Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Solving Ar-7 Light Strikes (misfires)
#1
ML

Registered User

Solving AR-7 Light Strikes (misfires)

Posted: 5/22/01 4:13 pm

--------------------------------------------------------------------------------

Solving AR-7 Light Strikes



Probably no single firearm has generated more discussion among Forum members than the AR-7 .22-caliber "survival" rifle. It’s inexpensive, unique, and has an extreme cachet about it. Yet shooters continue to complain about misfeeds and misfires, and I for one am convinced that they are easy to cure. I’m also surprised nobody has ever written with any meaningful authority about this before. I intend to resolve that presently. Here’s the solution.



Light strikes (misfires) occur on the blowback .22 AR-7 for (primarily) one of two reasons. First, the chamber and/or bolt face is/are dirty. The .22 Long Rifle is a notoriously dirty cartridge in that it typically leaves behind much powder residue and lead shavings from the lead bullet itself. The blowback nature of the action exacerbates this. This accumulation of junk either keeps the cartridge from fully chambering or keeps the bolt face from fully contacting the cartridge rim. Remember, in these simple blowback guns (the AR-7, the Ruger 10/22 and Mark I and Mark II pistols, the Marlin 60 family, and countless others) the bolt does not lock in position--only spring pressure holds it up against the base of the cartridge and the breach-end of the barrel. An accumulation of debris in the chamber keeps the cartridge from fully chambering. Thus, when the firing pin strikes the rim, much of the strike energy is absorbed in driving the cartridge forward. Or, if the bolt face itself is dirty, then the firing pin is held away from the rim as it falls, resulting in a light strike. Total firing-pin protrusion for a .22 is (typically) only 0.035 inch (minimum) and 0.039 inch (maximum), so you can see that a little fouling is all it takes. Scrub your bolt face, extractor, and breach face with a toothbrush, and clean the recessed area in the bolt face with a sharp splinter of wood or a toothpick, digging all the crud out. Finally, make sure there are no debris in the firing-pin channel itself to slow or limit the pin’s fall.



The second problem is unique to the AR-7 family (as produced by Armalite, Charter Arms, Survival Arms and Henry Arms to date). I’m convinced this is where 99 percent of the light-strike problems with these guns lie. The AR-7 has a detachable barrel held to the receiver by a captive threaded ring, and the reassemble of the barrel to the receiver is where the problem occurs.



When you remove the barrel from the receiver, the bolt moves forward a small amount--my measurements indicate an average of 0.047 inch (this comes from measuring two Armalite AR-7s and two Charter Arms AR-7s). When reassembling the barrel, if you simply drop the barrel into the receiver and snug down the captive threaded ring, the barrel will not be fully seated in the receiver by this 0.047-inch amount. Now, consider this: a .22 has a headspace (in this instance, the distance between the back of the barrel and the face of the bolt) of 0.044-0.046 inch, and as mentioned a firing-pin protrusion spec of only 0.035 inch (min.) and 0.039 inch (max.), so this 0.047-inch clearance easily outweighs the other clearances.



How to eliminate the 0.047-inch clearance? It couldn’t be easier. When reassembling the barrel to the receiver of your AR-7, first retract the bolt and hold it back so it does not contact the barrel face, then, while continuing to hold the bolt rearward, drop the barrel into the receiver and fully tighten the captive threaded ring so that the barrel’s shoulder makes full and positive contact with the front of the receiver. Release the bolt and you will see that it (the bolt) will not travel as far forward in the receiver as it did with the barrel removed.



Another Forum member has recommended removing material from the rear of the barrel, "maybe 1/64 [inch] with a fine file." I really do not want to cast aspersions upon someone else’s council, and I’m sure that his advice is well meaning, but in this case I feel it is ill informed. While removing material from the front of the receiver or from the barrel shoulder would indeed allow the barrel chamber to move closer to the firing pin, removing material from the barrel face will actually put the rim further away, lightening the firing -pin fall. I must say I think it a poor course of action for anyone to remove material in an area which alters headspace on any firearm. Perhaps in "cleaning up" this area a burr or a chip was removed from the chamber area. A flaw here may indeed keep the cartridge from chambering fully, just as fouling or lead shavings can, and may result in a light strike. But the flaw or burr should be peened back into place without removing material, and a burr protruding into the chamber may be "ironed out" with a chamber-forming tool. The difference between minimum and maximum headspace on a .22 Long Rifle is 0.002 inch, and the decimal equivalent of 1/64 inch is 0.0156 inch--more than seven times the total go/no-go headspace dimension! Give your AR-7 a good detail cleaning, but please don’t start filing on it. And pull that bolt back when you fix the barrel into position. Between those two things, I’ll bet you’ll solve all your light-strike woes.



