Just bought parts to start my first AR .308 build. Went with a Mega Maten MKM  set and a matching Mega 16" barrel. The rifle will serve more as a battle rifle / normal shooter role than a high precision one. I also bought, on recommendation on the instructions from Mega, an RCA BCG and bolt combo.
I purchased Clymer .308 Win Go/NoGo gauges. I stripped the bolt last night and tried the gauges, Passed the Go gauge and failed the NoGo as it would close and rotate.

Upon watching the 8541 Tactical YouTube series on a similar build where he has the same issue, but with a Rainier Select barrel, he used a piece of cellophane tape to add 0.002" to the NoGo gauge to bring it's tolerance from 1.634 to 1.636. I tried this and it passed the NoGo test as I could not turn the bolt.

I sent an email to Mega and alerted them of the problem and to ask if they adhered to the .308 win specs or more to the 7.62 NATO specs. Jason responded first thing this morning  stating that they are more in line with the .308 Win match specs. He stated that if I liked he would have me send him my barrel and bolt and do the checking themselves (The customer service with this company has been a positive one for sure).

I am just curious about your opinion, if you know more about head-spacing than I do (which is next to nothing). Is this worrisome to anyone or am I making more it than I should. I just want to make sure I am building a safe rifle and do not want to ruin any parts that I spent a lot of money on.

Thanks for your input,


-Sean
(Please god, don't tell me to read the Mega FAQ, been down that road for other questions and quite frankly would rather stick a red-hot poker in my eye)

My opinion is that you're okay.

It's under the "field reject" length for 308 Win (1.6380"), and it sounds like it's right at the 7.62X51 "go" length (1.6355").

If you want the HS a little tighter, I would talk to RCA to see if they might let you try a different bolt.

Shipping bolts back and forth is cheaper than shipping barrels.

Mega is a great company to get a second opinion from too, if you decide to go that route.

Did Jason tell you that your measurements indicated excessive (unsafe) HS?

If not, I'd say you've already got their opinion and wouldn't worry.

As a comparison, HS with my 20" Mega barrel and Aim nitrided bolt is around 1.631".

Not in so many words but he did say that their barrels adhere more towards .308 win match than 7.62 NATO so that makes me believe that the bolt should not have have been allowed to close on the NoGo gauge.
So something is either up with the chamber or the bolt. I assume that is why he made the offer to have me send it in and they can check it there. I am sure if the barrel was out of spec they would make it right.

I tried sending it off yesterday evening but alas, the idiot at the UPS store said they are not allowed to ship gun parts out of fear that someone would put together a gun from the parts and do violence. (not kidding).
So now I have to bring it to the actual UPS shipping center or FedEx or something.

Thanks for your reply.

I think that your UPS clerk is an idiot.  Just tell him it is an engraved steel rod.

Why not use USPS? Never have issues with them.

UPS and FedEx can suck a fat one.

However, i never disclose what I'm shipping, just that is not hazardous material.

How the hell is the clerk gonna day that, when a shit load of companies use UPS to ship their parts?

I would've raised hell over that. They just didn't like you. You were shut down from an SJW. Haha! That fucking sucks.

Anyways, I'd send the barrel back first. Mega has had some issues with the mfg of their barrels in the past. Nothing major, but really just letting bad stuff slip past QC. It's gonna happen. So, I'd give mega the first attempt at rectifying. Then go with whatever they recommend. Really good guys in that bunch.

FWIW, it's true, UPS policy specifically bars The UPS Store from shipping anything firearm related. UPS itself (the hubs) will ship anything. So the clerk was just doing his job. No idea why this policy is in place.



-Stooxie

It's a good thing my UPS stores don't read the rules. I've shipped everything from barrels to complete guns through mine.

Greg

Ultimately I went with USPS and they didn't even bat an eye so I know where I am going from now on.

I usually receive in a lot of parts and pieces and don't send many out so it was my mistake when I went to the UPS store and she asked me what was in the cylindrical package that said Mega Arms and .308 WIN barrel on it that I said, "Oh, it's a rifle barrel". I wanted them to pack it in something else, so my bad. After that I picked up one of those triangular shipping tubes from USPS and packed it in there and then went back to the post office to ship it.

The reason that I went with Mega in the first place, besides having an outstanding product, is that I heard that their customer service is one of the best in the business. For me, so far, that's been spot on.

My Rainier .308 select barrel was 7.62 Go, which is slightly over .308 No Go. According to my gunsmith this is normal for a 7.62 chamber and preferable for a gas gun.

Received an email from Mega. Jason says they checked the barrel and bolt and both were under-spec. He was able to match a new barrel to my bolt and the combo is in spec and it's already in the mail.

I am extremely pleased with my experience in dealing with Mega Arms and Jason Curns in particular.

I can wait to get this thing together and get it dialed in at the range.

I've had very similar experiences with them, meaning both MEGA and RCA. That's my go-to combination for all my AR 308 stuff. Jason Curns (MEGA) and Chris Cerrino (RCA) know what customer service is all about-- AND they take pride in their products.





-Stooxie