Bullit OVERSIZE

[johned]

How many thousandths can I oversize a bullet and safely fire it through a 308 bore?

Thanks

John

 

[jonbearman]

What purpose would there be in doing such a potentially dangerous thing.

 

[fdshuster]

This also has me scratching my head and saying, Why? Have I been missing something in 52 years of competition shooting & reloading? ???

p.s.: It's spelled "bullet".

 

[Eddie Harren]

Are you referring to cast bullets? I normally try for .002" over bore diameter. One of my .308 barrels likes .003" larger bullets.

 

[jonbearman]

Doc,I think you are right as there is a cast bullit(yep thats the spelling) forum.

 

[fdshuster]

How many thousandths can I oversize a bullet and safely fire it through a 308 bore?

Thanks

John

The question seems to imply that the poster will be making the bullets. So that leaves out jacketed unless he wants to spend $$$$$$$$$$ having a set of dies made to a special oversize diameter.

Cast bullets can be "oversize" and that depends on the mold maker's choice of diameters when the mold blocks were cut. Sizing & lubricating die choices can also determine final bullet diameter.

This question raises more questions than answers. And, for what purpose? Still scratching my head, but someone else can try to sort it out.

 

[Tozguy]

The question might be about using a .311 bullet (for 303 British I believe) in a .308 bore. Not recommended at all. Whoa, stop, not at our range you don't.

 

[jonbearman]

Johned,are you going to reply or keep us in suspense? Seriously ,what is the question about.

 

[Eddie Harren]

I think his question was for drawing.

 

[johned]

Guys,

I answered this a couple days ago. Obviously my post went in the bit bucket.

I have an assault rifle chambered in 7.62 X 39. The bore of the gun is .3121. Some are getting 4 inch groups from this config but I get 12 inch (almost) patterns.

I have thousands of rounds of Soviet Bloc rounds. All of it measures .308. I purchased 5 different brands of 7.62 X 39 and every one of those measures .308. While others have seen their group size shrink dramatically when using Commercial I have not. My "groups", and I use that word loosely, are consistently terrible regardless of what I feed that bad girl. I love the gun, a CZ VZ 58, and am impressed with everything about it.... except barrel bore size. CZ advertises the 58 as having a 312 bore so they haven't made any mistake. CZUSA also makes a really nice bolt gun and they advertise the bore on it as .311. That really throws me as they have a reputation for exceptional accuracy. They also make a 308 so I know they are familiar with the bore size. What to do?

There is a VZ 58 clone that uses made in USA parts and its called: VZ 2008. That USA barrel is bored to .308 and it works well at the range. I intend to build a "kit Gun" VZ 58 and I will barrel it in .308. My heart burn is: will the thing blow up if someone down the line ( I won't live forever) were to feed the rifle some 7.62 X 39 that is .312. .311 used to be found regularly and that is why the thing was bored to .312. .312 will safely handle all the know variances safely if not accurately. It's an assault rifle...right? I am not trying to make a bench gun out of the design but I would like "to be all that she can be".

My Sierra reloading manual shows .308 as the correct bullet diameter for the 7.62 X 39 round so lots of guys out there must be building these guns to .308 spec. I figure 309 or 310 ammo should present no problem other than a slight bump in pressure...... but I have no credential in this area. On instinct, I think 311 or 312 will be pushing the safety envelope but I wanted those with more experience to give a better opinion. I will mark the barrel "NON STANDARD CHAMBER" .308 Cal. Should I do anything else?

To do this I will have to have a reamer made for 7.62 X 39 with a 308 bullet loaded.

Soooooo. Ergo, my original question was "is it safe to fire a 312 bullet in a 308 bore"? 311, 310 309? I left all the gory details out to avoid boring you. Pun Intended. I still don't see my answer...except " .004 over isn't good".

This applies to jacketed bullets and not cast.

Thanks again for all your comments,

John

 

[articmp]

Ruger did it with the early mini 30's using a long tapered throat to sqeeze the bullet down to .308 from .311-.312. There was a huge jump to the rifling. Accuracy suffered as a result. Shooting Times or Guns and Ammo did a comparo with the Mini 30 and an SKS, if I recall correctly it was a chinese. The Ruger was tested with a Leupold scope (2-7?) and the SKS was ironsighted. Ruger's best 10 shot at 100 yards from the bags was like 9 inches using everything from .308-.312 commercial and surplus. The SKS with iron sights averaged little over 2 inches, best was like 1.5 with Russian HP's. But somehow they considered the Ruger the best gun for the money.

