# Understanding Sectional Density of a Bullet



## Bo0YaA (Sep 29, 2008)

Ok I'm trying to come up with a load for my muzzy that can reach velocities of 2200 -2300 fps with a bullet that has good ballistic coefficient . Now what I have found is, to do so I am going to have to move to a lighter bullet which means pistol type bullet. 

My concerns are, if I am to take a pistol bullet and push it to the ballistics I'm talking about, will it hold together? The only comparison I have is to look at the sectional density of the bullet itself right? Its my understanding that all things being equal, the bullet with the highest SD will hold together better and penetrate deeper.

One of the bullets I'm looking at is the 230gr .451 Hornady XTP which has a SD of .181. Now, according to the Hornady website its only rated for speeds up to 1300fps. However, the 240gr .452 XTP MAG has a SD of .168 but is rated for up to 2100fps. I'm a little confused now because that goes against what Ive read about SD. Shouldn't the bullet with the higher SD be rated for higher speeds?

Another one I'm considering is the 200gr .400 SST using a MMP .50 HPH sabot. SD of .179 rated for up to 2100 fps (cost per 100 $87.00) vs (230gr. XTP $44.00 per 100)

Help me out here guys am I all wrong in my thinking? does SD matter when it comes to a bullet holding together on impact?


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## chet (Sep 7, 2007)

SD has nothing to do with how a bullet "holds together"

bullet construction does. "thicker jacket"  "partition design" "bonded core" etc are things you want to look for to help a bullet hold together.

trust the manufactures suggest impact velocity - if you push it, it will fail.


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## Bo0YaA (Sep 29, 2008)

Thats what I was afraid of, looks like $87.00 per 100 for me lol. Not bad if they shoot good and hold together I guess. 
I figured all the XTP bullets were constructed the same just different weights, guess not.


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## Loke (Sep 7, 2007)

Sectional density is a ratio of the bullets weight in pounds to the square of its diameter in inches. It is an indicator of how well a bullet should penetrate compared to a bullet of another caliber or weight of identical construction. Notice the part that says "identical construction". It has nothing to do with the bullets shape, construction, or manufacturer. Every 180 grain .308 caliber bullet will have the same SD. Their BC (ballistic coefficients) will change depending on bullet shape, construction, testing procedure, marketing department, velocities that they are traveling, and every other imaginable variable that can be introduced into the environment.


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## chet (Sep 7, 2007)

man if those SST's shoot good you'll be in fat city!!!!! any idea what the BC is on those?


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## chet (Sep 7, 2007)

hey just a thought.... there was a website that sells bullets in small increments to "test". Can't remember their name, but they might be worth tryin???????


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## Bo0YaA (Sep 29, 2008)

That's actually what I'm hoping for, but I was looking to spend a little less if I could. The BC on them is .265 which is the best BC Ive found so far other then the solid lead .377 Dead Centers which boast .300 but you have to use a combination of 2 different size sabots to get them to fit in a .50. If you want to use the .400 SST you have to buy them in the .45 cal set then toss the sabots that come with them and buy the MMP HPH sabots to make them fit in a .50.


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## Bo0YaA (Sep 29, 2008)

Here is how you buy them http://www.midwayusa.com/product/450531 ... -box-of-20 Then buy the right size sabots.


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## chet (Sep 7, 2007)

I'm worried about the thickness of the sabbot. It doesnt take much to rob the accuracy out of a muzz.........

Would it be cheaper in the long run just to buy a 45 cal muzz? or have your 50 re-barreled?????

however, having a 1/2 inch diameter powder column would kinda give it a "short-mag" effect!!! I like it!!!!


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## DallanC (Jan 13, 2009)

Loke is dead on. Sectional Density is the ratio between bore and bullet weight. Its the difference between a semi-truck and a freight train, both have similar surface area but the train has many times more weight behind it.

Good luck getting an accurate load at that velocity, and I mean that seriously. It can be done but its going to take ALOT of work, lots of components and/ fine-tuning. I find I shred sabots if I get too heavy of a load of powder. .429" bullets vs .451" behave differently, most guns prefer size one or the other. This will affect the sabot pellet thickness etc etc.

