine for barrel extensions.

https://www.ucwrg.com/materiel/weapo...l-33ms-grease/

I like Umbrellas disclosure, "Not Suitable for Personal Lubrication". Not sure what there implying and not to use it on but bet it isn't lip balm they are referring too. Wonder if they have had employee usage issues

I used a grease for break rotors and all aluminum products. If it's ok for aluminum and if it can withstand the heat from a break rotor I know it can handle the heat of an AR.

[Keep The Change]

Tedward, yes the disclosure is hilarious. They have some other humorous stuff on their website as well. Their descriptions are pretty funny.
I think they have some tactical chop sticks or shop sticks or something. Kinda funny.