Loading 300 BLK, or any bottleneck cartridge

[Damon Larsen]

Getting ready in the near future to start loading rifle rounds. Started loading pistol, and reloading in general last October on a Dillon XL750. I’ve been very successful with loading 9mm and 45ACP. Developing 10mm and 40 soon as well.
The wife just bought a 300 Blackout AR(bless her heart). I realize I need to step up my game and learn bottleneck. Not just the insane prices of ammo right now, but it’s just something I need to learn.

My biggest head-scratcher is how do I determine COAL for it, aside from what load data is given and the size of the magazine
? For example, with pistol, I seated my 9mm 115 FMJ’s deep enough to where it would fit all 5 of my 9mm pistol’s barrel. To where it would plunk, spin freely when I’d rotate it, and then drop right out.
Im just gonna say, I don’t think this is how things work with rifle. I hear you don’t necessarily determine the COAL by where the cannelure is. I don’t fully understand what ogive is...but I think it’s where the bullet begins to taper down towards the top?

The more I’ve learned about reloading, the more I realize how little I know. I don’t want to do anything unless I’m doing it exactly right. Please drop any and all knowledge you’d like on this in general. And please explain it like I’m 5 years old. Thank you guys in advance

 

[ms6852]

First and foremost I recommend that you buy yourself and read the ABC"S of reloading manuals. After you have read it a couple of times I recommend that you buy several different types of manuals because you will soon find out that every manufacturer has their own loading data for each of their bullets and will differ from other load data from other manuals, even though they are the same caliber. For example, if the bullets you are buying are Sierra bullets, I would use a Sierra reloading manual. If you buy Hornady bullets I would use a Hornady reloading manual, if you buy Nosler bullets I would use a Nosler reloading manual and so on infinitum.

You will see that each manufacturer will have different powders and primers they recommend for their bullets and have tested that round so if you follow their data you will be safe. It is confusing.

When it comes to loading 300 blackout most people use a jig for convenience and some may even have bought a saw from Harbor Freight with which that jig can screw into to cut the cartridge and than you can deburr the cartridge with your case prep accessories or station. I purchased the following jig from the company that I am providing the link for. But can also fashion your own jig if you like. I don't know if Harbor Freight still sells the saw but I believe it is a 2 or 3 inch blade that it comes with, research that yourself. Here's the link.

https://www.squirreldaddy.com/Rigid-Brass-300-Blackout-Case-Trimming-Jig-2-0-p/sd24-105.htm

 

[Metal God]

The more I’ve learned about reloading, the more I realize how little I know.

haha welcome to the party pal . I started with rifle then went to pistol which was easier but messed with me because I started loading pistol like I would for pression rifle and that's just more then needed . In your case you're in fact going to need to step up your game . There's much more to pay attention to when loading bottle neck cartridges .

9mm , 45 , 10mm 40 S&W all headspace off the mouth of the case while many bottle neck cartridges headspace off the shoulder like 308 , 223 , 300 blk . This requires you to size your case to the correct size from head to shoulder in order for it to fit in the chamber of your rifle . To little sizing and you'll have failure to feed because they don't fit in the chamber and to much sizing and you can reduce case life or even have head separation which could be catastrophic . This IMO is much more important to learn how to do correctly then COAL . COAL is simple because when you are starting a new , just use the manuals recommended COAL and you should be gtg .

However in many cases following the die manufactures directions will cause you to size your case to short and you will reduce case life to as little as two loadings before case head separation .

These are cases only reloaded 3 times and were sized each time as Redding's instructions say to adjust your FL sizing die .



When your case is sized much shorter then your rifle's chamber the firing pin strikes the primer and pushes the case fully forward until it stops on where it headspaces off of . In the 300 blk that would be the case shoulder stopping on the chamber shoulder . If the case is sized .008 or more shorter then the chamber when the case is pushed forward that leaves a gap of that same amount between the head of the case and bolt face .

Ok almost simultaneously the firing pin strikes the primer , case moves forward and pressure starts to build expanding the case sealing the chamber and the case actually grabs the chamber walls and is stuck in place until the pressure drops . Well what happens to that gap between the case head and bolt face because the case is stuck to the chamber walls and can't move rearward . As the pressure builds , at some point the pressure gets high enough to actually stretch the case at the web ( section of the case above the head ) and the head of the case is forced back against the bolt face . When that stretching accrues it is actually thinning the case wall at the web each time the case is fired and resized to short for the chamber . As you can see with the picture above it only took 3 sizing and firing cycles to stretch the web so thin the case failed ( NOT GOOD ) .

