Oal and pressure question

[Zombie Steve]

As you seat a bullet deeper, there's less case volume and pressures go up... as you already know. In 9mm, this is huge as there's very little case volume to start with. In .308, pushing back .005" or .010" isn't going to matter much at all. Bigger cases like .30-06 or .300 win mag even less. If the problem truly is that you're too close to the lands, what you're doing will lower pressures.

When you run into the bolt not closing, pull the cartridge out and look for marks on the bullet where the lands have scraped. If you don't see them, it's most likely a sizing issue (this happens eventually if you're just neck sizing). I generally neck size a few times, then give it a full length sizing again for just this reason.

Remember some bullets are just going to be longer than their counterparts. They aren't all the same. Set your die so that the long ones don't exceed 2.800" (for example). The majority of your bullets will come a few thousandths shorter, and some quite a bit shorter. It's a normal statistical bell curve. Depending on your level of OCD, you can sort them by weight and length.

[Jamnanc]

I smoked the bullet at the range with a marker. The bullet was definitely going into the rifling. I took them home and shortened them, the case is not touching, but the bullet definitely was. I will rework from a shorter oal after measuring per the video. Thanks guys.

[Zombie Steve]

Know what's nice when you rebarrel? The blank comes 27" or so, and the last inch or so isn't usable, so take what's cut off and ream it like the chamber. Custom case gauge that's an exact match for your throat / leade. I wish all rifles came with one, but that will never happen.

[spqrzilla]

As Zombie Steve describes above, the relationship between shorter OAL and higher pressure is not significant in rifle calibers as it would be in higher pressure pistol. At this point, the relationship is more dominated by the relationship between the initial contact of bullet to rifling and the pressure curve. Back off a bit should bring that down a bit.

[Tim K]

Know what's nice when you rebarrel? The blank comes 27" or so, and the last inch or so isn't usable, so take what's cut off and ream it like the chamber. Custom case gauge that's an exact match for your throat / leade. I wish all rifles came with one, but that will never happen.

My smith supplies one when he puts on a barrel. They are great tools. It's an exact match until you shoot a few thousand rounds. Throat erosion screws it up to the tune of about 0.003" - 0.005" per 100 rounds fired.

[Hound]

As Zombie Steve describes above, the relationship between shorter OAL and higher pressure is not significant in rifle calibers as it would be in higher pressure pistol. At this point, the relationship is more dominated by the relationship between the initial contact of bullet to rifling and the pressure curve. Back off a bit should bring that down a bit.

Got it that Rifle rounds are more tolerant and not thinking about pushing in 1" crazyness but 'typically' where is the danger zone when going under the posted OAL for a given round (understanding the larger the less it matters). On a .223 is it at .001, .01, .1, .5 etc? I am curious where you guys place your tolerances before the flags start going up.

[Zombie Steve]

Got it that Rifle rounds are more tolerant and not thinking about pushing in 1" crazyness but 'typically' where is the danger zone when going under the posted OAL for a given round (understanding the larger the less it matters). On a .223 is it at .001, .01, .1, .5 etc? I am curious where you guys place your tolerances before the flags start going up.

I generally try to go as long as I can without hitting lands or impacting feeding. The only time I've ever tried to see just how short is if I'm dealing with a really light / short bullet that I'm having trouble getting neck tension with. The old rule of thumb is one caliber width seated into the case (boat tail doesn't count as it's not touching the neck). I've never gone much more than that. If you're looking for some guide, check out the OAL for the lighter bullets for caliber in a manual. Beyond that I can't tell ya.

[Zombie Steve]

My smith supplies one when he puts on a barrel. They are great tools. It's an exact match until you shoot a few thousand rounds. Throat erosion screws it up to the tune of about 0.003" - 0.005" per 100 rounds fired.

He look like this?




...and per 100 rounds? How overbore is the cartridge you're shooting?