carcano & cruise missile

[bkbville]

I cast up some of these "cruise missiles" this morning (just got the Midsouth package yesterday) - they dropped .270 and around 175gn WW. I hand fit gas checks, and pan lubed in NRA formula.

I loaded them over 15 grain of 2400, and went to the range with a Vetterli, which is gain twist like the M91's.

The results I could almost call a group, but all the bullets went through sideways. Clearly a stability problem.

Anyone have wisdom or suggestions on this?

[jonk]

I've had the same issue with the same bullet and same load. I'm thinking that you may need (as do I) to UP the velocity..... Hmmmm..... sounds like a good project for the weekend.

[SierraWhiskeyMC]

What is the length of the boolits?

Do you know what the barrel twist rate is as the muzzle?

[geargnasher]

Ask 45 2.1, Buckshot, or a few others, they'll tell ya!

Gear

[bkbville]

The Cruise Missile is 1.256" long; at .270 caliber applying Greenhill's formula I come up with 1:8.7 as optimal twist.

Italian issue carcano bullets are 1.19" and 160grain. This would work to 1:9.

That includes the whole length of the bullet, olgive and all.

I read the Carcano M91 gain-twist starts 1:19 at the breech and ends 1:8 at the muzzle. My assumption is this is the same, but I can't accurately measure the gain twist using a cleaning rod.

So, none of this looks out of scope. In fact there are a few notes in the forum about folks getting this mould for the Carcano.

My thinking is I will try a more powerful charge of 2400, as per Jonk. (Jonk, let us know if got to this.)

I'll also try a slower burning powder, maybe 4895, with the idea of a more steady pressure through the tighter twist. It's suggest with the Vetterli to not use high-pressure loads, so I am limited in how far I can take that.

I've gathered bits and pieces of the RPM theory, but haven't found a post that explains it fully, so it's like listening into someone elses conversation.

I'd like to hear from 45 2.1 or Buckshot on their thoughts?

[Buckshot]

................Did you say what model Carcano you were using? The M91/24 carbines were made by shortening the 1891's so the barrel lost the fastest part of the twist.

..............Buckshot

[bkbville]

It's a Vetterli 70/87/15, full length barrel.

Definitely a big difference in the twist from the breech to the bore - very visably noticable.

Given the lack of detailed information (at least in English) on the Vetterli, I'm assuming the gain twist rates of the M91 barrel applies to the Vetterli liners for the same cartridge.

[StarMetal]

http://translate.google.com/translat...N%26start%3D10

Joe

[SierraWhiskeyMC]

I plugged some numbers into Don Miller's stability calculation Excel spreadsheet, available for download from this page:
http://accurateshooter.wordpress.com...and-stability/

Caliber: 0.263 Inches
Bullet Weight: 175 Grains
Bullet Length: 1.256 Inches
Barrel Twist: 9 Inches/turn
Muzzle velocity: 1200 fps
Temperature: 20 degrees Fahrenheit (59 is standard)
Pressure: 29.92 inches of mercury (29.92 is standard)

Sg = 1.51 (needs to be 1.5 or higher to be fully stabilized)
RPM = 96000

I have zero experience with those rifles. However, I think that the groove diameter is supposed to be around .264 maximum. Isn't the bore diameter supposed to be around .256"? In that case, it would be reasonable to re-do the stability calculations using .260", the average of the two.

Temperature and altitude also have a large effect on stability. Rounds stable at high altitudes and/or temperature can become unstable at lower altitudes/temperatures; it's a function of air density.

I have Lyman's 45th edition reloading guide. It suggests that there are wide variations in groove diameters which exist in these surplus military rifles, we suggest that you proceed with caution. Slug your bore to determine the correct bullet diameter for your rifle. If your groove diameter is larger than .264", you could experience gas blow-by when using the listed starting loads with the standard bullet size. They also suggest using cast bullets sized to the exact groove diameter of your particular rifle.

The heaviest J-word bullet they have load data for is 160 grains.
The heaviest boolit is 143 gr Lyman #266469 w/GC; it's a Loverin RN design w/ 6 loob grooves; comes out of the mold @ .267"

I'm just guessing that you were getting around 1200 fps muzzle velocity using 15gr of 2400 but I think using more could be risky.

As Buckshot says, the carbines were made by lopping off the barrels.

Even if it isn't a carbine, it's possible that someone shortened the barrel to get rid of a worn bore at the muzzle.

Arguably, the safest thing to do would be to try out a shorter boolit.

H4895 is safe to use down to 60% of maximum loads, according to Hodgdon's website. I don't have any load data for a lead boolit that heavy. In any case, I don't think I'd go above 31gr of H4895 at that boolit weight without a chrony.

[bkbville]

I checked and the barrel is not cut - 33-1/2" - which is the correct length for the Vetterli Carcano.

I did Chrono these cruise missile shots - Avg 1542 fps (1515-1566 fps). This would work to about 139K RPM. Using the spreadsheet above Sg=2.33 (Seems like they should be stabalized.)

For reference I also shot PRVI .264 FMJ 139 gn. These were stable and about 100fps faster, but did not group well: I think from being undersized. From examing a squib I found they are not touching the bore - which is what I expected from everything Carcano folks tell me - these bores are typiclly .268 or larger.

160gn is the weight of the Italian military round used for Carcano's; 175 doesn't seem that far off.

