New ACR L1A1s - back sight moves on recoil

[Charlie303]

The rear sight of my new L1A1 jumps forward whilst firing, presumably due to the re-coil.

Has anyone else experienced this?

Peter has suggested that I need to hold it into my shoulder more firmly (!). True, I could do with a size larger Butt Plate.

Another suggestion is that the rifle might be giving a more powerful recoil now that the gas operating system etc have been removed.

Charlie

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Peter Laidler]

Look at it logically........... The sight can ONLY move forwards if a) you push it forwards against the spring and balls in the detents or b) the rifle moves back pretty sharpish, in effect leaving anything moveable - such as the backsight slide and leaf - to remain where it is as the rifle moves back. There is NOTHING else. You can tie the backsight slide and leaf down with some string or sticky tape or you can replace the ball and spring. The acid test is to hold the rifle butt first, against a solid brick wall and fire it. If the slide doesn't moive forwards then, then it's operator error! It is nothing to do with lack of gas because............ it's going to get technical now so I'll stop!

Tuck it into the shoulder hard, get the sight picture........ man laying at the edge of the hedge............hold...........tight, slightly exhale....... squeeeeeeeeeeze the trigger and bang. Target falls when hit. Backsight remains upright and at the set range

[nzl1a1collector]

I think the first thing to try is :-

Try moving the backsight up and down the ramp, if it move easily there is a serious problem.

A backsight that has its Ball and Detent correctly fitted (or fitted at all) will require substantial pressure to get it to change position up or down.

How easily can you move your backsight?

[Charlie303]

The backsight is quite difficult to move, as one would expect. I've tried 2 now, both exactly the same, as Peter says, must be the other variable - me!

[David TS]

The rear sight of my new L1A1 jumps forward whilst firing, presumably due to the re-coil.

Has anyone else experienced this?

Peter has suggested that I need to hold it into my shoulder more firmly (!). True, I could do with a size larger Butt Plate.

Another suggestion is that the rifle might be giving a more powerful recoil now that the gas operating system etc have been removed.

Charlie

Well, that must be three of us at least so far, that cannot shoot - or it's Newton's Third Law of Motion

Mine does it too, and someone else mentioned their also does it (Oxford Andy or Daryl, IIRC) - EDIT - checked my PM's, it was Daryl.

First time out with it, whilst trying to zero at 100 yards mine shot up from 200 to 600 every shot....except I didn't notice until I was on the 300 yard mark

Mine also kicks like hell (it was pulled VERY tight in my shoulder, and I still had a 4" square bruise next day), and removal of the gas recoil mechanism MUST have something to do with that.

I also have wood furniture and an ally butt plate on mine - no give anywhere, except my shoulder.

What ammo are you using - is it pokey stuff?

I've got a new sight/detent spring/ball for mine, but haven't bothered fitting it yet as I have scoped it now.

Still love the rifle though

[kar66]

My L1A1 did the same thing. Not every time just when I wasn't watching for it to do it. I would look up and it would be moved. The bad thing was it was real hard to move back. Now I have it tied back with a small black nylon slip tie. You don't even notice it, but I know it's there. Just looks kind of cheep, but I guess I can live with it. I'm glad to know it just wasn't only mine that moved. I've been watching these fourms for a few years to see if anybody else had the same problem as me. YES finely!!!!!!

[Charlie303]

I wouldn't bother messing about with the rear sight. I've tried 2 and Peter gave me a new spring and some new balls (no comments please). Although I haven't tried the new ones whilst firing yet, they all measure exactly the same, the backsight feels the same when being adjusted. I just don't think there's anything wrong there.

I'm using Privi .308. The rifle is as bought (plastic furniture) and I get an average kick, much as with a .303 No.4 and not as much as the No.5.

The fact is, even if well tucked in, there's still going to be an immediate backwards movement, even if it's not a great distance. My shoulder is muscle, bones and tendons, it's not a brick wall.

I think that it's significant if 3 of us are getting the same effect with a new rifle. The dynamics between the old 7.62mm L1A1 gas operated SLR and new .308 L1A1 'bolt action' have altered something.

I just scraped a pass in O level physics and I wouldn't dare argue with Peter on this, but if the energy that previously knocked back the breech block, carrier, hammer, return springs isn't being used, it surely must be going somewhere?

---------- Post added at 06:15 PM ---------- Previous post was at 06:13 PM ----------

Karr66,

Not sure where you are, so is your L1A1 gas operated or like ours in the UK, bolt action?

Charlie

[David TS]

Charlie

I'm also using PRVI. The L1A1 recoils more than my Enfield .303 No 4 Mk II.

It must be something to do with the removal of the gas mechanism. Not only does Newton's Third Law come into play, but weight is physically removed from the rifles by way of the deleted gas components, and that can't help.

That wasn't a criticism of Peter in my previous post by the way, he's forgotten more about these rifles than I will ever learn!

I suspect .308 ammo has more powder behind it than the milspec 7.62 - I keep meaning to check, but keep forgetting

In comparison, my deer stalking rifle is a .308 CZ 550 - 26" heavy barrel, laminate stock, it weighs a ton, and it's a pussycat to shoot

[David TS]

From the posting style, my bet would be that Kar66 is from the USA

My further guess would be that he has a Century or DSA kit based L1A1

[Peter Laidler]

Maybe someone ought to try using bog standard UK Milspec NATO ball.

Regarding the loss of the gas system, it could get complicated so I'll keep it simple. The gas vent is all tied up with Boyles law and you need to remember that the mechanical safety ensures that the bullet has already left the bore and 2 metres down the range and the gas in the barrel has been reduced to atmospheric pressure before the breech block has even commenced to unlock and that is on a standard L1A1. Yours haven't even got that. It's also worth remembering that on the old L1A1, recoil had already taken place by the time the breech block unlocks. What I am saying is that the amount of extra gas and therefore muzzle velocity and recoil available to your rifles WITHOUT a gas port compared to the standard L1A1's WITH the gas facility, is absolutely unnoticeably minimal. It would take very accurate and calibrated measuring equipment to discern the difference. I know this because we did similar trials and tests with AK47's (Ok, ok, I know it's not exactly like for like........) But when we did other trials with doctored L1A1's at Shrivenham, the m/v differentials were so slight that they could be put down to ammunition variables. Also, it's worth bearing in mind that we COULD disconnect the gas system of our L1A1's by rotating the gas plugs. And shooting them like that didn't move the backsight slide upwards.

Nope.......... I'd like to suggest using bog standard RG NATO ball for a start and then on the Enfield layer in the test range in order to eliminate the human factor