Flat base vs boattail charges

[tcoz]

After having reloaded pistol exclusively, I'm starting to study rifle reloading, specifically .223, in hopes of starting to reload it in a couple of months. The question I have is whether 55gr FMJ flat base is loaded with the same charge weight as 55gr FMJBT.

 

[rcmodel]

Do you have a Reloading manual?

Hornady for instance lists five different 55 grain bullets of different types.
Four are flat base, and one is BT.
They all use the same data.

Speer lists three, two FB and one BT.
They all use the same data too.

Rifle bullet construction & weight are what makes a big difference in pressure.

For instance, a solid copper Barnes bullet, or a Nosler Partition bullet is harder then a conventional cup & core lead bullet.
So for the same weight, they use less powder to reach the same pressure.

Seating depth, or OAL may also be different between the two types of bases.

rc

 

[tcoz]

I saw that in my manuals, but I've been looking at a ton of load data from lots of different sources and I've seen some where they're a bit different. I always put most of my stock in the published data, but I just want to see what everybody has to say about it. Thanks.

 

[rcmodel]

If you look long enough at enough data?

You can see about anything you want to see, or make out of some of it!

More has to do with test gun barrel length, test conditions, and powder lot tested then bullet bases.

Don't over-think it!

rc

 

[rg1]

I shoot the same charges for Hornady 55 FMJ and flat based 55 gr. Spire Points.

 

[Conservidave]

thats the great thing about reloading .223, the bullet/powder combinations are endless. eventually you'll settle on a few pet loads just like with pistol, and once you have that down, then you can tinker with oal and the process repeats itself. never ending fun!

 

[tcoz]

thats the great thing about reloading .223, the bullet/powder combinations are endless. eventually you'll settle on a few pet loads just like with pistol, and once you have that down, then you can tinker with oal and the process repeats itself. never ending fun!

It's all pretty confusing to me right now, but just like it did when I started loading pistol, it'll all sort itself out. At least, other than case prep, the process is pretty much the same and I'm very familiar with that.

 

[Maj Dad]

I used to obsess about all the variables - how much bearing surface for a given weight with different style bullets was a real agonizer - until I fell back on what is supposed to happen, anyway: begin with the recommended starting load, and work up. If you follow that one basic rule, you will always be at least safe, and likely to find an accurate load with that powder (or rule it out as not good in your set up). rc has it right: don't over think it.

 

[Sunray]

Load for the bullet weight. Who made it or its construction doesn't matter.
Except for Barnes solid copper bullets. Copper being far less dense than lead, they fly differently and need their own data,
Generally, BT's are used for longer ranges that flat based bullets, but the same loads will be fine.
What does matter is if you're loading for a bolt action or a semi-auto. Semi's require full length resizing every time(so do levers and pumps). A bolt action you can neck size for, but only using brass fired out of that rifle. Buy some once fired or brand new brass, you'll have to FL size those too. You need to watch the case and OAL for a semi too.
Biggest difference between rifle and handgun loading is there no flare put of a rifle case. They get the case mouth chamfered instead. One time thing until you need to trim the case. Nearly all of it is easier to do than describe.
"...If you look long enough at..." And it can be proven with statistics. snicker.

 

[tcoz]

Buy some once fired or brand new brass, you'll have to FL size those too.

So, what you're saying is that ALL brass has to be full length sized, regardless of whether it's once-fired or new? I thought brass cases lengthened when they were fired and new brass was already sized.

 

[spitballer]

The weight of the boat tail will be the same but the length increases slightly, so the rate of twist might need to be considered.

 

[oldpapps]

55gr FMJ flat base... loaded... the same... 55gr FMJBT

Beginning, load for the weapon, not what is listed in a book. The book is to provide a safe starting point. This doesn't mean that the highest listed loading is a level to try to exceed. It is not a competition.

Pick a starting loading with a comparable bullet weight and structure. Your bullet is not what you find listed, start with the charge/s listed for a heavier bullet, but don't go to extremes.

Using this, does it matter if the bullet is a round nose or boat tail?

No matter how 'fast' you can push the bullet, if it doesn't hit the target, it matters not.
Priorities in order: Safe, fits, safe, velocity to get to the target, safe, accuracy to hit the target, safe, energy on target, safe, economical enough to use, safe and If I didn't make it clear, safe.

As I see 'boat tail' bullets. The big plus to me is they slip into the case neck easy. But they also have better ballistic coefficient (I seldom shoot far enough to know the difference). Some think they cause more barrel erosion (I've shot lots of them and haven't had any problem). Some think they are more difficult to find a good loading with (not me). The tail makes them longer and this could impact stability (I have a 1 in 14 twist barrel that does well with 55 grain FB but not BT. Is it the boat tail or me not finding the best loading? I run 50s most of the time anyway.)

I hope I have helped a little. If not, ignore the old coot Many do.

 

[Catpop]

Sunray, why does new brass have to be resized?