How much neck tension does Crimping create

[Magwa]

Ok so I am puting the final touches on the LR6.5 CM and that is the load but I am not sure how much neck tension and or pressure Crimping causes Learn me up!

[sketch]

I've only crimped one time on some 223. And it was the most accurate round I ever made. I followed the instructions with the die set, that's all I know. Does it create more pressure (cfm) I don't think so? I believe that is generally the powder load. But I can see there being a small,  if any changes in ignition. Once the prjo starts moving forward all give in brass should be normal. My thoughts on crimp was to prevent bullet movement from full auto percussion in the mag.  Used for mill surp. It does not hurt but it's another step when steps count. I wish I had more time to reload.

[Magwa]

7 hours ago, sketch said:

I've only crimped one time on some 223. And it was the most accurate round I ever made. I followed the instructions with the die set, that's all I know. Does it create more pressure (cfm) I don't think so? I believe that is generally the powder load. But I can see there being a small,  if any changes in ignition. Once the prjo starts moving forward all give in brass should be normal. My thoughts on crimp was to prevent bullet movement from full auto percussion in the mag.  Used for mill surp. It does not hurt but it's another step when steps count. I wish I had more time to reload.

I think I agree with you all military loads are crimped, I just need to make sure i am not pushing my bullets into the case while firing that would ruin accuracy . thank my man.. how you doing? about ready to leave that state ?

[dpete]

A Lee factory crimp die is your friend.  It is the last stage of the press for every load I do.  Set it so it leaves a very slight ring around the mouth of the case.  Just that you can barely see it.

[Magwa]

19 hours ago, dpete said:

A Lee factory crimp die is your friend.  It is the last stage of the press for every load I do.  Set it so it leaves a very slight ring around the mouth of the case.  Just that you can barely see it.

Yep agree got one and I have a good Idea of how much to crimp was just wondering how much a difference in neck tension there would be guess i will find out :)

[Albroswift]

Agree on the Lee die

My opinion neck tension from properly sized fresh brass is 99% of the equation and crimp is the final 1%. Crimping can and will reduce neck tension, replacing it with, in my opinion, a less desirable and weaker hold. Any crimp that pushes down on the edge to create a roll falls into this category. Lee uses a collet that does not move in relation to the case when crimping, so huge improvement but don't want to overdo it. Any more then absolutely necessary, even with the Lee, is not your friend. One thing that factors into this is bullet is not as springy as brass, so bullet squishes, (Technical term) brass springs back bullet doesn't.  Just my $0.02, taken apart a lot of loads over the years.

 

[98Z5V]

^^^  That does happen, and you'll see the ring on the projo when you pull loads.  Pulled projectiles, for me, turn into training rounds, when I reload/reuse the projos. 

So, neck tension.  IMHO, that's a bolt gun term, not a gas gun term.  PRS guys and benchrest competitors are into the "proper amount of neck tension" for their loads, but those guys are running bolt guns.  They're not "measuring neck tension" in any kind of "measurement" way - they're using a bushing to downsize the mouth of the brass by the thou - until they like their group size, and chrono numbers.  There are true methods for measuring neck tension, in real numbers, but that's some labratory-grade equipment to be able to translate the chamber pressures into numbers that you can compare.

 

Again, IMHO, I wouldn't worry about a number, or spiking a pressure on a loaded round - just crimp them until you like the crimp, and test the loads.  All the increased pressure you're going to see, based on the amount of crimp that you apply - will show in the brass you're shooting for testing those loads.

I'll get some comparison pics in here today of uncrimped loads vs. what I like for my proper crimp, with the Lee Factory Crimp Die.

[98Z5V]

Alright, grab the popcorn...  

Crimping 101.  These are old pics, because I intended to do this post a long time ago.  The info is pertinent, and I've been slacking for way too long.  These are from early December, loading up some 6 ARC.

ALL of this data is only useful if your brass is trimmed to the same length.  ONLY.  If your brass is shorter, you'll have less of a crimp.  If your brass is longer, it will give you more of a crimp.  With that, your load performance will vary, rounds will be all over due to slightly different pressures, and you hate yourself when you can't or don't figure it out - brass that's the exact same length is the key to running a batch of loaded ammo through your crimp die.  If your brass isn't the same length, you're just pissing into the wind making test rounds...  Okay, now that the Public Service Announcement is out of the way, let's look at it...

