Hey Guys, I have my 375 H&H and during load development I did not crimp my loads (260 gr Accubonds & 270gr TSX's) cause I single fed it, and they shot pretty well. So I loaded up a bunch of them for the hunting season (40rds) and went out to the range to double check the gun and they are shooting pretty poorly. I went from a 1" groups to 2.5" scattered groups. All rings & bases are tight as well. If the crimp is too tight, does it cause this to happen?? I don't normally crimp anything unless it's tube fed, but had been suggested to crimp the H&H. I thought to just pull the remaining bullets and neck size them and remove the crimp?? Any idea's are appreciated. BTW I crimp in a separate step using a Lee factory crimp die.
Too Heavy of crimp = Bad groups??
- Thread starter DIGGER2
- Start date
- Location
- Montreal, Quebec
Yes, over crimping will affect accuracy.
I too use the Lee factory crimp dies for various calibers. Less is best.
You just want to "snug" the neck around the bullet to provide consistency in the loads. Heavy crimping will increase pressures in the rifle which will open up your grouping as you have seen for yourself.
Plinking ammo, I don't crimp.
Semi-auto ammo, I always crimp.
Hunting ammo, I always crimp.
You are often prone to over crimp as we want to "see" the neck biting into the bullet. A slight crimp you will be able to feel with your fingernail. It doesn't look like much, but it is doing the job.
Try a light crimp, then disassemble the cartridge, you will see a ring around the bullet proving that the crimp did indeed marry the case neck to the bullet.
I too use the Lee factory crimp dies for various calibers. Less is best.
You just want to "snug" the neck around the bullet to provide consistency in the loads. Heavy crimping will increase pressures in the rifle which will open up your grouping as you have seen for yourself.
Plinking ammo, I don't crimp.
Semi-auto ammo, I always crimp.
Hunting ammo, I always crimp.
You are often prone to over crimp as we want to "see" the neck biting into the bullet. A slight crimp you will be able to feel with your fingernail. It doesn't look like much, but it is doing the job.
Try a light crimp, then disassemble the cartridge, you will see a ring around the bullet proving that the crimp did indeed marry the case neck to the bullet.
- Location
- The Conservative part of Ontario
Crimp can do funny things for sure. I've heard the horror story's about how it kills accuracy.
My own experience has been that crimp is just another tool in the reloaders arsenal.
Some loads, and cartridges benefit from crimp, (In my case that would include 44 mag rifle loads using H110) actually improving accuracy, many do not, including most if not all high accuracy target style loads.
But as was said above, you should have been crimping throughout your load development, if that's what you intended to do in the end.
Properly applied, crimp can change (depending on the powders sensitivity to this, and other factors, such as case volume) the burn rate of the powder charge within the cartridge, by introducing additional restriction and hence pressure, and heat to the release of the bullet from the case.
Consistency is the crimpers downfall. Getting them all the same is pretty much impossible for the home reloader. The Lee factory crimp die is about as close as you can get, but not perfect, too many variables.
My own experience has been that crimp is just another tool in the reloaders arsenal.
Some loads, and cartridges benefit from crimp, (In my case that would include 44 mag rifle loads using H110) actually improving accuracy, many do not, including most if not all high accuracy target style loads.
But as was said above, you should have been crimping throughout your load development, if that's what you intended to do in the end.
Properly applied, crimp can change (depending on the powders sensitivity to this, and other factors, such as case volume) the burn rate of the powder charge within the cartridge, by introducing additional restriction and hence pressure, and heat to the release of the bullet from the case.
Consistency is the crimpers downfall. Getting them all the same is pretty much impossible for the home reloader. The Lee factory crimp die is about as close as you can get, but not perfect, too many variables.
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Someday I'm going to see a load shoot consistantly better when it's crimped. In the meantime I'll look at the many accurate hunting bullets, and all the match bullets that don't have crimping grooves and ponder that a mite. Turns out there are more points to be made with varying length to land distance than any amount of crimp. Even factory match ammo isn't crimped, you wouldn't think that manufacturer sells to the precision market would give up any accuracy trick on thjeir flagship product sold to a knowledgeable and skilled market. Benchresters would have late-night discussions on the newest crimping tools.