 

[4xforfun]

If you are getting 12 inch groups, I would suggest a different choke...something like a full. ;D ;D

 

[Tozguy]

John,
Thanks for filling us in on the question. It would be a surprise to me if a credible someone came forward to endorse using anything else but .308 bullets for a .308 bore, like the loading manuals specify. If CZ made their bores .312 for the possibility of feeding it up to .312 bullets that speaks volumes about the responsable thing to do.
If you have a custom barrel made up with a .308 bore as you mentionned, what about marking it 308x39 so that there is no mention of 7.62x39? Just a thought.
Good luck.

 

[jonbearman]

I have an armalite rebarreled with a colt heavy barrel in 7.62x39mm,it shoots great. Whose barrel shoots patterns,what brand I mean? I also built a savage bolt gun with a mcgowen barrel with a .310 bore and shoot sierras fine 125 grain pro hunterbullet and get under .300 groups at 200 yds,yes 200. I would send your barrel back.

 

[johned]

.
If you have a custom barrel made up with a .308 bore as you mentioned, what about marking it 308x39 so that there is no mention of 7.62x39? Just a thought.
Good luck.

Toz,

That's some exceptional advice. Of course, I didn't think of that. I guess I still could mark it VZ 2008, the Century Arms variant, as that is what I seem to be building. I wonder if the 2008 thing also did the "in the chamber throat swedging" like the Mini 30 mentioned? It shot much better than the 30's 9 inch groups though.

 

[johned]

I have an armalite rebarreled with a colt heavy barrel in 7.62x39mm,it shoots great. Whose barrel shoots patterns,what brand I mean? I also built a savage bolt gun with a mcgowen barrel with a .310 bore and shoot sierras fine 125 grain pro hunterbullet and get under .300 groups at 200 yds,yes 200. I would send your barrel back.

Is that the 311 #2305 125 grain or is it the 308 #2020 308? What is your bore dimension?

I am certainly not looking for any such performance from a "Hunting" bullet. Let alone a Hunter in a auto loader. I am surely not saying you are wrong, really I am not, but you should contact Guinness. McGowan has an excellent reputation even among bench shooters. With .3 inch groups at 200 yards you are competitive in the 30 BR class on the national level. Did you possibly move the decimal point?

Thank you,

John

 

[spclark]

p.s.: It's spelled "bullet".

Those partial to breathing lead fumes as well as throwing lead down range like to spell it "boolit" I understand. As in cast 'boolits'.

 

[Tozguy]

.
If you have a custom barrel made up with a .308 bore as you mentioned, what about marking it 308x39 so that there is no mention of 7.62x39? Just a thought.
Good luck.

Toz,

That's some exceptional advice. Of course, I didn't think of that. I guess I still could mark it VZ 2008, the Century Arms variant, as that is what I seem to be building. I wonder if the 2008 thing also did the "in the chamber throat swedging" like the Mini 30 mentioned? It shot much better than the 30's 9 inch groups though.

John, Don't know for sure but marking the barrel with VZ 2008 might be misleading if the model is actually VZ 58. It would confuse the real model number of your gun and it might even have some ugly legal implications.

I'm sure glad you brought this ammo question up as I was looking at buying some surplus ammo and didn't realize that there is a variety of boolit sizes in 7.62x39 stuff. 'Cartridges of the World' says the nominal bore of a 7.62x39 is .311. In that case any bullet .311 or under would work in an army surplus gun but running a .308 bullet through a worn .311 bore is not something I would want to do.

Considering the above, technically, putting a .308 barrel on your VZ58 might mean that it can no longer be a 7.62x39 no matter how you chamber it.

 

[jonbearman]

No I didnt move the decimal and actually it was a .285 group. I just rounded up. I see because it isnt a 30 br and I built it,it couldnt possibly do what I said it would do.LOL

 

[johned]

. I see because it isnt a 30 br and I built it,it couldnt possibly do what I said it would do.LOL

Now, I didn't call you out on anything. I was careful to say it was possible and very special. You need a plaque on the wall for that achievement. No joke.

Thanks,

John