M4 "Feed-Ramp" vs. A3 Ramps?

[patriot53]

I have been told...very confusing, that in a AR15 "upper receiver" ...as well as AR15 barrels there are "M4" type, deep-cut/angle FEED RAMPS vs. non-M4 "type" or "A3" ramps[/B]?
Then at Daniel Defense website...further confused as they call theirs "A4" feed ramps and say that that is the deeper cut/angle "type"?
So "M4...A3...and now A4" which seems to sound like a "hybrid term" of the 1st TWO???

What's the deal with this...
...I thought you could just "change" the barrel on a 5.56 rifle to a .300AAC BO. barrel, since the bolt carrier & mags are the same...(especially, one that allow that easily, like the LaRue...?)
Was completely unaware that you could have un-evenly "matched" feed-ramp issues and potentially have bought the wrong "type" barrel?

Also, what about AR10 "type" of rifles in 7.62x51/.308 and
switching calibers to .338 Federal, with just a NEW barrel in that caliber
[/B]...could you could do that on a Rifle like LaRue PredatOBR,
"quick change barrel / suitcase rifle", WITHOUT these "FEED-RAMP" matching issues, that 5.56 vs. .300AAC BO. suffers from...
... as, uppers & barrels, apparently use differing feedramps that MUST be "matched" barrel to upper?

 

[Onmilo]

I believe all Mil-Spec M16 type weapons now incorporate the M4 style feed ramps.

Simple rule of thumb.
The wider M4 style ramps cut on barrel extension work fine on M4 or standard cut upper receivers.
Old style barrel extensions do NOT work with upper receivers cut with M4 style feed ramp extensions.
There will be jams,,,,

 

[dogmush]

There are really only two types of ramps that I am aware of. Rifle, and M4.

See the picture I'm going to hotlink.


Some manufacturers call the their uppers "A4" or "A3" but all pretty much use the M4 cuts. I honestly don't recall what the M16A3 and M16A4 used for feed ramps. Either way it's pretty easy to look at the upper and see.

Picture:


ETA: All the uppers I saw on DD's website specified M4 feed ramps.

 

[4thPointOfContact]

I'm with Ommilo and Dogmush that you're going to find only two basic types. I'll further and say that it's pretty much immaterial in a civilian AR. The "M4" feed ramps were designed to overcome some deficiencies noted when the military developed the M4 - - mainly a higher cyclic rate than in an M16, weak magazine springs (from using an item developed as disposable as though it were a durable item) and the newer, heavier bullets with a different profile than were used in the A1.

Will your carbine suck without M4 ramps? Nope.
Are there any drawbacks to M4 ramps? Not a one. The slightly steeper angle of the ramps shouldn't affect feeding.
Will your carbine be better with M4 ramps? Possibly, especially if you ever decide to go with a cartridge conversion such as .300 Whisper (anecdotal evidence says that the ramps feed larger diameter cartridges better than non M4 ramps).

 

[patriot53]

I believe all Mil-Spec M16 type weapons now incorporate the M4 style feed ramps.

Simple rule of thumb.
The wider M4 style ramps cut on barrel extension work fine on M4 or standard cut upper receivers.
Old style barrel extensions do NOT work with upper receivers cut with M4 style feed ramp extensions.
There will be jams,,,,

LaRue Tactical & JP Enterprise Rifles...
...spoke to Techs from BOTH, they both said that their rifles us NON-M4 Ramps in BOTh the Receivers & Barrels...
,,,the guy from LaRue, said that if I added a third party (since they do not yet make .300BO barrels or guns) to their PredatOBR 5.56, it would NOT match-up 'cause ALL .300BO barrels are M4 type Ramps...
...now the guy from JP, told me that is not correct "not ALL .300AAC BO barrels are M4 type feed-ramps...JP's barrels & upper receiver use NON-M4 ramps?
Both companies spokesperson said there is no need for M4 deeper cut feed-ramps for 5.56 and the guy from JP Rifles, said he would think even LESS necessary for .300 BO, since it is a more "tapered" cartridge than 5.56 with it's steeper shoulder.

 

[Onmilo]

LaRue Tactical & JP Enterprise Rifles...
...spoke to Techs from BOTH, they both said that their rifles us NON-M4 Ramps in BOTh the Receivers & Barrels...
,,,the guy from LaRue, said that if I added a third party (since they do not yet make .300BO barrels or guns) to their PredatOBR 5.56, it would NOT match-up 'cause ALL .300BO barrels are M4 type Ramps...
...now the guy from JP, told me that is not correct "not ALL .300AAC BO barrels are M4 type feed-ramps...JP's barrels & upper receiver use NON-M4 ramps?
Both companies spokesperson said there is no need for M4 deeper cut feed-ramps for 5.56 and the guy from JP Rifles, said he would think even LESS necessary for .300 BO, since it is a more "tapered" cartridge than 5.56 with it's steeper shoulder.

1. ANY manufacturer can, at any time, decide to make a caliber specific barrel.
2. It is up to the BUILDER to identify the feed ramp angles employed on the barrel extension and upper receiver regardless of the manufacturer.
3. If any doubt exists in the builders mind, refer to the above posted picture and/or obtain full details of the barrel and upper receiver specifications from the manufacturer BEFORE attempting the build.
4. M4 style feed ramps are a good idea if you elect to use heavier, (i.e. 69-80 grain), slightly longer 5.56 cartridges in any weapon, be it rifle or carbine, select fire or semi automatic as the ramp design makes it less likely the round will impact on the roof of the chamber as it feeds driving the bullet back into the case and raising chamber pressure on ignition to potentially dangerous levels.
5. M4 feedramps were designed and incorporated on heavy barrel M4 SOCOM issue carbines to prevent and/or eliminate barrel bursting issues on full auto select fire carbines when utilized in the deep s*** emergency light machinegun role.
The benefits of M4 feed ramps with the use of heavier bullets was discovered later down the development line.

