Sort of dissapointed in this caliber

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Re: Sort of dissapointed in this caliber

Postby wrangler » Mon Sep 17, 2018 8:52 pm

Forgot to answer the question. The barrel nut feed ramp is dished out in the center for feeding from a single stack mag with the 450 B follower.
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Re: Sort of dissapointed in this caliber

Postby wrangler » Mon Sep 17, 2018 8:56 pm

Sorry meant to say....the barrel extension is dished out and is not of the standard AR 15 223/5.56 type.
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Re: Sort of dissapointed in this caliber

Postby wrangler » Thu Sep 20, 2018 6:50 pm

So....I got the ejection port opened up. The rifle would barely eject a spent round. Anemic on gas so I tore the rifle down and measured the gas port. It was .070" (#50 drill). I opened the port with a #49 drill to .073" and went to the range. Still anemic! Back home, tore the hand guard and gas block off AGAIN and opened the port to .076" (#48 drill) and NOW the rifle ejects out at 1600 and the bolt locks back! Wouldn't have been such a big deal if I had a range in my back yard or better yet, the manufacturer of this barrel had the specifications on gas ports tested and proven before shipping them to Midway USA! Ha! Read a review there on this barrel earlier. The fella reported the same issues as I am having. Wait until I post my review!

Now to address the feeding issues! With Nam era 20 round mags with the blue follower from eBay, the 240 gr. Hornady XTP mag bullets are getting hung up on the large feed ramp at 6 o'clock. I put a round in a mag, insert the mag into the lower and hit the bolt release and BAM.... the round jams! I can see a copper speck on the center of the barrel extension feed ramp. I did cut a U notch in the front of these mags. These were functioning mags in a standard AR with 223 rounds prior to installing the blue follower over the GI follower.

Looking at the random cuts on the lands, I can see copper fouling sticking in them. At 38 rounds fired .... on functioning issues, I have at best a 1 1/2 moa barrel at this point.

Any suggestions on the feeding issues as to what tweaking of the magazines may need done would be appreciated. I guess I am going to have to remove the barrel and polish the feed ramp too. What a problem "child"!
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Re: Sort of dissapointed in this caliber

Postby wrangler » Thu Sep 20, 2018 7:09 pm

Looking at a jammed round with a flash light, it goes beyond the feed ramp in the barrel extension far enough into the chamber that I can not see the bullet. The head of the case is just about to leave the the magazine with the bolt face still pushing the round It is a dead stop at that point with the full force of the bca having been locked back by the bolt stop and released.
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Re: Sort of dissapointed in this caliber

Postby Hoot » Thu Sep 20, 2018 9:06 pm

If you haven't already done so, take a few turns off the magazine springs. They don't need to be nearly as strong as they are. I cut all mine down (from the bottom windings up) until there's only a modest upward lift with the last round in.

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Re: Sort of dissapointed in this caliber

Postby wrangler » Fri Sep 21, 2018 6:14 pm

Hoot....I haven't been able to get the first round to chamber reliably out of either magazine. I could see if I had several rounds in the mag and having spring tension problems.

Today I polished the feed ramp like I would do on a low end 1911. The feed ramp on the barrel extension, under the phosphate finish looked like a wash board! Also made a minor adjustment to the feed lips on the mags. Made a dummy round and played with the feeding from the magazines in the shop today only to ruin a new unfired case. The bullet actually gets pushed back inside of the case even with a good taper crimp.

I am set up with nine tables at at big gun show for this weekend. I'll have to wait until Monday to range test again. I can not believe Larry would sell an inferior or rather a poor quality product as this 450 barrel. I sure would like to know the manufacturer! LOL....Thinking back over the years, I paid for the furniture in his house and never bought a poorer quality item!
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Re: Sort of dissapointed in this caliber

Postby wrangler » Tue Sep 25, 2018 8:36 pm

Okay......FINALLY got this AR Stoner TRAIN WRECK barrel to operate and function! Barrel 16" carbine length Gas port needed to be enlarged from a as received #50 drill of .070" " gas port diameter" to a # 59 .073" diameter still under gassed to a #58 .070" diameter just to function/cycle. Yes......several take a parts and trips to the range! Good thing I have tools because that is so much better than talking to the phone heads at Midway USA who have no clue what you are having problems with but offer only return authorization numbers!

Then came the feeding problems. Okay.....my GI Nam era mags with the blue ebay followers needed the feed lips / ramps lowered. Yes lowered. My rounds were too high in these magazines to properly feed. Did all the suggested modifications (thanks to all here on this site) with U notches in the front of the mag etc and I polished the barrel extension feed ramp that looked like a wash board or rather like someone needed a tool change at least 100 barrel extensions prior to the one I received!

The spiral tool marks in the lands of the rifling collect copper like nobody's business! No bore scope needed here! The grooves are nice and shiny to the naked eye. Net accuracy.....thus far at 100 yards is at best a three shot group of 1 1/2"....nothing to write home about here!

I was not aware that I had to open up the ejection port on a standard AR upper for the caliber 450 Bushmaster round. Okay.....my fault.....I did not read up on these forums before I made my purchase at Midway USA. I am sure it wasn't in the best interest of the manufacturer selling me the barrel, bolt carrier, brass, reloading dies etc. etc. to make that known....to the average shooter, that would turn them away! Well no big deal for me.....I own tools.....I am a grey haired gunsmith wringing out a product that I would hope the gun magazine writers over at Guns & Blammo etc. should write in detail about but they will not because the manufacturers check had already hit their desks!

I'll wrap up this thread that I started by saying this to the average AR builder.... Eugene Stoner designed his rifle around the 223 / 5.56 round.... and if you want another caliber and lack skills / tools you may want to make a purchase from a company that offers a completed build WITH a 100% money back guarantee and hope for the best!
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Re: Sort of dissapointed in this caliber

Postby MOOSE EARS » Wed Sep 26, 2018 5:08 am

Glad you at least got it working. I'm sorry you had such an unpleasant ordeal but it's not the caliber or the original design that's a problem. It's parts that were not made for the specific caliber except for the barrel which should have been refunded and replaced. As you said, an upper designed and made for the 450BM runs like a Swiss watch and shoots sub MOA. It's a very impressive round when components are compatible, including the ammo. Hope you have a better experience with your next build!
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