Reloading for the 1891 Carcano, Part 2

[RBruce]

After reading previous advice on loading the 6.5x54 Carcano using Hornady 160 gr. .2675 bullets, I pulled the bullets from the rounds I had trouble with before. Using the recommended chart, I loaded ten rounds, carefully measuring each power load and seating the bullets to the correct COL.

The results were surprising. The first round went off OK, although the bolt required more than normal effort to extract the case, but not a great deal more than normal. The second round went off, and I don't think it was louder than the first, however immediately smoke was curling up from the receiver around the bolt. I did not feel any gas on my face, but was surprised at the smoke.

When I tried to extract the spent case, the bolt would not turn. By using the top of the wooden shooting bench, I was able to rotate the bolt and pull it back. The case remained in the chamber. The primer fell out on the bench with a hole burned through it. I had to use a cleaning rod to remove the case.

Note: The bore and chamber had been cleaned prior to firing. Four rounds of 140 gr. Nosler Partition bullets have been fired first. In the photos, the left case is the bad one, and the middle case is the first 160 gr round fired. The right case is from the Nosler 140 gr. round.

Needless to say, I am going to stick with .264 bullets for the rifle. I did fire ten rounds of 160 gr. Hornady .264 bullets after the incident. I had no problems with them.

Information

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[Patrick Chadwick]

As far as I can tell from the photos:
No. 1 is presumably the one you described, where the primer fell out.
No. 2 shows cratering.
No. 3 seems OK, but the depression appears to be rather wide. Is your firing pin going too far forwards?

I suggest that you measure the neck diameter of the extracted cases as accurately as you can. Then measure the neck diameter of a case loaded with one of the ".2675" bullets. If the second measurement is not at least couple of thou less than the first, then maybe the loaded case was so tight that the neck was effectively jamming in the chamber. That would indeed cause very high pressures, as the neck cannot expand to release the bullet.


Patrick

[RBruce]

Yes, No.1 is the case that was stuck and the primer was blown out. No.2 was also a .268 load, and yes there is cratering of the primer. No.3 was loaded with Nosler .264 spitzer bullets with a beginning load.
The neck of the case that was stuck with the blown primer measures .2975 outer diameter. The unfired loaded rounds with the same .268 Hornady bullet measure .2925. However, the neck measurement of the fired rounds loaded with the 140 gr Nosler measure .2925.

With regards to the deep firing pin impression on the primer, what is the correct extended length of the firing pin?

Bruce

[Patrick Chadwick]

The neck of the case that was stuck with the blown primer measures .2975 outer diameter. The unfired loaded rounds with the same .268 Hornady bullet measure .2925. However, the neck measurement of the fired rounds loaded with the 140 gr Nosler measure .2925.

So the neck of the Hornady load started with the diameter at which the Nosler load finished!
From your figures, not quite a neck jam with the Hornadys, but not much space either. I think it would be a good idea if you could slug the bore. Typically, old service rifles have bores wider than modern specs (so, typically, they work better with slightly larger bullets), but there are exceptions.


Patrick

P.S: I am looking for firing pin data
P.P.S: If one assumes that a cartridge neck will be expanded to fill the section in the chamber, and then spring back a little, say 1/2 a thou, then the Nosler neck indicates that the chamber neck space is about .2975, maybe a tiny bit more. Since the Hornady neck finished at .2975, it must indeed have been very close to a neck jam!

[westkraut]

Privi will be offering their Carcano cartridges with bullets of .268" diameter. Would you have any experience or concerns with such factory ammunition? or is it trial and error with each rifle? ......karl

[Patrick Chadwick]

Privi will be offering their Carcano cartridges with bullets of .268" diameter. Would you have any experience or concerns with such factory ammunition? or is it trial and error with each rifle? ......karl

"Trial and error" is not the expression I would use. An error could be unpleasant. Rather take the advice printed over and over again in the Lyman reloading manuals "Slug your bore and size accordingly".


Patrick

[Patrick Chadwick]

With regards to the deep firing pin impression on the primer, what is the correct extended length of the firing pin?

The "Atlante del Materiale d'Artigleria" specifies:
Length of firing pin 21.7mm = 0.8543"
Length of firing pin hole in bolt body = 20.0mm = 0.7874
Protrusion of firing pin 1.7 mm = 0.0669"

Firing pin diameter 2.0 mm =0.787"
Diameter of hole in bolt body 2.2 mm = 0.866"

If you dismantle the bolt, it is easy to check these dimensions and draw your own conclusions.
Unfortunately, I cannot find any tolerances for these dimensions.

Based on my experience with other bolt-action service rifles, I would say that anything from 0.050" to 0.070" is fine, but 0.04" or less is likely to result in doubtful ignition, because the firing pin will push the cartridge fowards as far as the head clearance will permit, and above 0.080" could result in punched-through primers. Since the usable limits are determined by factors such as the head clearance and the extractor, I cannot give "absolute" values. Some cases where the measured values of large head clearance and short pin lead to the conclusion that it should not work, do in fact work because the extractor, rather than the shoulder, is holding back the cartridge enough for the primer to be detonated.


Patrick

[RBruce]

I measure the protrusion at about 0.045". I'm going to avoid the .2675 bullets since the .264 are actually quite accurate. I have listed my supply of .2675 Hornadys on the WTS page. Thanks for the assistance. --Bruce

[Parashooter]

"97 Hornady 6.5 mm 180gr round nose bullets for the 6.5 Carcano .2675 diameter. $40 shipped and insured within the lower 48."

If that's your listing you might want to reconsider the listed weight and perhaps the price. (Graf's is selling "blemished" 160-grain .268" Hornady's at $26.99 per 100.)

[RBruce]

Thanks for the headsup. Turns out that they changed prices since I bought, and I actually have 197 rather than 97.