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A pause for the COZ
02-12-2014, 11:24 AM
Ok I have a question.
I always hear that it is super important to slug your barrel.
Why?
I haven't found any of my rifles I cant get a good load to shoot and I haven't slugged a one.
In my 308 cal I haven't seen any accuracy issues sized to .309, .310, or .311 they all shoot about the same.
Seems the bullets expand upon firing to fill the grooves any way.
What am I missing?
Is it only important if your going to be shooting them super fast? Or using hard cast?
I haven't played there yet. Most of my accurate loads shoot about 1600 fps or so.
There must be some cast boolit voodoo I have yet to learn.

Doc Highwall
02-12-2014, 11:35 AM
Maybe you got lucky with the .309" bullet size but only by slugging the barrel will you know for sure. Also think about a modern such as a 308 Winchester that has been shot a lot and the throat has been shot out and eroded forward vs. a new gun.

Also members here have found their chambers to have been off center showing no rifling on one side which is why they were not able to get accuracy no matter what they did.

Knowing what your gun bore/groove measures lets you know how precisely how much larger your bullet is in order to get the best accuracy.

A pause for the COZ
02-12-2014, 11:57 AM
How does slugging let you know "throat has been shot out and eroded"?
A chamber cast would show that.
Do you do it with all your guns or just ones your having trouble with?
When I said this"I haven't found any of my rifles I cant get a good load to shoot and I haven't slugged a one."
That was not exactly true.
I have slugged my two groove 303 Brit. because I was (am) having trouble with it.
Did not help. other than figuring out I have a .303 bore and .317 grooves.
Other than knowing I was hosed. Wont chamber any thing bigger than .316 so going for .002 over groove diameter wont happen.
Just trying to get my head around what I am trying to accomplish.
Is it more for trouble shooting or for normal load development? Maybe I am over thinking it and should go have coffee.

ShooterAZ
02-12-2014, 12:07 PM
I'm in the slugging it if I have problems corner. As you have also found, foreign Milsurps are the ones that typically give me the most problems.

mdi
02-12-2014, 12:22 PM
I like to know all I can about my guns, just like I do for my truck. For my guns, I like to know what the groove and bore diameter is, what the cylinder throats are, if my barrel is "straight" (diameter consistent from chamber to muzzle), inspect innards for condition overall. For my truck I like to know what weight /type oil is in there, the tire size, age of oil, last inspection, latest updates on maintenance, etc. Same idea. I could go through life not knowing squat about my toys/possessions just using them and when done putting them away, but that just ain't for me. I take care of my stuff and since there is no down side to slugging a barrel, I have done all my guns, except my .22 rifles (I did do my Ruger MkII when I bought a rimfire cartridge bullet forming tool).

If you don't know what you are working with, facts/measurements, as in shooting lead bullets, it's all a WAG...

geargnasher
02-12-2014, 12:46 PM
A good pound cast of the chamber and throat will tell you all you need to know.

If paper patching and bore diameter is a must-know, a pin gauge in the muzzle will tell that. Sometimes, when diagnosing leading problems, slugging a revolver barrel twice (in the muzzle an inch and back out, and another all the way through) is necessary to determine if thread choke is the cause. Other than that, no need to slug the whole barrel.

Gear

Maven
02-12-2014, 02:03 PM
"If you don't know what you are working with, facts/measurements, as in shooting lead bullets, it's all a WAG." ...mdi

mdi is exactly right. Not only is it a WAG, but also a supreme waste of powder, alloy, and time. Who wants to diddle around and get inaccurate results when a few simple measurements (which take much less time) can increase accuracy and lower the level of frustration? In fact, my experience with factory rifles and revolvers as well as milsurp rifles is 180 deg. different than the original poster's. For ex., in my .30-06 Mod. 70 Win., slugging the bore showed that the oft suggested .309" [CB] diameter was questionable at best. Sizing to .310" was better, and .311" better still IF the bore riders' noses were at least .302" in diameter. My Finnish Nagants also preferred different bullet diameters, which I wouldn't have known unless I slugged the bore of each.

felix
02-12-2014, 02:24 PM
Mdi, a gun is no different than your truck engine's operation. Not in the least. Compression ratio is the name of the game, and the resulting ignition curve of the "powder" given to each bore by the cartridge (computer). Tolerance, and only tolerance, is the name of the game. ... felix

Larry Gibson
02-12-2014, 02:46 PM
As mentioned the throat of a rifle is the important measurement to know. I seldom slug a rifle barrel but either cast or slug the throats. I try to size rifle bullets to fit the barrels throat for best accuracy.

Larry Gibson

A pause for the COZ
02-12-2014, 02:54 PM
Ok back to my original question..
What I am trying to figure out. Is when and why is it important?
I can pretty much say when using a soft alloy ( range scrap ect) and shooting at low to moderate velocities.
It has not even been a issue. Pretty easy to get a workable load.

I can also say, I have had little luck getting Hard Cast boolits to shoot worth a darn. The ones I had were sized to .310 and were 23bn.
Best I could do was get them to pattern. I could get them to shoot accurately with Trail Boss. because thats a very high pressure powder.
But they shoot very slow. 900fps range.
The same boolit cast with range scrap lead, loaded with the same load of 2400. Shot just as well as any other.

I dont know if that makes sense to you guys or not.
I feel pretty confident hanging around the shallow end of the casting pool. Soft alloy at moderate speed.
Feel like I am missing some thing important.

mdi
02-12-2014, 03:18 PM
The why's seem to have been covered; low/no barrel leading and accuracy. When is important if the accuracy is off, and if leading occurs. I'd say cut that 23 BHN stuff with enough pure lead to bring it down to 10-12 BHN as a start, and size .002 over groove diameter (but if you don't want to slug your barrel you won't know what that +.002" is so just make a wild guess at any old bullet diameter)...

Doc Highwall
02-12-2014, 04:30 PM
There is a very good post here by Goodsteel about making a pound cast along with pictures that say a 1000 words. Not sure where it is posted but I am somebody here knows where.

s mac
02-12-2014, 04:41 PM
I think this a sticky on this page.

geargnasher
02-12-2014, 07:10 PM
It is. If you fit the boolit to the throat and the cartridge to the chamber, the rest takes care of itself unless there is a problem with the barrel (reverse taper, restrictions, etc.) which you will know after shooting. I'm not saying DON'T slug the barrel, I'm just saying that for me at least it has become a waste of time since I started making pound casts.

Gear