To Crimp Or Not To Crimp, That Is The Question?

[fourfive8]

I figured that was the case- no problem,
After extreme set back, the bullet is so loose it can “rattle” back and forth in the neck. This is especially true if neck tension is loosened to begin with during the roll crimping process.

 

[CBH Australia]

This guy has a done a bit of testing around crimping and has posted a lot of stuff on another forum or 2 .

 

[steve white]

"to crimp or not to crimp" says the OP
--if the magazine is somewhat short for the cartridge, crimp.
--if the cartridge is a heavy recoiler, crimp
--if the cartridge neck is short by design, crimp
--if standard resizing doesn't seem to hold, crimp
--if you are OCD, crimp
--excess ES, try crimping
Plus 1 on the Lee FCD

 

[Wyatt Smith]

I’ll ad any cartridge to be used in tubular magazine to the always crimp list.

 

[Nevada Mike]

I notice that the ES for the crimped rounds in the OP’s post is much less (9 fps) than the uncrimped rounds. This suggests to me that a bit of tweaking may be in order.

 

[Woodcarver]

I notice that the ES for the crimped rounds in the OP’s post is much less (9 fps) than the uncrimped rounds. This suggests to me that a bit of tweaking may be in order.

That's something I have experienced as well; crimping reduces the ES consistently. What is very possible, and others have mentioned, the higher velocity of the OP's crimped rounds might be just over the velocity his rifle, with that bullet, likes. As pointed out, 3 rounds isn't statistically relevant, but it might be an indicator of what to aim for, velocity wise.
I'm another who uses the LFCD on everything I load for that Lee makes a LFCD for.

 

[Rare Breed]

I notice that the ES for the crimped rounds in the OP’s post is much less (9 fps) than the uncrimped rounds. This suggests to me that a bit of tweaking may be in order.

just curious. i have found no need to crimp in big bore DRs. yet in bolt actions i do since they run against each other…to me i know this is a no da… just curious if people think crimp needed in 450-400 and up in DRs? again i do not and never any problems whatsoever

 

[Shooter375]

I'm interested to see if anyone else has performed a similar test to mine. If so please post the results. I repeated this test yesterday and had similar results. Although this time I used Varget powder instead of RL-15 because my RL-15 supply is nearly gone. I also did not run these rounds over the chronograph so I don't have velocities only targets. I shot the none crimped rounds first. Then shot the crimped rounds second after letting the barrel cool. The results were similar. 0.897" (0.816 MOA) for none crimped round group. 2.249" (2.046 MOA) for the crimped round group. Please run this test or similar test with your own rifle and rounds so we can get more data.

 

[TucsonFX4]

The load you developed…was that a crimped load or uncrimped? My questions is, are you trying to turn a non-crimped load into a crimped load or vice versa. If it was originally a non-crimped load, changing to crimps may not result in a better load. Whereas if you develop a crimped load from scratch, you may end with a better load. That load may be equally unimpressive if you then shoot it without crimping.

 

[Frederik]

Sorry for this responce but I test loads all my rounds untill they are accurate on my 375 and all of them are crimped.

Could it be that you case preparation is done different do you anneal the brass?
That might give you the big difference hard vs soft brass you could even expereiment with that?

Next thing you know hunters will not be able to kill buffalo as the round was not crimped.

Sorry been reading the Lion hunt thread.

 

[Troubleshooter]

just curious. i have found no need to crimp in big bore DRs. yet in bolt actions i do since they run against each other…to me i know this is a no da… just curious if people think crimp needed in 450-400 and up in DRs? again i do not and never any problems whatsoever

The only source I can recall which specifically calls for a crimp on the .450/400 NE is the Hornady reloading manual, which states that "When loading the 450/400 3"it is important to crimp the case mouth tightly on the cannelure as this will aid in ignition and help provide consistent performance."

I don't think that Lee makes a FCD for that cartridge, however.

