Can a bullet be bumped to increase diameter

[burbank.jung]

I have a T99 that slugs at .3115". And so, .312" is desired. Sierra is known for making accurate bullets but their 7.7 bullets measure .311". Can this bullet be bumped up to .312; and if necessary swagged to .312" Will accuracy be compromised as a result?

 

[Bazoo]

It's common to shoot jacketed bullets that are .001 or even .002 undersized in other cartridges/guns and get good accuracy. I suggest trying them before going through any trouble.

 

[burbank.jung]

thanks

 

[JonB]

The dies/tooling to do that properly, would probably cost a grand.
The incorrect tooling to do that, usually lead to bend bullets and broken tools.
.
Really, a jacketed bullet only needs to engage the bore solidly, you don't need to fill the grooves.

 

[Outpost75]

Hornady and Speer both make .312 diameter jacketed bullets for .303 Beitish, etc.

 

[300BLK]

POWDER COAT!

 

[LEC Guy]

I think the advice above is good. I would shoot with off the shelf bullets and see if it works. I shot a bunch of 7.7 years ago using .311's and they worked well. I would even pull bullets from old .303 synchronous machine gun ammo(stuff that shot between prop blades on a fighter) and loaded 7.7 Jap. AP. There was probably some old Brits rolling over in their graves to hear someone was doing this in an Axis caliber.

Bruce

 

[Missionary]

And you can also "bend" them. Had some .311 hard cast I decided needed to be bumped to .316.

 

[CWLONGSHOT]

It's common to shoot jacketed bullets that are .001 or even .002 undersized in other cartridges/guns and get good accuracy. I suggest trying them before going through any trouble.

EXACTLY!!

Don't try and fix a problem that is not even known to exist!!!!!

SHOOT SOME!!

 

[BudHyett]

I have a T99 that slugs at .3115". And so, .312" is desired. Sierra is known for making accurate bullets but their 7.7 bullets measure .311". Can this bullet be bumped up to .312; and if necessary swagged to .312" Will accuracy be compromised as a result?

Flat-base jacketed bullets will swell several thousandths to fit the barrel.

 

[RicinYakima]

The starting resistance into the bore of a jacket bullet is so high, that the base part will expand to groove size in normal loads. Just Like Bud says.

 

[Gary]

Watch this video:

 

[burbank.jung]

Flat-base jacketed bullets will swell several thousandths to fit the barrel.

Wow! Really?! Would you suggest a Sierra 180gr flat base spitzer point or Sierra 180gr HPBT for long range target use if my bore slugs at .3115?

 

[BBerguson]

POWDER COAT!

This is what I would try before I would try to ”expand” them.

 

[BudHyett]

Wow! Really?! Would you suggest a Sierra 180gr flat base spitzer point or Sierra 180gr HPBT for long range target use if my bore slugs at .3115?

Flat base spitzer. You can try the HPBT by seating it into the land with the barest of a witness mark. Then back off .010 and shoot for group. Shoot ten-shot groups at 100 yards to select and 200 yards to confirm the best selection.

 

[358156 hp]

I've seen a lot of reports about shooters loading .308 Nosler Partitions in .303 Enfields for use on heavy game because Nosler never made .311 Partitions. The story was that the bullet bases would slug up to fit the bore, exactly as Bud and Ric stated above. I mention this because the .303 is a moderate pressure cartridge so super hot loads would not be required to achieve the desired results.

 

[RicinYakima]

The Partitions have a pure lead, easy to swage, rear core so it expands easily.

 

[358156 hp]

Thinking about it, with the partition in the jacket there's really no place else for the displaced base to go except outwards.

 

[burbank.jung]

Thanks so much for sharing.

 

[GRMPS]

POWDER COAT!

PC works with lead, I've never thought to try it on a FMJ bullet