AR bolt and carrier groups

quinnjoblow

quinnjoblow

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I may have a chance to buy an new flat top carbine length 16 inch upper that doesnt have a bolt or charging handle. It has a standard feedramp(non M4). Will any standard bolt group fit? Can I buy say carrier parts from this company and bolt, firing pin from another company?
Are all the parts made pretty much standard? Im just not sure how the AR bolt headspaces properly if bolt/carrier group are made separate from the upper.
 
AR parts are usually plug 'n play provided the barrel extension is installed correctly in your case. It is always a good idea to check headspace if you can when flipping an flopping parts.

I would take note of used bolts mated to used barrels more than newer parts combined from different manufacturers.

Keeping in mind mil-spec is not a standard, stick to top shelf, proven manufactured components and you should be good to go.
 
There's no way to tell if a new bolt will fit with proper head space on an existant barrel besides trying it. If you take the risk and headspace's not ok:

1-if it's too tight, you can get a gunsmith to work on the bolt and resolve the issue.
2-if it's too loose, noting can be done except trying another bolt.

From what I've read in Pat Sweeney's books, he recommends buying a bolt with the barrel when purchasing a barrel from a manufacturer.
 
hbean said:
it is an acceptable range of variance.
Click to expand...

Good answer. :)

Mil-spec is not a standard, but a guideline. You can easily exceed mil-spec and badly fail to meet it.

Often people reference this terminology randomly. It doesn't mean much to me as I expect my stuff to perform above mil-spec guidelines.
 
easy said:
Keeping in mind mil-spec is not a standard, stick to top shelf, proven manufactured components and you should be good to go.
Click to expand...

The technical drawing package owned by the government(or Colt for the M4) is the standard, with given tolerance. Since FN and Colt got the TDP from the government, that is the military specification as the bid specified the TDP is to be used. The specification is not a guideline - it is a set of condition the end product must satisfy for contractual purposes.

In the case of the dimension of a part, it makes no sense that you do not follow the specification because you believe you can go "beyond and better than the milspec". it is a dimension, with a given tolerance, that a part needs to conform to achieve parts interchangability. If the dimension in the TDP does not mean anything, I am not quite sure what does!
 
Any body like the chromed bolt's (Not Carrier's)?
Are they really that much easier to keep clean?
Is there any company's that you would recommend?
 
greentips said:
The technical drawing package owned by the government(or Colt for the M4) is the standard, with given tolerance. Since FN and Colt got the TDP from the government, that is the military specification as the bid specified the TDP is to be used. The specification is not a guideline - it is a set of condition the end product must satisfy for contractual purposes.

In the case of the dimension of a part, it makes no sense that you do not follow the specification because you believe you can go "beyond and better than the milspec". it is a dimension, with a given tolerance, that a part needs to conform to achieve parts interchangability. If the dimension in the TDP does not mean anything, I am not quite sure what does!
Click to expand...

The Technical "Data" Package (TDP), is a military specification for the M4, which was put forth by the military to Colt as an "outline" for the manufacturing process, materials, tolerances, assembly, finishes, proof testing and dimensions needed for manufacture of the weapon by Colt to meet their contract with the U.S. military.

Though the military specifications “milspecs" and the military standard “milstds” which Colt must abide by to satisfy their Military contract consist of rigorous inspections, tolerances, endurance and interchangeability of parts, are not adhered to religiously by every firearms manufacturer out there. Therefore, parts may vary drastically as opposed to what is designated by the Military. Could be more, or could be less, especially with worn parts from questionable manufacture.

And so, I say to only procure top shelf components from known manufacturers and avoid the stacking effect with parts tolerances which may cause catastrophic failures when flipping and flopping parts of your gun without proper quality assurance. Especially with questionably "used" components.

Quality assurance with milspecs and milstandards are maintained by an onsite U.S. government inspector who keeps an office at Colt’s factory and by a number of Colt’s own inspectors. I doubt such government inspectors keep offices at other firearms manufacturing facilities that cater to the civilian market, or other agencies around the world.
 
On a different note, I was under the impression that the M4 carbine TDP is proprietary to only Colt, and the U.S. government has designated Colt its only source and supplier of M4 carbines.

FNs US court challenge for Colt being the only procurement source of M4 carbines to the US Military was struck down and dismissed in 1999.

So, it is my opinion that all other manufacturers, including FN, may not really be following Colt's TDP as the Military specification, nor standard, but merely a guideline. I sure have seen my share of out of spec AR15 components. Who's to say a barrel extension and bolt might not find the same fate.
 
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