I'm relatively new to reloading having just completed my first full hunting season using my own handloads. To date I've had great success loading for my 270, 300 WM, and 470NE. Now I need to work up a load for my 375 H&H. After going to Speer's web site, I noticed that they say in regard to their 375 TBBC data, "We strongly recommend a firm crimp." Well, I've never crimped a bullet that I have made before. What is the process for doing so? FWIW, I use RCBS dies.

I crimp all my big bores...375 and up. Purchase a Lee Factory crimp die thats what I use and they work..

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I noticed that they say in regard to their 375 TBBC data, "We strongly recommend a firm crimp." Well, I've never crimped a bullet that I have made before. What is the process for doing so? FWIW, I use RCBS dies.

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Welllll.....mostly it's BS IMO....I've not found the need to crimp the old .375 in any of my loads and I;d say that you might want to reload as usual and see if you notice any reason to do so.

I've not (yet) found the bullet pushed back into the case from recoil nor any other effect due to not crimping.

However if you decide to crimp, the seating die from RCBS will allow you to do so and I usually do it in two steps but it can also be done in one.
first.....seat the bullet so that the case mouth covers about 2/3rds of the cannelure. The bottom of the seating die must stay away from the shell holder by more than 1/16 inch.....

second.....back off the seating stem and screw the die in with the ram in it's upmost position until you feel the die hitting the top of the case.....IT MUST NOT BE THE SEATING STEM as it must be retracted to not touch the bullet again. Turn the die downward about 1/16 turn and work the ram. Remove the cartridge and visually inspect.....you should notice a little crimp.....move the die downward again and crimp more....repeat until you are getting the crimp you want.

With the seating die lock ring fastened at this location, you may now move the seating stem down to touch the top of the bullet and you're ready to seat bullets and crimp in one operation.....however most folks will prefer to seat and crimp in sepoarate operations.

Vapodog,
In regard to Speer's recommendation of a crimp on a 375, they say, "The H&H case is so nearly straight that a crimp improves ballistic efficiency." Any thoughts on that?

My preference is not to crimp, however, on the larger calibers (heavier recoil)and compressed loads I do crimp them. I guess my starting point is with the 375.

I like to set my dies (and do check them regularly) do not like going back and forth setting them from seating to crimping, etc...That is why I purchased the Lee Factory Crimp Die..along with the advice of others here.

I believe the Lee Factory Crimp Die is a standard offering so it is very cheap (less than $10, if I remember correctly) and ususally available from Midway or others. It is well worth the $10 than to keep adjusting dies and the crimp seems better to me...

jjs,
So after reloading your large caliber bullets in the normal fashion, you go back and run them through your Lee Crimp Die as the last step in your reloading process?

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In regard to Speer's recommendation of a crimp on a 375, they say, "The H&H case is so nearly straight that a crimp improves ballistic efficiency." Any thoughts on that?

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Frankly I don't have a clue what they're talking about.....

Efficiency is generally regarded as an amout of outper per an amount of imput.....I assume they mean velocity as an amount of powder used.

Why does having a straight case have to do with this?

Further it's true that I'm interested in getting a certain velocity and I use a chronoghaph to measure it but I truly don't care about efficiency....as I have no way to measure it without a whole lot of work and suspect that it's just more poppycock.

I've never yet killed anything with ballistic efficiency and doubt that anyone at speer has either. I personally know an engineer there and can assure you that bullshit abounds anywhere people congregate to perform one-up-manship on the other.

I might also ask why wouldn't you crimp the bullet? It's easy to do and you already have the equipment.

The only times I find a need to crimp is loading for a tube fed lever action and loading for a heavy revolver load. However the largest round I have experience with at this time is the .375 H&H as the larger stuff I load are always crimped.....why?...I don't know.....they just are !

Spring,

Exactly....Load as you normally would, then put the Lee Crimp Die in your press (set-up per instructions)...You can crimp a cartridge as fast as you can put them in/out and work the lever on your press.

