M4 Feedramps

[SilverEagle]

Roughly 500 rds since my dremel job, I've had zero function problems. So maybe those M4 ramps do help a little. They sure seem to have helped in my beater carbine.

Full auto aside, is the issue here the length of the gas tube? I understand that a miss-matched receiver and barrel will cause problems feeding, but in a stock "rifle cut feed ramp"- M4 Length system will there be problems? Does anyone have operating experience about that? Do these beasties even exist?

Additionally, is there an increase in problems if you run a true SBR M4 verses a 16" with carbine length tubes?

[austinN4]

Great post! Thanks for taking the time to put it together.

[Robb Jensen]

Full auto aside, is the issue here the length of the gas tube? I understand that a miss-matched receiver and barrel will cause problems feeding, but in a stock "rifle cut feed ramp"- M4 Length system will there be problems? Does anyone have operating experience about that? Do these beasties even exist?

Additionally, is there an increase in problems if you run a true SBR M4 verses a 16" with carbine length tubes?

In theory the 14.5" guns are cycling a little faster than 16" guns (as most 14.5" bbls have bigger gas ports) BUT they usually don't since many people who have 16" guns are running lighter bolt carriers (semi-auto) which then places the cyclic rates closer to the same. This is why I recommend running M16 carriers. The XM177/CAR/M4 wasn't designed around using a semi auto carrier.......why dick with what we know works? There are still some people out there with very tight tinfoil that think that semi auto carriers somehow then define your rifle as a machinegun.

The length of the gas tube protruding in to the upper receiver is the same whether it's CAR, ARmaLite midlength, KAC midlength, intermediate, or rifle.

What do you mean by a 'true SBR M4' ? Do you mean a 14.5" M4? If so yes, rifle ramps in a rifle ramped receiver works for most people, most don't have full auto.

The ramps cure rare problems, most of the time they aren't needed BUT if you have M4 ramped receiver you should have a M4 ramped barrel. The ramps help with weak mags, fast cyclic rate guns and rounds with odd projectile ogives.

I recommend having M4 ramps for anything that cycles faster then a midlength.

I have a VLTOR MUR upper receiver (with M4 ramps) on my 3gun rifle and I 'Dremeled/WECSOG'd/Hack-Fu'd' the ramps myself on its midlength RRA barrel extension. It still works even with the new JP LMOS 6.25oz carrier and the damn thing shoots like my 10/22 now with the light carrier and muzzle brake combo. It feeds even 50gr American Eagle hollowpoint and the PMAGs have no problem keeping up with the increased bolt speed. To ensure that it works ALL the time I may still add Wolff +10% mag springs to my dedicated PMAGs for this rifle. Sunday I did find out that I do need to lube my Geissele trigger more often than I have been (which was never ). I relubed it after it failed to reset a few times and all was good.

[AR15barrels]

In theory the 14.5" guns are cycling a little faster than 16" guns (as most 14.5" bbls have bigger gas ports)

I disagree on most 14.5" barrels having bigger gas ports.
Having measured 100's of gas port diameters, I can tell you that there is more variance from manufacturer to manufacturer than there is from 14.5" to 16" barrels within any single manufacturer, or even amongst every major maker averaged together.

[Iraqgunz]

My understanding for the reason of faster cycling is due to the shorter distance that gas travels through the gas tube (faster) therefore causing a more violent extraction. I have examined some barrels that were 14.5, 16, and 20 inch. with a bore scope and my Mk1 Mod0 eyeball couldn't see a difference in the sizes.

I disagree on most 14.5" barrels having bigger gas ports.
Having measured 100's of gas port diameters, I can tell you that there is more variance from manufacturer to manufacturer than there is from 14.5" to 16" barrels within any single manufacturer, or even amongst every major maker averaged together.

[Robb Jensen]

I disagree on most 14.5" barrels having bigger gas ports.
Having measured 100's of gas port diameters, I can tell you that there is more variance from manufacturer to manufacturer than there is from 14.5" to 16" barrels within any single manufacturer, or even amongst every major maker averaged together.

I should start writing down what I've encountered. I'm finding differences of about .003-.004" between 16" and 14.5"s bbls usually from the same manufacturer......some of it might be the wear of the barrels.

[rockm4]

I also shoot, 75gr, 77gr and 80gr, HP and match grade ammo with a rifle feedramp configuration. Absolutely zero issues.

I hand load 98% of the ammo that i shoot witch, mind you is only about 3oo to 4oo rds at a time every two weeks or so but i load 40gr. sxp, through 77gr. in all types of sp,hp and fmjs. and never had any feeding problems w/ my RRA or old COLT SP1. but i am very anal of specs. on my cases and conditions of the wear on my mags and wear on my mag release catch.

[opticalc]

so for "rifle feedramps", the barrel cuts are not extended, and the upper receiver has no cuts at all?

and assuming that i did want to mod my own upper to have m4 feedramps, what size round file would be needed?

[Shihan]

so for "rifle feedramps", the barrel cuts are not extended, and the upper receiver has no cuts at all?

and assuming that i did want to mod my own upper to have m4 feedramps, what size round file would be needed?

Its best not to mess witht he feedramps unless you are having problems as you will remove the protective hard annodizing.

[RallySoob]

is it possible to swap your standard bbl extension out for a M4 bbl extension? I have m4 ramps on my upper and not my bbl. I have had not 1 hitch in 2500+ rnds but I would feel better with M4 ramps...
Any advice would be most appreciated