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Old 06-27-2010, 05:33 PM   #1
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Default Replacement Bolt for AR Question?

I've owned a Bushmaster for 8 yrs, put close to 10,000 rounds through it, and have begun experiencing "failures to feed". 1st round chamber fine, rifle fires and ejects, but does not strip the second round from the mag and I end up pulling the trigger on and empty chamber. Charging it manualy works fine but pull the triger again and I get the same result.

I have a second, new, complete long range scoped upper that works fine using the same lower and the same magazines.

Much of the 10,000 rounds I've put through the Bushy upper was, yes, I know, STEEL CASED, EEK and I can see visible wear on the bolt lug that engages the top round in the mag.

So...I think I've worn out this bolt face and need to replace the bolt?

My question is:

1. does my analasys make sences to you AR building guru's and:
2. should I order from bushmaser only? do i need to be worried about headspace on a mil spec rifle?
3. any thought on the new "Fail Zero" products? Thier bolt is twice the cost of a standard mil spec but given what I've read about it and the amount of ammo I shoot, it might be a wise investment?

Thanks for your input fella's!

TACK

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Old 06-27-2010, 05:39 PM   #2
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In general, I would not consider ANY bolt on ANY firearm to be a "drop in" part- and yes, headspace CAN be an issue.

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Old 06-27-2010, 06:16 PM   #3
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Quote:
Originally Posted by Tackleberry1 View Post
I've owned a Bushmaster for 8 yrs, put close to 10,000 rounds through it, and have begun experiencing "failures to feed". 1st round chamber fine, rifle fires and ejects, but does not strip the second round from the mag and I end up pulling the trigger on and empty chamber. Charging it manualy works fine but pull the triger again and I get the same result.

I have a second, new, complete long range scoped upper that works fine using the same lower and the same magazines.

Much of the 10,000 rounds I've put through the Bushy upper was, yes, I know, STEEL CASED, EEK and I can see visible wear on the bolt lug that engages the top round in the mag.

So...I think I've worn out this bolt face and need to replace the bolt?

My question is:

1. does my analasys make sences to you AR building guru's and:
2. should I order from bushmaser only? do i need to be worried about headspace on a mil spec rifle?
3. any thought on the new "Fail Zero" products? Thier bolt is twice the cost of a standard mil spec but given what I've read about it and the amount of ammo I shoot, it might be a wise investment?

Thanks for your input fella's!

TACK
Not a guru but I believe headspace would be an issue with any new bolt, especially in an upper with 10,000 rnds through it. Which leads to my actual point, does it make sense not to rebuild both the bolt and receiver? Over those 10,000 rounds the bolt and receiver have worn and smoothed their respective contact points and now fit each other like well worn slippers to your feet. A new bolt may or may not fit well enough given the changes in the original receiver's tolerances. If it were me, and again I am certainly not a guru, I would bite the bullet and rework the entire upper at this point. JMHO
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Old 07-01-2010, 02:43 PM   #4
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Thanks guys.

I think I'll ship the upper in to Bushmaster for a new 16" barrel and bolt. I've been wanting to replace the barrel anyway since it's a 14.5 post ban w/welded on 1.5" muzzle break. Certainly don't need the break on a .223

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Old 07-02-2010, 05:45 AM   #5
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I'd like to see some pics of the wear areas, Tac. Especially the bolt lugs.

It sounds like more of a mag issue, even though they work with the other upper. Each upper will fit the lower differently.

How is the gas flow? Clean tube? Any obstruction in the carrier key? Gas rings worn? With 10K rds they could be well worn, causing short stroking.

If you run it wet does it work?

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Old 07-02-2010, 10:13 AM   #6
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I agree with m14srock, I think that sounds like a bad mag.

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Old 07-02-2010, 02:51 PM   #7
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That does not sound like a FTF issue. It sounds like a short stroking issue. I would look at the gas tube/gas key. Insufficient gas can be caused by fouling in the tube. Use a good solvent like Sweets 7.62 or Shooters Choice and dribble it into the back of the gas tube. Let is soak for a few hours and use a long pipe cleaner to clean it out. Repeat as necessary. It may take several applications. If you get green sludge, that is copper fouling.

With that kind of round count, I would probably take out the gas tube and soak it more thoroughly. Plug one end and let it soak few days to a week filled with solvent and pipe clean it out.

A new gas tube would not be a bad idea.

Likewise, soak the bolt carrier/gas key in solvent to remove any stubborn gunk there.

Before you take out the gas tube, look at the exterior of the tube where it meets the front sight base. If there is more than a little soot, you need a new gas tube. Tubes are cheap, rebuilds are expensive.

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Old 07-07-2010, 01:57 PM   #8
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Quote:
Originally Posted by slowryde45 View Post
As far as your ? on whether or not you have to stick with the Bushy upper, no reason you can't put whatever upper (brand) on your lower. Go with what catches your eye, serves your function, and fits your wallet

10,000 rounds sounds like a lot to some folks out there, but it really isn't if you do alot of practicing, varmint shooting, target plinking, etc. I typically go through 1K rounds in a couple weeks. So doing the math, it's easy to see where you can go through 10K in a few months if you shoot regularly. But I shoot that many rounds through several guns, not just through 1.

If you think you need or want to replace the upper and bolt, I would probably go with an all new upper receiver assembly and BCG. As for Fail Zero, yes, you can spend the money on them - or save quite a bit by going to something like Bravo Co. or LMT. If you want something a little better, go with Young.

But like a few of the folks have already suggested, try it with a new or at least different magazine. Make sure everything is clean and LUBED. Make sure there are no gas leaks or plugged gas tube. Make sure your BCG carrier key is still staked and not loose. Might even be a good time to invest in an extractor upgrade, too. All of these cost less than a new upper, and could solve your problem.

Slo
Slo gives very good level headed advise.

I have a Yound BCG in one of mine and it works well. My Spikes bolt works great as well. I have heard good things about RanierArms BCGs if you can find one in stock. Guys have said BCM makes operator grade parts and are put through many tests before sold.
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Old 07-08-2010, 04:46 PM   #9
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For about $30.00, Brownell's has a "How to Build An AR-15" DVD. After viewing this DVD two or three times, you should know wether or not you want to take on gunsmithing duties on the AR. If you don't wish to buy the DVD, the contents of this DVD can be viewed online from the Brownell's site. If you have a fast internet connection at home, have a look at Brownells online info.

Len

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