bullet diameter

[Hank45]

How much over grove diameter is it unsafe to use a cast bullet? Thanks Hank

[felix]

That dimension which causes the boolit size to be less than 0.001 total loaded cartridge neck clearance. Soft boolits require about 0.002 total neck clearance. ... felix

[williamwaco]

I am not sure what Felix is saying but I think I agree with him.

You need a clearance between the outside of the cartridge neck and the inside of the chamber neck so the cartridge neck can expand a little and release the bullet. Most loaders agree that .001 is enough. I know this from experience. If the neck of the cartridge is large enough that you can feel it touching the neck of the chamber when you close the action, you are at the point that chamber pressures are going to be affected. If you go beyond that point, chamber pressures will rise quickly.

The best way to be sure is to make a chamber cast and measure the diameter of the neck of your chamber.

Most people are not equipped to do this. If you want to try an easier test, take a loaded cartridge that you think may be too large. Clean and dry the neck carefully. Paint it with a black marking pen and be sure it is completely dry. Insert the cartridge and close the action. You will probably wipe off a little black where one side of the cartridge touches the shoulder area as it enters the neck. If you wipe off black in two or more locations around the neck, that cartridge is too large.

You can do the same test with mold release or with molly spray lube but they are much thicker coatings and may give a flase alarm. On the other hand they will provide a double margin of safety.


Safety is like ammo. You can't have too much.



.

[357shooter]

As far as safety goes, I shoot +.003 over groove all the time with no problems. I've read on the LASC site where they load .004 over with no problems or bad effects. FYI, I load handgun cartridges only, no rifles calibers.

I believe the other replies address size in the chamber... not bullet to groove size. Maybe I didn't understand the question.

As always, work up slowly to max pressures.

[williamwaco]

As far as safety goes, I shoot +.003 over groove all the time with no problems. I've read on the LASC site where they load .004 over with no problems or bad effects. FYI, I load handgun cartridges only, no rifles calibers.

I believe the other replies address size in the chamber... not bullet to groove size. Maybe I didn't understand the question.

As always, work up slowly to max pressures.

I think you are correct but, I think the original questioner misunderstood the problem.

He is asking about safety.

If you can get the cartridge to chamber and release the bullet. The bullet size in relation to the bore size is not going to be a problem.

It takes very little pressure to "size" the bullet down in the bore.
With cast bullet loads, pressure peaks are going to occur before the bullet ever leaves the cartridge case. Once it is in the bore and moving, pressure is going to decline rapidly.

There is one old practice that was used frequently in "olden" days in which lead bullets were fired routinely through bores that were 44 thousands smaller than the bullet.

I am not going to describe it because I don't want anyone trying it out.

I just want the original poster to understand that if he gets in trouble over bullet diameter, it is going to occur in the cartridge neck, not in the rifle bore.

I will say that I have tested .362 bullets in a .3565 .38 special trying to create leading. Two things. They did not raise pressures at all over bullets sized .356 AND, they did not lead the bore. ( but that is an entirely different discussion. )

[MtGun44]

The groove diameter fit is NOT the safety issue.

It is whether the chamber will let the neck expand enough to safely release the boolit.

Bill

[Hank45]

Sorry, I did not state my questeon right, I am not loading the bullet in a cartridge I am breech seating and the diameter I am discussing is the groove riding diamention, Hank

[dubber123]

Sorry, I did not state my questeon right, I am not loading the bullet in a cartridge I am breech seating and the diameter I am discussing is the groove riding diamention, Hank


Well, if I am understanding correctly, boolit release from a case isn't an issue, due to your breech seating. If that is the case, I doubt you will ever have an issue with a boolit being too large, unless your loads were at absolute max to begin with. I have a 50-70 Contender, with a .510" groove, and I have fired .516" boolits with no issues at all. As stated, it really doesn't take much pressure to swage a boolit down.

Is there a reason you need to shoot more than .001-.002" over groove size?

[felix]

Breech seating, if done 100 percent correctly, you'd need a swage die to EXACTLY make the boolit match the gun's leade and freebore, and then use that die to size your boolit before entry into the gun. Any boolit bleed out of the die will let you know your casting lead/equipment/method needs adjustment. ... felix

[Hank45]

Dubber123, No just wanted to fill grove for a tight fit, Hank

[MBTcustom]

Heck, lead boolits are blobs of silly-putty compared to jacketed boolits. I dont think there is a boolit made of a lead alloy that wont squirt out the barrel upon firing, no matter how far oversize it is. There is virtually no danger in that regard. The only time you might start to have a problem is in the specific situation that Felix mentions.

[BAGTIC]

Great tip Waco. I am going to try it as soon as I get my new loading bench set up.

[HpGuy420]

How much over grove diameter is it unsafe to use a cast bullet? Thanks Hank

Hank,

The bullet MUST bump-up to seal the chamber neck. So if the round will chamber there should be no pressure related problems when shooting cast bullets. For instance, if sizing a 45-cal, 45-70 bullet to 0.458" with brass that is 0.010" thick at the neck, typical of Starline, and the chamber neck is 0.484" here's what happens if there is no powder-fouling blow-back on the case necks after firing. The math looks like this:

Chamber Neck Diameter - Twice Brass-neck Thickness = What the bullet will bump-up to before leaving the case.

For this example the numbers are:

0.484" - 0.020" = 0.464"

That is quite large to be recommending to some with regard to sizing they bullets, no? But, that is how large the diameter becomes before the bullet moves from the case. It will be swagged back down as it inters the freebore and/or leade. The larger the bullet bumps-up, the larger the fins on the base. The bane of accuracy.