AR15 should = happy...but

Dont drill the gasport!
The only time you would drill a port is if it is undersized - and that is not a reported occurance with SP1's.

If the previous owner used a lot of .22LR in a subcal kit - your gas port may have been partiall gummed up - but I agree that this is not a gas issue since the first two rounds cycle - but.
Try the empty mag drill - chamber a round from the mag (only load one into it) and fire the round -- see if the bolt catch is engaged - if it does you know the bolt is traveling rearward enough.
 
Couldn't be possible as jstreet says, that if the bolt is just barely passing the rear of the round that when less mag spring tension is present that the round just doesn't make it in time for the bolt to catch it. Usually the short strocking i've seen does not even allow the bolt to clear the rear of the round, but this one may just be borderline ??
 
:oops: Major omission here guys, I have to tell you that I forgot one fact.. That after the 3rd round did not chamber, I pulled the charging handle back full lenght and released it and it still never picked up the third round. Hard to get help when one does not present all the facts first. Me very red in face :oops: :oops: :oops: .....please continue with possibilities of repair....
 
Same stuff applies. That revelation points it a bit more towards a worn buffer spring or crappy mags. You seem to have ruled out the mags, so just give it the overhaul that Sparrow suggested and all should be well.
 
What are you using for ammo? Some of the old military stuff is a bit too long for most mags and drags on the forward part of the mag. Will sometimes fail to strip from the mag after the first 2 or 3. Did a joint training thing with the CF last year and experienced the same thing... guns that were working fine just all the sudden failed to pick up rds after a few shots. We thought we had mag problems, but we were using several types of mags. Eventually clued in that the ammo the CF guys brought had a slightly longer overall length and the bullet tips were in contact with the mag body. When we looked at their older thermold mags could see where rds were cutting grooves in the plastic.
Opening the gas port. Last resort on anything. On an SP1. Can't see why you'd ever need to.
 
icecold said:
:oops: Major omission here guys, I have to tell you that I forgot one fact.. That after the 3rd round did not chamber, I pulled the charging handle back full lenght and released it and it still never picked up the third round. Hard to get help when one does not present all the facts first. Me very red in face :oops: :oops: :oops: .....please continue with possibilities of repair....

Is the bolt hanging up on the round (staying open) or is it simply gliding over it (bolt closes but no round) ??
 
To me it sounds like a mag issue. Perhaps a problem with how they are pinned is causing poor spring tension? My advice would be to try someone else's mags in the gun or (shudder) drill out your limiting rivet and try cycling the action with an unblocked mag. If it works OK like that, then you need to find another method of limiting your mags to 5 rounds.

Oh, and make sure you re-limit the mag right away so you're not an evil crazed "assault rifle" owner...
 
Claven2 said:
To me it sounds like a mag issue. Perhaps a problem with how they are pinned is causing poor spring tension? My advice would be to try someone else's mags in the gun or (shudder) drill out your limiting rivet and try cycling the action with an unblocked mag. If it works OK like that, then you need to find another method of limiting your mags to 5 rounds.

Oh, and make sure you re-limit the mag right away so you're not an evil crazed "assault rifle" owner...

Claven2 I have tried other mags and still the same trouble. My mags are pinned with an aluminum strap riveted from the floor plate up to the base of the pusher plate. My buddies mags are riveted in the conventional style with the rivit place on the back side of the mag at the proper height. All mags new, used, green, black, unpinned for testing, all have the same effect. I truly believe from the testing I have done it is not the mags. I appreciate your input, Thank you


icecold
 
Just in case it wasnt said enough ... Dont drill the gas por !!!!!

I had done this to a short stroking 10.5" bbl. This was done to help from short stroking. I ended up scaping the barrell. As said before a standard rebuild with good parts is a great way to start (tune-up).

I doubt that its the mags.

Make sure that your bolt is put together properly.
 
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