 

[fourfive8]

I'm interested to see if anyone else has performed a similar test to mine. If so please post the results. I repeated this test yesterday and had similar results. Although this time I used Varget powder instead of RL-15 because my RL-15 supply is nearly gone. I also did not run these rounds over the chronograph so I don't have velocities only targets. I shot the none crimped rounds first. Then shot the crimped rounds second after letting the barrel cool. The results were similar. 0.897" (0.816 MOA) for none crimped round group. 2.249" (2.046 MOA) for the crimped round group. Please run this test or similar test with your own rifle and rounds so we can get more data.View attachment 576985View attachment 576986

That’s quite a lot of difference. I always trim cases to same length. I lightly and carefully chamfer inside and outside mouth after trimming. I do not use the de-priming/neck expander plug in the sizing die. I remove that stem and only use the die for resizing. I resize then use a separate neck expander die. I do not use the crimping shoulder in the bullet seating die by turning the seater die out a turn or two so the crimping shoulder cannot contact the mouth. I only use a Lee FCD for crimping. I do not attempt to crimp on bullet shank if there is no cannelure or crimp groove. I use the FCD as last step in reloading process. I have not noticed significant difference between crimped and non-crimped for - POI, group size, SD of velocity or mean of velocity.

 

[Joker12]

The only source I can recall which specifically calls for a crimp on the .450/400 NE is the Hornady reloading manual, which states that "When loading the 450/400 3"it is important to crimp the case mouth tightly on the cannelure as this will aid in ignition and help provide consistent performance."

I don't think that Lee makes a FCD for that cartridge, however.

Lee used to make custom FCDs on order. I had them make one for a 264wm on special order. I'm not sure if they still offer that service but its certainly worth a phone call to their customer service.

 

[PHOENIX PHIL]

Lee used to make custom FCDs on order. I had them make one for a 264wm on special order. I'm not sure if they still offer that service but its certainly worth a phone call to their customer service.

They still did just a couple years back. I had one made for my .470NE double.

 

[benchracer]

The operative question is NOT To Crimp Or Not To Crimp. The operative question is: How do you intend to use the rifle/ammunition? Half MOA groups are nice, but are not necessary for anything normally hunted with a 375 H&H. Conversely, 1.25 MOA, or even 2 MOA groups are perfectly adequate, for any game you are going to hunt with a 375 H&H, out to 300 yards. If Dangerous Game of any kind is on the menu, RELIABILITY should rightly be the #1 priority. If you can tweak your crimp technique or tweak your load AND improve your accuracy, that would be a bonus.

If Dangerous Game is NOT on the menu, there is a part B to the question: Do I actually have a problem with bullet setback for rounds loaded in the magazine? On non-Dangerous Game, the stakes are much lower. You can afford to prioritize accuracy over reliability to some degree, if doing so makes you feel better.

 

[fourfive8]

Common and interesting theme of discussion on many reloading forums. Having some spare time yesterday I dug back through years of my reloading data for multiple cartridges trying to get a sense for any crimp vs accuracy correlation. Generally, my data is both sketchy and skewed because so many cartridges, for proper function, absolutely require a crimp while some require only a specific kind of crimp with others requiring no crimp at all.

The only correlation between crimp and accuracy I noticed was within the “intermediate and smaller” caliber group of cartridges. For regular stacked magazine, jacketed bullet loads in bolt action rifles, I could not detect any difference in accuracy in either the 416 Rem Mag or the 450 Watts between crimped and uncrimped, all other things equal. I detected a small correlation in the 338-06, 35 Whelen AI and 375 HH with a very small loss of accuracy showing in the crimped group. This data tends to agree with that presented by the OP, but to a lesser degree. This correlation I would call marginally statistically significant. I could detect a slightly larger loss of accuracy crimping the 260 Rem and 270 Win and would say this correlation to be statistically significant. I never tried crimping bolt action ammo in calibers smaller than 260 Rem so have no data. All 223 ammo was crimped because of the requirement given its semi-auto use.

IMO, the correlation between crimping and accuracy suggests it may be caliber dependent. And, the priority for absolute function and reliability in the larger, DG calibers overrides all but the most negative affects on accuracy crimping may have.