450 Bushmaster Feeding Problems

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: 450 Bushmaster Feeding Problems

Postby BigBore Newb » Sun May 30, 2010 9:26 am

SpinKiller wrote:Shot the 450 Bushy this weekend. It stovepiped every time I pulled the trigger.
Took it home, took the lower off. I chambered an empty round....had to use a cleaning rod to get it out. It was catching in the same place, on the extractor, between the lugs. I took the file to it and this time took it down until the empty round would come out, no problem. Took it back out to test fire. This time it functioned flawlessly, ejecting brass with authority. Awesome!!


I'm having issues with my 450 as well. Can you please post pictures of where you are filing?

Thanks
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Re: 450 Bushmaster Feeding Problems

Postby Siringo » Tue Jun 08, 2010 12:08 pm

I just had issue similar to this using 284 brass. Diameter of the 284 case groove is larger than 450B cases. Enough so that the extractor sides caught on the locking lugs. Those little bumps are a close tolerance fit. Designed to add strength to the extractor. I also suspect that too tight of a fit could cause the extractor to break.
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Re: 450 Bushmaster Feeding Problems

Postby Blood » Mon May 22, 2017 12:35 pm

I know this a old post but I also would like to see the area that was filed.
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Re: 450 Bushmaster Feeding Problems

Postby Hoot » Mon May 22, 2017 2:18 pm

Blood wrote:I know this a old post but I also would like to see the area that was filed.


Blood, I don't know how comfortable you are with the bolt subassembly. Lets try looking at a few things. Take the bolt out of the carrier.
1) Can you depress the ejector plunger all the way flush with the bolt face without it binding or feeling too crunchy on the way in?
Yes = continue to next number
No = Carefully drive out the roll pin holding the ejector in carefully and remove the plunger and spring. Make sure the spring isn't broken and BTW, they don't have to be so long that it flings your brass halfway across the shooting line. just clear of the rifle. I have removed a few turns off of every one I own. Continuing- Set the plunger and spring aside. Blow out that hole with some compressed air or better yet put the tube from a can of spray degreaser, carb cleaner, brake cleaner, whatever (No WD40!) down into the hole and give it a squirt, followed by some compressed air to accelerate drying. If you just use a degreaser solvent, put a drop or two of high quality lubricant down into the hole. take a toothpick or equivalent and pump it in and out a couple of times to encourage the lubricant to get all the way down into the bottom of the hole in case there's a bubble trapped down in there. Clean the spring and plunger with a little of that degreaser on a paper towel while they're out, roll them dry and put a little of the same lube on them. Before you reassemble, take a round and with it tilted to the left away from the extractor, rock it into position and see if the extractor rides up and over the rim, then snaps down into the extraction groove. Its easier to do with the ejector out. If the ejector hook cant get past the thickness of the rim, you have found the spot where you have to slowly stone off a little metal from the ejector hook so it clears the rim. If it does snap down into the groove, is the extractor bottomed out in the groove? If the point of the hook bottoms out before the ejector is parallel to the bolt (in far enough) then you have found the spot to slowly stone some metal off of. In an ideal world, the hook point just bottoms out in the bottom of the groove at the same time as the arm supporting it rests upon the rim. If the hook point is not bottomed out, is the arm supporting it already resting upon the rim, preventing it from going in further, before the arm is parallel to the bolt body? If so, you need to slowly stone off a little of the arm where it contacts the rim, so that the hook can drop down into the groove a little further. The emphasis is that the hook clears the thicknet of the rim and drops down into the groove fare enough to allow the arm to rock down to where it is parallel to the bolt. Usually when one of these dimensions is not right, you will see some scrape wear on the outside of the extractor arm where it is rubbing on the barrel extension as well as wear on the barrel extension. Once everything is honky dory, put the ejector back in and try cycling some rounds.

2) Assuming the ejector plunger goes in and out without binding and the extractor is dropping far enough down into the groove but the rounds still do not reliably cycle. Borrow a Go/No-Go headspace gauge set from someone and make sure your chamber is not cut too long. You don't want the case going into the chamber so far that the extractor hook can't reach it. This is usually indicated by not being able to thumb the forward assist enough to hear that snap you get when the hook drops into the groove. In a perfect world, assuming the chamber is not cut too long, the forward momentum of the BCA is sufficient to strip the round, shove it into the chamber and the hook slip over the rim in one continuous motion. Some of that begins a little stiff on a new rifle until the mating surfaces get shined up from repeated cycling. I know members who have sat and cycled their actions over the course of evening TV viewing until it smoothed up.

An added option is to carefully remove the extractor and polish it up on a polishing wheel. Some times, just giving it a good shone, provides that small change in resistance tat allows it to do its job. I'm going to have to break off and actually do some work at work right now. See if you get past the ejector/extractor as the culprit in the short run. We can continue where we left off later.

Hoot

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