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+--- Thread: Fixed: 18" Alexander Arms barrel: 2.5+ MOA (/showthread.php?tid=20208)
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Kswhitetails - 02-20-2020
Surely you're not suggesting this is the standard practice over at AA? I don't for a minute think any company has the time to hand select the extension based on barrel timing, but honestly I've been wrong before. I don't think they'd leave headspacing the barrel to that kind of chance?
That aside, how does one account for a pinned extension coming loose?
I've always been under the impression that after the barrel tennon had been set and the extension has been torqued in place, the extensions were then drilled and pinned permanently to time the barrel, and the gas port was drilled in the same lateral location as to time the two. Maybe the idea is that after the first one came off, the gas port is already drilled, and the extension has to be set, but I can't imagine the extensions already have the holes in them? There's a lot about this I apparently don't know, which surprises me actually, as I read about it back when I started building my own...
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 02-20-2020
I'm no gunsmith, but I'd think the opposite would be easier: take the pre-pinned extension, torque it onto the raw barrel, then, using the pin and the extension, mount the raw barrel into a drill rig and drill the gas port.
In the case of my barrel, I'm curious if plugging the existing port is possible (heat, stress, intrusion into bore), and then simply re-drilling a new port would not be possible? (I'd assume the old port would intersect with the new one, so drilling through the plug would be necessary. The biggest issue would be the effect of plugging the port would have on the barrel.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - rabiddawg - 02-20-2020
I just don’t get why they didn’t send a new barrel from the get go. That’s what I would have done. Done with it and no back lash.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Lastrites - 02-21-2020
C3k I expect you will be in for disappointment if you want a replacement with the exact same spec's as they haven't offered that particular barrel for a while now, hope you get lucky and they can find one stuffed in a back corner of their parts room if they can't spin a new extension on the current barrel.
Eta: my bad still have the fluted 18, I mixed it up with their newer 16.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - A5BLASTER - 02-21-2020
Lastrites Wrote:C3k I expect you will be in for disappointment if you want a replacement with the exact same spec's as they haven't offered that particular barrel for a while now, hope you get lucky and they can find one stuffed in a back corner of their parts room if they can't spin a new extension on the current barrel.
When did they stop offering the 18 inch fluted? They even sell it on midwayusa now.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - 1075 tech - 02-21-2020
Corporate mentality?? They'll spend more in labor costs with someone trying different extensions than if they had just sent a new barrel from the beginning.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Kswhitetails - 02-21-2020
Lastrites Wrote:C3k I expect you will be in for disappointment if you want a replacement with the exact same spec's as they haven't offered that particular barrel for a while now, hope you get lucky and they can find one stuffed in a back corner of their parts room if they can't spin a new extension on the current barrel.
This would make more sense, as if this was the agreement they'd have to have a single barrel spun up to meet their end. This is time consuming and expensive. However, if the hope was to avoid this a simple email to the customer explaining the situation with a question of whether a current in stock barrel was sufficient would have solved all issues.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 02-22-2020
Since this build was meant to be a piston setup, I'd greatly prefer any proffered replacement to have the same mid-length gas and .75" gas journal. As well, 18" length: I'd rather not go shorter.
Within that, the weight is a minor concern. (I'm assuming the same twist rate and stainless.)
However, that has not been mentioned. I'll continue to wait and see what happens. I'm sure whatever it is, AA would not return something to me that they would not be satisfied with themselves.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Herzo - 03-10-2020
Kswhitetails Wrote:This would make more sense, as if this was the agreement they'd have to have a single barrel spun up to meet their end. This is time consuming and expensive. However, if the hope was to avoid this a simple email to the customer explaining the situation with a question of whether a current in stock barrel was sufficient would have solved all issues.
With today's CNC machines, to replicate a previously manufactured barrel is a simple matter of pulling up the old program and producing the assembly. The cost to them would be minimal over their regular production and well worth maintaining their reputation. That they have not addressed this problem indicates that AA has serious corporate problems and should be viewed skeptically as a worthy supplier.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 03-18-2020
Update: My wife has informed me that a long cardboard shipping tube has been delivered. The return address is "Alexander Arms". As I am currently traveling, and she does not want to open it, I will have to wait a few days to find out what's in it.
Woot.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - rabiddawg - 03-18-2020
Best of luck c3k!
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 03-18-2020
rabiddawg Wrote:Best of luck c3k!
Thanks!
I'll post a few more updates here. First, when I open it up, I'll report on what was sent.
Next, I'll take some pix as I build it since far more skilled have offered some feedback. I'll do that here, rather than in a new thread.
Finally, I'll take it out to the range and post the results.
