7.62 x 39 .310 ammo in .308 bore

[joeanybody]

What is the likelihood of having a pressure spike from
Using .310 bullets in a .308 bore.
Should I turn the minimum charge into the maximum and lower the minimum charge 10%?

Using hornady 123 gr sst bullet
Accurate Lt-30 powder
Accurate lists minimum charge at 23.6 gr for that specific bullet

[Marco Califo]

100%. You may survive. Don't do it. I don't think Western Powders publishes any load to use 310 bullets in a 308 barrel. Really, what part of using only the correct diameter bullet do you not understand?

[Gemmer]

What Marco said!!
Think constipation.

[joeanybody]

Thank you Marco for caring enough to question whether I understand the differences of bullet diameter vs bore diameter.

Lee manual states u can. Gun manual says u can. I will go with their expert opinions. Thank you. Po Ackley stated that you can load a much larger bullet diameter in a gun provided the throat was reamed properly. If the gun manual says i can load a .311 diameter bullet then its probably a safe bet that i can.

My question is what would a safe starting point be.
Lee says for .311 diameter bullet start with 10% below starting listed. But that is for a .311 mine are .310.
Don't want to start too low cause that could potentially cause problems as well.

[mikejonestkd]

Why would you propose to load a bullet that you know is the wrong diameter for the rifle bore, and then come here looking for our approval?

.308 bullets are literally one of the most common bullets out there, and are fairly cheap. Buy .308 bullets and use them.

[joeanybody]

Mike Jones don't confuse asking a question for looking for approval.

Before anybody else answers with the same thing keep this in mind: All factory ammo for 7.62 x 39 is .310 .311 or .312. Lawyers simply would not allow a gun maker to mass produce a rifle with .308 dia bore if it was going to be that dangerous. It is just a matter of finding the appropriate starting load to work from.

I've used 308 before. However, the .310 seems to be far more accurate out of my ak. I just need to know a safe place to start. If need be I will change powders to something lee has in their manual however I liked the lt-30 with the 308 bullets just not what I got right now.

[hammie]

I don't see the problem. Your ak-47 should have a groove diameter of .310-.312, and a .310 diameter bullet should work fine. I would just use the starting loads in the manuals and go from there.

What threw everyone off was the first post. It seemed as though you were asking if it was okay to use a .310 bullet in a barrel with a .308 groove diameter. the answer to that is generally "no". However an exception is the early Ruger Mini Thirty, which had a groove diameter of .308, but was throated to safely accept factory and military ammunition with the slightly larger bullet diameter.

[joeanybody]

Hammie yeah I know. My writing is horrible due to being so horribly dyslexic.
My rifle is .308 bored but throated to accept larger bullets.
Don't know why century did it that way but alas.....
I know it can accept larger bullets cause I've shot every brand thru it.

I'm more worried if 10% would be too much to lower the starting charge by (as indicated for .311 dia by lee). 8d rather not have a stuck bullet either. Those aren't fun at all. I've sent an email to accurate powders...let's see what their lawyers say

[Marco Califo]

Century is known for selling firearms assembled from surplus parts. If it will assemble, they will ship it. If it is an AK, why are you so sure it has a 308 barrel? AK's are expected to have the larger barrel diameters. Have you slugged the barrel and then measured the slug?
If the barrel being stamped 7.62x39, that is not an indicator of an actual 0.308 barrel. I would expect a .311 diameter barrel.
I would never try to fire a 310 or 311 diameter bullet in a 308 (chamber and) barrel. Maybe with cast bullets if I had loading data to support it.
I have to think your AK has a barrel diameter for those 7.62x39 bullets which are not really .308 in diameter. As to guessing what will work: I don't.

[joeanybody]

Marco, I can't say without a doubt it has a 308 barrel. I'm actually reasonably sure its closer to 309. No I have not slugged the barrel. I have, however, read the manual which states it has a 308 barrel but can accept 311 it will lower bore expected lifespan.

Just to ease your worried mind on that aspect...century also owns its own ammunition company (i forget if its red army or one of the other smaller name steel jacket companies). It was produced to shoot in the century arms ak and it has a diameter of .310

Without actually slugging the barrel, I have to go with what I'm told
by the manufacturer.

I'm not really concerned with an exploding gun. I have shot .311 ammunition out of it before. If the barrel was made proper and it seems to have been, I should have zero issues with that.

I am more worried about the unknown factors. Size just isn't one of them in this. If I lower the start load too much it might have adverse effects as well.
Lee calls for a 10% drop from published start load to begin with. But that is for a .311 bullet.
There is still .001 to play with. You can get pressure spikes from too little powder too.


So that means :
Published start load is 23.6 gr
10% below that is 21.2
5% is 22.4
Which is the closer answer to the question at hand?
I know that .310 bullet dia is not too big for it to accept. Its how hard do I punch it thru

[HankC1]

A 7.62x39 barrel with .308 bore typically has more generous lead in, not a problem. I load Nosler .310 125 (or 123?) gr and shoot in my 308 bore 7.62x39 mauser regularly. It is a Green Mountain small ring mauser 7.62x39 barrel made for Numerich. If you are thinking loading .310 in a 308WIN, better be a cast bullet or down load the charge.308 bullets are plenty and generally cheaper, no reason to shoot .310 jacket bullets in 308Win.

