What if your boolits are sized too fat?

[the_ursus]

What would be the side effects, if any, of a slug that was too big for a barrel? Let's say a .431 slug running through a .429 or smaller. Reason being, I slugged a barrel that my calipers say is .428 and I've been shooting .430.

[OLPDon]

Rule of thumb is a thou. larger just a starting point, ifin it fits the case and chambers well shouldn't be a problem some of us shoot as cast.
Don

[jforwel]

A lot of shooters, myself included, measure the chamber throats and shoot a bullet that matches that. Hopefully for best results the throats will be larger than the groove diameter.

I normally shoot cast bullets that are .002 - .003 over groove diameter and get the best results this way. If you have a load near max then make sure you reduce your charge before increasing bullet size and work up again.

You can check throat size by pushing a bullet through it or getting a set of pin gauges. Pin gauges are great if you have several revolvers and be alert for different size throats on the same cylinder.

[Boerrancher]

I shot 431's through a 427 bore for a long time. I didn't have any problems just a bit more pressure. I did find that when I went down to a 429 my groups started shrinking tremendously. On the other hand with one of my 30-06's it has a 301 bore, and likes 309 gas checked boolits to the tune of sub MOA groups at 100 yds. Don't ask me to explain why one gun likes them 2 thousandths over sized and another likes them 8 thousandths. I guess it is the same reason some people like their mashed potatoes with gravy and others don't.

Best wishes from the Boer Ranch,

Joe

[the_ursus]

So maybe more importantly than barrel size is chamber size? I heard of guys measuring the cylinder throat with calipers but slugging seams more accurate to me. Am I on the right track?

[mroliver77]

If we are talking revolvers here, the cylinder throats are most imortant and boolits should be sizwd to fit this measurement assuming throat is same or larger (larger prefered) than the barrel. Now some size to .0005 smallerthan this to somewhat oversize jf said boolit will chamber behind the throat. The latter has never worked for me. I load my revolter boolits as long as components and cylinder will permit with boolits sized to just fit in the throat.
J

[missionary5155]

Greetings
Lead is reasonable soft and as long as you are not running at MAX+ loads and /or lodging a boolit there should not be a structural problem to firearm.
Germany for instance used a "choke bore" high velocity cannon during WW2 that reduced a brass shell as it zipped down the barrel. I have not seen a report what the pressures were at the breech or inside the barrel but it worked well.
On the M60A1 tank the m68 main gun had a wear factor on the tube. Regular practice and HP rounds had a low wear factor whereas the SABOT round 5000fps had a wear factor of 2. If the brain is still remembering correctly the total wear factor for a new tube was 200 then was supposed to be recalibrated. I would think any lead boolit no matter how oversized would have a wear factor of several lifetimes.
God Bless you !

[Lloyd Smale]

the result would probably be small groups shot on your target

[Thumbcocker]

What Lloyd said.

[buck1]

What would be the side effects, if any, of a slug that was too big for a barrel? Let's say a .431 slug running through a .429 or smaller. Reason being, I slugged a barrel that my calipers say is .428 and I've been shooting .430.

Great accuracy and little to no leading. IMHO....Buck

[Bret4207]

I have run .003-.004 over before with no issues, usually when I don't have the correct sizer die. If you are working with oversize boolits even though they're soft lead you still need to work loads up carefully. You'll sometimes run into a gun that reacts very badly to oversize boolits. Most of mine seem to handle them fine, even prefer them