Here's the 6 ARC Lee Factory Crimp Die just making contact with the brass case.  This is how far it's open, which is standard, just what it looks like.  It's just barely screwed down to touch the brass...

 

Now, here's where I have it set to, what I like to crimp to in order to run loaded rounds through a gas gun.  This is dialed down to where I like it, and the ram handle is all the way down - this is the crimp I like, with these dies - almost touching, not quite, just enough to prevent bullet setback, every single time:

 

Here's that crimped round, from above, compared to an uncrimped round:

 

Here's a little closer view - notice that there are no 4-corner marks from the Lee Factory Crimp Die - I'll have an example of "too much crimp" in a second.  This is just a better view of those same two rounds above:

 

Now, here's that round on the left above (uncrimped) after I crimped it, and set it back beside the round on the right that was already crimped:

 

NOW...  we have a 3rd round - far right in the pic.  IMHO, this is too much crimp.  You can see that it's pressed in there pretty far, and this would deform the projectile's copper jacket, if you pulled it and looked at it. 

 

Now, what effect would that have on the loaded ammo?  Too much crimp WILL change your chamber pressure, very slightly.  It's not anywhere close enough to blow up your gun, or anything that serious.  BUT - that round above that's crimped tighter than the rest - it's gonna have a higher chamber pressure, and it's gonna fly somewhere else on the intended target.  It's gonna be "that flier" in your group that you were shooting.  It doesn't mean you're gonna blow your gun up, and it doesn't mean that your loads suck.  It just has a different crimp on it, it's tighter, and it's gonna have a different (higher) chamber pressure, and you'd see a higher velocity from it if it was going through a chronograph. And, it's gonna land on that load-development zero target in a different place.  That one is one of your "fliers."

#1 reason that you'll think your loads suck, even when you're doing everything "right?" - you didn't trim your brass to the same length, and when you crimped those loads, they all got a different crimp.  Of course they're gonna be all over, and not give you tight groups... 

Glad I found these pics.

Thus Endeth the Crimping Sermon... 

Edited April 23, 2023 by 98Z5V

[Magwa]

On 4/23/2023 at 3:14 PM, 98Z5V said:

Alright, grab the popcorn...  

Crimping 101.  These are old pics, because I intended to do this post a long time ago.  The info is pertinent, and I've been slacking for way too long.  These are from early December, loading up some 6 ARC.

ALL of this data is only useful if your brass is trimmed to the same length.  ONLY.  If your brass is shorter, you'll have less of a crimp.  If your brass is longer, it will give you more of a crimp.  With that, your load performance will vary, rounds will be all over due to slightly different pressures, and you hate yourself when you can't or don't figure it out - brass that's the exact same length is the key to running a batch of loaded ammo through your crimp die.  If your brass isn't the same length, you're just pissing into the wind making test rounds...  Okay, now that the Public Service Announcement is out of the way, let's look at it...

Here's the 6 ARC Lee Factory Crimp Die just making contact with the brass case.  This is how far it's open, which is standard, just what it looks like.  It's just barely screwed down to touch the brass...

 

Now, here's where I have it set to, what I like to crimp to in order to run loaded rounds through a gas gun.  This is dialed down to where I like it, and the ram handle is all the way down - this is the crimp I like, with these dies - almost touching, not quite, just enough to prevent bullet setback, every single time:

 

Here's that crimped round, from above, compared to an uncrimped round:

 

Here's a little closer view - notice that there are no 4-corner marks from the Lee Factory Crimp Die - I'll have an example of "too much crimp" in a second.  This is just a better view of those same two rounds above:

 

Now, here's that round on the left above (uncrimped) after I crimped it, and set it back beside the round on the right that was already crimped:

 

NOW...  we have a 3rd round - far right in the pic.  IMHO, this is too much crimp.  You can see that it's pressed in there pretty far, and this would deform the projectile's copper jacket, if you pulled it and looked at it. 

 

Now, what effect would that have on the loaded ammo?  Too much crimp WILL change your chamber pressure, very slightly.  It's not anywhere close enough to blow up your gun, or anything that serious.  BUT - that round above that's crimped tighter than the rest - it's gonna have a higher chamber pressure, and it's gonna fly somewhere else on the intended target.  It's gonna be "that flier" in your group that you were shooting.  It doesn't mean you're gonna blow your gun up, and it doesn't mean that your loads suck.  It just has a different crimp on it, it's tighter, and it's gonna have a different (higher) chamber pressure, and you'd see a higher velocity from it if it was going through a chronograph. And, it's gonna land on that load-development zero target in a different place.  That one is one of your "fliers."

