Why is does my French Berthier 8mm carbine have flyers always to the right

[rayg]

The sights are not offset just that when you bore sight the bore points slightly right of the target while the sights are center.

Maybe to simplifly my question leaving out the cast bullet factor. Would a full power military rd shoot the same in a left hand twist bbl 31-1/2" as it would in a 17.8" barrel at 50 yrds if the sights and the bore of each were aligned to center aim, or would the shorter barrel cause the bullet to impact to the left of center? There must be a reason the sights on the carbine were made to have the bore point to the right of the sight. The only thing I can think of is that the longer and the shorter barrels do not shoot to the same point of aim with the same bullet, Ray.

[vintage hunter]

The only way you can answer that question is to try it and see. Theoretically, they should but thats not always the case. As far as rotational drift is concerned that does'nt begin to have any noticeable effects until you get out to 400-500yds and beyond, if then. Asuming both rifle and carbine have the same twist it stands to reason that the carbine bullet would have less rotational drift than the rifle due to the bullet rotating at less rpm's out of the shorter barrel but at 50yds this is not a factor anyway. Ever measured the trigger pull weight? Is it consistent? That could explain a lot.

[Patrick Chadwick]

There must be a reason the sights on the carbine were made to have the bore point to the right of the sight.

Rayg, you are assuming, quite naturally, that the rifle is as made. I think that this is something you need to check very carefully. There is one very simple possible explanation for what you observe - that the barrel has been overtightened at some time, and that is the reason why the foresight appears to be over to the left.

Simple eyeball judgement may not be adequate to check barrel alignment. One way of doing it is as follows:
1. Use a stable, flat tabletop or large sheet of glass as a surface plate.
2. Place a suitable block of hard wood or metal on the table, so that you can place the rifle upside-down and rest the base of the backsight on this block.* This is to ensure that the backsight base is parallel to the surface.
3. The front end of the barrel should also rest on a block, so that the foresight blade is not touching the table surface. Depending on the position of the center of balance of the carbine, you may need to weigh down the barrel so that everything sits stably. A wobbly setup will invalidate the measurement.
4. Now simply place an engineers square (or a suitable trued-up block) on the table surface in front of the muzzle, and on the bore line (i.e. central) and sight along it towards the foresight. The foresight blade must point vertically downwards. If it is visibly skewed, for instance so that the blade is to the left of six o'clock as you look at the muzzle, then the barrel has (probably) been overtightened. Or the blade is in a dovetail, and has simply been pushed over. Or - wierd but possible - the blade itself is bent.

Of course the answer may be that the barrel is bent! I hope not. But even that can be fixed.

Check it anyway.

Patrick



*This will require folding the backsight leaf right over to expose the backsight base.

[rayg]

Patrick I took the barreled action out of the stock and checked the alighment lines on the action and the barrel and they are dead on and there is no damage to the front blade. There carbine is a M92 model with a 1897 dated barrel and has never been refurbed or upgraded and it is as it came off the assembly line back then. I have to think that the sights weer made that way for a reason. As example I have a 1896 Long Lee Enfield MkI that also shoots right of center and you can see were the blade on the front sight was purposely off-set to the left. This is the way they made the sight at the factory with that model. They centered the blade a couple years later in the MkI* model. Ray

[rayg]

For some reason the site won't allow me to post any photos which I have in the past posted photos. Go to this French thread on gunboards where I asked the question about moving the sight and where I posted photos of the Long Lee Enfields MkI's front sight so you can see how much offset to the left the sight is compared to the upgraded Mk* sight . Ray

Click on this,

Moving rear sight on Berthier Carbine?

[rayg]

Photo up and running now

Attachment 26127

[jmoore]

That's good because I couldn't see the photos on the other site.

Don't recall my carbine shooting off to one side, but it's been a while, and 200gr FMJs were the projectile. Will have to investigate further.

These carbines do have very thin profile barrels. Or could it be some asymmetry in the action?

[rayg]

I have only fired low velocity cast bullets in it. Possibly if I fired full power jacketed loads it would shoot center.

The blade on my carbine is not offset like the Enfield's however I followed Patricks instructions and when a ruler is placed along side the barrel on both sides, you can see that the sight block is canted to the left or set further left on the barrel. That would cause the sight to aim more to the left with the bore to the right. Now the question is, was the bbl overtightened or was it purposely made that way.
If your carbine is an original barreled early Berthier. Could you bore sight it to see if your bore points to the right of the front sight, Ray

[jmoore]

Okey dokey.

[Patrick Chadwick]

I have followed all this, checked the link on Gunboards, and I must confess - I am baffled! If, for instance, you take a close look at the Buffington sight on a Springfield trapdoor, or the mystery sight I posted some time ago on the Lee-Enfield forum, you will find that the sight leaf is slightly tilted for very long ranges - as a drift correction. But this effect is just not detectable at 50 yards. The massive offset at 50 yards referred to for this carbine cannot be explained in terms of wind drift. And it is a carbine, where short ranges would be more important than any fancy 1000 yards stuff. On the other hand, I do remember once trying out a MAS36 that made a group about 1" wide, but also about 6" to the right of center at 50 meters.

Maybe all French carbine shooters were left-handed and pulled their shots horribly? Nope, I don't think that can be the answer ... any other suggestions? I can only guess that it is indeed something to do with the original ammo.


Patrick