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COL for AR15 using a Mic?

 
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  #1  
Old 01-02-2012, 11:07 AM
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COL for AR15 using a Mic?

I was reading a piece in my sons Guns and Ammo the other day and the author mention that loading too long can cause feeding problems. He specifically mentioned that the ogive had to fall behind some reference point on the mag. Well no sh..tuf??? I did a build of an AR a few years ago and it's basically been sitting because it doesn't like my reloads. It'll shoot factory garbage but I don't buy ammo so it's just been sitting. I took a look at my reloads in the mag and sure enough, the ogive tags the lip of the mag as the bullet is shoved out. A lot of it has to do with my choice of bullet and penchant for seating .020 off the lands.

In my long guns I favor the longer "missiles" like Bergers and SMK's. I may have to find another bullet but I think I can just re-seat what I have and shoot those up before I switch. Then again, maybe I just need to seat them deeper.

Does anyone here have a MIC reading for .223 ammo that works in their AR?
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Old 01-03-2012, 09:30 AM
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Re: COL for AR15 using a Mic?

Mike6158,

didn't see the article in G&A, but I'm already more than a bit suspicious of it. Do you know what issue that was? Anyway, forget the comparator and load to mag length. With virtually all types of chambers and a 7-cal ogive bullet (more or less), this will work just fine. The OAL, not the ogive's placement re the throat is the limiting factor in loading for ARs.s The only loads in which I worry about the relationship of ogive to throat are my Long Range (600 yard) loads using 80s or 82 grain Match bullets. Since this stage is fired as single loaded only, this allows us to load out to actually touch the rifilng, or place it where ever the load shoots best. For the rapids that must run through the magazine, be they 69s or 77s, they get loaded to 2.250", period.

You mentioned that your rifle has had some issues with reloads. What sort of problems have you seen?
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Old 01-03-2012, 09:58 AM
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Re: COL for AR15 using a Mic?

Quote:
Originally Posted by Kevin Thomas View Post
Mike6158,

didn't see the article in G&A, but I'm already more than a bit suspicious of it. Do you know what issue that was? Anyway, forget the comparator and load to mag length. With virtually all types of chambers and a 7-cal ogive bullet (more or less), this will work just fine. The OAL, not the ogive's placement re the throat is the limiting factor in loading for ARs.s The only loads in which I worry about the relationship of ogive to throat are my Long Range (600 yard) loads using 80s or 82 grain Match bullets. Since this stage is fired as single loaded only, this allows us to load out to actually touch the rifilng, or place it where ever the load shoots best. For the rapids that must run through the magazine, be they 69s or 77s, they get loaded to 2.250", period.

You mentioned that your rifle has had some issues with reloads. What sort of problems have you seen?
January 2012 Page 25. Right under the pic of the magazine

Quote:
The COL is critical for AR Function. The bullet ogive must clear the two ridges in the sides of the magazine, or the round may fail to feed.
Turns out that wasn't the problem. I reseated 5 rounds to about .015 shorter than they were and the same as some factory rounds that my son had. I used an RCBS Mic to check the difference and adjust the seater. It measures to the ogive. I also broke out an H&K magazine that a friend of mine gave me last year. It's markedly better than the mag that came with my "store bought" Rock River Arms AR. I stepped out the back door and dumped all five rounds. Success! But... I wasn't seated anywhere near where the article said, at least not that I could tell. "must clear the two ridges in the sides of the magazine" seems kind of arbitrary to someone like me. I shoot mostly bolt guns and my bullets are seated to the nearest .001 not some mark on a box. So, I loaded up three of the "long" bullets in the H&K magazine (these are .020 off the lands. The barrel is a Hart barrel). Dumped them no problem.

I was having feeding problems. Sometimes the first round wouldn't charge right. When it was fired it would eject but the next round would misfeed. It's been over a year so my recollection might be a little off. What I mainly remember is that I have a custom built (by me) AR15 that wasn't at all fun to shoot. At this point I'm ready to start over and see if I can develop a good load for it and see what kind of range I can get out of it. I'm on the hunt for a good bullet / powder / primer combination so if anyone has any suggestions I'm listening (reading, whatever)
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Old 01-03-2012, 10:18 AM
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Re: COL for AR15 using a Mic?

Mike,

Firsty thing to do when loading for an AR, is to forget about 95% of what you know from loading bolt guns. Most bolt gun techniques not only aren't applicable to ARs, they can be seriously problematic. They're different, and they need to be treated differently. Most chambers don't "require" a Small Based die, but it'll never hurt anything, and may resolve some chambering issues. It also makes extraction and functioning much more positive,something most folks don't realize or readily assume. Use chamber gages (such as the simple gage from L.E. Wilson) to make sure that the rounds drop into and come out easily, with no resistance. That'll go a long way towards assuring reliability. Watch your OAL, and make sure you're a bit under magazine length to prevent the tips (which vary a few thou) from dragging on the front of the mags. This is normally 2.260" (according to the books, but I generally load to 2.250" just to maintain a .010" marging of error. Makes life easier.

