Pushing the limits...

[LoonWulf]

I've been working with my T99 Arisaka sporter in 7.7
I'm currently working with ppu brass, ppu 150 .312 bullets, and imr4895. The barrel on mine slugged at about .314 at the widest point of the slug.

Now I used quick loads and a 55k psi max pressure, similar but lower than the 06, to generate some heavier loads. After happily loading up a 20rnd pressure ladder I realized I was getting awfully close to max charge for a similar weight bullet in the 06. I then decided to do another ladder from below published max up to the start of my first ladder.

I shot 35 of the 40rnds I made, and I didn't see any pressure signs until my second to last set of charge weight steps(flat primer faces with edges still round). I didn't fire my last step.
Also I was getting rounded edges on the shoulders of the cases and soot down past the necks up until I was well beyond "published" data.

I did not Chrono these rounds it was raining. A while ago I did Chrono some h4350 backed loads that were just over published max, and they chrono'd bout 100-150 fps slower than qloads predicted.

Questions abound, but is it possible for the diff in bullet/bore diameter to be such that my rifle needs the extra propellent to reach proper pressures?

Also accuracy is quite good. Even shooting off the hood of my truck all the rounds fired (at different aiming points to do a questionably round limited OCW check), would have made about a 1.5-2" avg for all 35 rounds, all shot in 45mins.

Also I won't post the charges I used, I don't want anyone else just snagging them and going for broke.

 

[ArchAngelCD]

Why in the world would you want to push a rifle that's not be up to it? The 7.7 X 58mm is what it is, why try to make it something else, it might be dangerous.

Quick loads is not meant to give you exact pressures, you should not rely on itcaline for developing loads.

If you are actually getting 1.5" to 2" groups with 35 rounds in a WWII battle rifle you are doing well. What are you expecting from that rifle?

 

[GRIZ22]

I'm not one to load rhino roller loads. My attitude is when you get ammo shooting in the 2500-3000 fps range 1 or 2 hundred fps really doesn't make a difference in terminal performance or shooting out to 300 yards or so (except maybe for a sight correction).

If accuracy is good with the lighter loads I don't see any purpose in pushing it further. If you need more gun get more gun. Don't try to turn any caliber into something it wasn't intended to be.

 

[Grumulkin]

I did not Chrono these rounds it was raining. A while ago I did Chrono some h4350 backed loads that were just over published max, and they chrono'd bout 100-150 fps slower than qloads predicted.

Questions abound, but is it possible for the diff in bullet/bore diameter to be such that my rifle needs the extra propellent to reach proper pressures?

Also accuracy is quite good. Even shooting off the hood of my truck all the rounds fired (at different aiming points to do a questionably round limited OCW check), would have made about a 1.5-2" avg for all 35 rounds, all shot in 45mins.

1. You shouldn't use velocity to determine if pressure is OK.

2. Your rifle might tolerate more powder if the barrel diameter is larger than that of the test barrel. That said, if accuracy was pretty good, and it appears to be, I would call the pressure "proper" and given the age and and make of your rifle would probably not push the load further.

 

[LoonWulf]

Only reason I went ahead and shot rounds from my higher ladder group is my lower one produced no signs or pressure and accuracy was good, I won't be using any of the top loads and I'm very comfortable with the mid range loads which was about where the cases started to not come out all dirty.
One of the reasons I ended up going up in charge weight, is my previous tests with 4350 produced poor accuracy until I was hitting the end of my pressure ladder. Defective reasoning I know, since i switched powders mid stride.
Again with 4895, i dunno maybe cause it's faster, the groups are good, pretty much start to finish.
I agree velocity on its own is a poor indicator of pressure, but I do take it into account when deciding if I go onto the next step when working up loads. The loads in question, showed low velocity (I remember SD being high but can't recall numbers), sooty cases, and shoulders that weren't sharp. This suggested lower pressure than expected to me.
I'll be loading for two of these rifles, and I'll need a load that works in both, so I'll be doing pressure work up for my other one when it comes back from the Smith, If the load that works fine in this one seems at all hot for the other I'll back down to where it's comfortable for both.

I'll post some pictures of the cases when I have a chance, perhaps I'm reading things wrong also.
Sorry the pictures are hard to organize on my phone, in the group pic they go right to left low to high. other pictures are mixed up, but the one with the flater primer is my high load.

View attachment 226270 View attachment 226271 View attachment 226272 View attachment 226273

 

[kingmt]

I only see one primer that if think looks about right. Nothing I read from you sounds like you are to high in pressure.

4894 is really good powder. Only reason I don't use it is it doesn't work in my powder throw.

 

[DeadEye9]

First of all hello from a fellow loader/shooter that really loves to experiment. Let me first ask the same as a few others, what exactly are you looking for from these heavier loads. Better accuracy? More speed? More terminal effectiveness? That would be the most important thing to consider when working up a load is what it's to be used for. As for the bullet/Bore question, the short answer is yes the Bore size can very well effect how much velocity is produced from a given load. This is something pistol shooters notice often when shooting pistols like Glocks, HK etc with polygonal rifling back to back with pistols using traditional rifling. The difference in pressures and velocities in two barrels equal in length but with different bores or rifling is there for sure. Being that the rifle your working with is older, I would be cautious but not adverse to going for max loads personally. I've gone pretty extreme with 91/30 Mosins, Jap Arisakas, old model 99s etc. I've taken .300 Savage well into .308/.30-06 and loaded pills for my Mosin that were questionable at best, but the old rifles always took it in stride. I say this merely for encouragement though not to say that safety rules do not apply. You are 100% doing the right thing by using whatever tools you have available to track pressures and step up your loads slowly. If you continue to do things properly like this, there is nothing wrong in working up heavy loads for your classic rig. Keep closely checking up on your cases as you have been, careful inspect the action after testing each new load etc, and if you want to keep testing go for it, don't let anyone discourage you just because they would choose not to do it. Reloading manuals have a great safety margin built into their data because they are a main stream publication used to cover thousands of different firearms in hundreds of calibers for millions of reloaders. Each chamber is different, each case is different, etc. Loading manuals are just a safe guideline to use as a starting point, testing like you are doing is the only true way to find the best loads for a particular rifle/pistol.

 

[LoonWulf]

Thanks guys for input.
I have no Issue pushing the T99 action (both of mine are early war, chrome everything and had wing sights) to between the .308 and .30-06 in performance. If I felt any reservations in the actions (both checked or being checked by gunsmith), i wouldnt do it. But from what I can SEE, it dosent seem like im pushing pressure much, but i wanted to get a reality check.
Sanity does play a role in what I do some times!
When something odd like this comes up Im happy to bring it to you guys even knowing im gonna get hosed for doing things that some folks find questionable, and im tottaly cool with that. I do appreciate the input
My reasoning for going for heavier loads, was primarily accuracy from earlier experimentation, and not just the H4350 (that was just the one i documented) ive tried a few others (imr3450, 4831, and supform) that i had on hand, all showed similar results with max or over that producing better groups. I considered some of the faster ball powders, but nixed the idea and only recently just got my can of 4895.
As to why push it beyond standard loads (which i do for most of my rifles)? Personal quirk, character flaw, I dunno. It bugs me knowing Im leaving performance on the table even from these older gun. Also these ARE hunting rifles speed may not kill but it does help so I'll always take what I can get along as I'm not losing too much accuracy.