In a bolt gun properly sized cases can be reloaded 10 , 20 and even 40 times . In semi auto's you may not get as many as a bolt gun but if you size your cases correctly you should get 6 to 10 reloads and if you anneal maybe many more . OK so what is the "correct" size to size a case ? I don't know , I just made all that crap up , lol just kidding .

In bolt guns you want to size your cases .001 to .002 shorter from head to datum then your fire formed cases from the same rifle they will be fired in . For semi autos you want to FULL LENGTH size your case .003 to .004 shorter then your fire formed cases from same rifle .

OK so size your cases correctly , trim every time at first and use the bullet manufactures recommended COAL and you should be gtg . My point here is just get some good safe loads down range and then start thinking about advanced techniques like playing with seating depths although with the cartridge you are starting with you will likely be stuck with mag length .

 

[Steelworker]

Seriously, buy a Wilson case gauge for 300blk. It does 2 things. It will show you if the shoulder is bumped back far enough, and if the resized case is too long.

It’s makes setting up your press much easier.

 

[Metal God]

The LE Wilson case gauges work well , here's them explaining how to use them .


You could also try the Hornady case headspace comparator . I use/have both and find the Hornady tool to be more convenient . I'll add that I'm not sure if the standard set will come with the 300blk insert .

See video on left side
https://www.amazon.com/Hornady-HK66-Lock-N-Load-Headspace-Gauge/dp/B000PD5VN8

 

[mstreddy]

OP, I agree with the case gauge for the 300 blackout, but I would recommend the Sheridan slotted one. Particularly if you plan on using many 223 formed 300 blackout cases. I found that some brands will end up with necks that are too thick and then when you add the bullet you end up with problems chambering.
These rounds were OK in the Wilson, but the Sheridan showed where it was hanging up. One of the forums has a list of which cases are good for forming and which to avoid.
Another thing to be aware of in 300 Blackout is the crimped in primers. A lot of 223/5.56 has them, and I've also seen a variety of factory 300 with the crimps as well.

 

[Damon Larsen]

First and foremost I recommend that you buy yourself and read the ABC"S of reloading manuals. After you have read it a couple of times I recommend that you buy several different types of manuals because you will soon find out that every manufacturer has their own loading data for each of their bullets and will differ from other load data from other manuals, even though they are the same caliber. For example, if the bullets you are buying are Sierra bullets, I would use a Sierra reloading manual. If you buy Hornady bullets I would use a Hornady reloading manual, if you buy Nosler bullets I would use a Nosler reloading manual and so on infinitum.

You will see that each manufacturer will have different powders and primers they recommend for their bullets and have tested that round so if you follow their data you will be safe. It is confusing.

When it comes to loading 300 blackout most people use a jig for convenience and some may even have bought a saw from Harbor Freight with which that jig can screw into to cut the cartridge and than you can deburr the cartridge with your case prep accessories or station. I purchased the following jig from the company that I am providing the link for. But can also fashion your own jig if you like. I don't know if Harbor Freight still sells the saw but I believe it is a 2 or 3 inch blade that it comes with, research that yourself. Here's the link.

https://www.squirreldaddy.com/Rigid-Brass-300-Blackout-Case-Trimming-Jig-2-0-p/sd24-105.htm

I will definitely look in to that, thank you! Also, I don’t have a manual so I should start there for sure. I’ve relied on the Internet heavily up until this point.

 

[Damon Larsen]

haha welcome to the party pal . I started with rifle then went to pistol which was easier but messed with me because I started loading pistol like I would for pression rifle and that's just more then needed . In your case your are in fact going to need to step up your game . There's much more to pay attention to when loading bottle neck cartridges .

9mm , 45 , 10mm 40 S&W all headspace off the mouth of the case while many bottle neck cartridges headspace off the shoulder like 308 , 223 , 300 blk . This requires you to size your case to the correct size from head to shoulder in order for it to fit in the chamber of your rifle . To little sizing and you'll have failure to feed because they don't fit in the chamber and to much sizing and you can reduce case life or even have head separation which could be catastrophic . This IMO is much more important to learn how to do correctly then COAL . COAL is simple because when you are starting a new , just use the manuals recommended COAL and you should be gtg .

However in many cases following the die manufactures directions will cause you to size your case to short and you will reduce case life to as little as two loadings before case head separation .

These are cases only reloaded 3 times and were sized each time as Redding's instructions say to adjust your FL sizing die .

