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Posted: 5/25/2007 4:56:16 PM EDT
I am in the process of building an A-1 clone using a NODAKSPUD retro receiver and a surplus A-1 upper. Although I will have the headspace checked after I build it, I was wondering if the headspace on any AR rifle is similar. I am really hoping that when I get my new bolt assembly and put it in I will not have to have the headspace adjusted. Has anybody had any luck with changing bolts and not affecting headspace?
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While you are right there is no adjusting par se. The barrel isn't nessasarily a Tomato stake. Headspacing on a Chrome-lined AR is a combination of the tolerance stack of 3 parts. The barrel, the barrel extension & the bolt. If the barrel don't headspace try a different bolt. It helps when you have a lot of parts. M9 |
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Headspacing has been a big thought of mine. I'm new to AR's & currently having one built (my first). I've shot a lot (long range rifle) & reload for all my guns. I guess what I was thinking is the round has to be so long or short to fit in the mag & feed properly then worry about headspacing & work from there to find the pet load. Anything to help a new guy reload for an AR? |
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99% of the time, any mil spec bolt will properly headpsace in any milspec barrel/barrel extension assembly. It is remotely possible to get parts on extreme opposite limits of the allowable tolerances that may not produce proper headspace when assembled together, but it would be very rare to encounter this. ------ Reloading wise, it depends on the AR, and more directly the barrel lenght and barrel twist. In my SP1 and M-16A1 clone (1 in 12 twist, 20" barrel), I get 1.0 to 1.25 MOA accuracy with bulk 55 grain FMJ's from either Hornady or Winchester (with a slight accuracy edge to Hornady) in military brass with CCI primers and metered 25.0 grain charges of BLC-2. It very closely approximates the M193 ball loading although I will chronograph the load and adjust the charge accordingly when I change lots of BLC-2 to keep the velocity the same. To simplify life, when I buy powder, I either buy 8 lb kegs on-line or I buy everything the local gunshop has in a particular lot of BLC-2. This same load in my 20" bull barrel varmint AR (1 in 9 twist) will produce 3/4 MOA accuracy. In a 16' carbine, (1-9 twist) it is less spectacular at around 1.75 to 2.0 MOA. Faster 1-8 or 1-7 twists are not nearly as freindly to 55 grain bullets as accuracy tends to degrade slightly, and heavier bullets tend to be more accurate. Personally, I like the trajectory and usually low cost of 55 grain bullets (compared to heavier .223 bullets) and tend to select barrel twists that accommodate them. You can get a little more accuracy if you get very anal about your reloading with much more extensive case preparation, weighting, indexing, handweighing charges and bullets, using match grade bullets, etc but in a .223 caliber AR this will produce only about a .25 to .5 MOA increase in accuracy and personally, I'd rather spend more time shooting than relaoding. Consequently I tend to prefer larger scale production of my reloads in preference to squeezing the ultimate in accuracy out of each round. Whether it is 1 MOA or 1 hole accuracy is more or less irrellevant as both make the target equally dead unless the target is very, very small. In the field at long range, the difference is also a mute point as the wind is a much larger factor. In my opinion you will hit a much higher percentage of the time at long range by shooting lots of quickly and inexpensively produced 1 to 1.5 MOA rounds (and gaining much more shooting experience) than you will from putting in the time on the bench loading much more expensive .25 MOA rounds that you will shoot much less often. |
It shouldn't be. Headspace is one of the least likely problems for an AR-15. Unless your barrel and bolt are very old and excessively worn, there is unlikely to be a headspace problem. Remember, THOUSANDS upon THOUSANDS of M16's and AR-15's are assembled without problem. The manufacturers do not go through bolt after bolt trying to find a combination that headspaces correctly. They drop in a part out of the parts bin, and check it. And it will work. I've never encountered a headspace problem with an AR-15. Not that it can't happen, it is just very rare. Always full length resize for semis. Always. Yes, it reduces brass life, but when you reload for a semi, reliable functioning is as important as accuracy. Otherwise, you would have just bought a bolt action or single shot. The headspace issue on military rifles comes from the 1950's and '60's, when gazillions of WWII surplus rifles were dumped on the market. Many were quite worn. Gunsmiths were right to be concerned about headspace on military rifles. But you don't hear the average bolt action guy worry about headspace, do you? How many Fudds do you know that are concerned about headspace on their Winchester? have you ever brought a rifle to a gunsmith for having a scope mounted or something and had him say, "I'd better check the headspace, it might blow up on you." I don't think so. And it should be of no more concern on your AR-15. Kabooms? I will guaran-damn-tee you that kabooms are not from headspace, but from (a) obstructed barrel or (b) bad brass / case head separation. It is impossible to doubleload centerfire rifle cases. And even if you fill them to the top of the neck, while it may be overpressure, it is not likely to blow up. See (a) and (b). If you are a reloader already you know how to check your brass for incipient head separation... shiny rings just above the head. |
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