450 Bushmaster Bolt Extractor/Ejector function test.

[Hoot]

Here's my spin on this and both you guys can check it if you have a caliper. The original 45 Pro was based upon the .284 Winchester case. That case had a rim spec'd to .473 and an Extraction groove spec'd to .409. The SAAMI drawing for the 450b is the same for those two dimensions.

Around the time of the spring sale in 2010, Bushmaster's production got held up for bolt availability. I heard it boiled down to the sub-contractor who made the extractors couldn't or wouldn't deliver the ones needed to fit the above tolerances at a price Bushmaster wanted to pay. Some said Bushmaster and Hornady actually had a backdoor deal for Hornady to change the specs to .463 on the rim and .393 on the groove, for two reasons. Hornady wanted to make sure folks didn't have too easy a go using .284 brass and cutting them out of a revenue stream on brass. At the same time, Bushmaster could get extractors for 7.62x39 bolts cheaper. It was a Win-Win for them. So, Hornady started making their brass to work with the 7.62x39 extractors and Bushmaster used them in their bolts. The tolerances on those extractor were such that the extractor would not drop into the extraction groove enough to allow it to clear the barrel extension and a few folks attempting to use them with .284 brass were experiencing broken and/or dragging extractors depending upon when their particular upper was built. The solution was to buy new Hornady brass, reload 1-fired Hornady ammunition, or turn every .284 brass rim and groove down to the smaller dimensions. I know as I had to do exactly that with the two bags of .284 Winchester brass I bought. That and variations in case mouth thickness causing bulging was enough of an imposition for at least me to give up on the .284 brass approach as my bolt had the extractor that was toleranced for the narrower dimensions. When I used the narrower dimensioned Hornady brass my problems went away and life moved on.

Fast forward to the present. There is a possibility that some of the recent Hornady ammunition has brass with rims and extraction grooves closer to the actual SAAMI specification as opposed to the low end of the tolerance. If your bolt goes in and comes out without a fight when you don't have a cartridge in it, but hangs with one in it, it may be for the reason of the rim and extraction groove dimension actually being to SAAMI spec of .473 and .409 respectively. Here's where the caliper comes in. Take some of the cases you used where your extractor dragged or seized up in the barrel extension and measure the rim and extraction groove, or measure all the ones you have in the case where some worked and some didn't. If you see a trend that the ones that work have narrower dimensions and the ones that don't have the SAAMI spec dimension, then you have your answer. You can turn down the rims and extraction grooves of the problem cases, or relieve the inside of the extractor hook to allow it to work with both narrow and wider ones. That's what I ultimately did. I did not do that with my spare extractor, figuring I'd do so if I ever needed to put it into service. We're talking .010 relief, not much, but enough to make the difference in it working.

That's a big reach for a culprit, but there is precedence for it. If you discover that the cases which give you trouble, are indeed .463 rim and .393 groove already, but still give you trouble, then the problem lies elsewhere. It's just too similar to what we saw two years ago to pass off as coincidence.

Now some will say the tolerances in the SAAMI drawing allow for -.010 in the brass dimensions I've mentioned. While that's true, the same tolerances apply to the SAAMI spec for .284 Brass, not to mention .308 brass as well, yet if you measure a sample of those two, you will find that most if not all measure at .473 and .409, not the lower tolerance. That's more than a little suspicious. You should not be forced to rely upon all the 450b brass being made all the way down at the lowest acceptable tolerance in order for them to work. You be the judge. You decide what course of action you want to pursue. It smelled fishy two years ago and IMHO, it still does. Grab those calipers...

Hoot

[scottbander]

Scott, did you get the name of the person @ Bushmaster?
Texas Sheepdawg
I am also in north texas

Sorry I did not get his name. But I did however talk to them again today about this issue. The guy I talked to this time had not heard of this problem before, but he said that its possible for the extractor to have been manufactured out of spec. He is sending me a new extractor for free which is nice. I'd rather not have to send the upper back for them to look at. I didn't catch his name this time either. I did ask him about still making the 16"ers and he said they should still make them just not right now. He said they manufacture them in seasons maybe only once or twice a year.


Hoot,
That sound like good insider info on the cases. That scenario fits the problem im having. I was thinking .010 maybe .015 at most. I thought, if nothing else I could take some material off the case flange of the brass I have, and just not loose them.
If the new extractor doesn't do the trick. I will probably try filing the extractor .010 and go from there. I will try to mic the case flange itself but I don't know if my calipers jaws are small enough.

Thanks, Scott

[tridentarmory]

when we used the bushy extractors, we had to file them a smidge also.... this is a common problem with our older rifles before we started doing most of this stuff ourselves.

I noticed that on some of the extractors that they fit tight in the rear, meaning that the hole may have been drilled a couple thou' too far back in the bolt body.
a small amount of work with a file will fix the issue...

simply pull you bolt carrier ass. out and push the base of a loaded cartridge into the face of the bolt. you will hear a decided click sound when the extractor mates to the rim. if you have to "angle" the cartridge to make the clicking sound, then you need to continue filing.
I wouldnt worry about extractor weakness with a bit of filing, as we nearly never see extractor failure with the ones that we've done.


D.I.Y. fixes are great.

