.311 verses .312. 7.7 jap Arisaka

[Peter R]

Didn’t mean to get things stirred up. This multiple diameter option is interesting. I’ve been doing my own hand loads for a while now, this is however the first time I have run into it.. I appreciate any info on the subject.
Thanks again.
Pete

[ernie8]

You did not get things stirred up . You just asked a reasonable question and got some bad answers . I told you good info , even identified your rifle with a weak description . Some people will learn form this , some never will .

[Bart B.]

It's well known by folks getting best accuracy with their rifles use bullets whose diameter is bigger than the barrel's groove diameter. Bullets at .3092" shot from .3077" groove barrels have tested under 2 inches extreme spread at 600 yards in a 40-shot group.

[5whiskey]

Bart B. I’m glad that you joined this thread. I’ve been reloading for nigh a decade now, but I think you have quite a few decades on me (reloading that is). Have you ever heard of “powder melt down” as described here?

. An oversized chamber , too small a case , too long in the throat for a bullet , too small a bullet , cold weather , and certain powders . What happens is when the primer goes off it pushes the bullet out of the case and it does not seal in the throat . The powder then just melts into a blob and the bullet is stuck in the bore . Some Type -99 rifles do this [ with some .303 loads ] and it is common in 8mm Lebel , 8x50 /56r and a few others . Listed loads do cause this problem . Hornady had this problem with some of their first loaded 7.7 ammo .

I don’t understand how this can happen short of lot of bum powder. I say this because I know with absolute confidence that a normally seated projectile of 168 grains in a primed 7.5 Swiss case, with no charge, will not unseat the bullet from the mouth of the case. I saw the same thing (for gins and giggles) in an 8x57 with with a 180 grain projectile. I started that test with the k31 that I was having intermittent light primer strikes, and seated projectiles to remove a variable (with a wood dowel and mallet in hand for backup, along with a safe backstop). At first I couldn’t tell the primers were actually going off. No pop that I could hear, the case extracted with bullet intact. When I pulled the bullet and deprimed (carefully) I realized that the primer did in fact go off. I repeated in 8mm to confirm, and experienced the same thing. The primer doesn’t produce enough gas to fill that large case volume, expand the neck, and unseat the heavy projectile. At least that was my theory. I’ve since made the same observation in magnum revolver cartridges (not on purpose ), except the projectile would unseat just enough to bind the cylinder. It did not fully unseat. I don’t know everything. If powder melt down is a thing I’m interested in learning more about it.

[5whiskey]

OP I use a .312 Jacketed in my type 99. Mine slugged at .313, and I plan to try a lead paper patch projectile sized at about .314 at 1700fps or so. I suspect .311 vs .312 won’t matter very much, but in theory the .312 should get better accuracy. All other factors being equal I personally would order some .312s first. If you’re happy with them, stick with them. If not, experiment.

FWIW my type 99 shoots very well considering it was cobbled together from a bolt pulled from a pile of bolts slapped into a mismatched rifle from another pile, sat in a closet rusting for the majority of 70 years after that, to now be shot with converted 30-06 brass and the cheapest on sale projectiles that fit the weight range of projectile I desired. I think that’s the general experience most people have with type 99s that are willing to find a load that works in them.

[FrankenMauser]

“powder melt down”...

It's a real thing.
The situations described by ernie are pretty extreme and unlikely to be encountered, but the phenomenon is real.

Basically: The bullet is unseated by the primer, and possibly some pressure from the powder charge beginning to ignite.
For whatever reason, a gas seal cannot be achieved after pressure is lost when the bullet was dislodged.
The powder stops burning.
And you're left with a melted clump of discolored crap in the case.

I've experienced it with .243 Win, .30-30, .30-40 Krag, .44 Mag, and .22 WMR (when coloring way outside the lines...).



I've never had it happen when using "wrong" diameter bullets. Most mil-surps have tall lands that displace bullet jacket material into the grooves. .308" bullets fired through a .312" barrel at 45,000+ PSI don't come out the other end as .308" bullets.
Copper and lead are malleable, and easy to make conform to the bore of a firearm. That's why we use these materials for bullets.

A somewhat extreme example...
I have a Mosin M38 with a .315" groove diameter and .304" bore.
It loves Hornady .308" 220 gr RNs.
Recovered bullets show no evidence of blow-by, and the sections of the jacket that were in the grooves of the bore are fully filled-out and show full contact with the bottom of the grooves. I must, begrudgingly, admit that I don't think I've ever measured the diameter after recovery. All I initially cared about was making sure I got a gas seal, and the bullets told me that I did. So, I pressed on without looking back. As long as it seals, diameter doesn't matter.

[BJung]

I have a T99 with 5 different test loads (and maybe another with cast bullet test load on the way) waiting to be shot. I have that large chamber problem too where I could not seat the bullet and have the ogive touch the rifling. I had to settle on an OAL based on what the inside magazine dimension was. I think the chamber diameter is only large enough for the bullet and not cutting a resized 30-06 brass to accommodate a longer neck would work, yes? A chamber cast would tell me.

Ernie, can you provide any tips for getting the best groups out of the T99? My test loads are using R15 and R19. Can I use Blue Dot than 2400 for my cast bullet with a GC? Will filling the case with cornmeal help ignition?

[ernie8]

Shooting a type 99 with the original sights will not give you benchrest accuracy . So the bullet distance from the lands is not that critical . Use a Hornady .312 150 or 174 . Seat with the whole crimp groove showing , that will give you enough bullet in the case neck to keep it straight . I listed some of my better loads earlier in this post . I would not use a cornmeal case filler ever . There was a local guy who used to do that and wrote articles on the old Surplusrifles website of how great it was . But in reality he had a hard time hitting the target at 100 yards and bulged about 6 barrels doing it .