I agree with the above noted manufacturers that a shooter will find no real benefit in M4 angle feed ramps when some calibers not being 5.56 NATO/.223 commercial are utilized in the AR15/M16 platform however, it is still up to the BUILDER to ensure proper parts compatibility.

As I stated in my earlier post, I believe ALL NEW PRODUCTION M16/M4 select fire weapons now incorporate M4 style feed ramps be they from FN or Colt USA or Colt Canada/Diemaco.
Rebuild procedures on older weapons now eliminate rebarreling of the older weapons and new production pre barrelled uppers are utilized.
This was done to standardize parts compatibility in military depot level and allows all the weapon systems to utilize the newer 77 grain 5.56 ammunition.
None of this has any bearing on what occurs in the civilian AR15 market.
Caveat Emptor HTH

 

[patriot53]

1. ANY manufacturer can, at any time, decide to make a caliber specific barrel.
2. It is up to the BUILDER to identify the feed ramp angles employed on the barrel extension and upper receiver regardless of the manufacturer.
3. If any doubt exists in the builders mind, refer to the above posted picture and/or obtain full details of the barrel and upper receiver specifications from the manufacturer BEFORE attempting the build.
4. M4 style feed ramps are a good idea if you elect to use heavier, (i.e. 69-80 grain), slightly longer 5.56 cartridges in any weapon, be it rifle or carbine, select fire or semi automatic as the ramp design makes it less likely the round will impact on the roof of the chamber as it feeds driving the bullet back into the case and raising chamber pressure on ignition to potentially dangerous levels.
5. M4 feedramps were designed and incorporated on heavy barrel M4 SOCOM issue carbines to prevent and/or eliminate barrel bursting issues on full auto select fire carbines when utilized in the deep s*** emergency light machinegun role.
The benefits of M4 feed ramps with the use of heavier bullets was discovered later down the development line.

I agree with the above noted manufacturers that a shooter will find no real benefit in M4 angle feed ramps when some calibers not being 5.56 NATO/.223 commercial are utilized in the AR15/M16 platform however, it is still up to the BUILDER to ensure proper parts compatibility.

As I stated in my earlier post, I believe ALL NEW PRODUCTION M16/M4 select fire weapons now incorporate M4 style feed ramps be they from FN or Colt USA or Colt Canada/Diemaco.
Rebuild procedures on older weapons now eliminate rebarreling of the older weapons and new production pre barrelled uppers are utilized.
This was done to standardize parts compatibility in military depot level and allows all the weapon systems to utilize the newer 77 grain 5.56 ammunition.
None of this has any bearing on what occurs in the civilian AR15 market.
Caveat Emptor HTH

Why then are TOP builders like LaRue & JP , NOT using the M4 feed ramps...
...but most good barrel / Parts makers like Daniel Defense & BCM are making barrels with them?

 

[Onmilo]

Why then are TOP builders like LaRue & JP , NOT using the M4 feed ramps...
...but most good barrel / Parts makers like Daniel Defense & BCM are making barrels with them?

I already answered that in the previous post.
M4 feed ramps were designed to address issues with full auto feeding issues using M855 62 grain ammunition.
The feed ramp angle was found to also prevent bullet setback when using the early non cannellured bullet design 77 grain ammunition when fired in full auto or semi auto.
The 77 grain bullet has since added a cannellure to the design.
MOST of the ammunition that MOST of the shooters are using in their weapons utilize cannellured bullets fired in semi automatic mode.
AS such, JP and LaRue probably feel the M4 feed ramps bring nothing advantageous to the table concerning their semi automatic AR15 rifle offerings.

 

[Tommygunn]

Well, I have a Bushmaster I bought in 2006 without the M4 feedramps and a Colt M4 I bought last year with the M4 ramps and both feed very well, no FTFs or anyhting, so I don't think it's a big deal.
Go back to Dogmush's post and look at his photo; the one in the lower left with the rifle extension and M4 ramps marked "bad" is probably the only one that I think would cause problems. It causes a definite "ledge" which could catch the bullet tip in some occasions.

 

[patriot53]

I already answered that in the previous post.
M4 feed ramps were designed to address issues with full auto feeding issues using M855 62 grain ammunition.
The feed ramp angle was found to also prevent bullet setback when using the early non cannellured bullet design 77 grain ammunition when fired in full auto or semi auto.
The 77 grain bullet has since added a cannellure to the design.
MOST of the ammunition that MOST of the shooters are using in their weapons utilize cannellured bullets fired in semi automatic mode.
AS such, JP and LaRue probably feel the M4 feed ramps bring nothing advantageous to the table concerning their semi automatic AR15 rifle offerings.

Ok...got all that, but if the major Riflemakers are usint the NON-M4 receivers & barrels...
...and say, you want to add a barrel in different caliber or profile to the rifle from a third party barrel makers which most seem to have those barrels
with the M4 feed-ramps, is that not gonna cause a problem?
Or am I still missing something?

 

[dogmush]

Not really. A rifle receiver and M4 barrel will work together. It's not the best, but for low rates of fire it's probably a non issue.

Can't do it the other way though.