Also, for your reference Lee will make "custom" crimp dies for most any caliber. I had them make up a 458 Lott and 416 Rigby. Just send a cartridge/bullet seated without powder and primer with $25 check..it will take about 3-4 weeks, however, the 375 H&H is standard die and you can purchase for probably less than $10 from a distributor...Good luck jjs

Hey Spring & Vapodog, I've not loaded a 375H&H in many years and even then it was not for one of my rifles. Just want you to understand I'm not speaking from 1st Hand Experience with them.

In many situations with a "Straight Wall Case"(meaning one with little to no sharp, distinct shoulder) there is a phenomenon that concerns the Ignition and Initial Burn of the Powder that causes the Bullet to begin moving too early for an efficient Burn Rate.

What happens upon Ignition is a Relatively Low-Grade Pressure is created ahead of - the remaining unburned Powder which is acting somewhat as a constantly changing "Solid". That Initial Pressure is enough to initiate forward movement of the rest of the Powder Column and the Bullet it is pushing against.

As this continues, the actual Internal Pressure can not reach it's normal Peak because the remaining Powder is now "effectively" burning in a Larger Chamber(longer). This results in less Peak Pressure and a less efficient burn.

It is easily seen in Straight Wall Revolver/Pistol cartridges using the "slower" powders listed for them and in the 444Mar and 45-70 cartridges. You end up getting very erratic performance and poor grouping.

{It is also possible to see it happening in sharp shouldered cartridges with light weight bullets and very slow burning powders. You can see it by "lower" PRE/CHE and Velocity with "increased" powder Loads.}

Since the 375H&H has a "relatively" small shoulder, there is not much there to prevent a similar thing from happening. Or in any other case with relatively Straight Walls.

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The Firm Crimp keeps the Bullet from easing forward before it should and you therefore get a more consistent Burn Rate and Pressure Curve.

To Crimp or not to Crimp that is the question. Whether to endure the claims and harrows of erratic pressures or by crimping to therby end them.

OK enough of that crap..

There's lots of valid arguements on both sides of the crimping issue. For me there are a couple basic rules. One, never seat and crimp in the same step - it almost always ends up ruining something while setting up. Two if you want to Crimp rifle cases -use the Lee Crimp die. The Lee crimp die forgives many crimping sins and is too good and cheap to not use.
I usually only crimp rifle rounds that don't have good loading density and heavy recoil, and semi-auto rounds (I taper crimp them). With pistol rounds I like to taper crimp automatics and use a heavy roll crimp with the big nasty's like 44 Mag, 480 Ruger and 500 S&W........DJ

Spring,

I crimp my .375Ultra handloads and use the RCBS dies............somewhere on this site there is a test that Saeed conducted on crimping or not and I found it very helpful. I also had a Lee Factory Crimp Die made for my .350RMs and it works great. I'm going to order one for my .375Ultra also.

Joe

Good discussion on crimping; I too like the Lee Crimping die. One thing that was not mentioned was how the bullet in a .375 can "creep" forward with a highly compressed load of IMR4350 (or other slow burning powder). I find a crimp most helpful in this situation, but have not found any significant velocity or pressure advantage when crimping for a bolt action (tube fed rifles or pistol, yes). Like magnum primers, if the powder or bullet manufacturers recommend it, I'd try it and see what the chronograph and target has to say about the results. (My 2 cents.) Mags

I haven't experimented with my 375 yet but when I started reloading 20 years ago I had a lot of problems with accuracy in my 44 Mag revolver. I was a hard core IHMSA (pistol silhouette) shooter so accuracy to 200 meters was very important.
After I bought a chrono I experimented with crimping the loads and saw significant improvements in velocity with standard deviations dropping 30% -50% and significant improvements in group sizes when the case were crimped uniformally.
When I bought my 375 H&H reloading dies (Lymans), I also ordered a Lee crimp die.

