Later L1A1 tech (workshop) documentation

[Bruce_in_Oz]

Do any old "gun-plumbers have the "late-issue" data for the L1A1 gas-port diameter and the "instruction about boring it out a few "number" sizes to keep the old girls chugging along until the various 5.56 replacements came on line. I am certain it was an approved practice / official instruction in that short time, . Some seem to doubt the existence of such an instruction, so I am throwing it open to the "Council of Elders".

I can find notes for several other "life-extension" instructions. Some personal notes may have been "misplaced" during several moves. Who knows

These other "instructions" included using a special "zinc-based" paste to better seal the gas-cylinder tube, , spot -welding the "riveting of various catch / latch assemblies, inserting "reinforcement "gussets" in the front of the trigger mech housing. Relieving the timber of the butt at the top of the wrist to reduce the chance of splitting. .

Probably other stuff i have forgotten.

[Frank LE]

Hi Bruce,

here the reference for reaming the gas port to stage 1 and 2 from EMER Regulations/Field Level Repair.

[browningautorifle]

Very interesting.

[Bruce_in_Oz]

I just received an email from a former "colleague" who tells me, as per the "instructions", that "if the gas vent in the barrel is "fouled", it is to be cleared with a "No. 42" drill bit.

I looked up the chart and it tells me that No 42 is 0.0935 inches or, 2.3749 mm.

But, he could not quote the the "last-ditch" oversized hole allowance.

I still cannot find all of my own notebooks, unfortunately.

Australian L1A1 documentation was in the D250 "decade" (series). The scan of D114 is a scan of an official document ; i.e.., a UK "Electrical and Mechanical Engineering REGULATION": a whole different family, but still a "rifle" reference. These were not something in my "system" back when I wore the "other" baggy green, down here in the Penal Colonies..

The Brit "numbers" for "adjustment" to the gas vent look 'reasonable" so I will file the excerpt in a sleeve in a ring binder for possible future reference. Perhaps something for a post-port game of "Military Mastermind"?

[Bruce_in_Oz]

Trawling through more old paperwork:

1982 vintage, official "section" drawing of the L1A1 gas system shows the angled port in the Gas Block aligning with a VERTICAL port in the barrel proper; .

A similar section illustration from June 1992 clearly shows the angled gas hole in the Block, continuing into the BORE at the same angle, very much like the way AK / AKM rifles (and their Finnish cousins like the RK62 (and the Valmet "Hunter" sporting rifles), are set up.

Associate "maintenance text refers to using a "suitable rod inserted in the bore to prevent damage to the bore and the "cleaning drill-bit / reamer.

The official drawing for the Barrel show no illustration or description of a "gas port"

Any further thoughts / experiences regarding this little detail?

[Bruce_in_Oz]

Regarding the drill-bit sizes:

No42 is somewhat smaller then the reamer sizes in that EMER excerpt; my "source" could be in error (heaven forbid). The trick with the L1A1 setup is that you can go to the range / firing tunnel with rifle, ammo and some tools. The desired result o consistent extraction and ejection performance at a specific regulator setting. I will try to find an actual copy of the performance specification.. (Something about gas setting 4 and cases landing nine feet away? Prone position?)

Fire a couple of rounds of NATO ball at the recommended setting. If the cases fall short whip out the trusty battery drill and set of Number drill-bits, clamp the rifle in a padded vise and have at it. Tiny increments at each adjustment, please.Remember to thoroughly remove the swarf from the bore, before resuming........

If on first firing, the cases end up in the next grid square, Bubba may have been busy, before you.

The saga continues..........

[browningautorifle]

We referred to this as "Balancing" the rifle. We didn't use drill bits and we did attempt to set rifles at 4 on the gas regulator...but when balancing with ball you'd find out where yours shot best. It's a wordy process but supposed to take place every time you're issued a new rifle and just before range practice with an unknown rifle.

I remember the picture you speak of with the gas port changing from angular to vertical too...but it isn't.

[Peter Laidler]

On active service I always used to leave my gas regulator fully closed. That way, it'd always re-cock. At a big shooting competition at Nee Soon ranges in Singapore with Aust, UK and NZ Infantry, the KSLI (UK Kings Shropshire Light Infantry) Armourers told me that they'd balance their rifles to just operate, probably on No4 gas. But I didn't trust it as some of the shoots were timed and you just didn't have time to start faffing around clearing a stoppage on the timed shoots.

After all, gas closed off, the actual RECOIL remains the same. It's the slightly harder kick of the breech block carrier hitting the TMH that gives the feeling of greater recoil. It's not, it's just a bit more mechanical inertia. But wonderful times.

Bruce is right..... Towards the end of their life, some of the L1's were definately getting tired and even short supply that meant some life extending mods were the order of the day. There was one that I remember reading here, that I never saw oor heard of, where the TMH was slightly modified to correct the loose/slack axis pin holes, by ring punching. A totally useless exercise! And spread the sides to do the same. Never saw it but definitely there.

[browningautorifle]

I always used to leave my gas regulator fully closed.

Our rifles were getting metal fatigue and started to break ejectors. There were two kinds in ours, one was a large wide block that filled the whole bottom and the other had just the ejector on it with the rest of the block fixed. The later had the replaceable ejector but we had none since CAL had sold Blake Stevens all their small stuff. We'd used our up. If we broke ejectors it was a BLR and that rifle was gone. All part of the penny pinching of the '70s and early '80s.