Bullet Length Question

[ngaither]

I started loading my first set of .270 rifle rounds last night and ran into a couple of problems. After placing a bullet (130g Sierra SBT) into an empty case and running it into my gun to find out what the length needed to be where the rifling in not touching and then back off .010. I would then measure the full length of the bullet and that was what I thought would be the length that I needed, but SBT tips are not accurate in length because of the lead tip. So when I started loading my rounds I would get a variance of .007 differance between each rounds total length. Is there a better why to measure so that I don't have this problem?

Second question is when the bullet is seated in case it is only pushed in about a .25 and with the bullet being a boat tail there is only about an .125 touching the case. Is this ok??

 

[Walkalong]

The bullets vary in length some. That is unimportant really. Where the ogive is in relation to the lands is what needs to be measured if you want the jump to be the same.

Anyway, it's not real important. In most stock rifles to fit the mag you will be pretty far off the lands. Many good bullets shoot well that way.

The rule of thumb is to have at least one calibers length in the neck (not including the tapered boat tail part), so you want at least .270 of the full diameter shank in the neck.

I would load to fit the mag and see how they shoot. Probably quite well.

Welcome to THR

 

[Blackrock]

That Sierra 130g SBT is a dang good bullet for the .270. I always load mine to COAL spec.

 

[NCsmitty]

I would load to fit the mag and see how they shoot.

That's good advice.

Most mass produced bullets will have some variation in the ogive, and trying to achieve .010 off the lands can be frustrating, if not dangerous, if you're playing with maximum loads and the bullet ends up engraved into the lands when chambered.

A bullet comparator will give you an accurate way to set your COAL to the ogive, if you want to carry it that far.



NCsmitty

 

[ngaither]

What I'm going to do then is to seat the one bullet .270 diameter of the shank (not including the BT) and one COAL. This why I can find out which one is longer and closer to the lands.

I know that I don't have mag problem because even with the bullet barely seated it still fits in the mag

Thanks for the advice!

 

[rcmodel]

It is very unlikely you can reach the rifling leade with a 130 grain 270 bullet in any modern rifle.

The SAAMI chamber is cut to allow use of way heavier & longer bullets then that.
And most of todays rifles are throated even deeper then that to satisfy the lawers looking for even lower chamber pressures.

rc

 

[GICO]

Surpisingly the rifling in my 270 is not deep at all ... some projectiles are seated quite deep and slower powders don't even allow enough room for a 130g bullet to fit deep enough.