#1 reason that you'll think your loads suck, even when you're doing everything "right?" - you didn't trim your brass to the same length, and when you crimped those loads, they all got a different crimp.  Of course they're gonna be all over, and not give you tight groups... 

Glad I found these pics.

Thus Endeth the Crimping Sermon... 

Freeking awesome sermon Brother Tom the pics make the words just jump into my heart! Amen! I totally get it comparing Bolt to semi I use a 2 thou mandrel to set my neck tension on the 6.5 284 and check everything through the chrono I will set a crimp that will be just enough to hold the bullet in place and then chrono them and adjust my load to get a good SD that should get me accuracy.. ok off to the loading room thank you everyone and Brother Tom see you on Sunday!.... 🙂

[98Z5V]

That 6.5 284 is a badass gun.  I hope I just didn't help you make a gas gun that's as good as that one.  Fuk me... 

[Magwa]

10 hours ago, 98Z5V said:

That 6.5 284 is a badass gun.  I hope I just didn't help you make a gas gun that's as good as that one.  Fuk me... 

ha ha ha That gun is a fun one to shoot I am in 4th position in the Gong shoots with two more weekends to go  and she is really shooting well I intend to get every ounce I can out of the 6.5 Creedmoor... AND I just bought a new can for the 6.5 x284 a Dead Air Nomad TI Titanium just weighs 9 OZ. 

[Cliff R]

The main purpose of crimping is to keep the projectile in place during cycling and firing.  In a bolt gun (unless you are single loading) a slight crimp on the load insures that the remaining bullets in the loads in the magazine don't move forward.  I've seen this happen, especially on hard hitting/heavy recoil calibers.  I'd also add here that this problem becomes more of a possibility as you "work" your brass with mulitple reloading operations expanding, stretching, thinning and weakening it.

Another purpose of the crimp is to keep the bullets in the tube magazine from pushing the seated bullets DEEPER into the cases during loading and once again under heavy recoil.  I've seen this happen with "high performance" 45/70 home grown loads in my Marlin 1895 rifles, for example.  

For auto loading rifles we need the crimp for obvious reasons like when the bolt slams home or quick cycling/rapid fire or full auto fire.  The LAST thing you want to happen is for a bullet to come loose during those events/processes.  

As far as accuracy one way vs the other I wouldn't have a clue but have never really done any testing in that area. I have done some testing with bullet distance to the rifle lands in the barrel for how far they have to "jump" to get there.  Most of that was with 22/250 and my bolt action .223 Remington 700BDL bull barrel rifle.  Once again one should use some caution there as some small light bullets don't have a lot of engagement left in the cases when you start moving them out to get close to the rifling.  You are also more times than not limited to how long you can make them due to restrictions in the magazine. 

For hunting rounds and this might help Magwa out a bit, if this weapon is being used for big game hunting I'd do a decent crimp on it and stay within recommended overall length for the round.  Any slight reduction in accuracy or potential higher pressure would be a LOT less of a concern vs leaving one too loose and have a weapon malfunction when you are miles from camp and have spent many hours working your way on a big bull Elk for a good shot.

IF you are using old style bullet seating/crimping dies one must make absolutely sure that you establish the crimp at the bottom of the stroke of the handle and NOT before.  If your crimp die isn't adjusted correctly you can deform the case and it's NOT going to be a happy day at the range when that round is slammed into the chamber.......hope this helps some........

Edited April 30, 2023 by Cliff R

[98Z5V]

3 hours ago, Cliff R said:

The main purpose of crimping is to keep the projectile in place during cycling and firing.

Yep, perfect explanation.  

3 hours ago, Cliff R said:

Another purpose of the crimp is to keep the bullets in the tube magazine from pushing the seated bullets DEEPER into the cases during loading and once again under heavy recoil.  I've seen this happen with "high performance" 45/70 home grown loads in my Marlin 1895 rifles, for example.  

As soon as I read your first sentence in this one, I thought of my 45/70 with the 405gr projectiles - I put a heavier crimp on those, and there's a crimp groove on those projectiles, just for that purpose.  I crimp the brass right into that groove (with a Lee Factory Crimp Die), and there's no way those projectiles are going to move, until firing.  Great points, Cliff.  I'll try to find some pics of my 45/70 loads and crimps, and get them in here.

