SmallCaliberCentral

I received a complete upper in .204 for Christmas with the intention of just swapping out uppers on my RRA AR15.

All went well until I took it to the range and I couldn't get it to cycle. I changed out the buffer spring and that didn't help.

Let me just say that I've only fired Hornady factory 45-grain through it, none of the cartridges I've reloaded yet.

I compared the BCGs from both the new rifle (on the left, for the .204) and from my old upper (on the right, in .223) and the most obvious difference would be the cutout on the bottom....vastly different.

Why would that be when the COAL for both rounds is 2.26 inches? Do you think this could be the problem?

I sure appreciate any insight you experts can give me!

HUH!! that's a new one on me... I hope someone else chimes in here... I'll take a look at my RRA ARs when I get home, I have .223 and .204 also. I'll let ya know!

Don't forget to try ar15.com! Great resource right there!

Wow! Looks like some body didn't enter the correct dimensions on the cnc machine? I looked at my bcg and it appears to be very close to your .223 rra bcg. Can you interchange and try them? Or would that be a no no? The dimensions on the head are the same I think is the problem that it won't run another cartridge into battery? If so could it be the extra weight not going back far enough to strip the next in the mag.?

stein wrote:Wow! Looks like some body didn't enter the correct dimensions on the cnc machine? I looked at my bcg and it appears to be very close to your .223 rra bcg. Can you interchange and try them? Or would that be a no no? The dimensions on the head are the same I think is the problem that it won't run another cartridge into battery? If so could it be the extra weight not going back far enough to strip the next in the mag.?

Your BCG in your .204???

The 204 Carrier on the left is the same kind I use in all my AR15's. It's an M16/AR15 legal to use carrier. That is not the problem. Was this a custom build or factory upper? Is it new or used?

A 204 Ruger chamber has a vey long throat. Loading to 2.260" is OK.

What is the exact problem you are haveing? What does it do and when does the failure occur?

Greyfox

Grayfox wrote:The 204 Carrier on the left is the same kind I use in all my AR15's. It's an M16/AR15 legal to use carrier. That is not the problem. Was this a custom build or factory upper? Is it new or used?

A 204 Ruger chamber has a vey long throat. Loading to 2.260" is OK.

What is the exact problem you are haveing? What does it do and when does the failure occur?

Greyfox

Thank you. It is a new custom build with DPMS upper receiver, Lilja barrel and Les Baer BCG.

I've had the setup less than a week, and it has NEVER cycled a round from the magazine into the chamber.....

What I'm saying is that, if the recommended COAL for both the .204 and the .223 is the same at 2.26", then why would the cutout in the carrier for the .204 be so much smaller?

The reason for the carrier cut out was to make the carrier not trip the sear an M16 fully automatic rifle. The BATF at one time ruled this carrier as a machine gun part and it would be illegal. That is why the manufactures used the more cut out one. See below.

The BATF has now changed thWritten by Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), Chief of the Firearms Technology Branch
...M16 bolt carriers are not designed and intended solely and exclusively for use in converting a weapon into a machinegun and are not any combination of parts from which a machinegun can be assembled. Further, an M16 bolt carrier is not a firearm as defined in the GCA or a machinegun as defined in the NFA. An M16 bolt carrier is simply a machinegun part and as such its domestic sale and possession is unregulated under the Federal firearms laws. It is not unlawful to utilize a M16 machinegun bolt carrier in a semiautomatic AR15 type rifle.


You built the rifle from excellent parts so that is good.

Are you saying that it does not feed from an open bolt and empty chamber? Or will it not cycle when you fire it?

Greyfox

Thanks for the intel Grayfox. Not that it matters now, but the BCG for my .204 and .223 (both RRAs) look identical, with the bigger slot.

Yeah the bcg in my .204. It looks like greyfox and bowshot how the situation well in hand. So I will not muddy the water any more sorry for not being clear.

bow shot wrote:
Don't forget to try ar15.com! Great resource right there!

Good point, I didn't even know it existed until now. Thanks!

I'm thinking that the cutout in the bolt carrier is too short....look at the dings on the shoulders of these two cartridges. These were the top rounds in the mags when the carrier tried to pick them off of the magazine.

I'm trying to get this on to AR15.com, but they haven't allowed me in yet....must have taken the holiday weekend off.

Texaz, did you try swapping the BCGs? Just a quick troubleshooting idea...

texaz, there is nothing wrong with your carrier/bolt group. This is a feeding problem betwen the magazine and feed ramps.Lead tipped bullets will drag alot on the feed ramps. Polish your feed ramps smooth.Next check where the steel ramps meet the aluminum receiver. The aluminum ramp (if it has the cuttouts) should be even or higher than the steel ramps.

Next check your magazines. Take the spring and follower out the bottom of the magazine. Hold the spring and follower straight up. If the front tip of follower tilts down, you need to adjust this. Bend the spring at the top so the follower sits level or a tad higher at the tip. Put it back together and load it with two less rounds than maximum capacity. This will let the magazine spring work better.

At a safe location put the loaded magazine in the rifle. Now check to see where the bullet tip is in relationship to the feed ramps. The bullet tip has to be above the bottom of the feed ramp. push the bolt stop in and see how it feeds now.

What we want to happen is the lead tip does not drag or catch on the feed ramp. The magazine should hold the bullet tip up when the bolt pushes it foreward into the ramps .

The dents in the shoulder should go away when it feeds better.

Greyfox

Great trouble shooting advice right there.

Grayfox wrote:texaz, there is nothing wrong with your carrier/bolt group. This is a feeding problem betwen the magazine and feed ramps.Lead tipped bullets will drag alot on the feed ramps. Polish your feed ramps smooth.Next check where the steel ramps meet the aluminum receiver. The aluminum ramp (if it has the cuttouts) should be even or higher than the steel ramps.

Next check your magazines. Take the spring and follower out the bottom of the magazine. Hold the spring and follower straight up. If the front tip of follower tilts down, you need to adjust this. Bend the spring at the top so the follower sits level or a tad higher at the tip. Put it back together and load it with two less rounds than maximum capacity. This will let the magazine spring work better.

At a safe location put the loaded magazine in the rifle. Now check to see where the bullet tip is in relationship to the feed ramps. The bullet tip has to be above the bottom of the feed ramp. push the bolt stop in and see how it feeds now.

What we want to happen is the lead tip does not drag or catch on the feed ramp. The magazine should hold the bullet tip up when the bolt pushes it foreward into the ramps .

The dents in the shoulder should go away when it feeds better.

Greyfox

Good stuff, I will try that, and thank you very much.