Hope this has been of interest and of some help,



--ML













--------------------------------------------------------------------------------

Posts: 127 | IP: 38.186.249.115



Bill Hay

Registered User

ezSupporter

Re: Solving AR-7 Light Strikes (misfires)

Posted: 5/22/01 5:08 pm

--------------------------------------------------------------------------------



Oh, yes! Useful and interesting both! Thanks again for your input, ML.



I had similar problems many years ago (20? 30?) when I got mine, and stumbled onto the business about holding the bolt back.



All problems resolved...



Bill









--------------------------------------------------------------------------------

Posts: 768 | IP: 205.162.250.135



vector001

Registered User

great stuff. i'm gonna try a Henry variant then...

Posted: 5/22/01 7:12 pm

--------------------------------------------------------------------------------

(This message was left blank)

FAITH is the pivot -point of your fate ;

FACT is the outer limit of your circle;

TRUTH is the radial connection,...without which,

the Faithful and Factual have no common ground....







--------------------------------------------------------------------------------

Posts: 1625 | IP: 24.30.159.174



SandmanCA

Registered User

Re: I know it can be a pain but...

Posted: 5/22/01 9:28 pm

--------------------------------------------------------------------------------

check yer rounds. lots of them come from the box with extra lead hanging off them. I've even

cut them with a knife to reduce the crud.





--------------------------------------------------------------------------------

Posts: 57 | IP: 209.216.221.49



wmerrin

Registered User



Re: Solving AR-7 Light Strikes (misfires)

Posted: 5/25/01 8:13 pm

--------------------------------------------------------------------------------



You've done it again, ML. I've archived this one,too, and I don't even own the damn gun.

==================

Wally Merrin

wmerrin@san.rr.com





--------------------------------------------------------------------------------

Posts: 341 | IP: 204.210.0.185



Plainsman

Registered User

He almost got me talked into buying one!

Posted: 5/25/01 8:29 pm

--------------------------------------------------------------------------------

Considering the ease of this fix on the AR-7 that ML described...I'm ready to buy one if I ever find a good deal on a 'jammer.'



I'd like to hear some feedback from guys that previously had trouble and see if this cures most of the problems out there.



I have a feeling it does.



Plainsman

"Aim small, miss small!"

Plainsman's Email

Plainsman's Cabin Homepage





--------------------------------------------------------------------------------

Posts: 508 | IP: 65.162.96.186



Rik Palm

Registered User



WOW!

Posted: 5/25/01 8:46 pm

--------------------------------------------------------------------------------

(This message was left blank)

WitchBlades





--------------------------------------------------------------------------------

Posts: 412 | IP: 205.188.200.138



alco141

Registered User

Re: ML for president...

Posted: 5/26/01 4:21 am

--------------------------------------------------------------------------------

great fix on this rifle, i think we should elect you hoodlum firearms editor in chief. of course there is no salery that goes with the job, you get to answer inane questions from the rest of us, and the job allows you to work 24/7.



so what about it?



thanks

alex





--------------------------------------------------------------------------------

Posts: 76 | IP: 64.210.52.18



Eric Stoskopf

Cool Calm Calamity

Re: Great Info ML, Thanks!

Posted: 5/26/01 6:08 am

--------------------------------------------------------------------------------

(This message was left blank)





--------------------------------------------------------------------------------

Posts: 654 | IP: 172.136.18.66



wmerrin

I survived WASP

ezSupporter



Old post brought back to the top

Posted: 7/16/03 11:30 am

--------------------------------------------------------------------------------



I'm bringing this one back to keep it from falling off the last page.



Wally



==================

Of all the things I've lost, I think I miss my mind the most.

Wally Merrin

wmerrin@earthlink.net





--------------------------------------------------------------------------------

Posts: 872 | IP: 66.82.208.1



Fred Tanner

Registered User

Re: Solving AR-7 Light Strikes (misfires)

Posted: 1/25/04 2:15 pm

--------------------------------------------------------------------------------

(This message was left blank)





--------------------------------------------------------------------------------

Posts: 277 | IP: 67.23.245.165



wmerrin

I survived WASP

ezSupporter



Thread copied to FAQ section

Posted: 1/25/04 3:39 pm

--------------------------------------------------------------------------------

(This message was left blank)

==================

Of all the things I've lost, I think I miss my mind the most.

Wally Merrin

wmerrin@earthlink.net





--------------------------------------------------------------------------------

Posts: 1029 | IP: 64.157.32.1
Hind sight is an exact science until historians or politicians get involved.



Nothing is so simple that it can't be misunderstood.



I have regular bowel movements, I just wish they were voluntary...



My dad started walking five miles a day when he was 60. Now he's 91, and we don't know where he is.



Understand?


Forum Jump:


Users browsing this thread: 1 Guest(s)