happening with 2 different windowed p-mags of 6/08 date code-basically unused, i bought them just before the election and have been sitting on them since.
wolf ammo and handloads- 24 grains of TAC 55 grain hornady about .020 over min OAL.
mags work fine in my friend’s M&P 15 carbine. (using the same wolf mil classic 55 grain)
bolt locks to rear every time on an empty mag-so i don’t think it’s short stroking.
the malf seems to occur with the 3rd or 4th to last round in the mag.
apparently this upper was 100% reliable for the previous owner. 2000 rounds of no troubles.
makes me think the mags somehow don’t get along with my lower.
hmm that might be worth a go…
i assumed a middy would want a lighter buffer… though given that mine has 2000 rounds through it, it’s entirely possible the gas port has opened up a little…
Read the post above yours. The M-16 BCG does not have much overtravel, the magazine has little time to present the next round and for the ‘surging’ of the magazine spring to dampen. (think a plucked guitar string). While this is going on, the next round is being bounced against the feed lip and until the spring settles, it is not being held as firmly. Add the BCG slamming into the bottom of the buffer tube while this is still occuring and you get what you get. Everything has to happen in time and the M-16 family does not have alot of fudge-factor in this regard like a Kalashnikov with its generous overtravel.
Certain things are adding to one another. The slick cartridge case, the coincidence of the timing of the bottoming of the BCG and the feed rate of the magazine at a certain point in its load (around 3/4’s thru its thrity rounds when the spring is more extended), slick polymer or teflon-coated feed lips and you get all of these events compounding with one another, a perfect shit-storm. Change the timing with a heavier buffer and you break the effect as these are not happening in coincident with one another anymore.
Sometimes slick ammo like the steel case wolf can be ‘jarred’ off of the feed lip when the BCG bottoms out.
I have seen it and changing the buffer could turn it on and off like a light switch. So could switching to less slick (even thought it was hotter ammo) brass ammo.
The fact that these same magazines evidenced no flaws with the feed lips upon observation and worked 100% in another rife was a big clue.
The fact that felt recoil was greater than a carbine length rifle was another that this was cycling stoutly.
To add: My buddy’s rifle would not do it with the Wolf ammo from USGI mags. My rifle would not do it with his mags either.
I’ve spent the last 5 minutes trying to reproduce the double feed with dummy rounds by rapidly hand cycling the gun. feeds perfectly.
this makes me think that heavy metal is onto something with cyclic rate being an issue.
to clarify, i’ve tried this now with wolf, AND my low power brass cased handloads.
I guess it is probably a combination of the mags and the buffer, but I’d really like to make this gun as mag-insensitive as possible for obvious reasons.
My preference is for the heaviest moving weight-type buffer that will cycle the weakest ammo from a lightly-held rifle on a cold day.
Generally, the slower the BCG goes, as long as there is sufficient energy reserve for off-normal conditions, the better the rifle will function. Gives more time for things to sort themselves out.
Remember, you are trying to get as close to the timing of a full-length rife as you can without compromising reliability.
Wolf is great ammo to use to test for minimum functional conditions.
Damn Tweak, you mean I could have said all of that in eight words and saved myself all that typing?:suicide:
While the magazine is usually the culprit, it is not always the curprit. Sometimes it is a group effort too where several parties are just a bit guilty.
what are my spring options? it seems like you usually just see “carbine” and “a2” listed for sale…
i cant’ very well make the gas port smaller, so it would seem compensating for the expanding gas port size with a heavier buffer would be a lot more economical than buying a new barrel.
99% of the double feed issues I have seen have all been magazine related. You shouldn’t need an H buffer, but if it will cycle with it reliably then there is no downside.
I encourage you to ditch the O-ring as it is not needed. It is entirely possibly that this was a “on of”. When it is a continuous problem that is when you get concerned. Mark the magazine and drive on.
2-3 times with only 2 magazines with only one kind of ammo would not determine the issue was the rifle. Not even close.
Certainly not good enough to start screwing around with my set-up.
I’d take IG’s comments to heart. Maybe get a few more magazines, many few more - and some more, different ammo, then see if it still happens.
