View Full Version : Determining if new barrel is needed?
Bruce in WV
10-11-14, 15:16
I have my son's carbine in the safe. It's an older BM patrol carbine with about 7-8,000 rounds through it. Over the past 8 years I've replaced everything on it except the lower receiver and upper receiver/barrel. I want to finish fixing it up before he returns to CONUS and wish to determine if it needs a barrel. I don't have a borescope to look at the throat, but the bore looks OK to the naked eye. I have no idea if accuracy has fallen off or remains OK. I'm thinking about doing a preventative maintenance barrel replacement with a quality barrel before the next panic (assuming money is not an issue). Opinions?
Inkslinger
10-11-14, 15:26
Couldn't you just go shoot it with some quality ammunition to check accuracy?
Bruce in WV
10-11-14, 15:31
Couldn't you just go shoot it with some quality ammunition to check accuracy?
Great idea, and it shoots 1-3 inch groups with a 4moa T-1 off a bench without keyholing out to my practical limit of 100yds. Seems good to go: however, we're talking about preventative maintenance and I don't know if accuracy degrades gracefully or falls off a cliff when the barrel reaches its end of life. Buy now when I can find a barrel and afford it or wait until it has to be replaced and take the risk that it will be hard to find one?
Inkslinger
10-11-14, 15:45
I don't think the accuracy of chrome lined barrels drop off quickly. If it does, it would probably be from something else like copper fouling. Stainless from what I understand can degrade quickly, and at a lot lower round count. I'm no expert so... A new barrel certainly won't be a bad idea. Is it needed? Probably not. If I was your son I would be very happy to have a dad that would do something like that for me.
At 8,000 rounds the boy deserves a new barrel, quality is in the pocket book of the beholder...
Heavy Metal
10-11-14, 20:01
1) Buy a spare barrel and bolt head for piece of mind (along with installation tools).
2) Put stuff away.
3) Shoot current barrel till it fails.
Problem Solved.
vicious_cb
10-11-14, 21:16
Or the dump the POS bushmaster upper and get him a brand new BCM upper.
You could also check it with headspace gauges. Brownells has a throat erosion gauge, but since you don't have data from when it's new it will not help. If it were my rifle I'd keep shooting it. Depending on what you want for an FSB/Gas block it might be easier to simply buy a new upper.
You could also check it with headspace gauges. Brownells has a throat erosion gauge, but since you don't have data from when it's new it will not help. If it were my rifle I'd keep shooting it. Depending on what you want for an FSB/Gas block it might be easier to simply buy a new upper.
It is fine. I have rifles in my armory that have 3 times that many rounds through it and still pass all gauging with flying colors. Even when we had non chrome lined M16s and A1s they would go much more than 8K rounds without ever being an issue.
If it were me, I would replace the barrel with a better one and install a good free float tube simply, because it's for my son
I ran an old 14.5 bushmaster barrel well over 20k... With a moderate firing schedule, it'll go another 10k no problem.
I ran an old 14.5 bushmaster barrel well over 20k... With a moderate firing schedule, it'll go another 10k no problem.
Same here. I had a 1993 Bushmaster 14.5" upper that I bought used. I put almost 10k through it and sent it off to be rebarreled thinking it must have been due. The new barrel didn't shoot as well as the old one, so it was put back on and returned to me. Sold the rifle off and last I checked its still doing well.
Rick
With the round count it should still be ok.
BCG has some great deals on complete uppers right now, and they come complete with BCG for free. Depending on his preferences, I'd see if I could manage to afford this: http://www.bravocompanyusa.com/BCM-BFH-16-LIGHT-WEIGHT-Mid-KMR15-KEYMOD-p/bcm-urg-mid-16lw-bfh-kmr15.htm or something similar when it comes back in stock.
Bruce in WV
10-12-14, 17:14
1) Buy a spare barrel and bolt head for piece of mind (along with installation tools).
2) Put stuff away.
3) Shoot current barrel till it fails.
Problem Solved.
I appreciate the info on barrel life and suggestions for if/when to replace the factory BM barrel. I 'll save for the BCM Standard 16" M4 (SOCOM) Upper Receiver Group on sale.
Thank you everyone.
Gauging is near useless. Groups at 300m is a sound barometer of barrel life.
Dano,
Are you saying that performance is a more valuable indicator of barrell condition or Are you saying that the Throat will erode before the chamber gauges will register a difference? Or did your point just completely fly over my head?