There's a couple of pretty good resources that I'd recommend checking out, specific to loading for gas guns. Most of these explain some of the differences, and why they need to be followed, as opposed to just loading ammo as if it were for a bolt gun.
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Old 01-03-2012, 10:36 AM
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Re: COL for AR15 using a Mic?

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Originally Posted by Kevin Thomas View Post
Mike,

First thing to do when loading for an AR, is to forget about 95% of what you know from loading bolt guns. Most bolt gun techniques not only aren't applicable to ARs, they can be seriously problematic. They're different, and they need to be treated differently. Most chambers don't "require" a Small Based die, but it'll never hurt anything, and may resolve some chambering issues. It also makes extraction and functioning much more positive,something most folks don't realize or readily assume. Use chamber gages (such as the simple gage from L.E. Wilson) to make sure that the rounds drop into and come out easily, with no resistance. That'll go a long way towards assuring reliability. Watch your OAL, and make sure you're a bit under magazine length to prevent the tips (which vary a few thou) from dragging on the front of the mags. This is normally 2.260" (according to the books, but I generally load to 2.250" just to maintain a .010" margin of error. Makes life easier.

There's a couple of pretty good resources that I'd recommend checking out, specific to loading for gas guns. Most of these explain some of the differences, and why they need to be followed, as opposed to just loading ammo as if it were for a bolt gun.
Kevin, Thanks a ton. I'm good on length, even with the "long" bullets (which means that I'm NOT loaded to x off the lands. It's been a while since I've loaded for the AR so I probably misstated that). That said, the two rounds I tested last night were 2.174 and 2.2505 (different bullets) COL. But if I'm reading this right no neck sizing. FL sizing only correct?

BTW- The "symptom" that I saw was a distinct "stripe" down the side of the bullet that didn't chamber when the rifle misfired. Like it was dragging on something. Like the mag for instance. but it wouldn't do it every time. I don't know what that was about...

I'm interested in those resources. I think I have a good combination in my build so any info on loading for it is going to be beneficial.
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Old 01-03-2012, 12:33 PM
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Re: COL for AR15 using a Mic?

Hey Mike,

You got it, and that's a biggie right there; no neck sizing, ever, under any circumstances in an AR. Or any gas gun, for that matter. It's nothing but trouble looking for a place to happen, and I assure you, it'll find that place. AR's really aren't that fussy to load for, as are, say, an M1 or an M14. The gas system in the AR family is a lot more durable, and far less subject to port presure issues than the Garand family, which can be damaged by improper powder selection. No damage in an AR, just poor performance with some combinations. Choose a powder that's well suited to the bullet weights you're using, and it'll run like a turpentined cat. I generally tend to use more 77s and 82s than anything else (I'm a High Power Service Rifle shooter) and these get either Varget or N140. RL-15 works very well, too. If you're going to a lighter bullet, say the 55s or thereabouts, try something a bit faster like H322, N135 or the like.

Make sure you're pushing the shoulders back .003"-.004" to provide adequate clearance for cycling, and make sure your primers are seated slightly below the case head. Contrary to what you may hear, there's generally no reason to crimp with an AR, so long as you've got adequate neck tension. Should try crimping in bullets that don't present a cannelure anyway. You might pop over to the relaoding section on usrifleteams.com and read through some of the threads dealing with reloading for ARs. There's also a couple pieces pinned in that section that deal with Service Rifle reloading that may be worth your time. One is a reprint of the section I did for the Sierra manual some time back, but it's still mostly relevant. That, and don't hesitate to ask questions here as need be!
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  #7  
Old 01-03-2012, 01:33 PM
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Re: COL for AR15 using a Mic?

Quote:
Originally Posted by Kevin Thomas View Post
Hey Mike,

You got it, and that's a biggie right there; no neck sizing, ever, under any circumstances in an AR. Or any gas gun, for that matter. It's nothing but trouble looking for a place to happen, and I assure you, it'll find that place. AR's really aren't that fussy to load for, as are, say, an M1 or an M14. The gas system in the AR family is a lot more durable, and far less subject to port presure issues than the Garand family, which can be damaged by improper powder selection. No damage in an AR, just poor performance with some combinations. Choose a powder that's well suited to the bullet weights you're using, and it'll run like a turpentined cat. I generally tend to use more 77s and 82s than anything else (I'm a High Power Service Rifle shooter) and these get either Varget or N140. RL-15 works very well, too. If you're going to a lighter bullet, say the 55s or thereabouts, try something a bit faster like H322, N135 or the like.

Make sure you're pushing the shoulders back .003"-.004" to provide adequate clearance for cycling, and make sure your primers are seated slightly below the case head. Contrary to what you may hear, there's generally no reason to crimp with an AR, so long as you've got adequate neck tension. Should try crimping in bullets that don't present a cannelure anyway. You might pop over to the relaoding section on usrifleteams.com and read through some of the threads dealing with reloading for ARs. There's also a couple pieces pinned in that section that deal with Service Rifle reloading that may be worth your time. One is a reprint of the section I did for the Sierra manual some time back, but it's still mostly relevant. That, and don't hesitate to ask questions here as need be!
Sounds like I need to read more than the load tables in the Sierra manual
I'm afraid I crimped the loads that had a bullet with a cannelure. I can shoot them up pretty easily and start over.
Thanks for the references.
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