[Cliff R]

I use close to 60 grains of Reloader 7 to push 300 grain bullets thru my 45/70's.  They go across the chromy at 2400fps.  They can be very hard on the shooter, and pretty hard on the remaining loads in the magazine tube, so a very tight crimp is not optional.   Don't even bother to wear glasses or a hat sighting it in, they will be on the ground after you touch a round off anyhow!

Couple of years ago I used a metal rifle rest to make sure the Marlin 1895 was ready for our deer hunting season.  The idea was to save my shoulder a little punishment.  I touched off a couple of rounds and went to pick the rifle up and the stock was split nearly into two pieces....oops!

I was on the list for a new one for couple of years and finally found a pretty nice used one on Ebay.  I repaired the original stock by drilling, pinning and gluing it, you really can't see the repair unless you are looking for it.  I decided to just leave it in place and save the new one for the next time pull a STOOPID move like that!.....

[98Z5V]

4 hours ago, Cliff R said:

I use close to 60 grains of Reloader 7 to push 300 grain bullets thru my 45/70's. 

I'm at 50.0 grains of IMR 3031 for my 405gr projectiles.  It kicks like a pissed off mule.  One reference listed 55.00 grains as the max for that load.  No way am I taking this load up any further...  

[Cliff R]

That would be PLENTY.  After trying several powders for 45/70 I settled on Reloader 7.  The chrony tells me it's very efficient in that caliber and I've never observed any signs of excess pressure even with a full charge of it.  In the B-78 and Ruger #1's you can use 60 grains of it w/o issue with the 300grain bullets.   Probably a good idea to back off a bit for the Marlin 1895's but they are still very strong rifles.

If you ever want a lesson in recoil put a full charge of Reloader 7 behind a 500 grain bullet in a Ruger #1.  A friend handed me his Ruger #1 back at a range in the late 1980's and I fired it ONCE......and it still hurts!.........

 

[Magwa]

when I hunted bears full time I carried a ruger Number 3 in 4570 and shot 405 grain bullets behind 49 grains of 3031 IMR that little fuker would kick the crap out of you but it was hell on bears in thick cover , but the worst beating i ever took at the hands of a gun was a win,458 Mag with 500 grain round nose I fired it offhand ONCE... I thought I had lost a tooth fuk that!

[98Z5V]

16 hours ago, Cliff R said:

That would be PLENTY.  After trying several powders for 45/70 I settled on Reloader 7. 

I've learned alot over the past 20 years-ish, playing with gas guns and reloads.  And other guns.

Rule #1. 30 Carbine powders are commonly used for modern 300 BLK loads.  Use 30 Carbine powder references if your 300 BLK loads suck.  Think outside the box.

Rule #2.  There are 3 different 45-70 load patterns, and you need to know what gun you have before you blindly pick a referenced load, and load it up.  There are Trap Door Loads, Ruger #1 Loads, and "Modern 45-70 Loads" - which cover all the Marlin 1895 guns, and the like models of Modern Lever.  Traps door loads will SUCK in your 1895.  Ruger #1 Loads will blow your 1895 UP, if you like "hot loads" and used Ruger #1 info.  Pay attention to the reference for your 45-70 - and make sure you're using a reference for the gun YOU have...  

Rule #3.  Alot of 45-70 powders are also GREAT 300 BLK powders, for modern 300 BLK loads.  Use 45-70 powder references if your 300 BLK loads sucks.  Again, Think outside the box.

Rule #4.  Don't blow up your 300 BLK gas gun, just from something I stated here.  Do THE RESEARCH on it.  It all works, at the appropriate load levels. 

Edited May 2, 2023 by 98Z5V

[98Z5V]

I use RL-7 for my 25/45 loads, with Sierra 90gr Game Kings.  Have it on-hand.  I'll look into that one, too...  

[Cliff R]

You'll love Reloader 7 in 45/70.  If nothing else it measures about 8000 times easier that IMR 3031!.....

Sadly I've replaced most of my older rifles (hunting) with modern black rifles.  My go to rifle these days is my 450 Bushmaster.  DEADLY one hole accuracy, don't have to reload for it, and if you miss something out to 250 yards without holding over you just should have stayed at your day job instead of hunting.......LOL.....

 

 

Edited May 4, 2023 by Cliff R