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Posted: 9/29/2007 11:25:19 AM EDT
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1. What exactly are M4 feed ramps? 2. What is staking when it comes to the bolt carrier? 3. What exactly is headspacing and how do you meansure it and what should it be? I have been reading a bit about these but would like some clarification. thanks |
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I am no expert but as far as I know... M4 feed ramps are cut into the barrel extension and reciever to improve reliable feeding. I've never had an issue without them, but whatever works... Staking the gas key on the bolt carrier involves using a "punch" to displace the metal in the 2 screws in the gas key to prevent them from working loose. Headspacing is the relationship between the bolt and chamber (AFAIK). There are headspacing guages that can determine whether or not your tolerances are in spec or not. |
M4 ramps courtesey of Randall of AR15 Barrels.com Gas Key Staking  Headspace is set when the barrel extension is installed on the barrel, by the manufacturer. Any in spec bolt should headspace correctly. Correct headspace ensures that the cartridge is seated deeply enough that the thin walls of the cartridge case are supported by the chamber, and that only the more solid case head is in the unsupported feedway area of the chamber. |
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The M4 feed ramps are not necessary if you shoot only semi auto. They are something that evolved for aiding feeding in select fire carbines. Really the only semi autos they are an aid in are those chambered in 6.8 SPC. Because the tip of the bullet is generally blunter than a 5.56 FMJ and they sit lower in the magazine. The little extra feed ramp can help feeding in many cases here. |
| You're quibbling over $25 on a $900 rifle? Spend the $25 and get a more reliable rifle. The M4 ramps were found to aid feeding with M855 (even in semi-auto). If your magazine spring starts to weaken (or get dirty) the extended feed ramps will allow the round to feed instead of getting slammed into the upper receiver. This can be a problem in carbines (which cycle faster due to the higher gas port pressures). |
yeah you are right. i shouldn't worry about it. i was just trying to build the least expensive AR i could. I can basically build one right now complete for about $580 which is awesome! only thing i would need is a rear sight. or i could even just get a gas block on the front and throw a scope on it. gaurenteed no less than $650 complete (depending on which scope i put on it). |
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