The Cruise Missile ("6.5 Swed") is mentioned herein by several posts for use in Carcanos with "good results". In fact, I shied away from the the Lyman Moulds on what I've read in here about those dropping narrow for carcanos.

[StarMetal]

It's not the weight of the bullet you want to look at, it's the length. That cruise missile is very long. It's longer then the military 160 for the caliber.

As an aside I have a 260 Remington. It was playing with some cruise missile that a former member Oldfeller had given me. I was seeing where they would destabilize in my rifle and found it to be below 1400 fps. My twist is a 9.

I do believe you may be better served with the Kurtz group buy bullet or the Lyman 266469 if you can find a mould that drops them fat enough. The Kurtz will but the newer Lyman's won't.

Joe

[TAWILDCATT]

I think you need more speed but you may need another powder.I use red dot in all my military but not yet in 6.5 jap or carcano.as I think I may have to drop the charge some for those two.
lyman lists 18 grs 2400 for 1783 for 143 gr bullet.castbullet lyman
in the jap they give for 4198 26 gr for 143 gr " at 2159 castbullet lyman
in 6.5 jap =156 bullet=27..3 gr of 4064 at 1985=33,200 NRA hand book

[SierraWhiskeyMC]

OK, I'm not sure what to suggest other than trying to slug your barrel to find out how worn it is at various points. I'm suspecting that the muzzle is worn so much from cleaning that you have more like a blunderbuss than a rifle. My hunch is that the boolit is disengaging from the rifling as it gets near the muzzle.

I'm moderately surprised that you're clocking that 175gr round at 1,542fps; the starting load for the 143gr boolit in Lyman #45 is 15.0gr 2400 @ 1,545fps, max 18gr @ 1763.

In other words, you're getting the same velocity for a 175gr boolit as Lyman reported with a 143gr boolit with the exact same powder charge. The difference is that Lyman used a 21" barrel on an Italian service carbine with gain twist.

That would also explain why they used lighter (shorter) boolits in their loads.

[bary]

Would the Universal 16/2400 load be a good place to start with an M91?

[303Guy]

Have you checked the straightness of the boolits themselves? I have found long boolits that were bent inside the mold! I have heard from these forums that a boolit can bend after a while after being cast. Easy to check. Just roll them on a flat surface.

Oh, a projectile needs more twist rate closer to mac 1, so below 1400 it would need more but below 1000 or so, a little less - to do with air flow over the projectile as it approaches the sound barrier. (A projectile that is slowing down already has a higher spin when it slows to mac 1).

[bkbville]

303Guy - I took a dozen or so of these boolits and rolled them on table - they roll fine and show no day light. I water-dropped these into a towel drapped in a bucket of H2O.

SierraWiskey - I agree - the velocity seems high - higher than I expected for the heavy 175gn boolit given 16gn 2400 on the 139 FMJ gave me 1610fps (1581-1665fps)

Perhaps the gas checks came loose, effecting the chrono, but I didn't find any (I actually looked because this is the first time I hand seated GC's.)

I used CCI mil LR primers though - and I understand these to be magnum, or at least hot. As I had a couple of rounds that needed to be struck twice, I'll use my dwindling supply of Win LR primers.

Later I'll attempt to re-verify the velocity for the 15gn A2400.

First though I've already loaded 22.5-25gn H4895 with hopes slower burn gives these pressure as they run the tighter twist on the long barrel.

As for the rifling - its distinct throughout - some muzzle ware, but not terrible. This is a decent bore overall, no visable pitting, and I used electrolosis to clean out a lot of copper.

TAWILDCAT - red dot goes the other way

[dromia]

You really need to slug your barrel. Pust a soft lead slug through to find the smallest bore/ groove diameter and them slug the muzzle.

If the muzzle slugs larger than another point on the barrel then thats your problem.

If you slug then you'll know either way.

Its the first thing anyone should do when shooting cast boolits in a particular gun, it will save a lot of grief, wellbeing, powder and components.

[semtav]

what is the consensus on gas checks? 264 or use 277. I need to order some and wonder if the 264 will defeat the purpose of the bigger 268 or 269 bullet?
thanks

[leadhead]

I use the cruise bullet in just about every type carcano made and they
shoot just fine in all of them. Even the 91/24 that has been cut down
from M91's will shoot half dollar groups at 50 yds. I settled on 14.5 to
15 grs of 2400. I size in a .270 dia die.
Denny

[bkbville]

You really need to slug your barrel. Pust a soft lead slug through to find the smallest bore/ groove diameter and them slug the muzzle.

If the muzzle slugs larger than another point on the barrel then thats your problem.

If you slug then you'll know either way.

Its the first thing anyone should do when shooting cast boolits in a particular gun, it will save a lot of grief, wellbeing, powder and components.

Dromia - I've sort of been down this road.

When I try to slug this rifle the progressive twist takes it's toll on the engraving - the changing pitch removing the engraving - so by the time I get the slug out the other end I have no indication of the actual groove side.

I have to wonder how that works on an actual shot.

Slugging the muzzle (if I recall correctly - I'll have to dig up the slug to verify) I get a tight .266 on the grooves, and .258 on the lands. So, I don't think it's shot out.

None the less I'll give slugging it another try.

BTW: the H4895 loads - both keyholed - 24.2 at 1614fps and 25.2 at 1853fps (velocity based on only 3 shots each)