Oversize bullet rules, do they apply to jacketed.

I've always used oversized cast bullets, although I am mostly a gas check guy so it might not matter. And I mostly shoot pistols,...(I'm not sure I would be a good enough shot for size to make a difference in accuracy anyway). My question is: I do NOT cast for my kid's 223s (at least up until now), I just buy bulk 55 grain slugs and use those. I recently had some that were all about .2247 or so inches, wheras in the past, they've always been nearly right on at .2240. I've been giving it some thought, and my instinct tells me that at some point it's really not a good thing to be shooting bullets that are too big (when talking about jacketed). Does anybody have any experience in this matter (before I switched to cast,..I do remember that Sierra (at least I think it was sierra??) had bullets for some of my pistol loads that were a half a thousandth different from the other mfgrs (on purpose...although I have no idea what their purpose would have been). Well, let me know on that. I really can't find any definite info. on any chatboards, etc., And I do appreciate any input you may have.

I doubt you will have any issue with the oversize bullets, but you probably need to work up your load again, just like changing lots of powder.

At one time Lapua made their 167 secenar in .308 and .309 dia. I found that on a high round count barrel in 308 win the 309s would sometimes shoot better. I had a sleeve of Hornady 55 grn soft points that measured a true .2245 that did well in the shot out throat of my swift. In a known load with standard size bullets you will want to drop back and work the load up again. A .0005 to .001 over may not make a big difference.

I am going to say 3% over bore is safe. That's what Quickloads tells me and it has been a pretty reliable program. Of all things I have tweaked though, bullet diameter has had the least effect to anything. No documentation other than the warning message that pops up with I am being inquisitive with the program. When it comes to jacketed bullets I haven't really seen much information on this subject. I am curious now.

I guess if you wanna test yourself, just pickout the ones that mic the largest out of the batch and re workup the load with the fat ones. if you don't get any more pressure signs than normal consider the diameter variation non issue

3 Percent over bore is a fair bit more than I expected. If I can get out this weekend I'll take the chrony and see what gives with these I've loaded up. I've never chrony'd a 223 before. I have not mic'd or slugged either of the kids 223 barrels either. Sometimes the kids act more like lead dispensers than someone trying to learn to shoot.,. Originally I was hoping they would learn to aim,..but at this point I believe one of them is starting to learn to aim, but the other one is probably permanently in the "quantity over quality" department. HA.

Is there any chance these are pulled? Maybe they aren't large, just out of round.

They are not pulled. I mic'd a bunch of them and they are quite round and fairly consistent. At first I thought my mic was not zero'd but it is. So I checked some 53 and 52 grain Sierra's I have in case we go coyote hunting,. and they are right at 224. I just happened to get these at the gun show for loading target practice ammo. The thing that surprises me is that they are fairly consistent and quite round.

I think you would get that much variation in barrels going by some I have slugged. Regards Stephen

It's common to have 7.62x39 ammo that measures .311 but run it through a .308 diameter bored rifle. If you look that up you'll find some threads and info about it. I was looking it up because I happen to have some .311 bullets and am thinking about running them through my 30-06. What I found as a result of the research I did was that the increase in diameter doesn't raise pressure much, and that the difference in bearing surface plays a more significant role in pressure differences.

Hope this helps.

Bazoo

The famous 8x60 Mauser had a .318 bore with deep grooves. Ammo was loaded w/.323 J-bullets to raise pressure and velocity. Works just fine.

If .224" bullets are safe and work well in your gun, I doubt if .2247" is going to make any difference. jacketed bullets aren't solid like hardened steel and will obturate and swage quite easily. The .0007" is really pretty small, it's just a few atoms larger than one half of one ten thousandths of an inch; seven one hundred thousandths of an inch...

FWIW; even ambient temperature can skew fine measurements. I made some precision parts for the Air Force that had +.0006"/-.0001"" tolerance, we had the Inspection Department measure them just to be sure. The parts were made in So. CA and when they were checked in Alaska, they all were too small (80+ degree vs. 50 degrees ambient temp). Even cold fingers can give a "bad" reading when using calipers or micrometers...

Years ago I tested .303 British MkVIIz, MkVIIIz and commercial sporting ammunition in two pressure-test barrels chambered with the same SAAMI-specificiation pressure and velocity test barrel reamer. One barrel was of standard .303 British commercial sporting dimensions with .303" bore and .312" groove, rifled in the 5-groove Enfield pattern. The other barrel was made from a cal. .30 Ball M2 (.30-'06) government specification test barrel blank having .300" bore and .308" groove with 4-groove government form rifling as used in the M1 Garand.

As long as the chamber neck has adequate release clearance and the throat prior to origin of rifling is large enough to accept the bullet without constricting it during initial shot-start, the pressure rise resulting from the smaller barrel groove diameter, while measureable, is not dangerous.

In our tests the .308 groove diameter test barrel chambered in .303 did produce somewhat higher pressures approximately +3,500 to 4,000 c.u.p., with both the SAAMI reference 180-grain softpoint, as well as FMJ WCC and DAC service ammunition, all considered to be within safe design limits for a sound No.4 rifle. The huge throats seen on many wartime .303s which permit excessive base-upset of the bullet, which must then be extruded into the rifled portion of the barrel, causes a greater pressure rise than the tighter groove diameter by itself.

Having the throat fit the bullet and the bullet fit the throat, so that initial shot-start occurs without base upset, the throat proving a gradual transition into the rifling mitigates against pressure spikes. This is exactly how the Germans converted early "J" bore '98 Mausers to "S" bore, not by rebarreling, but simply by increasing neck release clearance in the chamber, while increasing the throat diameter to fit the new bullet and cutting a more gradual forcing cone angle to enable a "slow squeeze" and gradual pressure rise of the larger bullet when fired in the tight barrel.

Oversized jacketed bullets will raise pressures quite a bit. They are just harder to push down the bore.

I remember finding that out in my first machine shop class in college. I milled a shaft perfectly,,. and after it cooled down it was .001 or more undersized. It was a good lesson to learn, but I really wished the professor would have warned us ahead of time. That was downright dastardly of him to let us all ruin parts.

.0007" is a nothing burger. Load 'em and shoot 'em.