Crimp or not to Crimp 300 Blackout on a Dillon XL750

[damon32382]

Loaded plenty of pistol on my XL750. Finally gearing up to load 300 Blackout as my first rifle round. I’ll be loading mostly subsonic to help preserve the brass(lower pressures and I got a Rugged 45 can on the way that’s rated for 300 Subs)

Anyway, I plan on trying either Hornady or RCBS dies with a Lee FCD. (Please let me know if this is a bad choice) 

Not starting a debate, but in other forums/posts that I’ve read, people act like crimp will save the day from bullet setback. After countless hours of researching and messing around with my press, it’s my understanding that preventing bullet setback is neck tension, not crimp on pistol rounds. All crimping does is eliminate flare/belling. 
Wouldn’t this apply to loading rifle as well(aside from flaring/belling, I know you don’t flare the case mouth on a rifle round).  
 

Edited August 30, 2022 by damon32382

[HesedTech]

11 hours ago, damon32382 said:

After countless hours of researching and messing around with my press, it’s my understanding that preventing bullet setback is neck tension, not crimp on pistol rounds. All crimping does is eliminate flare/belling. 

Okay, you are moving from pistol loading to rifle and the crimp issue changes a little. Consistent neck "tension" is about accuracy of the round, while crimping is more about the auto loading function. Although if you do a search, it will be found a slight crimp in rifle rounds seems to improve the accuracy of the ammo also. The bolt shooters have a lot to say about this.

 

You are correct that a poorly fitting, neck too loose, will/can cause set back no matter how much crimp is put on the bullet.

 

In short all my rifle rounds, no matter what caliber, are necked for a consistent tension and crimped slightly. The only caveat is if you are going to be using coated subsonic bullets and then, like pistol, more than a very light crimp removing the bell may damage the coating resulting in leading issues.

 

Like all load development, try various amounts of crimp and see what works best in your gun.

 

Here's an article where a shooter tested crimping:

"Now if we look at the groups, we find that the crimped ammo shot approximately 10% better. "

http://www.accuratereloading.com/crimping.html

[Farmer]

Generally on rifle rounds your sizing die sets your neck tension (sometimes more than needed) and you simply seat your bullet into the case without any neck expansion except for a slight chamfer on the mouth edge. I’ve never loaded rifle on a progressive but can see where starting a bullet could present some difficulty. On the crimp, I have had some rifles get improved accuracy (like an 1” better) to others that didn’t matter. None really got worse by much. Proper neck tension and/or crimp give good ignition and alignment. Poorly done or excessive can be detrimental. 

Edited August 30, 2022 by Farmer

[damon32382]

7 hours ago, HesedTech said:

Okay, you are moving from pistol loading to rifle and the crimp issue changes a little. Consistent neck "tension" is about accuracy of the round, while crimping is more about the auto loading function. Although if you do a search, it will be found a slight crimp in rifle rounds seems to improve the accuracy of the ammo also. The bolt shooters have a lot to say about this.

 

You are correct that a poorly fitting, neck too loose, will/can cause set back no matter how much crimp is put on the bullet.

 

In short all my rifle rounds, no matter what caliber, are necked for a consistent tension and crimped slightly. The only caveat is if you are going to be using coated subsonic bullets and then, like pistol, more than a very light crimp removing the bell may damage the coating resulting in leading issues.

 

Like all load development, try various amounts of crimp and see what works best in your gun.

 

Here's an article where a shooter tested crimping:

"Now if we look at the groups, we find that the crimped ammo shot approximately 10% better. "

http://www.accuratereloading.com/crimping.html

That was seriously some great info sir, thank you very much! Cleared up quite a few questions I had about loading rifle. 

[plinker625]

That article is 30 plus years old.

That is HIS experience with his guns.

It by no means is a definitive answer to the age old question.

 

If you are going to crimp...then do it right with consistent length cases so that the crimp is applied evenly and consistently.  Most of all do it as a separate operation.

 

The 300 BO has such a short neck, and the quality of brass conversion done might be suspect.  So crimping might be a good idea with a Light Taper Crimp vs a roll crimp.

 

Some reloaders over work their brass and thus contend that crimping is necessary to prevent bullet set back during recoil or feeding from a magazine.

These reloaders use poor brass care processes as need for crimping.

 

In my reloading experience loading for Mini 14, M1A, M1 Garand, AR 223, AR 308, HK 91 and 93, FAL crimp has not been necessary....

Is crimping necessary in some applications you bet tube fed lever guns & heavy recoiling bolt guns.

 

Handgun crimping is a must..