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Originally posted by Spring:
I'm relatively new to reloading having just completed my first full hunting season using my own handloads. To date I've had great success loading for my 270, 300 WM, and 470NE. Now I need to work up a load for my 375 H&H. After going to Speer's web site, I noticed that they say in regard to their 375 TBBC data,_ "We strongly recommend a firm crimp."_ Well, I've never crimped a bullet that I have made before. What is the process for doing so? FWIW, I use RCBS dies.

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There are two things I always crimp: revolver ammo and shotgun shells. There are two kinds of ammo I never crimp: ammo for bolt actions, and ammo for single-shots.

There is a big difference between the requirements for revolver ammo and rifle ammo. Revolver ammo needs a crimp if one is using powders like H110, 2400, etc., in order to get uniform burning of the powder. In addition, a heavy crimp on revolver ammo is needed to keep the bullets from backing out of the case under recoil. Neither of these conditions apply to a rifle barrel/chamber system, BUT some have found that their accuracy has improved when they use the Lee factory crimp die after the round is completely reloaded. I have not tried this, so have no basis to judge one way or the other.

I hate crimping but succumb in certain scenarios. Shotshells are obvious, and potent loads for wheelguns too. I shoot a fair number of single shot rifles and find little need for that, even in my one sample of SxS combos, a Capegun, 12 ga x.405. Largest bore rifle I have any experience with is a 45-70 levergun, no crimp required w/ 510 gr PP lead. That one surprised me a bit, but shows you never know until you try. I shoot over a chronograph and only rarely do I see an improvement in ES resulting from crimps, a notable exception being .44 Mag in a rifle w/300 gr PP over Li'l Gun. It helps with that one for sure.

For more modern cartridges I've not seen the need, even with some of Roy's cases to include the .300 WM OTH, I'm usually working with .002 neck tension as a minimum and think that adequate for most circumstance. I think neck tension is the key to a point but am unsure when and why that is no longer valid. Would probably crimp big bore doubles, but only because I'm a pussy sometimes.

I agree with jjs, I use Lee factory crimp die and it's working very fine.
Ciao

I ordered a Lee crimp die last night and look forward to using it. I did notice that many of you felt that a crimp was needed on calibers of about 375 and larger. I have not been crimping my 470NE loads over the past 6 months. I even checked a factory loaded Federal Premium cartridge and did not see a crimp on it. Based upon your experience, would a 470NE also have the need for crimp based upon the "ballistic efficiency" issue needed by a 375?

. . . . that's spelled "bullistic efficiency".

I agree, that unlike straight-walled handgun cartridges using relatively fast powders, the resistance added by crimping does nothing significant for a rifle cartridge. Unless the crimp is needed to secure the bullet from movement (as in some autoloaders or cartridges with extremely short necks) crimping adds nothing and CAN (though not necessarily) diminish accuracy.

If you feel compelled to crimp, by all means take the advice to do it in separate operations, and preferably with a collet-type crimper like the Lee. Seating and crimping in the same die in the same operation unavoidably scars the bullet as the bullet is pressed deeper against the ever-tightening crimp. Despite what Lee's propaganda may indicate, I would never crimp anywhere other than in the cannelure, in other words, leave an uncannellured bullet alone!

Lee's factory crimp die is an excellent tool and makes the best crimps by far. You can control the amount of crimp from light to very heavy depending on what you are doing.

It's around $10 or less and an excellent investment. I use it on alot of my rifle loads now.

Spring,

Not sure about crimping in a Double rifle. You may want to post that question on the Big Bore Forum. Good luck! JJS

If you do decide to crimp, make sure all your cases are exactly the sasme length.

El Deguello has stated the reasons for crimps very well. The "ballistic effeciency" Speer is alluding to is complete and uniform burning of powder. In a straight wall case that usually means a crimp, but there are no hard and fast rules. Experimentation is the key. If I were hunting dangerous game, I would crimp for the safety reason of not wanting to take any chances with bullets being shoved out by recoil, other than that I'd let accuracy be my judge.