Alexander Arms has stood behind their product and deserves credit for that. I had the barrel in my possession for 9+ months and they still accepted it without doubting my word on what happened. It would've been easy for them to say that I must've done something to cause the barrel/extension separation.
Thanks to them and this makes them stand higher in my regard.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Usmc1974 - 03-18-2020
WOW!!!Just wow. I took a Spike's Tactical upper and lower, through on a Armory 20 match Barrel torqued it 45 fp added a 6 port comp torqued 10 fp timed at 1 o'clock. I got sub Moa American Gunner ammunition let me grab a gun
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 03-18-2020
I'm impressed. Here's a pic of the barrel Alexander Arms sent back.
[ATTACH=CONFIG]15750[/ATTACH]
Of note, the NEW extension, and the original (sent back in the plastic bag). There was a note included. Class act.
I'll put this on an upper and hopefully get WAY better groups.
Alexander Arms stepped up. Thanks.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - peak98 - 03-29-2020
Glad to hear they made it right. Id like an update on how the new barrel performs once you put some rounds through it.
peak98
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - Herzo - 04-08-2020
c3k Wrote:I'm no gunsmith, but I'd think the opposite would be easier: take the pre-pinned extension, torque it onto the raw barrel, then, using the pin and the extension, mount the raw barrel into a drill rig and drill the gas port.A number of years ago, I had an over gassing problem with my first carbine build. After determining that the gas port was substantially over sized, I drilled and tapped the gas port for a #8-32 , being careful to leave the hole 1/8" short of the bore. I then installed a stainless set screw in the hole and drilled the screw for the proper diameter. After that, I filled the screw to match the od of the gas plug journal. Problem solved.
In the case of my barrel, I'm curious if plugging the existing port is possible (heat, stress, intrusion into bore), and then simply re-drilling a new port would not be possible? (I'd assume the old port would intersect with the new one, so drilling through the plug would be necessary. The biggest issue would be the effect of plugging the port would have on the barrel.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 04-23-2020
Well, as promised, here's the build thread and final results of the fixed barrel. (No, I won't make a separate thread...because.
)As noted upstream, some questions about how I put this together were raised. The purpose of this is to show how I assembled the new build. I kept the previous lower with the Hiperfire trigger. Love em...
First, the upper is an Anderson upper. I put in my rotatable vice, pointed it up at the ceiling and then used my Wheeler lapping tool to hone the front of the upper. (Vertical, so that the weight of the Wheeler tool and drill combo would not induce more friction on the bottom during the honing process.)
Here's the upper, after truing:
[ATTACH=CONFIG]16001[/ATTACH]
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 04-23-2020
Here's the same upper on my marble slab with a speed square next to it:
[ATTACH=CONFIG]16000[/ATTACH]
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 04-23-2020
I took the new barrel and used some stainless steel to make a shim around the extension. (I'd measured the upper and the barrel extension on 4 axes with a caliper: they differed by 1/2 to a full one thousandth.)
I ordered three sizes of shim material (lead time): .004, .002, and .001. Here's a pic of one of them: [ATTACH=CONFIG]16002[/ATTACH]
Since the upper and barrel extension were so close, I ended up using the .001 material for my shim. I cut a section, ensuring the M4 cutouts weren't obstructed, and made a "V" around the barrel alignment pin: [ATTACH=CONFIG]16003[/ATTACH]
With the .001 shim, the extension would not fit in the upper. Perrrrrfect.
Next, I put the barrel (with shim rubber banded around it) in a plastic bag and tossed in my freezer, set to -6F. Yes, minus 6. Then, a day or two later, I took the upper and tossed it in the oven. [ATTACH=CONFIG]16004[/ATTACH]
I pulled it out a bit later. (30-45 minutes? 300 plus degrees?). Then, I tossed the upper on a wood cutting board, grabbed the barrel out of the freezer, and here you go: [ATTACH=CONFIG]16005[/ATTACH]
It slid in like butter. No slop, just slid right in. A few moments later, it was NOT going to come out.
Fixed: 18" Alexander Arms barrel: 2.5+ MOA - c3k - 04-23-2020
As previously mentioned, I use timing shims for the muzzle and the barrel nut. I did the same, again. I had to time the barrel nut for the Adams Arms piston. (But, I would've had to do that for a gasser, too.) With the shims, it was about 40 lb-ft to time it.
I screwed on the muzzle brake/compensator (oh, now ya'll gonna be mad because I forgot what kind it is...LOL...), snapped the lower onto it, put the scope on, and here it is (forgive the poor staging, but I wasn't meaning to use this image): [ATTACH=CONFIG]16006[/ATTACH]
The sling isn't adjusted, etc., etc. This was right after putting it together.
So, it sat like that for a week or so. I got it out to the range...