my 7.5" AR

danny1444

danny1444

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Northern BC
well here it is.. my project in the making. i've been slowly putting it together for a couple years and now i've decided to get up off my ass and finish it. the only things i plan on adding to it are:
1. add an eotech sight
2. buy a noveske KFH flashider
3. install an extra power ejector spring
4. possibly a BUIS
the last time i shot it, it actually jammed!! it wasnt ejecting the empty casing out of the weapon. it would feed both an empty casing and a live round at once, jamming the weapon. what im planning on doing is installing an extra power ejector spring, does anyone have one?

thanks smgcon for the upper, and telteco1 for the stock
CGN rules!!


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Nice rifle, I am seriously looking at trying to find a 9mm conversion and doing the same thing. Good job, and let us know how you make out.
 
I say he wants the extra weight of a heavier carrier and an H buffer.

Those ER Shaw barrels come with an awesome tuned gas port, but they want the M16 carrier.
 
Grrr. I won't jump into this one, as there'll have to be a physics lesson, but I will say that you do NOT want a heavier buffer or carrier, as that would only WORSEN the short stroking.

EDIT: I was incorrect in identifying the problem as short stroking, thanks for correcting me, guys! :redface: Spreading misinformation is bad.
 
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I don't see how there's short-stroking if the carrier has picked up the new round and is jamming it in with the spent round.

This from the Bushmaster site:
FAILURE TO EJECT: This looks much the same as failure to extract, except that the fired case is removed from the chamber. The bolt will either jam the fired case back into the locking lugs on the barrel extension (crushing it), or pick up a round from the magazine and try to stuff both of them into the chamber at the same time (looks like a double-feed, except one of the cases is fired). There are a few possibilities as to the cause of this problem, and one is the ejector. For whatever reason, the ejector is weak or sticking and just not clearing the round out of the receiver. A good cleaning might solve the problem, or it may require replacing parts. Try the cleaning first. The other is that the extractor is letting go prematurely. A new extractor spring will usually solve this right away. Lastly, the bolt carrier might not be traveling back far enough, but if it is in fact picking up a new round from the magazine, this isn't the problem. If it isn't picking up a new round, you probably have a gas leak somewhere.
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i already have a heavy bolt carrier, which has worked fine up until last time i shot it.

many thanks to sigger69 for helping out with the parts i need:D
 
You are getting warm. Problem is the extractor is letting go prematurely as it is trying to extract while pressures are still high in the chamber (this is due to the high pressures that are bled off using a 7 inch barrel). Once the extractor is no longer holding it, the ejector just pushes it forward a bit and the case sits there. The carrier and bolt continues back far enough and picks up a new round just like it is supposed to and then pushes it forward. Problem is the empty case is still sitting there and it is forced forward with the live round. Both cannot go into the chamber at the same time! Several things need to be done; put a heavier extractor spring and insert in it along with a "D-fender" insert. The heavy extractor spring from Colt is copper coloured and insert is the black one. You can also delay time before opening with a heavier carrier and using a "HH" buffer. Good Luck. AA
 
PaveHammer said:
Grrr. I won't jump into this one, as there'll have to be a physics lesson, but I will say that you do NOT want a heavier buffer or carrier, as that would only WORSEN the short stroking.
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Dude, it is not short stroking, the issue is as arwen ace has mentioned, the case is still expanding in the chamber and the extractor is jumping the rim, slowing the timing and getting a better grip on the case rim is what is needed...short guns don't short stroke, they run too fast, full sized guns don't have these issues as the case has relaxed in the chamber when extraction takes place. The issues can be fixed but the problems will occur again. Remember that Gene Stoner was a genius, a veritable rocket scientist...finger banging with his design by people without so much a highschool degree is going to have consequences. JMHO, YMMV.
 
CobraGT said:
Cool... you just need a holster for it now :p

(I've got a 10.5", and that's what I always hear at the range LOL)
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Guy came in to the shop today as a buddy was checking out his MG34 we ordered for him, he casually saunters up and says " all you need now is a matching ankle holster"...:D
 
Just like last time, I saw "7.5" AR" and people suggesting "H buffers" and "M16 Carriers", and assumed the problem was short-stroking, as these are usually the *cough* miracle fixes for a low gas volume. Skipped reading his ad, and was embarrassed.
 
hutchster said:
this may sound dumb as i'm not a black rifle owner but...
what kind of accuracy do you get from a .223 in a 7.5 " tube?
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...in a lab shot by a machine the 7.5" barrel will be as accurate as any barrel out to 200m or so, in field conditions outside variables will cause shot dispersion, in this case the main cause will be a lack of down range velocity, the shorter barrels exhibit less whip than longer ones, 20" and 24" barrels seem to hold up best in adverse conditions from my match and target shooting experience...I won't comment on soft tissue performance as many here like to do as that is outside my lane...paper don't care as long as the gun works...;)
 
danny1444 said:
i already have a heavy bolt carrier, which has worked fine up until last time i shot it.
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I realize I specifically referred to an M16 carrier, but if you had a true M16 bolt and carrier set, the bolt includes the appropriate extractor spring and insert. You shouldn't need a D-fender, or a rubber washer under the extractor, or a heavier spring.

danny1444 said:
many thanks to sigger69 for helping out with the parts i need:D
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What parts were these??

I have noticed that with short barrels set up for specific timing which Pavehammer refers to as miracle fixes, will not cycle weak commercial ammunition or weak handloads 100% of the time.
Out of short barrels, I only cycle full house loads such as C77, IMI M193 and that African surplus stuff and never miss a beat.

Simply put, after being sure the gas port is the proper hole size for the length of the barrel, install a true M16 bolt & carrier kit making sure it is clean, the gas key is solidly staked on, a clean gas tube, install correct new springs and correct insert for the extractor, a heavy buffer and a new carbine buffer spring. Aside from that, I'd stay away from pigtails and cutting springs.

With this, I'm pretty sure you'll never have problems again.

Regards.
 
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easy,

the M16 bolt i bought has the regular extractor spring installed.... the funny thing is that it worked fine for about 200rounds or so, now im just having problems. im going to the range on saturday, and i'll bring my camera to take pictures for you all to see what is happening.

as for parts, sigger69 is sending me heavy extractor spring, heavy buffer and noveske KFH flashider.
i havent taken the front sight off to measure the gas port. i read somewhere the hole size is 0.063", can anyone verify this?
i wouldnt dream of cutting springs, and the gun has a straight gas tube.

easy, what barrel lengths do you have on your AR's?
 
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