Faxon barrel and heat ?

[eldogg]

Today i went to the range. i was testing a new build.
12.5 in. 7.62x39 faxon ar barrel socom profile, and was shooting suppressed. i was shooting 5 round strings, let it cool 3-5 min. i was getting good groups with a 1x4. after about 40 rnds., my groups started rising. buy the time i shot 60, it was about 4 in high, but still tight. never had this problem with my 16 in. 7.62x39 DPMS heavy barrel. you think the socom profile is to "thin" for a 7.62x39? i don't have this problem with a 11.5 in 556. todays temp was about 82.

[alamo5000]

Are you using an optic and if so how is it mounted? Double check all that stuff if applicable.

[eldogg]

Bushnell's 1x4 ak optic on an American Defense mount. it locked up tight.

[alamo5000]

My best guess at this point without looking at or being able to check the rifle is that the problem isn't the barrel. I assume you're are running on an AR platform and if so I would take off the handguard and give the barrel nut some more torque. If it were my gun I would check there and examine your optic mount and the optic itself. I would try to trouble shoot in that order and cross my fingers that I found the problem somewhere.

[alamo5000]

Another thing to mention or rather ask... is your barrel free floated? Is it making contact anywhere with anything?

[fledge]

If you're on M4C, Faxon has a thread and they will answer your question directly (or you can email them). That's who I would talk to first to make sure the barrel is behaving in spec. If not, look to other issues. I wouldn't tinker with anything yet.

[SINNER]

Did the original zero return after the weapon cooled?

[Stone]

If it is the barrel, brand new barrels can take anywhere from 50-150 rounds to "settle in"

[eldogg]

Another thing to mention or rather ask... is your barrel free floated? Is it making contact anywhere with anything?
yes it's a free float

Did the original zero return after the weapon cooled?
i'll pay more attention this time. this was it's second outing. I do remember the rnds were hitting low, but I made a few adjustment and they stayed true for about 20 more rounds. the groups didn't really open up. the just kept gaining elevation


My best guess at this point without looking at or being able to check the rifle is that the problem isn't the barrel. I assume you're are running on an AR platform and if so I would take off the handguard and give the barrel nut some more torque. If it were my gun I would check there and examine your optic mount and the optic itself. I would try to trouble shoot in that order and cross my fingers that I found the problem somewhere.
the optic mount is locked up tight. retightening the nut will be my last resort. all those damn shims, ie brake for the suppressor, and I've installed a Griffin rail also that uses shims for line up.

I guess I should have went back to the range today instead of bird hunting, no luck at that either.haha

[UWone77]

retightening the nut will be my last resort. all those damn shims, ie brake for the suppressor, and I've installed a Griffin rail also that uses shims for line up.

I guess I should have went back to the range today instead of bird hunting, no luck at that either.haha

This is basically why I hate timed barrel nuts / barrel nuts that use shims.

I wouldn't be surprised if the barrel nut wasn't torqued properly. Hopefully it's something simpler.

[eldogg]

i thought i would take it back out 1 more time before i did anything to it. today, I only shot about 80 rnds. there was no rise in grouping today. i don't know if both me and the rifle needed to settle in or what. i do know that golden tiger groups a lot tighter than wolf. 100yrds 2 1/2 groups. 12.5in 7.62x39, well here it is...

http://i58.photobucket.com/albums/g258/eldogg/12.5%207.62x39.jpg (http://s58.photobucket.com/user/eldogg/media/12.5%207.62x39.jpg.html)

[UWone77]

I'm not too familiar with what the optimal barrel profile for 7.62x39 is, so hard for me to say if it's too thin. I know that's one of the main reasons I don't do Pencil barrels when it comes to 5.56. Too much compromise in favor of going too light. Groups will shift/open up when the barrel gets hot.

I'd have a couple of more shooting sessions and maybe have a buddy shoot it to determine if your groupings were an anomaly or something to be followed up on with Faxon.

[SINNER]

Both my 7.62 barrels are a heavy profile barrel and I've never experienced groups opening up even when really burning them up. Honestly the only lightweight barrels I have are my Faxon .300 BO and my SCAR's. Never had an issue with either of those stringing shots. Subs don't really seam to heat up the .300 that much and those SCAR barrels just defy logic.

[The FNG]

Nathan over at Faxon is awesome. Get ahold of him for some help. Faxon in general is great at CS. I have 2 barrels of theirs and they have been great help


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[223reasonstobang]

That is a really nice looking rifle eldogg.

[556BlackRifle]

That's a great looking rifle. I only have one Faxon barrel (16" pencil) and it took longer than usual to settle in. I was shooting 9-10" groups at 100 yards. I thought might be my optic so I moved over to 50, used iron sights and shot 6" groups. I ran about 150 more rounds through it and called it a day. Cleaned it, remounted my optic. A few days later I was shooting 3-4 inches at 100 yards. I'd still like a little more accuracy but it is a pencil barrel and 3-4 inches is a lot better than 9-10".

Here's a crappy pic.

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