If I were an ammo maker who was trying for a one size fits all product, that would be fired in chambers of unknown throat length I might consider it. Same thing with cartridges that might be used in auto-loaders, repeatedly roughly chambered but not fired each time. Same thing for cartridges that produce considerable recoil. Since I have no control over you want to top up your magazine instead of shooting it dry, I also don't know if its going to get banged 100 times in the magazine or never. Then there's the guys that are carrying 20 year old ammo on their belt. Then there's the military market, better crimp that too.
I'll crimp solids in heavy cartridges, cast bullets, revolver ammo and anything in a tube mag. That's about it. My factory crimp dies gather dust.
If I were an ammo maker who was trying for a one size fits all product, that would be fired in chambers of unknown throat length I might consider it. Same thing with cartridges that might be used in auto-loaders, repeatedly roughly chambered but not fired each time. Same thing for cartridges that produce considerable recoil. Since I have no control over you want to top up your magazine instead of shooting it dry, I also don't know if its going to get banged 100 times in the magazine or never. Then there's the guys that are carrying 20 year old ammo on their belt. Then there's the military market, better crimp that too.
I'll crimp solids in heavy cartridges, cast bullets, revolver ammo and anything in a tube mag. That's about it. My factory crimp dies gather dust.
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Thanks for the replies fellas. I ended up just pulling the bullets I had, and neck sizing the case again and re-seating the bullets again with no crimp. I am going to shoot the gun and seeing if the bullets move in the cases under recoil and that will determine whether or not I'll crimp. My moose hunt is getting pretty close, and I don't have the time to be working on load development again. I didn't think that crimping would change things that much (that's why I did it after getting a load developed 
), but I guess you learn something new everyday
. A big thanks to everyone for your info, it is greatly appreciated.
Scott
), but I guess you learn something new everyday. A big thanks to everyone for your info, it is greatly appreciated.Scott
Farlsincharge
CGN frequent flyer
- Location
- Saskatchewan
I read some interesting tests just yesterday, as i was experiencing high SD's during an OCW development and was attributing it to neck tension. I have reloaded the test again using a light crimp and will try again when the weather smartens up.
There are a couple individual tests out there, that are quite extensive. The one showed an average result of 10fps gain, lower SD, and 10% increase in accuracy, using a light crimp from a LFCD. I think the key word here is LIGHT.
I did my own crimp "test" a few years ago with a swiss arms black special. There was a very slight increase in accuracy with no poi change. I did not own a chrony at the time though.
I honestly don't see the downside to a light crimp for most people. I think it can only serve to improve consistency as well as provide piece of mind with the heavy recoilers.
I have no experience with neck turning and bushing dies, but I imagine these tools, coupled with quality brass, provide better performance than crimping.
There are a couple individual tests out there, that are quite extensive. The one showed an average result of 10fps gain, lower SD, and 10% increase in accuracy, using a light crimp from a LFCD. I think the key word here is LIGHT.
I did my own crimp "test" a few years ago with a swiss arms black special. There was a very slight increase in accuracy with no poi change. I did not own a chrony at the time though.
I honestly don't see the downside to a light crimp for most people. I think it can only serve to improve consistency as well as provide piece of mind with the heavy recoilers.
I have no experience with neck turning and bushing dies, but I imagine these tools, coupled with quality brass, provide better performance than crimping.
I never crimped any of my bullets in my .375, from 235 grain up to 300 grain. I always shot from the magazine and never had a problem with the bullets moving.
As mentioned, in your load development, you should do it the way you want to end up. If you really, really think you need to crimp, do it from the beginning.
In my experience, not necessary.
As mentioned, in your load development, you should do it the way you want to end up. If you really, really think you need to crimp, do it from the beginning.
In my experience, not necessary.
