.311 verses .312. 7.7 jap Arisaka

I went through my old manuals some time back, looking at this very question. Data for both rounds is either identical or 1 (one) grain difference, some had the Jap at 1 gr more as max, some had the Brit in that spot.
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I wrote this based on my memory at the time, and have since gone back again and looked, and so I need to further expand/explain my statement.

With some powders and load levels the difference in the data is small but with others it can be 4grains or so at max, which is nearly 10% and therefore something considerable.

However, the "middle range" of the data for both rounds is an overlap. For example, with bullet and powder XXXX, data for the Jap might show 48gr as max and for the Brit show 44gr as max. If you're loading 42gr, so the same in both, that's what I call "overlap".

I've never heard of a problem with squibs (and what the heck is "powder meltdown??) but anything is possible if you're not loading correctly matched components and arms.
 
After test firing over 200 T-99 rifles and having several other friends do the same with their's , we all ran into the same problem . It also happens on other military rifles . It is caused by several problems , and happens when all of them are present in a rifle . 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 . As I showed you before the 7.7mm round is almost exactly the same as a 8x57mm , and the rifle is just as strong . I have test fires over 200 T-99 rifles with over 50 different loads and I can tell you for sure the bullet size does make a big difference .
 
It is caused by several problems , and happens when all of them are present in a rifle . An oversized chamber , too small a case , too long in the throat for a bullet , too small a bullet , cold weather , and certain powders .
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I've only had a couple dozen "milsurp" rifles over the years (that stayed in "issue condition), and have never run into that "perfect storm" of conditions you describe.

That might be serendipity, or it might be that, combined with my loading practices, choice of bullets and powder.

I use bullets that are "right" for the nominal bore size (.311/.312", not .308" for 7.62x54R, .303 Brit and 7.7mm Jap, .308" for US .30s, .264" for the 6.5 Swede, .323" for 8mm Mauser, etc.), and for most of them I used IMR 4895, and loads from my old (1970s) Lyman manual. And CCI standard large rifle primers.

I can see where, if you load unusual combinations, you can get unusual results, but not doing that myself, I've never seen any.
 
What bullet do you use for a Type-99 with a .316 groove , or a 8x57 rifle with a .326 , a 8mm Lebel with a .329 ? ? How do you deal the major part of the problem like the extra large chamber or leade ? Most military rifles do not have groove sizes in the standard US bullets sizes .264 , .284 , .311 , .323 and so on . Published loads can cause the problem . Using .303 Brit data with some powders in a 7.7mm will cause the problem . The load I gave the guy is a good , safe load . With limited loading experience , you may not have seen it , but the does not mean it does not happen .
 
Calm down, little fella.
There's no need to try to establish dominance.
You're not the only person here that knows how to select a bullet for a particular groove diameter.
 
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
 
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 .
 
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.
 
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 .
Click to expand...

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 :o), 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.
 
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.
 
“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.
 
big chamber, short cartridge.

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?
 
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 .
 
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 .
 
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?
 
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 .
 
flat base bullets

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