If it reduces neck tension, then why is crimping used to keep bullets seated under heavy recoil?
300 WM. Crimp or not to crimp?
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MagnumManiac
Well-Known Member
It is used to stop rearward movement of the bullet.
Essentially it is a mechanical lock, and it is NOT needed if neck interference is sufficient.
Even if a neck was half a calibre in length, a crimp should not be needed.
If my 300WM's, with a neck of .264" length, is able to handle having the tip of nearly all bullets in the mag smash the mag box and not move is a testament to how well even .0015" interference fit works.
Neck tension is ONLY hoop tension, and even .0001" movement of the neck away from the bullet is enough to have all perceived neck tension gone. Albeit, a crimp would still be holding the bullet in place.
Even primer pressure is enough to expand the neck and have the bullet leave the case.
Cheers.
Just so I'm clear, you are saying the crimp is used for rearward movement of the bullet and decreases neck tension. So, to test this, if I pull bullets from the same lot of brass, the crimped ones will be easier to pull. Correct?
MagnumManiac
Well-Known Member
Are you being a deliberate asinine twat?
Are you seriously asking if a crimped bullet will be easier to pull??
Crimping has NOTHING to do with neck tension.
If you cannot figure this out, then I suggest you ask elsewhere.
Some people?!
I was hoping for a different response
Call me crazy for assuming neck tension went hand in hand with the force required for a bullet to leave the case. I can see we use different terminology.
hunter0528
Well-Known Member
A simple way to tell if you need to crimp. Measure the length of the first cartridge you load in the magazine, now fill the magazine. Fire all but the last one, and refill the magazine. now fire all but the last one, take it out and measure the length. Did it change and if so how much.
Great thread.I have watched this thread as it was an important question I have had for years.I don't crimp for light kickers like 308,358,270,30-06 but do for 300 win mag.
Since many do not crimp the 300 win mag I am going to try not crimping and just get a smaller bushing for my Redding Bushing dies and see if accuracy increases or degrades.
I see both sides and have enjoyed the knowledge and experience expressed here.
Old Rooster
Since many do not crimp the 300 win mag I am going to try not crimping and just get a smaller bushing for my Redding Bushing dies and see if accuracy increases or degrades.
I see both sides and have enjoyed the knowledge and experience expressed here.
Old Rooster
D
Deleted member 107796
Guest
I was hoping for a different response
Call me crazy for assuming neck tension went hand in hand with the force required for a bullet to leave the case. I can see we use different terminology.
Incredible how you stayed so positive in your response. I had to delete my snarky retort. IMO, you are correct if you look at dynamic neck tension vs static but regardless of linguistics, crimping can have a positive effect on accuracy and that is what most data concludes. In my case, the 7wsm has about the shortest neck around which has less bearing surface.
Ha. I'm guessing it wouldn't have helped the situation in his case. Maybe I'm wrong and I'm not smart enough to know it
freddiej
Well-Known Member
I used to crimp my 300 win/mag. then I tried not crimping and I have never crimped ever again.
Freddie I'll be the guinea pig.Do you use a bushing die to control neck tension and if you do can you get away with .001 or .002 undersized bushing?
BartB suggested using .002 neck tension so I will shoot them also from a lead sled not worrying about the chrony.
I'll try the same on both my 300 win mags with 1 in the magazine to see if the bullet recedes into the case after 5 shots as per hunter0528.His advice sounded correct.
I'll even check for accuracy to see if the lightly crimped round was any more accurate.
We have a warm spell coming so I'll get it done then and report.
Old Rooster
BartB suggested using .002 neck tension so I will shoot them also from a lead sled not worrying about the chrony.
I'll try the same on both my 300 win mags with 1 in the magazine to see if the bullet recedes into the case after 5 shots as per hunter0528.His advice sounded correct.
I'll even check for accuracy to see if the lightly crimped round was any more accurate.
We have a warm spell coming so I'll get it done then and report.
Old Rooster
There are all levels of reloaders, brass, bullet types, etc.. Many reloaders will never spend as much time as some others on prep, brass, bullets etc.. IMO there is quite a difference between a roll crimp and like Lee's Factory crimper, the later I do think increases neck tension. I've only used roll type crimps on large pistol rounds with crimping grooves. I do use LFCD's for some rounds if needed, currently I get better grouping with my 6.5 cm and 300wsm with a very light crimp. My 30-06, 7RM I do not crimp. A Lee FCD can be a help in tuning a round just like any other form of increasing neck tension, it might not be the way a purist or guy with lots of time on his hands would do it but for avg guy reloader it works. Sort thru the purist and the worst and somewhere in there is a good method for you. Always remember increase neck tension will increase pressure. Never crimp a load that you worked up with out a crimp. And crimp as lightly as possible to get where you want. You do not have to crimp a 300WM but can if you fell the need.
