Canalure importance

[RH300UM]

My question is how important is it to seat the bullet to so the brass rim is on the canalure? Also then the use of crimping?
My rifle will be a custom 375 RUM. Using the 300 grain accubonds.

 

[Trnelson]

First, Seat the bullet where you find the best accuracy. If that falls on the cannelure that's where it falls. You can still get a sufficient crimp if it doesn't fall on the cannelure.
As far as crimping, it generally doesn't take much to do the trick and is not usually a necessity. I only lightly crimp ammo (150g Hornady SST) I intend to shoot in my C-308, similar to a PTR-91 or G3, as it has an exceptionally violent resciprocation and has proven to be able to move uncrimped bullets in the magazine. Even that isn't a huge deal, from a safety standpoint, if there is enough powder behind the bullet so that it can't get back into the case. That could be catastrophic. Load the magazine and shoot a few rounds and pull the rest to measure. If they move crimp them as heavily as you have to to hold the bullet in place. If they do not move it's up to you. I have found no NEED to crimp, and do not crimp, anything I build for either of my 30/338 win mag, any of my .30/06 or 6.5/06. YMMV

 

[CatShooter]

My question is how important is it to seat the bullet to so the brass rim is on the canalure? Also then the use of crimping?
My rifle will be a custom 375 RUM. Using the 300 grain accubonds.

No importance at all...

 

[g0rd0]

absolutely no importance. Unless you are loading for a large capacity mag in a platform like an ar I see no reason to crimp.
As stated above adjust your seat depth for accuracy and if you do want a crimp a light crimp anywhere on the bullet is more than enough in bolt action rifles

 

[Lefty7mmstw]

the above mentioned posts are correct that crimping is of no importance... in lesser rifles. I agree with trnelson on this rifle though...
I have a lightweight 375h@h- she weighs 8# scoped and ready to rock. I've never pulled or deep set a bullet with my rifle; that DOESN'T mean you will not. I would try to load without crimping first, but you will need to check for bullet creep after you fire. If the bullet is moving in your mag. rounds, crimp the suckers in the cannelure. I would try your loads at a seating depth compatible with crimping to minimize re-tuning loads if you make the choice to crimp.
You will need to be very careful with trim length if you crimp; any variation will show up as inconsistency in the load.

 

[RH300UM]

the above mentioned posts are correct that crimping is of no importance... in lesser rifles. I agree with trnelson on this rifle though...
I have a lightweight 375h@h- she weighs 8# scoped and ready to rock. I've never pulled or deep set a bullet with my rifle; that DOESN'T mean you will not. I would try to load without crimping first, but you will need to check for bullet creep after you fire. If the bullet is moving in your mag. rounds, crimp the suckers in the cannelure. I would try your loads at a seating depth compatible with crimping to minimize re-tuning loads if you make the choice to crimp.
You will need to be very careful with trim length if you crimp; any variation will show up as inconsistency in the load.

Understood
But the reamer is already being made otherwise to the 3.80 coal
I will move ahead. Might have to change

 

[HARPERC]

If there is a weakness in your ammo, a .375 RUM will find it. I've seen the H&H batter rounds loose.

Generally I agree with likely don't need a crimp, but qualify it with if you have a good friction fit. I think given as you are taking on a professional role, the rifle and rounds may see a lifetimes use in a season, it changes my thinking a bit.

Expander balls aren't created equal, the bushings I haven't messed with much, but would seem a size change would tighten fit.

Some trial and error may be necessary.

There are cannelure tools, that will put a cannelure where you want it. That opens the conversation how much effect you have on the bullet.

Maybe this is a case of having loads for long range, and another for in the magazine.

 

[J E Custom]

My question is how important is it to seat the bullet to so the brass rim is on the canalure? Also then the use of crimping?
My rifle will be a custom 375 RUM. Using the 300 grain accubonds.

Crimping serves two main purposes. One is to keep heavy projectiles from moving and changing the COAL.

The second reason is that with heavy loads of slower burning powder, it sometimes makes them build more pressure before the bullet starts to move and burn more consistent.

With lighter bullets neck tension is normally enough and crimping may not be necessary.

Sometimes crimping can also lower SD if everything is done correctly.

Is it necessary ? in many cases no. but don't rule it out all together.

J E CUSTOM

 

[mrultramag]

I dont crimp my 375 rum ammo. 260AB @3000 FPS. no issues with bullets migrating in the case due to recoil

 

[J E Custom]

I dont crimp my 375 rum ammo. 260AB @3000 FPS. no issues with bullets migrating in the case due to recoil

Most bullets in 375 and larger calibers have Cannelure's to give you the option of crimping or not. some don't, but they are typically for single shot or target use. If you use a bullet that has no cannelure you should not try to crimp them and you should set your dies accordingly of you can damage the bullets.

It is common not to have to crimp in many situations. When hunting dangerous game it is recommended because it eliminates another potential problem.

When bullet weights start in the 350 grain and go beyond 500 grains it becomes more important in Most situations. It also becomes beneficial in helping huge cases full of slow burning powder to get more consistent ignition start.

As stated earlier, recoil can become an issue and crimping can eliminate bullet movement in the magazine during firing of other rounds.

Some cartridge/powder/bullet combinations can benefit from crimping when SDs are important.
I have a 416 that simply crimping the same 400grain load improved the SDs from 11 to 3 and shot a .034 100 yard group. so it definitely didn't hurt. I also have several large bore pistols that crimping helps the accuracy in addition to keeping the bullet in place.

These examples are the reason I don't ever rule out crimping. It can be beneficial depending on the use and needs.

J E CUSTOM

 

[Pdvdh]

What JE said.
I don't think the 300gr Accubond has a cannelure, does it?

I doubt the crimp would be required to keep your bullets from moving under recoil. Just don't lube your case necks with any lubricant. But test for bullet movement under recoil by leaving the same cartridges in the mag during several firings.

If my bullets had a cannelure I would use it and crimp with the RUM. Won't hurt a thing. Will remove worry of bullets shifting in shells in the mag, and might even improve ES/SD, and accuracy.

I've never seen bullets move in my 375 Weatherby, and it's a Sako Lightweight version that kicked like a mule. And I've never crimped my bullets for that rifle. Until I put a brake on it, I would only shoot it if my life depended on it - due to recoil. Would give a guy a headache, and I don't see how that could be healthy!

 

[RH300UM]

What JE said.
I don't think the 300gr Accubond has a cannelure, does it?

Yes they do

 

[Pdvdh]

Yes they do

Then I'd crimp the loads carried in the mag, when the gun is in use for backup on bear.

If you want to toy with another seating depth to eek out the utmost accuracy for your own personal use and enjoyment, that option is always there.

Nosler likely places the cannelure on this bullet knowing it may be used for dangerous game, and that some will desire a crimp for peace of mind.

 

[HARPERC]

....... .Sako Lightweight version that kicked like a mule. And I've never crimped my bullets for that rifle. Until I put a brake on it, I would only shoot it if my life depended on it - due to recoil. Would give a guy a headache, and I don't see how that could be healthy!

Vicious little brutes...a friend has one, and it was generally a one and done type of thing. Magazine never saw much use.