reloading 300blk. factory loads from 150-220gr are all close to the 2.260" max. why do my manuals have a 110gr c.o.l. listed as 2.050? seems like a significant difference. isnt the goal to get the bullet closer to the barrel?
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c.o.l. ?
- Thread starter thood
- Start date
There are several factors at work here most likely- the most important one is that the 110 grain bullet is half the size of the 220 grain factory bullet and 2/3 the size of the 150 grain. They're all basically made from the same thing, so making one lighter means less material- i.e. shorter bullet because the diameter has the be .308".
The internal case volume has a lot to do with how the powder burns, so bullet seating depth has an effect on how the powder charge burns- therefore more or less powder is recommended for a particular projectile.
All that said- you are right about the bullet's distance to the lands and grooves in the barrel. I've read that a minimum bullet "jump" is best for accuracy. However you do need a bullet comparitor gauge to know what that overall length is. The comparitor gauge measures to the ogive on the bullet and not the bullet tip. There's a modified brass cartrige that you use with their gauge to check the projectile fit in the barrel.
Sorry- lot of words in this post. And the most important thing to remember is follow the published data. I cannot recommend experimeting outside of the recommended load recipe. I have read about cases where even using too little powder in a fairly large rifle case causes pressure spikes that can destroy a rifle- not to mention what can happen to the shooter. I'd think less powder is always ok (and more room in the case is always ok) but that is not the way the real world works. I don't understand enough about interior ballistics to tell you what's right and wrong for this case.
The internal case volume has a lot to do with how the powder burns, so bullet seating depth has an effect on how the powder charge burns- therefore more or less powder is recommended for a particular projectile.
All that said- you are right about the bullet's distance to the lands and grooves in the barrel. I've read that a minimum bullet "jump" is best for accuracy. However you do need a bullet comparitor gauge to know what that overall length is. The comparitor gauge measures to the ogive on the bullet and not the bullet tip. There's a modified brass cartrige that you use with their gauge to check the projectile fit in the barrel.
Sorry- lot of words in this post. And the most important thing to remember is follow the published data. I cannot recommend experimeting outside of the recommended load recipe. I have read about cases where even using too little powder in a fairly large rifle case causes pressure spikes that can destroy a rifle- not to mention what can happen to the shooter. I'd think less powder is always ok (and more room in the case is always ok) but that is not the way the real world works. I don't understand enough about interior ballistics to tell you what's right and wrong for this case.
Best thing to get when loading 300 blackout is, a Head Space Gauge!! you won't regret it
That's probably the issue. Rule of thumb, allegedly, is you want one caliber of bullet in the neck... shorter bullets may need to be seated deeper to get enough friction to 1.) Hold the bullet in place while chambering, and 2.) Provide enough resistance for consistent powder ignition.
However... if you are a handloader, have your process under control, and are single-feeding cartridges, you can vary OAL safely. Precision reloaders control neck tension, and precisely set the OAL to keep the ogive a fixed distance from the lands. The distance that makes that rifle most accurate, with those cartridges. This length often won't fit in the magazine.
BTW, I don't have the magazine handy, but in a reloader's mag a couple of years ago (two? three?) there was an article claiming that seating depth wouldn't affect pressure in bottle-necked rifle cartridges running modern propellants. They called that a "myth". Take it for what's it worth.
If you run the bullet out so far that it hits the rifling, that WILL increase pressure, as there's a lot more force to overcome before the bullet starts moving. For most folks, it won't be an issue-- the off-the-shelf rifles I'd measured have so much free bore that a cartridge loaded to hit the lands can't fit in the magazine.
One other comment: sometimes the book OAL is what it is because their bullet has a cannelure, and that's the length that puts the case mouth in the cannelure.
Thanks for the responses. romilayu after putting some together your right there isnt enough bullet. except for the barnes ttsx which their #s called for 2.25 o.a.l. i set them a 2.20 and at the range today, 3 groups,100yards, smallest was right at 1" largest 2". the hornady, and nosler set at 2.050(buy the book) groups opened up 3" to 6". definitely gonna pick up a head space gauge,bullet comparitor and looks like some heavier bullets.