[tridentarmory]

Im telling you all, 90% of the extractors ive seen from bushmaster in the 450 flavor need work..... do the work... keep a good "claw" angle on the extractor though, you dong want it slipping off the rim once its on there, or slipping off some old crappy brass thats beaten down.

This is almost a guaranteed fix.... ive done the filing of lugs, the polishing of this and that, almost all of those things develop "self wear" and work themselves into function after only a hundred rounds, but the short extractor groove cant fix itself. YOU ALL NEED TO LOOK INTO THIS

[Texas Sheepdawg]

Im telling you all, 90% of the extractors ive seen from bushmaster in the 450 flavor need work..... do the work... keep a good "claw" angle on the extractor though, you dong want it slipping off the rim once its on there, or slipping off some old crappy brass thats beaten down.

This is almost a guaranteed fix.... ive done the filing of lugs, the polishing of this and that, almost all of those things develop "self wear" and work themselves into function after only a hundred rounds, but the short extractor groove cant fix itself. YOU ALL NEED TO LOOK INTO THIS

Well, I guess I'll raise my hand and ask a dumb question.
James, I like doing business with companies who are plugged in to their clients' needs. If I ever decided to get a spare bolt, would you consider selling assembled 450 Bushmaster bolts or maybe even just the modified extractors? I'm gonna be honest and tell ya I've had a belly full of the "New" Bushmaster. I got burned pretty bad last year. My current 450 Bushmaster ended up living and breathing fire due only to Midway USA, DPMS, Stag Arms and Daniel Defense. (and of course our lovable geniuses, Gunnut and Ross Schuler. I want to support the guys who keep us shooting by keeping them in business. I like it that you decided to join the forum. It shows me you are indeed keeping your finger on the pulse of the future of the 450 Bushmaster. I know my request could mean some headaches for your business by going I to the parts business, but if possible, would you consider becoming a source for the 450 Bushmaster complete bolt assemblies, bolts or extractors?

[Jim in Houston]

simply pull you bolt carrier ass. out and push the base of a loaded cartridge into the face of the bolt. you will hear a decided click sound when the extractor mates to the rim. if you have to "angle" the cartridge to make the clicking sound, then you need to continue filing.

For those of us who want our BM450's to shoot properly but didn't invent it, exactly what are you filing? A photo would help.

[9x19MdM]

simply pull you bolt carrier ass. out and push the base of a loaded cartridge into the face of the bolt. you will hear a decided click sound when the extractor mates to the rim. if you have to "angle" the cartridge to make the clicking sound, then you need to continue filing.

For those of us who want our BM450's to shoot properly but didn't invent it, exactly what are you filing? A photo would help.

I THINK (notice the caps, so if I'm wrong...) it's the lip as seen in this pic.

[Hoot]

Sorry for the hurried drawing. The area of the extractor in red needs to clear the rim so that the claw can sit down in the extraction groove far enough for the entire extractor outside to not run against the barrel extension. It also needs the extraction groove itself to be deep enough that the claw can go down in far enough to not make it drag. If the red area is sitting on the rim before the claw is all the way down to the bottom of the groove, you need to relieve some material where it is touching the rim. It is easily and controllably done with a fine cratex wheel for a Dremel. The only thing I do to the the claw itself is buff polish the leading edge (green) so that it slips over the rim as it picks up the cartridge and drives it into the chamber, with as little resistance as possible. Claws that are parkerized have a dull, rough finish that drags on the rim as it passes it requiring more force to overcome the return spring. Some extractors have better, lower friction types of coatings and don't need their leading edge polished. I do nothing to the remainder of the extractor (black)

extractor.jpg (9.71 KiB) Viewed 12207 times

Hoot

[9x19MdM]

Sorry for the hurried drawing. The area of the extractor in red needs to clear the rim so that the claw can sit down in the extraction groove far enough for the entire extractor outside to not run against the barrel extension. It also needs the extraction groove itself to be deep enough that the claw can go down in far enough to not make it drag. If the red area is sitting on the rim before the claw is all the way down to the bottom of the groove, you need to relieve some material where it is touching the rim. It is easily and controllably done with a fine cratex wheel for a Dremel. The only thing I do to the the claw itself is buff polish the leading edge (green) so that it slips over the rim as it picks up the cartridge and drives it into the chamber, with as little resistance as possible. Claws that are parkerized have a dull, rough finish that drags on the rim as it passes it requiring more force to overcome the return spring. Some extractors have better, lower friction types of coatings and don't need their leading edge polished. I do nothing to the remainder of the extractor (black)

extractor.jpg

Hoot

So you "under cut" the red area (just ever so slightly)?

[Hoot]

So you "under cut" the red area (just ever so slightly)?

Yes, emphasis on "ever so slightly". If the claw is bottoming out in the extractor groove and not riding on the rim, preventing the extractor from riding close enough to the bolt so as not to drag, then you have to relieve the end of the claw where it is bottoming out. Care should be taken not too lose the sharpness of the claw edge so that it maintains a firm grip on the rim as it retracts the spent case out of the chamber once it is spent. IE In shortening it, do not round it off. Once again a fine Cratex wheel, with it's painfully slow material removal rate is a good approach. Stop and check functionality frequently so as not to take any more off than absolutely necessary.

Hoot