SLR L1A1 STRAIGHT PULL

[Peter Laidler]

Gil says '............My ten P's worth, I believe it is caused by the lack of gas inertia to overcome the initial unlocking of the bolt toggle from the locking shoulder. It is a problem that all L1A1 straight pull variants have, M14icon’s and AR10’s suffer from it too, as they are a compromise and are simply not working as the original gas operated designers intended them to......'
The fact that there is no 'gas inertia' is irrelevant SP rifles simply because, by default, there is no gas inertia! There CANNOT be! So there is nothing to assist the opening of the breech because it is positively locked. That is mechanical safety. And even if there WAS gas, as on an L1A1, the breech CANNOT be unlocked until the gas in the barrel is down to atmospheric pressure. Let's wait and see what Gils video shows us about how the BB is locked by the BBC

[Gil Boyd]

Peter,
As I said it is because there is no enertia to assist which is why there is the problem from the outset, as we all agree. My money is probably on the expansion of the case, as I noticed a brighter ring at the back end of the casing. Might try three rounds leave it for a few minutes and try another three. It could simply be too much heat, but I am no expert!!

[Peter Laidler]

Ah, yes, I see where you're coming from Gil (and others) but while there is no gas to impart inertia to the BBC to unlock the BB, because it's a gasless S-Pull, YOU have to supply the inertia. In short, it is now a mechanically operated rifle, just like a No4. But I maintain that even then, the mechanical inertia (now called 'mechanical effort') that you as a 12 stone human can impart will be FAR greater than what could be applied by the piston. There must be some other cause. Think about this:
a) The 12 stone human easily absorbs the recoil forces plus the very small extra inertia when the gas operates the BB and BBC. So on that basis alone (it's not quite an equal and opposite forces thing, but a good analogy I say) the average bloke SHOULD easily be able to operate the cocking handle to open the breech. And
b) When the gas plus is turned to shut off the gas - now turning it into a mechanically operated rifle don't forget - the average crunchie/Armourer had absolutely no problems hand cocking the rifle again. I say that this is exactly how your rifles should be able to operate.

The more I see and listen, I am pretty sure that............. let's wait to see Gils video

And while we're here, the sticking working parts problem CANNOT be a fired case sticking in the chamber. If that were the case, the BBC would still slide rearwards for 3/8" until it tried to unlock the BB and unseat the stuck case. But clearly in these SP rifles it is the BBC that is stuck fast. And that is not influenced by a case that's expanded into the chamber. Nope....., the answer will come.

[Ex Crab]

Gil

Ah, so you got it! Well done!

---------- Post added at 08:39 AM ---------- Previous post was at 08:34 AM ----------




Jon

You are absolutely correct, one way or another this concerns all of us that shoot. There is also a plan to put a maximum MV on in the legislation. Once you have a maximum MV restriction, it is but the moment of a piece of delegated legislation to knock another nought off the end.........

The consultation closes on 9 December, and I intend to put my comments in well before time.



Offensive and dangerous weapons: new legislation - GOV.UK

Completed survey.

[Badger]

Post #58 updated for member to add two movies

Regards,
Doug

[Gil Boyd]

Thanks to Doug for achieving the harder things in life down loading footage successfully

[skiprat]

Good vids Gil.
It looks like the breach block carrier is free to move rearward until the unlocking cams contact the cams on the breach block, so the carrier is free to move, no problem there.
Thinking out loud.... if you were to fire again without the extractor you would eliminate any extra chamber friction, but would highlight any problem with rearward pressure acting on the breach block/locking shoulder. (extracting the good rounds would be a pain!)

The LSW L86 had a habit of throwing in the odd hard extraction, when you managed to remove the case you could see the dirt pressed into the fired case. The LSW had a habit of sucking in dirt to the chamber.. once the stuck case was removed all evidence had gone and the weapon would function as normal until the next dirty chamber,

That probably dose not help, but how much dirt would stop a civil made straight pull? ( not made to mil. Speck.)

[mrclark303]

Thanks to Doug for achieving the harder things in life down loading footage successfully

where would we be without Doug...

[Gil Boyd]

Skiprat,
Thanks for that. Not an easy one to achieve, firing and presenting a video without the actual rifle in your hands to experience the stoppage, from your perspective.

Both times the rifle had to be stood up and both hands to extract the spent round. On inspection of that round and interestingly enough both rounds in both calibres, had a bunished ring around the back end.
Almost as if it was held by heat. So my non experienced untrained REME eyes lends the problem to one of expansion.
At least my rubber hammer had a day out!!
I just wonder if a hand loaded 7.62 or .308 might help here, as in that way both could be loaded with a lesser charge.
My next port of call was GGG and Winchester .308 39 grains this time with fully pressed sized cases.
Any thoughts on that

[Peter Laidler]

Well, that's pretty conclusive then. Contrary to what has been said many times, Gils video shows that the BBC DOES retract 3/8" until it commences to unlock the BB. So it IS a breech block/spent case/hard extraction problem. If the primary extraction was operating as it should, then as soon as the BB lifts it tweaks the cast outwards by virtue of the top face of the BB acting as a fulcrum. Clearly if the BB cannot lift, it cannot cause primary extraction. End of story - it is not a primary extraction problem. But WHY isn't the BB being lifted..........? Think of this. The BB levers upwards and rocks on the top front surface in a 10:1 or so ratio. So it should lever even the tightest stuck case outwards. Even the tightest taper (say, your morse taper lathe or drill) just needs the slightest tweak to break the taper lock.

From this we can establish that the problem, certainly in Gils rifle, is a case so tight that it a) the rearward loading by the case on the BB is so great that it causes the BB to lock so hard against the locking shoulder that it b) defeats the leverage of the BB to lift and cause primary extraction.

So where do we go now.