IMO, the difference between 1800fps and 2000fps out of a non-scoped muzzleloader isnt enough to care about. IMO if you want to shoot long range with a smokepole, get an accurate, CONSISTANT velocity load, then get a good tang sight and practice practice practice! NRA Muzzleloader shoots routinely go out to 500 yards.

http://www.montanavintagearms.com/107_longrange.html

-DallanC


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## Bo0YaA (Sep 29, 2008)

I agree there isn't much difference between 1800 and 2000 fps but there is between 1800 and 2200 or 2300 fps. I'm always looking at ways to improve things that have already been proven. Sometimes it works and sometimes it doesn't but when it comes to shooting 3/4 of the fun is in the trying.

I wish Utah would just get with the program like most of the US and let us use magnified scopes greater then 1x (which is actually -1x)

Chet if the .45 cal had as many options as the .50 trust me I would shoot the .45. I think its actually a better caliber for black powder.


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## DallanC (Jan 13, 2009)

Bo0YaA said:


> I wish Utah would just get with the program like most of the US and let us use magnified scopes greater then 1x (which is actually -1x)


As a aging person with a really bad degenerating eye condition... I agree. I have permenant uncorrectable double vision in my dominant eye now. I've hunting with Smokepoles predominantly for 30 years now... I dont know how much longer I will be able to see through a 1x scope.

-DallanC


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## Bo0YaA (Sep 29, 2008)

Even if they went 1.5 or 2 power for hecks sake.


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## BPturkeys (Sep 13, 2007)

This thread kind of has me chuckling. It just seems to me if you guys want to shoot high power, high velocity weapons with high magnification scopes then why don't you just do it? They call that the "rifle hunt".


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## Bo0YaA (Sep 29, 2008)

because then I have to put my pumpkin suit on and hang out with all the other pumpkins. I prefer camo and pretending I have the mountain to myself (even though I know I dont)


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## BPturkeys (Sep 13, 2007)

Well I get the part about the pumpkin suits but seriously, the whole idea behind the muzzy hunt...what ever happened to "primitive weapons" hunt...was to have an opportunity the use old or old style weapons. The deal was, "we'll set aside a couple weeks for you guys that want to journey back in time and do it the way your grandfathers did. Sounded like a good idea then and it still does now. So, what ever happened to that? If we keep moving farther and farther from that ideal with the use of more modern weapons/ammo/sighting devises etc, I am for ending any special opportunities and just merging the two hunts together...as we are merging the weapons together. I don't think the fact that the rifle is loaded from one end of the barrel instead of the other is enough justification for a special hunt.

Oh gee, sorry Boo, I just noticed I jacked your thread. Maybe we should move this over to the Muzzy section


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## Bo0YaA (Sep 29, 2008)

No worries.. The way I look at it (right or wrong) is this, lets not get so caught up in "primitive weapons" I mean really are the bows of today the same as the bows our forefathers hunted with?? no. Its not uncommon to make accurate shots out to 60 yards right? The big reason is because the bows are now capable of doing so. Add a modern sight and voila 60yrd shot made easy. We have reached the plateau of what modern muzzys can do with black power/substitutes due to the burn rates of the powder ect. ect. ect. They are now capable of shooting accurately out to 250 yards but the difference is, they wont let us use a modern site system to match the capabilities. People will still attempt those 250+ yard shots which will result in more wounded animals. Lets face it, not much beyond 250 those bullets drop like turds so I doubt you will see people taking 350-400 yard shots unless they plan on aiming 14ft high. Like I said I may be wrong but who came up with 1x?? why not 2x at least then the target wont actually look further away.


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## Cooky (Apr 25, 2011)

Sounds like an entertaining project.

Have you considered cast bullets? My sons and I have killed about 6 deer with cast .45 SWC bullets from muzzleloaders. BC is lousy but I think they would hold together better at the velocities you’re going for than jacketed bullets designed to expand at pistol velocities (an educated guess, all our shots created good exit wounds). Cast bullets are a little larger in diameter than jacketed so are hard to load with some sabots but Harvester Crush Rib Sabots fixed that. Bullet weights were 200gr to 255gr, powder charges were 80gr-110gr. The only reason I use .45 bullets is I reload .45ACP and .45 Colt so I already had them. 

DallanC mentioned shredding sabots. I have seen that in a friend’s gun (a three pellet user). I polished the heck out of the bore with JB’s and he started keeping it liberally lubed with Bore Butter, accuracy became tolerable and the sabots looked fine after that.


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## stick_man (Sep 10, 2007)

I was going to suggest using cast bullets as well. If you cast your own, you can size them to pretty much whatever size you want/need. A soft cast bullet with a bhn of 7-8 in a sabot will not lead your barrel and will hold together upon impact, even at 2300 fps.


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