Very interesting! Thanks for the labor intensive research! SW

 

I did the majority of the spotting at the target today for Rapidrob and what he wrote was correct on

He posted his results with his loads, here is what I have been using ... Hornady .264 gr. 'Interlock' Round Nose, Flat-Base / Soft Point seated to an Overall Length of 2.995 which were not seated to the crimp on the bullet, they are longer. I made mine the exact OL of the original bullet / cartridge length Cartucce a Pallotola Ordinaria (Ordinary Bullet Cartridge) loaded with the 163 grain, long round nose ,concave flat base loaded with 35.2 grains of Solenite powder and I use a Lee 6.5x52 mm Factory Crimp on them to keep the bullet in place while chambering and from rotating as the bolt is closed.

Each test load was fired in two successive six-shot strings from the prone supported using a front rest at a range of 200 meters using a Beta Master Shooting Chrony® chronograph which was located 15 feet ahead of the muzzle to measure the velocity of the bullet. All test loads above were developed at the Albuquerque Shooting Range Park which is located at an elevation of 6,009 feet above sea level.

34.1 grs. of IMR 4320 ... I use this one as my accuracy load
40.1 grs. of IMR 4350
39.5 grs. of IMR 4831
37.2 grs. of IMR 4451 'Enduron'

These were clocked at 2160 FPS / 660 MPS out of the little Moschetto and will be faster in the longer barrel Model 1891, 1938 and 1941's. These are the correct velocity for the Moschetto's.

"All reloading data contained on this post is to be use at your own risk and any failures, mishaps resulting from this data will not be directed towards me or this group”, again these are be “USED AT YOUR OWN RISK", this should be used as a guide to help develop your own loads. I am not responsible for any accidents for using this reloading data.

Patrick

 

Under bore size bullets can be accurate and ok to shoot for two reasons. First, when the rifling engages the bullets the bullet is deformed and the metal is forced into the grooves. Second, the gas pressure will expand the base of the bullet. Pretty much or as far as I know, that requires a flat base. This second principle was key for siamese Mauser 8mm ammo. That ammo had a solid jacket over the nose and was open in the base. As the OP said, that bullet rode the bore, kept pressure down and engaged the rifling at the base. You would need to pull old ammo to see how Italy loaded back in the early years.

I am sure you all know based on my prior reading on this forum, long bullets at full bore diameter can lead to excessive pressure. There can definitely be too much of a good thing.

I would worry about bullets expanding enough to aquire an accurate spin while allowing gas cutting at either the breech or full lenght of the barrel. Think about that. All I am saying is, making do with what is available and works may be less than ideal. Or it could be great.

I would recover bullets for .263/4 firing in .267/9 bore for a look. I think an eyeball on the bullet will show if it filled in the grooves or not.

I measured the bullets in one of the PPU loads and it was near 267. That was the heavier bullet. I now have some 123 grain and did not measure those yet. Point being, PPU might be a source for bullets although not necessarily a full 160 gr. A full bore bullet.

Edit: Before anyone asks, I have some ammo and one clip. I am still waiting on Buds and DK for something to shoot.

 

This second principle was key for siamese Mauser 8mm ammo. That ammo had a solid jacket over the nose and was open in the base. As the OP said, that bullet rode the bore, kept pressure down and engaged the rifling at the base. You would need to pull old ammo to see how Italy loaded back in the early years.

Italian FMJ Military bullets like all milsurp FMJ bullets have an open base construction. You have to get that core in there from the rear in any FMJ bullet.

 

We might eventually find the bullets in the berm that missed the target but 99% of the time we never can recover them, they may come out if it rains and the dirt has changed position due to it. I can find the jackets from the bullets when they hit the steel and very little is left of them.

Patrick

 

Update on the brass extraction problem with "hotter loads". After crunching some numbers and readings off of the fired cases I found none of the loads were "too hot"
Thinking I had a dirty/bad extractor I removed it from the bolt and found no issues at all.
I then cleaned the fired brass and what I found was reamer marks in the chamber walls that only showed up with loads that duplicated the original military loadings. There was a series of stacked like a collapsing-camping-cup rings that were very fine towards the base of the chamber walls on one side of the chamber only. You could just see them in the fired cases that did match the original military loading pressures. The brass would expand into these very fine rings and not allow the extractor to pull the fired case from the chamber because the brass had expanded into the chamber walls gripping these rings. ( female grooves)
These very tiny grooves were many for about 3/8" and were literally at the web of the casing when chambered. A very sharp 90 degree dental pick would just catch them if you pushed down on the pick point.
I took a .45 caliber wool mop and soaked it in Soft Scrub and spun it with my hand drill. Within ten seconds of moving the mop back and forth these fine rings were gone and the chamber is now free from any tool ( reamer) marks and the chamber is bright and shiny. No dimensions were removed from the chamber that would cause any problems. The rifle was made in 1914 ( don't know if it was rebarreled in it's life)
My load of IMR-7383 of 36.7 grains is not too hot after all. It was just a "Rush-Job" of war time production. While the harder military brass did not stick the softer PPU brass did.
An easy fix.

 

I know this is an old thread, but I thought I would add my load development results here to keep relevant info together vs starting a new thread.

I couldn’t get the factory PPU .268 loaded ammo (123gr SP, 139gr FMJ) to shoot better than 3” groups, nor Steiner’s offerings, so I spent some time working up a load that I am very happy with. Obviously, every gun is different.

The gun: M41/91 Fucile. Good rifling. Slugged to .267.

Bullet: Hornady 160gr RN (.264)

Primer: CCI Magnum

COAL: 2.950”. 1/4 crimp.

I found GRT to be pretty good at predicting velocity. Predicted 42k pressure got me close to 2200fps (+/- 100) with just about every powder.

Powders tried:
Varget
IMR 4064
IMR 4895
SW Precision
Big Game
RL 23
W760

Started low with each. Hit target velocity and stopped. Then 10 shot ladder with each powder (.3gr increment to max) to see which powder the gun and bullet naturally liked and was most forgiving.

Top prospects were Big Game, IMR 4064, RL23, and W760.

I was running low on 4064 and can’t find it available, so kicked that one.

Did several 5 shot groups with the remaining three powders and averaged the results.

RL 23 (37gr) averaged just over 1.5” but strung vertically.

Big Game (35gr) averaged 1.4”.

W760 was the clear winner, averaging 1.07”!

Not bad at all for the old war horse! I didn’t expect that. But, as you can see, it took a big allocation of time and components to find it.

(Note: I can’t shoot iron sights worth a darn, definitely nowhere near good enough to do reliable load development, so I drilled and tapped the receiver and added a scope. On top of a picatinny base I put a cantilevered mount turned backwards. Gave me the correct eye relief for my standard 4-12x scope and lets me squeeze 3 rounds underneath in the clip.)

Hope something in here may be helpful.