French Gras question

[emmagee1917]

Looks like you did a good photo to me.
Chris

[jmoore]

The snag is that you do not have an "as built" Gras rifle, but a Chassepot (Mle 66) converted to take Gras center-fire cartridges (Mle 66/74). This was done by inserting a sleeved element in the Chassepot system, with a resulting "squeeze" section just in front of the Gras-sized chamber. The /80 modification was the pressure-relief groove milled out behind the chamber to handle burst cases in those early days of brass-drawing technology. The link above is worth studying to understand this, even if it it requires a bit of patience and a good dictionary!

Score another one for Patrick Chadwick!

I don't know about the reduction in bore size, but there's a well executed sleeve in mine. The rifling is good with a very defined origin. But that's because of the sleeve. Seam's invisible about 2/3's of the way around, but the bore scope picked it up after about giving up finding anything. Never did find the back end. Very nice workmanship. Thinking that any reduction in bore is likely due to vagaries in press fit or later corrosion in the joint. I'd about have to section mine to discern anything further.

[Aragorn243]

Does your chamber look like mine?

I'm trying to determine if mine is sleeved or if it was re-barreled. I don't know what to look for. The dates on the barrel could be when it was reworked.

[jmoore]

Does your chamber look like mine?

I guess. The area where the sleeve ends is all I could find and thats well out of focus on your photo. And it was hard to find even with the bore scope! Would think it likely yours is sleeved as well. But it ought not hurt anything.

As far as the outside goes, here's a couple old photos:

[Aragorn243]

So the sleeve includes some of the rifling? I wouldn't have thought it would go that far in. Your barrel has the later dates stamped on it as well so mine probably would be sleeved and not rebarreled. The dates must be when they did the work.

[Patrick Chadwick]

So the sleeve includes some of the rifling?

Alas, no!

If you look at the linked info from Mr. Sedent, you can read that the problem is that the sleeve has NO rifling - after all, it would be horribly difficult to match it up and keep extractor groove etc properly oriented. The rifling would need to be cut AFTER the insert had been fixed in position - a very expensive one-off operation. The cm or so in front of the sleeve in front of the case mouth is thus normally plain, and typically has a diameter somewhere in between the bore and groove diameters, hence the "squeeze" effect and the undesirability of trying to use jacketed bullets. The only way I could think of to get a truly matching rifling in this stub would be to use an adjustable cutter set in a carrier that is lead-cast into the barrel (similar to the method used for lapping a tatty bore) and to proceed VERY slowly and cautiously, cutting each groove one at a time. That would be right royal PITA, so, as previously mentioned, I sold my "Grassepot" when I found an original Chassepot.

IMOH. JM, if your "Grassepot" has rifling right down to the end, then you are very lucky in profiting from someone else's long, patient work!

[Aragorn243]

Patrick.

I can't read French but did translate the pages. I didn't find much mention of the "squeeze" although I did find a cross section drawing that looks like a straight tube. I don't think that is what is in my chamber. I think it's been rebarreled with a Gras barrel.

Can you check the photo and let me know what you think?

[jmoore]

IMOH. JM, if your "Grassepot" has rifling right down to the end, then you are very lucky in profiting from someone else's long, patient work!

It's as you describe above, but the sleeve is groove diameter, I think! As noted above it was invisible for about 2/3's of the circumference. A tiny seam was noted as the bore scope rotated over that area. May eventually do a cerrosafe cast, but I thin k I need to get the .43 Spanish project operational, first. Most shooting and load develpment has been centered around IHMSA of late. Haven't hardly shot a rifle since deer season, and not much then.

[Patrick Chadwick]

Sorry guys, I was working to much from memory and ignoring what was in front of me in the photos. Thus forgetting the motto I propagate myself: look at what you see! I plead jet lag as mitigating circumstances!

Finally taking my own advice and looking, I can see that both Aragorn's and Jmoore's barrels have rework dates post-1874. So both rifles have presumably been rebarrelled. No "squeeze" problem.

In both cases, to be quite sure, drive a soft lead slug into the muzzle end, remove and measure the outside diameter. Take a second slug and do the same at the chamber end, to get an imprint of the start of the rifling. If the second slug has an outside diameter at least as large as the one from the muzzle end, all is OK.

[Patrick Chadwick]

F.W.I.W. here is the passage from the article by J-P Sedent on a modern cartridge for the Gras rifle:

Le projectile devrait donc avoir un diamètre de 11,5mm pour les deux modèles d’armes, mais le tubage du fusil Chassepot modifié Gras ne permet pas l’utilisation d’un projectile calibré à fond de rayures. Les différents moules disponibles pour couler des projectiles destinés au fusil GRAS sont en général au diamètre de 11,25mm, et ces projectiles sous-calibrés ne sont pas, de ce fait, en adéquation avec le diamètre à fond de rayures du canon.

In other words, you are likely to have difficulty with a bullet diameter of more than 11,25 in a "Grassepot" with a chamber insert, because of the restriction in the "tubage" i.e. the front end of the chamber insert, but in a newly built Gras (or, one would imagine, a Chassepot-Gras that has been rebarrelled) one can use bullets up to the groove diameter.

Note that Sedent uses a bullet with 11.5mm (groove diameter) rings at the front, but 11.25 at the back, for the ring that are inside the case neck, to enable the cartridge to be chambered.

Repeating my previous post, in the end it is a good idea to slug your barrel at both ends!