Thanks
the Throat can be completely burned out and the Rifle still Group well.
Gauging is near useless. Groups at 300m is a sound barometer of barrel life.
I have to agree with this. Throat erosion and muzzle erosion are not always good indicators of the accuracy potential of a particular barrel. Unless you are shooting high power rifle competition at 600 yards or farther, I would not even bother with throat and muzzle erosion gauges.
If the headspace is safe, a 10 shot group at 300 meters is a good indicator of whether or not a new barrel is warranted on a carbine.
patrick sweeney
10-14-14, 10:03
At our last patrol rifle class, there was an SBR that practically had the erosion gage fall through, and out of the muzzle. It was still dropping 300 meter pop-ups on the RETS course with no problem. Granted, that's no guarantee of MOA accuracy, but it certainly is minute-of-felon accuracy ,and plenty good enough for practice.
That said, the current lull in AR sales is the perfect time to find a top-quality barrel, easy and not-expensive. (quality is never cheap.)
That way, you're set when the barrel does go toes-up. And Murphy;'s Law being what it is, if you don't have a spare, the toe's-up date will be right int he middle of another buying panic.
the Throat can be completely burned out and the Rifle still Group well.
I'll 3rd or 4th this. I've had barrels that I could see the erosion in that still shot fine.
I really would NOT re-barrel a Bushmaster. You're better off buying a complete BCM upper with the offerings out there now.
My old bushmaster's A2 sights were garbage. When I dialed up for distance, the POI moved like a windage adjustment. I pissed away a lot of time/ammo figuring out that mess.
I
I really would NOT re-barrel a Bushmaster. You're better off buying a complete BCM upper with the offerings out there now.
Yup - for the effort and hassle, have a complete upper already set aside, and once you're no longer happy with the accuracy of your bushmaster complete upper setup at the longest distance you have access to, swap over and relegate the bushy to a training only upper. Unless you've got piles of AR's, the cost of the tools and time/hassle/possibility of getting something wrong rebarrelling, it's simpler to have a completely good upper receiver (and yes, the BCM KMR uppers are such a good deal now it's silly to look elsewhere if that configuration works.).
Yup - for the effort and hassle, have a complete upper already set aside,
I never did figure out whether the Upper receiver or the sight base assembly was out of spec. It was an A2 fixed carry handle.... garbage.
I give another vote to replace the barrel. It's only money.
I keep an extra upper for shooting sketchy ammo.... Steel cased, Bi Metal jacketed bullets, etc. He could rotate the bushy into that role.
I keep an extra upper for shooting sketchy ammo.... Steel cased, Bi Metal jacketed bullets, etc. He could rotate the bushy into that role.
That's exactly it - use one upper as a trash chute for everything that looks safe to fire (but otherwise not worth feeding to nice equipment), and it's great fun.. Show up with cases of steel cased cheap nonsense, and spend a day running drills - by the end of it that upper is an absolutely phenomenal malfunction clearance tool, up until it's a great budget drill running tool.
I'll 3rd or 4th this. I've had barrels that I could see the erosion in that still shot fine.
I really would NOT re-barrel a Bushmaster. You're better off buying a complete BCM upper with the offerings out there now.
My old bushmaster's A2 sights were garbage. When I dialed up for distance, the POI moved like a windage adjustment. I pissed away a lot of time/ammo figuring out that mess.
Thanks Now I read you load and clear.
Bruce in WV
10-15-14, 14:32
I really would NOT re-barrel a Bushmaster. You're better off buying a complete BCM upper with the offerings out there now.
Done - ordered last night!
Now is about as good as it gets for a buyers' market if you're looking for uppers/barrels, etc.
Now is about as good as it gets for a buyers' market if you're looking for uppers/barrels, etc.
And complete guns.
Keith
Bruce in WV
10-22-14, 18:45
That's exactly it - use one upper as a trash chute for everything that looks safe to fire (but otherwise not worth feeding to nice equipment), and it's great fun.. Show up with cases of steel cased cheap nonsense, and spend a day running drills - by the end of it that upper is an absolutely phenomenal malfunction clearance tool, up until it's a great budget drill running tool.
Got the BCM upper and took off the BM upper; set aside the milspec BCG and BCM CH I had on it for spares, and have no use for what's left. I'll take some pics and move the BM upper to EE and trade it to somebody who wants a "trash chute" (great turn of a phrase!). Thanks for the suggestions.
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