450 bushmaster is short stroking

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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450 bushmaster is short stroking

Postby Dinoallison » Tue Dec 17, 2019 9:46 pm

I currently bought a 450 bushmaster complete upper receiver from radical firearms with the 20 in barrel. I installed it on my Daniel Defense ddm4 v11 pro. I use a 10 rd lancer mag with the Tromix center follower. The problem I am having is the BCG is not going all the way back and locking out. It only goes about half way and then leaves the spent shell in the chamber. I figured I had a gas issue so I realigned the has block which didn’t seem to be off. It still does the same thing. Any suggestions I’m running out of ideas and I’m starting to get very discouraged?
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Re: 450 bushmaster is short stroking

Postby coyote wacker » Wed Dec 18, 2019 9:28 am

With a new upper I always, oil the carrier and inside upper with a very heavy coat, work it 100 cycles by hand. Then wipe carrier down with a clean rag not paper towel, wipe inside of upper clean. Oil again carrier and upper, then test fire.

What ammo are you using factory or handholds ?
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Re: 450 bushmaster is short stroking

Postby Dinoallison » Wed Dec 18, 2019 8:02 pm

I’m using Hornady American whitetail 245 gr. I will try heavy oiling and manually exercising the action.
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Re: 450 bushmaster is short stroking

Postby Hoot » Wed Dec 18, 2019 9:15 pm

Food for thought...more info...

What length gas system does it use? Carbine / Mid / Rifle? Hopefully not Rifle.
Did it ever work properly? If no, is it still under warranty?
If yes, what changed prior to it stopping?
Does it fail to extract every time its fired?
If yes, chamber a round. Remove the magazine. Shoot it. Does it extract okay with the magazine out? Obviously you can't check the BHO without the mag in but getting to a point where it does extract under certain conditions, narrows the field of suspects. If taking the mag out doesn't help with extraction, it needs more gas. Some would argue that it may need more break-in to polish the moving surfaces. If that were the case all AR's wouldn't work without a break-in and I know from personal experience that is not the case.

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Re: 450 bushmaster is short stroking

Postby Dinoallison » Thu Dec 19, 2019 5:45 pm

It never functioned correctly and I do believe the gas system that comes on the 20 in barrel from radical firearms is a rifle style. It is still under Warrenty and I can return it. It has done the same thing every single time. It takes the action back about half way and then puts the spent round back in the chamber. It does the same thing without mag.
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Re: 450 bushmaster is short stroking

Postby Dinoallison » Thu Dec 19, 2019 6:00 pm

Here is the link from brownells where I bought it. It gives you the specs and according to their description the 20 in barrel has the rifle gas system. https://www.brownells.com/rifle-parts/r ... 00-025-549
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Re: 450 bushmaster is short stroking

Postby Hoot » Thu Dec 19, 2019 10:12 pm

Dinoallison wrote:Here is the link from brownells where I bought it. It gives you the specs and according to their description the 20 in barrel has the rifle gas system. https://www.brownells.com/rifle-parts/r ... 00-025-549


Without proper accommodation in the form of a bigger gas sample port, the 450b is challenged to work with a rifle length gas system. That length works well with a 5.56 system because the volume of the bore is considerably less than the 450b (4X less) and because the starting pressure is much higher in the 5.56. Some companies don't think that difference through when they decide to manufacture a 450b barrel using a gas port size appropriate for a 5.56 system. Secondly and more disturbing is the fact that some value based manufacturers use their customer base as their Quality Control / Design Review department. That is unthinkable! We're not their guinea pigs. We here go to great lengths correcting design or manufacturing quality issue among ourselves utilizing our ingenuity but we deserve to have our hard earned dollars go towards a mature product, not an experiment. Ooh, it just gripes my arse!

I too bought a 20" 1:24 barrel with a rifle length gas system and it too struggled to function consistently well across the same loads that ran successfully in either a carbine and later discovered, mid-length gas system. This problem came about of our own making with the promotion of the 450 Corvette idea. Sorry to cast aspersions on folks no longer here to defend their idea but you can't squeeze a gallon of performance from a 3 quart pail. Given how hard it was to get rifle length gas system barrels when I got mine, I chose to keep it and slowly open up the gas port until it worked and because I got a great price on it. I consider the whole experience to be one of my worse decisions in this caliber. Thankfully, it was less than a $200 worse decision. Since then, the availability of different barrel choices in this caliber has skyrocketed, so no one is forced to live with poor construction or design in order to keep their project rifle affordable. Hold the manufacturer's feet to the fire and send it back while you still can. You can do better with a 20" barrel and a mid-length gas system, especially if you intend to reload. If you only wish to shoot factory loads in the 250gr region, a carbine length system will serve you equally well. It was what the original 450b AR platform shipped with and it was well researched beforehand. There are plenty of good, affordable choices that have been testified to here on these forums by folks who have bought them. Read around...

Hoot

PS: Do the right thing and clean it up spic-n-span before returning it.
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Re: 450 bushmaster is short stroking

Postby Dinoallison » Fri Dec 20, 2019 6:27 am

Do you have any recommendations of a complete upper you like with a 20 in. Barrel? I wanted to go with a 20 in barrel because I Strictly am going to deer hunt with it and I was extremely happy with the accuracy of the gun at 200 yards. Just stinks it won’t cycle correctly.
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Re: 450 bushmaster is short stroking

Postby Hoot » Fri Dec 20, 2019 8:27 am

Dinoallison wrote:Do you have any recommendations of a complete upper you like with a 20 in. Barrel? I wanted to go with a 20 in barrel because I Strictly am going to deer hunt with it and I was extremely happy with the accuracy of the gun at 200 yards. Just stinks it won’t cycle correctly.


You need to preface that question with an acceptable price range. You can get excellent quality and reliability for a fee.

You're in good company with me as I prefer rifles with rifle length barrels myself, not pop guns. I'm not the president of the "rig of the month club" however, so my universe is pretty limited. There are plenty of members who are actively building and rebuilding rigs here, so I'll defer to their experience with readily available components. My first 2k reloads went through a complete 20" Bushmaster upper mounted on an A2 fixed stock, RRA NM lower. The only failures to perform were a result of my experimenting with hand loads on the fringes of what the rifle was designed for. That upper was made almost 10 years ago, before Bushmaster got sold to a wealth enhancement group so that experience may just be a glimpse of the past. I now hang my hat on a 20" Bartz upper. The fit and finish imply that they are hand made one at a time and definitely tested before they leave their U.S. factory. You pay for that however. With the Bushmaster upper sporting a carbine length gas system, the only time it behaved as "over gassed" was when I was feeding hand loads that were "over gassed" to start with.

At the risk of sounding like a broken record, I will once again state that IMHO, this caliber is plenty lethal at modest velocities. I don't mind pushing my hand load ladder tests up to where I begin to see pressure signs, but I stop there, back down and don't return, opting instead for the load that is most stable and accurate without living on the edge.

Do write off an entire evening or two to hunt around the sub forums and read about other member's experiences. We are pretty good about sharing them, both positive as well as negative. We go through the trouble of putting them up so that others can benefit from them.

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Re: 450 bushmaster is short stroking

Postby Dinoallison » Sat Dec 21, 2019 10:11 am

Thank you so much for all your help. I think I’m going to go with the 20 in bushmaster complete upper. The only thing I’m concerned about is it not having a rail on top of the grip. I’m not sure if the little section of Picatinny rail will be enough to mount my 3-9 vortex scope. It almost looks like by the picture that it has two bolt on pieces to put on top of the grip? Are you familiar with that at all?
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