View attachment 933377

When your case is sized much shorter then your rifle's chamber the firing pin strikes the primer and pushes the case fully forward until it stops on where it headspaces off of . In the 300 blk that would be the case shoulder stopping on the chamber shoulder . If the case is sized .008 or more shorter then the chamber when the case is pushed forward that leaves a gap of that same amount between the head of the case and bolt face .

Ok almost simultaneously the firing pin strikes the primer , case moves forward and pressure starts to build expanding the case sealing the chamber and the case actually grabs the chamber walls and is stuck in place until the pressure drops . Well what happens to that gap between the case head and bolt face because the case is stuck to the chamber walls and can't move rearward . As the pressure builds , at some point the pressure gets high enough to actually stretch the case at the web ( section of the case above the head ) and the head of the case is forced back against the bolt face . When that stretching accrues it is actually thinning the case wall at the web each time the case is fired and resized to short for the chamber . As you can see with the picture above it only took 3 sizing and firing cycles to stretch the web so thin the case failed ( NOT GOOD ) .

In a bolt gun properly sized cases can be reloaded 10 , 20 and even 40 times . In semi auto's you may not get as many as a bolt gun but if you size your cases correctly you should get 6 to 10 reloads and if you anneal maybe many more . OK so what is the "correct" size to size a case ? I don't know , I just made all that crap up , lol just kidding .

In bolt guns you want to size your cases .001 to .002 shorter from head to datum then your fire formed cases from the same rifle they will be fired in . For semi autos you want to FULL LENGTH size your case .003 to .004 shorter then your fire formed cases from same rifle .

OK so size your cases correctly , trim every time at first and use the bullet manufactures recommended COAL and you should be gtg . My point here is just get some good safe loads down range and then start thinking about advanced techniques like playing with seating depths although with the cartridge you are starting with you will likely be stuck with mag length .

Haha!! Die Hard is one of my absolute favorite movies of all time!

But wow, thank you for your time on explaining this process to me! I knew rifle was so much more precise on COAL, and how important head space is. It’s fairly intimidating actually. I got some series homework to do, but your post gives me a really good start on the scope of this.
What’s a good way of actually seeing if my rounds are chambered properly? I guess my goal is to mimic factory rounds so it’s safe to shoot my reloads through any 300 Blackout, as opposed to being rifle specific. I’m not looking to make precision ammo. Just cost efficient rounds that are accurate enough for plinking and running through an AR..or multiple AR’s.

 

[Cemetery21]

If you are loading a bullet and can't find the OAL for that bullet in a manual, here is a method that worked for me when I first started loading Blackout. It gets you the correct OAL for that bullet for feeding purposes. Optimal OAL for accuracy is another question, but may not matter much in a Blackout - it isn't a benchrest cartridge.

Measure the diameter of a 30 cal. bullet and place a mark at the .250" diameter. Inside of a 223 magazine, there is a "bump" about 1/2" from the bullet tip end. That serves to clear the neck of a 223 round. Seat your 30 cal bullet so the .250" mark aligns with that bump. Measure the OAL and record it for that bullet. I've never run into a bullet that was too long for the mag using that method, but if there is one, obviously you would have to seat to fit the mag.

 

[PWC]

COAL is the length from the case head to the tip of the bullet, and is used by bullet/powder mfgrs as a statement of safe seating delth vs pressire. Other than that it only determines whether the cartridge will cycle thru your magazine and action.

Metal god did an excellent job of explaining the process, but he didn't explain a new term he introduced; "datum". Go to the SAAMI website to see what the datum is and where it is located on your cartridge.

Once a case is fire formed to your bolt action chamber, you only need .001-.002 shoulder set back. If you are shooting semi-auto then follow die mfgr's instructions. Your understanding of ogive is correct, and is related to datum.

After you gain experience, you can try annealing cases to lengthen case life.

Sheridan case gauge is xpensive, but will give you the most useful information.

 

[AJC1]

Case forming is not a first time rifle reloading activity IMO. It adds to the things that can go wrong and annealing is part of the process and requires more equipment. Stick to figuring out proper shoulder sizing and getting the tools for measuring. I also use the hornaday tools for bro and btd but Sinclair also has the same tools. Finding or buying 100 pieces to get started with will be easy or cheap until your more comfortable. In the case of having a silencer and shooting heavy subsonic bullets casting bullets may be worth your effort.

 

[Another_Kelley]

One of the forums has a list of which cases are good for forming and which to avoid.

http://www.300blktalk.com/forum/viewtopic.php?f=141&t=88599&sid=823913f846171d0cf3981b544ca8843a