Feeding problems

Talk about the AR15 style rifles chambered in 450 Bushmaster.

Moderator: MudBug

Re: Feeding problems

Postby Mdl1911a1 » Tue Jul 09, 2019 6:04 pm

PyroRobby: Thanks for the table. Great information!! I'll give BCA a call tomorrow.
Mdl1911a1
 
Posts: 8
Joined: Fri May 31, 2019 4:44 pm
Location: Eastern NM

Re: Feeding problems

Postby Al in Mi » Tue Jul 09, 2019 6:38 pm

Posting for OP Ml1911a1


Image

Image
Last edited by Al in Mi on Wed Jul 10, 2019 4:30 am, edited 1 time in total.
User avatar
Al in Mi
 
Posts: 1559
Joined: Sat Jun 20, 2009 8:24 am

Re: Feeding problems

Postby Mdl1911a1 » Tue Jul 09, 2019 7:32 pm

PyroDaddy: Went back to check my original order from BCA in prep for a call tomorrow. I've been providing one false piece of info: Gas block is 0.875. I simply mis-remembered. I'll give this info to BCA tomorrow :-)
Mdl1911a1
 
Posts: 8
Joined: Fri May 31, 2019 4:44 pm
Location: Eastern NM

Re: Feeding problems

Postby 303hunter » Tue Jul 09, 2019 8:11 pm

I’ve got 18” mid length gas, and 16” carbine gas BCA barrels, and both eject to 4:00-4:30 using A2 buffer systems. Both barrels didn’t work well with the Tromix follower and Lancer mags with front cutout. Lancer mags work wonderfully with 5.56 followers and front cutout. I’ve got 4 Lancer mags with 5.56 followers and front cutout. All 4 are 100 percent reliable. ASC mag with black single feed follower also works well.

I’d try removing a weight from the buffer before I’d drill the port and void my warranty. YMMV
303hunter
 
Posts: 120
Joined: Wed Oct 31, 2018 2:23 pm
Location: Fayetteville, N.C.

Re: Feeding problems

Postby PyroRobby » Tue Jul 09, 2019 11:03 pm

Mdl1911a1 wrote:PyroDaddy: Went back to check my original order from BCA in prep for a call tomorrow. I've been providing one false piece of info: Gas block is 0.875. I simply mis-remembered. I'll give this info to BCA tomorrow :-)


The restriction wouldn't likely be the gas block, unless the block is misaligned with the port. The "bottle-neck" in the gas system is the gas port hole in the barrel feeding the block. A gas port in the barrel of .875 diameter would be really big. The .070 port size sounds more likely and a measurement of .0695 is close enough to maybe actually be .070. When I used my digital calipers to measure the port hole on my rifle, I was about .001" off in the reading from expectation. When I dropped a number 43# drill into the hole, it was a perfect fit, so it worked like a pin gauge and confirmed the hole size I expected. Regardless, if the rifle is short cycling e-mail or call BCA and let them know. Initially I took my rifle to a qualified gunsmith and paid them for an opinion to the issue, they said shoot it more and see if it starts working after a few hundred rounds. I decided to drill it out .004", that brought the performance to expectation and I have zero issues since. BCA will handle it for you though, they gave me the impression they were completely willing to have my purchase returned to them and replaced it with another one.

Note: your barrel diameter at the gas block, if it is like mine from BCA, is .750" or 3/4 inches. The .875 measurement is bigger than the barrel, the bullet diameter is .452, not sure how you are getting .875 as the gas port measurement.

another note:
I just re-read your post explaining that you can manually feed fine and that you have lancer mags that work fine. I think maybe I got confused about what you were saying about the gas block. Adjustable gas block will restrict but not increase beyond the volume allowed through the gas port in the barrel. So, if your barrel port is just ~.070 then that is the max port size you will have. If the issue is that the gas charge from the gas tub to the bolt isn't enough to properly cycle the bolt and feed a round; but it all works fine manually, I think this means your gas port maybe needs to be opened up a little more until you get the pressure to cycle the bolt. The bolt needs to blow back hard enough that it will lock open on the last round, and not any harder than that. If this is the case, then yes, contact BCA and tell them the barrel seems to be under gassing. Now if the issue is the bolt blows back hard and fast and isn't grabbing a round at all; but cycles manually fine, I don't know. I would maybe ask your local AR builder for an opinion if it were me. I live in Houston TX, so AR builder experts are in just about every gun dealer in every neighborhood, and are eager to talk ARs all day long.
Gun control is using both hands, good gun control is hitting your target precisely.
User avatar
PyroRobby
 
Posts: 28
Joined: Mon Jul 01, 2019 12:15 pm
Location: Houston, Texas

Re: Feeding problems

Postby Bmt85 » Wed Jul 10, 2019 4:19 pm

PyroRobby wrote:
Mdl1911a1 wrote:PyroDaddy: Went back to check my original order from BCA in prep for a call tomorrow. I've been providing one false piece of info: Gas block is 0.875. I simply mis-remembered. I'll give this info to BCA tomorrow :-)


Snip:
Note: your barrel diameter at the gas block, if it is like mine from BCA, is .750" or 3/4 inches. The .875 measurement is bigger than the barrel, the bullet diameter is .452, not sure how you are getting .875 as the gas port measurement.