[ernie8]

A too small of a bullet is only one of the factors , of several together needed for a meltdown . One being a too LIGHT of a load , not producing anywhere near 45,000 psi . Yes land and groove dia both play a part in what size bullet will shoot well . A long 220 rn .308 dia bullet will shoot just fine in a rifle if the lands are tight enough , even though the grooves are larger than .308 . All of the older military rifles used long undersized bullets in the original loadings . They also used different type of bullets [ like hollow bases for expansion ] then what we are using now . The problem with shooting too small a bullet with a short bearing surface or boat tail is that when it does bump up , it can do it off center , so then you have a lopsided bullet leaving the bore . A type 99 rifle with the shallow rounded rifling , and sometimes chrome on top of that , tend not to grab an undersize bullet well . Non chrome T-99 rifle do shoot different loads better .

[BJung]

Ernie. My honest opinion is that...the T99 front sights really suck! I'm thinking of drawing triangles on my targets or solder/glue a small tube that'll act as the front aperature sight so I can better line things up. Maybe even put a blinking diode in the center of the bullseye.

I was really wondering about the load. My first petload for my rifle was using a 150gr Speer SP and ( I forgot the charge ) enough powder that went off the reloading chart. There was sign of excessive pressure on the case but the rifle had quite a recoil.

Yes, I have test loads with both Hornady bullets. I also have a test load using Barnes bullets in Norma cases. CA doesn't allow hunting with lead bullets. I'd like to shoot a wild pig with the T99 someday. Maybe, put some fake wings on it and place the rifle next to it with the aerial sights showing. I'll attach my bayonet to the rifle too.

So, if I find a heavy 30 caliber bullet with a long shank, I can get decent accuracy with it? What about gases going around it? Maybe glue a .311" p-wad to the base?

[ernie8]

I have cut my T-99 group sizes in half by clipping a plate with a very small hole over the rear peep sight hole . The originals are a good battle sight but not a good target sight . The Hornady's always shot much better than the Speers in my rifles . Try the H-174 .312 rn bullet and about 43 grains of I-4064 . If you are doing repeatable 2.5 inch groups with the original sights you are doing great in my opinion .

[BJung]

Ernie, I've read that flat base bullets are more accurate in the Arisaka but I don't know why.

I like the disc idea. I'll do that.

[ernie8]

As stated in post #34 .

[BJung]

Thanks

[BJung]

Can someone tell me how to download my ladder test images? I've followed the instructions provided ( manage images) and it doesn't work.

[BJung]

I figured out how to post photos.

Here is a line-up of what I started testing: Barnes 150sp, Hornady 150sp, Speer 150sp, Hornady 175HPBT, Hornady 180RN

[BJung]

Here are photos of my target. The bullseye was centered to the rear aperture and the front blade was off to the left slightly. It appears that my T99 likes heavier bullets.

[BJung]

I'll post my photos on the reloading forum

[BJung]

These are my Ladder Test Targets. I will submit a follow up in December. I only shoot 1x-2x /year

[doofus47]

I've squibbed my Type 99 twice. Once was a PCI factory cartridge. that batch was later recalled by TCI b/c of contaminated powder. The second was a home built cartridge that looked remarkably similar to the failed PCI in that the powder was clumped up. I probably got case lube into the cartridge and that was the cause.

[BJung]

I tried lubing my dies once with WD40 and I got a squib load.

[Geezerbiker]

Originally Posted by burbank_jung

I tried lubing my dies once with WD40 and I got a squib load.

I tried that when I first started reloading and I stuck a case so bad that I had to get the die replaced.

After tinkering around with loading for the 7.7x58 over many years, I've found that resized .30-06 cases give the best accuracy. Back when I started I wasn't experienced enough to know that sometimes when you shorten a case the neck is to thick. However in the large neck tolerance in an Arisaka rifle the thick neck takes up some of the slop. I've never had any high pressure signs. I agree the easy way to make 7.7 case is to run 8mm Mauser cases though 7.7x58 dies once. The end up about 1mm too short but it's not enough to be concerned about.

I also got my loading data for it from a rather old RCBS manual and back then they were very conservative on pressure and the loads were in the .300 Savage territory. Later on I worked up to .308 Win load levels and I was very happy with the results. The latest Hornady book I have show even hotter loads but I don't see the point since I'm no likely to ever hunt with either of my 7.7 rifles again...

Tony

[BJung]

I like my resized military 30-06 to 7.7 x 58 brass. The brass does not have some other cartridge size stamped on the head. When I see the military stamps, I know it's for my Arisaka because I have no other rifle that chambers for it. The brass appears heavy too.

My load data comes from a Hornady Manual and the book Petloads. The author identified N-203 (translate to R15) is a very good powder for the heavier bullets. You can see the results above.

[BJung]

Here are my two targets with my best performing load so far for my T99 Arisaka. The load is a 7.7-174 Hornady 174FMJBT with 45.5 R15 and a COAL of 3.175". The 100 yard target printed a 3/4" group with flyers and the 200 yard group printed a 2" group with flyers. My targets were red paper plates that I centered in my peep sight. The second best result was 7.7-150 Barnes but I'll need to work on this load more. The heavier 180gr RN needs to be retested along with my tests for cast Lee 185gr bullets sized at .3115 and .3125". The bore was determined by casting a pure lead bullet using split shots, cutting the bullet in half, lubing it, and forcing the slug through the barrel with a wooden dowel.