The AR World is Nonsensical: Here’s My Latest Contribution.

[44 AMP]

If you wind up drilling the port in the barrel, I'd suggest getting an adjustable gas block to go with that. It's not impossible that opening up the barrel port could result in the gun being overgassed and an adjustable gas block should be able to compensate for that, if that condition does occur.

Good Luck!

 

[stagpanther]

This drilling the port thing--It's more than just putting a hole in the barrel. I've sent more than a few back to the manufacturer that were not done or finished well. Just sayin.

The recoil wasn’t bad at all, I’d dare say that it might be on par with my 10.5” 6.8spc, of course it’s considerably lighter than the 450 and it has no brake, just a 6” flash can pinned and welded. I’ll do a side by side one day and see.
Either way, the 450 recoil wasn’t near to what I was anticipating. I guess the panzer brake did it’s job.

What kind of load are you using in your bushmaster? I've never had any issues with my 458 socom--which is similar-- but when I fire it it always gives a very respectable thump and I always think to myself "yup, this is about as far as I want to go in an AR15."

 

[rickyrick]

I’m just running factory loads: Hornaday and Winchester 250gr.
I was expecting more recoil than it actually has.

Drilling will be my last option, however when I order things I take a gamble, I’m relegated to solving this one myself. I would probably send it back, but none of the carriers will pick up at my home in the forest and I’m never off work in time to get to one of the shipping places.

 

[rickyrick]

I took the gas block off and found no signs of leaks or misalignment. Measured the gas port and it came in at a whopping .109-.110”.

I checked everything over, read various internet sources and determined that it is not unusual to have a port of .120” on a 450 bushmaster with a rifle length gas system.

I went ahead and opened the port to .120” which is the maximum because that’s the ID of the gas tube.

Test fired today and it cycled properly at first for the most part, with a couple of hiccups in the first few magazines, but would feed rounds and lock back when empty.
After that, it would run through magazines just fine probably just needs more break-in.

Interestingly, it didn’t like to chamber rounds completely by using the bolt release, but chambered them just fine by slingshotting the charging handle. That’s something I could live with because I tend to be a slingshotter anyway.

Seems to have a touch more recoil now.

I guess I’m gonna have to get set up to reload for this one, and decide on an optic. It’s pretty fun to shoot.

 

[stagpanther]

Interestingly, it didn’t like to chamber rounds completely by using the bolt release, but chambered them just fine by slingshotting the charging handle.

I've had that happen a couple of times with AR 10 builds, sooner or later things went downhill--light pin strikes, not able to go into battery fully, double-stacking etc. By slingshotting, I assume you mean you need to fully retract the charging handle and let go to get the carrier to successfully chamber a cartridge from the magazine? Since your set-up is new, you might be able to see signs of uneven wear on the carrier and lugs.

My guess is that you have something that might be interfering with how the bolt/carrier rides in the upper; perhaps something to do with the magazine and how it interfaces with the lower. Might be something as simple as how the cartridges are stacking in the magazine; a bit of bulge or tilt by the follower. I know the bushmaster isn't identical to the 458 socom but I chose the lancer magazine and tromix single-stack follower right from the get-go though I did read someplace that the bushmaster can be more prone to feed issues than the socom (one of the reasons I chose the socom over the bushmaster when I did my build). I'm traveling at the moment and it's been a long time since I looked inside my 458 socom--I seem to recall that the barrel extension was ramped in such a way to facilitate straight-on presentation of the cartridge that you might have from a single-stacked magazine; IIRC it doesn't have a lug at the 6 o'clock position. My less than 2 cents.

 

[rickyrick]

Yes, when I hit the bolt release from the bolt held open position, it partially inserts the cartridge into the chamber, it can be jacked the rest of the way in with the forward assist. It doesn’t always do that.

When I fully retract the charging handle and release, the cartridge is fully inserted and bolt is seated. No problem while firing.

I am looking at possible magazine issue, the couple of hiccups I had after I got the rifle to feed on its own, the cartridge was tipped up in the action (I’m not sure of the term for that type of failure) It has since seemed to stop doing that. I currently have one magazine made by Bushmaster.

It has one big feed ramp instead of the usual two. I may give it a polish.

One disclosure, I don’t currently have a 45cal brush, so I haven’t given the chamber a good scrub as usual with a new gun. I’m sure if I dig around the barn I might have one tucked away, something that I overlooked until I went to clean it.

I did anticipate some of this when I researched the caliber ahead of time.
So far it ran well this afternoon.
If for some reason it becomes too unreliable, I might just convert it to a side charger, block the gas port and have a straight-pull bolt action lol. It’s not really a caliber you wanna do mag dumps with