He's saying his gas block journal is .875 in diameter, not gas port. Probably has a heavy barrel profile.
Bmt85
 
Posts: 616
Joined: Wed May 18, 2016 11:13 am
Location: S.E. Michigan

Re: Feeding problems

Postby Bmt85 » Wed Jul 10, 2019 4:22 pm

303hunter wrote:I’ve got 18” mid length gas, and 16” carbine gas BCA barrels, and both eject to 4:00-4:30 using A2 buffer systems. Both barrels didn’t work well with the Tromix follower and Lancer mags with front cutout. Lancer mags work wonderfully with 5.56 followers and front cutout. I’ve got 4 Lancer mags with 5.56 followers and front cutout. All 4 are 100 percent reliable. ASC mag with black single feed follower also works well.

I’d try removing a weight from the buffer before I’d drill the port and void my warranty. YMMV


I'd try this. Unless the OP is going to send the barrel back. It sounds to me like the port is to small.
Bmt85
 
Posts: 616
Joined: Wed May 18, 2016 11:13 am
Location: S.E. Michigan

Re: Feeding problems

Postby Mdl1911a1 » Wed Jul 10, 2019 6:22 pm

Looks like I may have confused things a bit.

Buffer and spring must both be at spec weight for the action to cycle. With any additional weight in the buffer, or with an extra power spring and stock buffer, the bolt won't cycle. (more evidence of under-gassed.)

Barrel external diameter at the gas port is .875; this is a heavy profile barrel as BMT85 mentioned.

I emailed BCA today, and they confirm the gas port on my barrel is undersized. The port diameter on a 16" heavy barrel in .450 Bushmaster with carbine-length gas system should be 0.076; or a #43 drill. The existing #50 hole is too small. I've requested an RMA and will ship it back for repair. I was really up in the air about doing it myself, but I have enough other things going on to keep me occupied until BCA can get it done. :-)

Thank you all again for your suggestions and information; it was a great help in zeroing in on the problem!

Al in MI: Thank you for uploading the photos. I'm going to cut a bit of a ramp in the upper's cross piece before I dismount the barrel for shipping.
Mdl1911a1
 
Posts: 8
Joined: Fri May 31, 2019 4:44 pm
Location: Eastern NM

Re: Feeding problems

Postby PyroRobby » Wed Jul 10, 2019 9:48 pm

Bmt85 wrote:
PyroRobby wrote:
Mdl1911a1 wrote:PyroDaddy: Went back to check my original order from BCA in prep for a call tomorrow. I've been providing one false piece of info: Gas block is 0.875. I simply mis-remembered. I'll give this info to BCA tomorrow :-)


Snip:
Note: your barrel diameter at the gas block, if it is like mine from BCA, is .750" or 3/4 inches. The .875 measurement is bigger than the barrel, the bullet diameter is .452, not sure how you are getting .875 as the gas port measurement.


He's saying his gas block journal is .875 in diameter, not gas port. Probably has a heavy barrel profile.

lol, yeah, didn't snap to that until my 3rd cup of coffee.
Gun control is using both hands, good gun control is hitting your target precisely.
User avatar
PyroRobby
 
Posts: 28
Joined: Mon Jul 01, 2019 12:15 pm
Location: Houston, Texas

Re: Feeding problems

Postby PyroRobby » Wed Jul 10, 2019 9:53 pm

Mdl1911a1 wrote:Looks like I may have confused things a bit.

Buffer and spring must both be at spec weight for the action to cycle. With any additional weight in the buffer, or with an extra power spring and stock buffer, the bolt won't cycle. (more evidence of under-gassed.)

Barrel external diameter at the gas port is .875; this is a heavy profile barrel as BMT85 mentioned.

I emailed BCA today, and they confirm the gas port on my barrel is undersized. The port diameter on a 16" heavy barrel in .450 Bushmaster with carbine-length gas system should be 0.076; or a #43 drill. The existing #50 hole is too small. I've requested an RMA and will ship it back for repair. I was really up in the air about doing it myself, but I have enough other things going on to keep me occupied until BCA can get it done. :-)

Thank you all again for your suggestions and information; it was a great help in zeroing in on the problem!

Al in MI: Thank you for uploading the photos. I'm going to cut a bit of a ramp in the upper's cross piece before I dismount the barrel for shipping.


That's great news, yeah BCA clearly seems steps up and handle warranty claims.
It took me a 3rd cup of coffee to realize you were talking about a bull barrel OD and not the port, should have been obvious to me, sorry for being slow on that.
I think a #43 is .089". the chart says .076" is a #48, no matter BCA will handle it.
http://www.gearhob.com/eng/design/drill_eng.htm
Gun control is using both hands, good gun control is hitting your target precisely.
User avatar
PyroRobby
 
Posts: 28
Joined: Mon Jul 01, 2019 12:15 pm
Location: Houston, Texas

PreviousNext

Return to AR15 Style Rifles

Who is online

Users browsing this forum: No registered users and 10 guests