[joeanybody]

Hankc1

A 7.62x39 barrel with .308 bore typically has more generous lead in, not a problem

Yep. AK's generally have extremely loose tolerances as well. Which makes it less worrisome to load for. Normally I don't even bother with this rifle cause I can buy ammo for a little over half the price I can load it for. However, ammo is really scarce around here right now.

I just don't want a pressure spike because of using too little powder due to the size difference. I might just pull a Mythbusters. Hook it up a vice and pull the trigger with a string.
For all who don't know me. I'm just joking.

[Marco Califo]

To clarify, my fear was about using bullets intended for a different barrel's specs. Rephrased, I wouldn't use those bullets in MY Savage 10 FCP 308 or FN-FAL 308's.
But, for enjoying a Century Arms parts gun, and using that guns specs, that's up to you. Let us know how that works out.

[Aguila Blanca]

Originally Posted by joeanybody

I'm more worried if 10% would be too much to lower the starting charge by (as indicated for .311 dia by lee). 8d rather not have a stuck bullet either. Those aren't fun at all. I've sent an email to accurate powders...let's see what their lawyers say

Start at 10% below the published minimum. It's highly unlikely that you'll get a stuck bullet, but that's easy to test. Fire the first five shots as single shots, and check the barrel after each shot if you don't see a new hole in the paper.

[joeanybody]

Originally Posted by Aguila Blanca

Start at 10% below the published minimum. It's highly unlikely that you'll get a stuck bullet, but that's easy to test. Fire the first five shots as single shots, and check the barrel after each shot if you don't see a new hole in the paper.

Thanks Aguila.

[7.62 man]

If you have shot factory 7.62x39 through your gun just load it as a normal round of 7.62x39. I wouldn't know why Century would say the bore dia is different. They should just say what ammo to used & let it go at that. What caliber ammo does the gun have stamped on it to take?

[hagar]

I shoot them in my FAL, but would not do it in the 300 BO,

[joeanybody]

Well I am totally shocked that I actually got a straight answer from accurate powder. They said I could use the posted data. There is no need to lower the charge at all.
Even so, I think will lower a grain for 5 rounds or so just to be on the safe side.

[Geezerbiker]

The early Ruger Mini.30 came with a .308" bore and I don't recall any of them having any problem.

Tony

[Jim Watson]

My thought, too. As P.O. Ackley said, by the time the bullet has traveled its own length, it will FIT the barrel and that is before the maximum pressure.
I would be leery of shooting steel core Chicom ammo in a tight barrel, but that was not the question.

[Bart B.]

People have shot .3092" diameter Lapua 185 grain FMJRB match bullets in barrels with.3075" groove diameters without issues.

SAAMI specs for most 30 caliber bullets are .306" to .309". Groove diameters .308" to .310.

USA military 30 caliber bullet diameters range from .3070" in service ammo to .3086" in match ammo.

[nhyrum]

If you already knew what the internets said about it, why did you bother asking?

FURTHER evidence is that anytime anyone offers a contrary opinion, you immediately dismiss it saying this guy, that guy said this.

It's fine to be confident, but at least try to see the merit of someone's experience, even if it differs from yours.

Sure. Sometimes .311 bullets go down a 308 bore. But why would you? It would be like putting race gas (unleaded) in a geo metro. Sure, it won't hurt it... But... Why...

More like putting diesel in a gasoline vehicle. I've known people who have (farm hands at a small farm) and the car, once you get the diesel out, runs fine. Other people, same thing, no matter what they did and how many times they flushed it, the car wouldn't ever start again.

You may live... But why? Would you play Russian roulette because you have a 1 in 5(1 in 6 or 8 if you're lucky) chance of surviving... Same deal here. You may loose your face. You might not. No one can stop you.

Sent from my SM-G975U using Tapatalk

[Bart B.]

For what it's worth, competitors getting best accuracy with centerfire rifles use bullets at least. 0004" larger than the barrel's groove diameter.

When the British commonwealth started using 7.62 NATO M80 ammo in their fullbore long-range rifles, they had to use barrels with .3065" groove diameters for best accuracy because most bullets were .3070" diameter.

[Unclenick]

Joeanybody,

If you look at government bore specifications for 30-06, the groove diameter and the bore diameter are ±0.0015" with no change in the ammunition. Indeed, in extreme cases, you hear of people getting their 7mm (0.284") and 30 cal (0.308") bullets mixed up and firing the fatter slug in the narrower barrel and not having the gun blow up. They do get high-pressure signs and you can't count on that being safe in every instance and the accuracy of such ammunition is terrible, but it is possible to do.

The reason for the above is the copper jacket has a yield strength that is a threshold value and that is the principal source of resistance to the bullet entering the throat and getting swaged into the rifling. Once there is enough pressure to surpass that and initiate the swaging, the added force requirement a small difference in diameter contributes is relatively less.

[Geezerbiker]

I read somewhere that a long time ago someone rechambered a 6.5mm Arisaka rifle for .30-06 but didn't change the barrel. The story goes that it kicked like a mule but didn't blow up. Not that I'd recommend something like that but...

If my info is correct that rifle is now in the NRA museum.

Tony