 

Edited September 5, 2022 by plinker625

[HesedTech]

23 hours ago, plinker625 said:

That article is 30 plus years old.

That is HIS experience with his guns.

It by no means is a definitive answer to the age old question.

You are correct that many don't crimp for precision rifle shooting, but many do and that is a debate. Similar things, like full length resizing verses fire formed and only neck sizing are debated. The absolute key is a consistent process which works and provides the desired performance.

 

As far as hand guns must crimp, well not true. Removing the bell, especially for coated and plated bullets, is all most of us do for autoloading pistols. The neck tension takes care of the setback and has been discussed in multiple threads here on the forum. As far as wheel guns go, I have no idea because I don't shoot them.

 

Even though that article is old there are multiple newer threads where others have had the same results. I think the reason is because the light crimp seems to even the pressures out. Unless one is willing to make sure all their brass has the same neck size, thickness, bullet seating pressures and such, a light crimp probably helps a little.

 

I know precision rifle people who check brass volumes, mill their necks to a consistent thickness, and literally spend hours verifying a couple hundred rounds for consistency. Of course they shoot some pretty tight groups at 1,000+ yards.

 

It's all about the level of participation we want to put in.

 

**** Clarification ****

 

I have to clarify, after looking at multiple threads across the internet forums on the subject of crimping it occurred to me there might be some confusion about the type of crimping being referred to. As most of us know there are two types, "taper" and "roll." Those showing improved accuracy are using the "taper" crimp. 

Edited September 6, 2022 by HesedTech

[looking4reloadingdeals]

Opposite of what you will be shooting, I load light supers. These lighter bullets are much shorter and I found when I do crimp that it helps prevent set back. However even when using jacketed bullets it isn’t hard to over crimp and if you do can cause more set back issues. 
 

I haven’t loaded 223 in a couple years, but iirc I did not crimp that. So as everyone else said it comes down to your bullet and brass selection. Try a couple different ways out with dummy rounds with only brass and bullets and chamber them a couple times and see what happens

[Farmer]

On 9/6/2022 at 9:28 AM, HesedTech said:

You are correct that many don't crimp for precision rifle shooting, but many do and that is a debate. Similar things, like full length resizing verses fire formed and only neck sizing are debated. The absolute key is a consistent process which works and provides the desired performance.

 

As far as hand guns must crimp, well not true. Removing the bell, especially for coated and plated bullets, is all most of us do for autoloading pistols. The neck tension takes care of the setback and has been discussed in multiple threads here on the forum. As far as wheel guns go, I have no idea because I don't shoot them.

 

Even though that article is old there are multiple newer threads where others have had the same results. I think the reason is because the light crimp seems to even the pressures out. Unless one is willing to make sure all their brass has the same neck size, thickness, bullet seating pressures and such, a light crimp probably helps a little.

 

I know precision rifle people who check brass volumes, mill their necks to a consistent thickness, and literally spend hours verifying a couple hundred rounds for consistency. Of course they shoot some pretty tight groups at 1,000+ yards.

 

It's all about the level of participation we want to put in.

 

**** Clarification ****

 

I have to clarify, after looking at multiple threads across the internet forums on the subject of crimping it occurred to me there might be some confusion about the type of crimping being referred to. As most of us know there are two types, "taper" and "roll." Those showing improved accuracy are using the "taper" crimp. 

There is actually 3 types of crimp for rifle rounds. Taper, roll and collet. The Lee collet crimp die has 4 collet sections that push the brass into the bullet similar to some military rounds. It will allow you to crimp any bullet with or without a cannalure This was the type I used on my friends 30-06 that shrunk the groups. I tried it on other loads and some improved while others were worse so it’s one of those things you just have to try with your combination’s. 

[HesedTech]

7 hours ago, Farmer said:

The Lee collet crimp die

I have one in a 6.5 Creedmoor set. I’ll admit I didn’t consider it a crimp die. I thought it was a neck resizer to use before bullet seating on fire formed brass. 
 

learned something new today. 

[Farmer]

4 hours ago, HesedTech said:

I have one in a 6.5 Creedmoor set. I’ll admit I didn’t consider it a crimp die. I thought it was a neck resizer to use before bullet seating on fire formed brass. 
 

learned something new today. 

I may have worded that wrong. The Lee Factory Crimp Die uses a collet to press the brass into the bullet like this. Whereas the Lee Collet sizing die is just for sizing the brass.  Sorry for the confusion. Pic is in next post due to size. 

[Farmer]

[plinker625]

In certain applications crimping is necessary, but crimping is not a solution to poor neck tension.  That is from work hardened brass.  Annealing may help with that.