Ongoing issues....extraction/ejection?

[mrclark303]

As Geoff said, looks a lot better. Very interesting to see if that does the trick.

[browningautorifle]

a few drill rounds

Don't know if they'll hang up though. They aren't expanded through firing.

Anyway, it looks worlds better. I'd just go to the range and start test from the ground level. Gas at 4-6...everything you did at the beginning of the last test. Otherwise we won't know where you are with it.

[82Trooper]

OK, so I got off work on time, and still had 3 hours of daylight. That made me smile.
Loaded the jeep and went to the range. That made me smile.
Weapon freshly cleaned and lightly lubed. Gas set at 5. Original top cover reinstalled. Still smiling.
Shot 2 5 round groups, 2 different mags (one oem, one aftermarket plastic), 2 diff ammo manufacturers. Worked fine. That made me smile broadly.
Changed magazines, 3 different ones, and problems started again. Smile faded.
Went back to 2 original magazines, same issues. No smiles.
Seems to jam on feeding occasionally, but not in the chamber but on the "ramp"....and on extraction once in a while as well...but it also seems to have cleared the chamber....see the pix.

Attachment 95038Attachment 95037Attachment 95036Attachment 95039Attachment 95040Attachment 95041

So....any new suggestions?

[browningautorifle]

Perhaps the sharp edge of the chamber is the culprit for the fails to feed...unless it's the butt return springs, but aren't those new? As for the chamber, I have a chamber reamer I use on something that seems questionable...new and sharp. You might be surprised how undersized it would be. Others may find me rash or harsh, but it's sorted out more than one obstinate feed/chamber/extraction issue.

Too, is something binding the breechblock and carrier on it's forward travel? Just enough to take the steam out of it's momentum?

Now, where's that Capt Laidler?

[82Trooper]

Yes,both inner and outer butt return springs were replaced with new (not used) from Arizona Response Systems.

[desperatedan]

Just my tuppence.....

Could it be that the bolt carrier isn't moving back its full travel, in other words "short stroking" as sometimes described?

Because of the sometimes slightly shorter rearward travel the ejector is having less (or no) effect and at other times the short stroke means a lesser effect from the springs giving lower forward inertia to chamber a new round from the magazine.

Does the new round failure to chamber happen on a full or nearly full magazine, when the mag spring will be most compressed and thus more force needed stripping the top round?

It might be worth checking that the gas piston is clean of any fouling, that it isn't slightly bent and that the piston tube is properly installed.

If this all checks out, you could run a test with only two rounds in each of your magazines and see if they run reliably. If it does try more rounds in a magazine and if the problem returns, turn up the gas setting to see if that makes any improvement.

[82Trooper]

I only loaded 3-5 rounds at a time into the different magazines. I hoped to rule out weak mag springs as a variable.
The gas rod and spring are new. But I will double check for straightness to rule that out as well.
What else might cause a “short stroke” scenario?

[mrclark303]

Might I suggest Mike, if you can't identify the issue, send it to Brian to sort out. Might be the easiest route....

[82Trooper]

I was kind of hoping he was going to show up here and make me that offer! I really like this rifle and want to get her squared away!

[Bruce_in_Oz]

Where, if anywhere, it it throwing the "empties", NATO-spec ball specifically? There are "minimum" regulator settings: "Unit level"; 4, 5 or 6. At Field Workshop level; 5 or 6. The general idea is to adjust the gas regulator until cases (fired prone) land about four or five feet away. If this cannot be achieved at those gas settings, there is something wrong; call the "gun-plumbers". If the brass is disappearing into the next county / province, etc., you need to open the regulator up a bit more.

If, on a warm-ish day, they are barely departing , or not leaving the ejection port with a bit of vigor, the problem will be gas, or lack thereof. This can be the result of:

1. An undersized port in the barrel
2. A misalignment between the barrel port and the gas block.
3. A badly worn gas block.
4. A badly worn gas piston. (Loss of hard-chrome coating was cause for replacement)
5.Too much gas venting via the regulator collar.
6. Gas cylinder (the thin steel tube) has incorrectly cut slots or has been incorrectly fitted.
7. Combinations and permutations of all of the above.

These are definitely NOT "shake and bake" bits of gear.

There was, in Oz, another "operation" in which the gas port in the block and barrel could be "cleared" to ensure there was plenty of gas arriving at the piston face, with the regulator still having "travel" in either direction.

That reference states:

"Gas vent may be cleaned using a No.42 drill (0.0935 inch diameter).

Another "modification" to the gas system:

The slots in the front end of the tube were to be "extended" and "radiused" to reduce cracking resulting from stress risers caused by the early "square-ended" slots.

Additionally, there was the application of a "corrosion-resistant" zinc coating to the threads of the gas cylinder to prevent corrosion and subsequent cracking of that tube. The stuff was a "2-pack" paste, (binder and zinc-powder filler) that had to be mixed frequently during the relatively short "work' time. The threads were to be wire-brushed free of phosphating before application. The brew dried fairly quickly, about ten minutes at room temperature.