Hammer Bullets - Neck Tension and Crimping

[JPatzig]

I've seen consistent feedback that Hammer bullets shoot better groups and have lower SD in speeds with "more" neck tension (typically .004"). Has anyone tested different neck tensions (.004, .003, .002, .001) and seen different results? Or have people generally seen that more is better across the board? I know I can just test for myself, but thought I ask before I buy mandrel sets and expend reloading supplies.

For crimping, I've seen mixed messages on crimping the "peak" vs. the "valley" of the bands. I feel like crimping on the peak actually applies pressure/tension, where crimping into a valley wouldn't actually do much if anything. Am I wrong?

 

[GLTaylor]

Neck tension of .003-.004 seems better.
I've tested down to .002 - which was my "normal" prior to Hammers (in a hunting rifle).
Crimping on a groove between PDR bands seems to do better than on top of a band. That way the bullet has to overcome the swell in the PDR band before being released.
Note that some do not crimp at all and still get excellent accuracy.

 

[K.E.C.]

Neck tension of .003-.004 seems better.
I've tested down to .002 - which was my "normal" prior to Hammers (in a hunting rifle).
Crimping on a groove between PDR bands seems to do better than on top of a band. That way the bullet has to overcome the swell in the PDR band before being released.
Note that some do not crimp at all and still get excellent accuracy.

What He Said. This^^^^^^^^^^^^^^^^^^^^

 

[Elkeater]

I crimp on absolute hammers and tend to not crimp on hammer hunters. I crimp in the groove.

 

[Tiny Tim]

Agree with others, crimping in the groove is more beneficial. Like crimping on the cannelure that many older style bullets had, or like a roll crimp on a revolver cartridge. They were placed there to help hold the bullet during heavy recoil. It provided a better grip in the groove, we just do it for a different reason on the Hammer bullets.

 

[1yotedog]

Recent range work using 92gr AH trying to keep a well worn M70 25-06 going; NT=3, no crimp, best was about 1in at 100yd while same load crimped 1/8 T into the first groove gave 1/2 - 5/8. over several reconfirming tests. Using Staball 6.5, velocity was just over 3400 fps. More crimp opened things back up a bit. Primers were starting to flatten so no effort was made to go faster.

 

[Mike Matteson]

Interesting thinking! I will have to see. with different loads. FOLLOWING.

 

[C-130 Dude]

Neck tension of .003-.004 seems better.
I've tested down to .002 - which was my "normal" prior to Hammers (in a hunting rifle).
Crimping on a groove between PDR bands seems to do better than on top of a band. That way the bullet has to overcome the swell in the PDR band before being released.
Note that some do not crimp at all and still get excellent accuracy.

Careful with that crimping. You can over pressure quick if your loading max charge weights.

 

[QuietTexan]

"more" neck tension (typically .004")

I stopped measuring on my hunting loads. I FL size without the expander button in and seat the bullet. Somewhere between that tight and whatever the case is if I were to pull a bullet after seating would be the "correct" setting, but since the bullet is one solid piece of metal it acts as it's own expander.

Crimping is the same thing - Cup and core bullets you can 100% crush with a Lee FCD, but I've never gotten a die tight enough on a Hammer to cause a problem. Brass in the case seems to displace more after a certain point, but it's not getting any tighter because the bullet doesn't deform. When I do crimp I use the ButterBean method of marking the die to get a good level of consistency, and this is one of few times that I consistently trim brass (full length, not WFT on the shoulder) to keep the crimp die setting consistent.

 

[GLTaylor]

Careful with that crimping. You can over pressure quick if your loading max charge weights.

When crimping, you start with a crimp and use the same crimp as you go up in your charge looking for pressure.
When you find pressure, it is prudent to drop back one full grain (or slightly more) and shoot groups.
If you start with a light crimp (I start with "0" to 1/8th crimp using B'Bean's method) - you typically do not see much change in pressure or velocity as you increase crimp (with Hammers). What you will see is a decided preference in a certain amount of crimp with the same powder charge. Many use crimp amount as the final tuning method (I do). Much like changing bullet seating depth in the old lead bullet days.
As you change crimp amount, you will likely see swings in ES and SD.

 

[KsKevin]

When crimping, you start with a crimp and use the same crimp as you go up in your charge looking for pressure.
When you find pressure, it is prudent to drop back one full grain (or slightly more) and shoot groups.
If you start with a light crimp (I start with "0" to 1/8th crimp using B'Bean's method) - you typically do not see much change in pressure or velocity as you increase crimp (with Hammers). What you will see is a decided preference in a certain amount of crimp with the same powder charge. Many use crimp amount as the final tuning method (I do). Much like changing bullet seating depth in the old lead bullet days.
As you change crimp amount, you will likely see swings in ES and SD.

@GLTaylor - do you also crimp in the trough of the bands (or do you do the peak)? What is the most you've ever adjusted your crimp to and in what increment do you tune (ie…1/8th increments up to 1/2 turn)?

 

[Calvin45]

I don't presently measure or seek to modify neck tension beyond whatever is achieved by running the brass through the full length resizing die (RCBS in this case). In my .257 weatherby that works fine, I use a Lee FDC to crimp the top groove of the 75 hammer hunter. It's as accurate a load as anything else in this rifle.

 

[GLTaylor]

@GLTaylor - do you also crimp in the trough of the bands (or do you do the peak)? What is the most you've ever adjusted your crimp to and in what increment do you tune (ie…1/8th increments up to 1/2 turn)?

Yes, I always crimp in a trough.
When developing a load, I start at "0" (which actually applies a light crimp). When I get my load, I increase crimp settings 1/8" at a time up to 1/2 turn. Somewhere in there, I find a "sweet spot" which I record and use going forward.
Note that several of my rifles (most?) are wildcats. Some I don't have Lee crimp dies for - and probably won't. I've had a friend modify some to work with my wildcats. Others use a standard cartridge die that works with the wildcat.
You don't Have to crimp. I just prefer it with Hammers. Many get excellent accuracy without crimping.
My accuracy standard is 0.5". I get it with and without the FCD. It's just easier with the FCD and faster. Jm2cw

 

[cbuck516]

I didn't used to crimp until I had a hammer bullet get stuck in the freebore of my rifle on a late season elk hunt. The cartridge neck has less grip on a hammer bullet than a bullet without grooves so it is way easier for the bullet to pull out. This may be less of a risk with a cartridge that doesn't have any freebore, but since hammer bullets are generally 0.0005" larger than nominal bullet diameter (i.e. when you order a 0.308" bullet it is actually 0.3085"), I think getting a bullet frozen or jammed in your freebore is a very valid concern. The crimp is cheap insurance to help keep that bullet in the case neck until you pull the trigger. Also, this is another good reason to use more neck tension with a hammer bullet. I currently use a mandrel that is 0.0035" smaller than nominal bullet diameter on hammers.
I have crimped every load since that incident last year and hope that I don't have the same experience on my two upcoming late season elk hunts. I'm also taking some extra steps on this trip to keep moisture out of my action during whiteout storms so hopefully that also helps.