Feed Ramps

Moderators: gds, bakerjw, renegade

300blk_kid
Member
Posts: 20
Joined: Thu May 23, 2019 11:25 pm

Feed Ramps

Post by 300blk_kid » Thu May 23, 2019 11:35 pm

Hi all,
I did a bunch of searching, even talked to AAC folks, none seem to have the info I am after.

Is there such a thing as "300AAC" ramp spec for AR15 barrel extensions? AAC tells me they use M4 cut ramps for their 300blk stuff. But, I do find various online vendors showing a much wider ramp for 300blk barrel. Some other barrel makers say the ramps they have on their 300blk barrels are bigger than the M4 ramps, but are these bigger ramps a spec or are they just arbitrary sized wider than M4?

If there is a real "300AAC" spec for feedramps, where can I find the spec? I forget where, but one site mentioned a "300AAC" ramp spec existed, but I can't find it.

Anyone shooting any AR15 in 556 or 300blk using a 458 socom ramp cut (one big ramp)?

I am in two 300blk builds and want the finished product to be able to eat any 300blk ammo. Feedramps seem to be key to being able to feed any ammo.

BulletFlight for Android
User avatar
dellet
Silent But Deadly
Posts: 6309
Joined: Fri Nov 30, 2012 1:25 pm

Re: Feed Ramps

Post by dellet » Fri May 24, 2019 12:23 am

It’s not really any kid of mystery.

AAC and anybody else that has any reasonable expectation of quality and reliability use an M4 feed ramp. All this basically means is that the ramps continue from the barrel extension down through the upper receiver tonthe magazine. It gives a longer ramp that is less steep into the chamber.

The so called “AAC spec” is another closely guarded trade secret, that way to many barrel manufacturers over look. That is using a 30 caliber barrel extension for 30 caliber bullets, instead of a .223 extension and ramp.

There are plenty of photos on the internet showing the the different ramps. Here’s one of the better ones.

http://ar15barrels.com/tech.shtml

Image
300 Blackout, not just for sub-sonics.

300blk_kid
Member
Posts: 20
Joined: Thu May 23, 2019 11:25 pm

Re: Feed Ramps

Post by 300blk_kid » Fri May 24, 2019 10:08 am

I was asking for the ramp specs. M4 is a Colt size/shape/angle spec. The Rifle cut also has a cut spec. But is there any spec for a "300aac" ramp cut?

And to note, the pic you posted is not accurate. The requirement for receiver to have the M4 cuts when extension has M4 is not true. The receiver does not need to have matching cuts, as long as no lip/edge exists between receiver and extension ramps.

Image

User avatar
dellet
Silent But Deadly
Posts: 6309
Joined: Fri Nov 30, 2012 1:25 pm

Re: Feed Ramps

Post by dellet » Fri May 24, 2019 11:39 am

300blk_kid wrote:
Fri May 24, 2019 10:08 am
I was asking for the ramp specs. M4 is a Colt size/shape/angle spec. The Rifle cut also has a cut spec. But is there any spec for a "300aac" ramp cut?

And to note, the pic you posted is not accurate. The requirement for receiver to have the M4 cuts when extension has M4 is not true. The receiver does not need to have matching cuts, as long as no lip/edge exists between receiver and extension ramps. That would the one labeled "ok". The one labeled "bad" M4 receiver/standard extension is the real problem

Image
I am not aware of a technical drawing out there of a 30 caliber AR15 extension, but i'm sure one is probably out there. Best bet might be contacting a barrel manufacturer that makes their own extensions. Lilja is one and they also sell them. Noveske used to make their own, and it is one of the most reliable for the blackout. Xcaliber is another.

AAC never made their own barrels and sadly with all the changes in the last few years, there may not be anyone there who would know where to find the specs.
300 Blackout, not just for sub-sonics.

User avatar
Flatliner
Silent But Deadly
Posts: 261
Joined: Tue Nov 17, 2015 4:43 pm

Re: Feed Ramps

Post by Flatliner » Fri May 24, 2019 6:09 pm

I am guessing from your post that you are doing machine work yourself. My request would be that IF you experiment and find a recipe for success, you post back here with the spec you end up using.

Thanks

300blk_kid
Member
Posts: 20
Joined: Thu May 23, 2019 11:25 pm

Re: Feed Ramps

Post by 300blk_kid » Fri May 24, 2019 7:10 pm

Flatliner wrote:
Fri May 24, 2019 6:09 pm
I am guessing from your post that you are doing machine work yourself. My request would be that IF you experiment and find a recipe for success, you post back here with the spec you end up using.

Thanks
I am not shaping anything just yet. A barrel I bought came with ramps, they are "300BO" ramps, they are shaped like M4 but are just slightly wider, but they are not the "300" ramps in the pic I posted.

I thought there was a std spec ramp cut for 300blk. I guess not.

300blk_kid
Member
Posts: 20
Joined: Thu May 23, 2019 11:25 pm

Re: Feed Ramps

Post by 300blk_kid » Sun May 26, 2019 5:46 pm

I got the data on the barrel ramps. The ones that came with my 300blk barrel are M4 modified. They are 0.100" wider at the edge of the extension (50thou wider on each side of ramp centerline). I will massage these ramps to be a tad more "mouthy". I'll grab some before and after pics.

nlvmike
Member
Posts: 14
Joined: Mon Mar 05, 2018 1:46 am

Re: Feed Ramps

Post by nlvmike » Tue May 28, 2019 11:50 am

I don't know if there is a standard, but I bought a couple of barrels from Classic Firearms that came with wider feed ramps, as in the pic. I loaded up some old 30-30 bullets I had into 300blk and they fed them well. Others wouldn't.

300blk_kid
Member
Posts: 20
Joined: Thu May 23, 2019 11:25 pm

Re: Feed Ramps

Post by 300blk_kid » Tue May 28, 2019 4:47 pm

nlvmike wrote:
Tue May 28, 2019 11:50 am
I don't know if there is a standard, but I bought a couple of barrels from Classic Firearms that came with wider feed ramps, as in the pic. I loaded up some old 30-30 bullets I had into 300blk and they fed them well. Others wouldn't.
Would not feed "others". What were the others that would not feed correctly?

The "300" in the pic I posted does seem like the angle has changed some because the inside edge of the extension looks lower. When I massage the ramps I'll keep the angle the same but just open the mouth of the ramp entrance a little.

golfindia
Silent But Deadly
Posts: 1350
Joined: Thu Jun 20, 2013 1:16 pm

Re: Feed Ramps

Post by golfindia » Tue May 28, 2019 9:01 pm

Looks like they basically eliminated 3 bolt lugs to widen the ramps. Not sure of that's a feature I'd consider beneficial.

Post Reply