is it better

[heelmark]

is it better to crimp or not for bottle neck cartridges ? thanks in advance

Information

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[catman]

I've heard lots of controversy on this topic. I have always put a "small" crimp on all my loads, It helps holds the projectile in place and helps keep moisture out. And it eliminates any shell casing edge from snagging.
JMHO,

Chuck

[Gun Surfer]

No need to crimp. If you have bullets without cannelure, then it really makes little sense to crimp them. But even with bullets that have a crimping groove, .223, .308 etc, I and many others do not crimp and experience excellent accuracy and reliable function.

If you do crimp and have bullets with the groove, then you will want to trim the brass for best results. Also you can get the Lee Factory Crimp die for best results. I do occasionally crimp M80 .308 "duplication" loads with 150 gr milsurp bullets using the Lee Factory Crimp die, they run great.

[CINDERS]

I give my 303 rounds a light crimp using the Lee crimp die as lets face it in a speed shoot your none to gentle in the bolt cycling, also not that it is really a requirement for the old girls it makes all the rounds have the same neck tension but that is more for F class shooting.
But as in all cases it is up to the personal preference of the shooter what ever works as long as it is safe and does not put you, or fellow shooters at risk.

[enfield303t]

Only time I crimp is when using in a semi-auto. Agree it may be a personal preference and no harm if you do.

Since I don't own a semi-auto .303 I never crimp those reloads.

[Bruce_in_Oz]

Neck crimping can have a couple of advantages, and one disadvantsge:

1. As noted by CINDERS, it helps prevent the projectile being displaced during "vigorous" feeding.

2. It DEFINITELY helps with combustion consistency, and thus muzzle velocity consistency, especially in rifles that have the typical long "military" throat, esp .303Brit.

The only REAL disadvantage is that it "works" the brass at the end of the neck. Thus, and especially if you do not regularly anneal case necks, the necks will start to split somewhat sooner than otherwise.

The Lee dies are capable of applying so much force that the "crimp" can also form a cannelure on the bullet. This does not seem to adversely affect accuracy.

I run "factory crimp" dies for .308, .30-06, 7.5 Swiss (essential for model 1911 rifles and carbines), .303 and 7.62 x 54R.

They are a boon to those lucky enough to be still able to run semi-autos. Those reloading for MGs should ALWAYS use such dies; much cheaper than having to strip and clean the toys on the line after a bullet gets rammed back into the case.

[WarPig1976]

[quote=Bruce_in_Oz;284883]I run "factory crimp" dies for .308, .30-06, 7.5 Swiss (essential for model 1911 rifles and carbines), .303 and 7.62 x 54R.[/quote

I don't load for Swiss but will at some point, why is it essential to use Lee "factory crimp" dies as opposed to run of the mill RCBS dies?

[Bruce_in_Oz]

The Lee "Factory Crimp" die is a "collet' type die. Probably better explained on their website, as per

Here: Factory Crimp Die - Lee Precision

Simple adjustment of the height of the die in the press determines the amount of "squeeze".

The actual "crimping" is done by a collet, not too dissimilar from work-holding collets commonly used on lathes etc. The trick is that the crimping force is applied radially and there is essentially NO axial displacement of the brass, thus not much chance of bulging the neck or buckling the shoulder.

The more "traditional 'roll" crimp offered on most other seating dies for rifle cartridges, requires that there be a cannelure groove, of consistent depth, in the bullet. The neck is essentially forced into the cannelure by the final secondary taper at the very top of the seating die "chamber". The trick is to back off the seating plunger AND the die itself and experiment until your bullets are seated (and crimped, if desired) to your satisfaction. It can get a bit fiddly.

I prefer to back off the seating die just enough so that the "roll-crimp" does not engage, then adjust the seating plunger down until the required OAL / depth is achieved.

The, if desired, it's time for the "Factory Crimp" die.

[Gun Surfer]

When the Factory Crimp die was rolled out (pardon the pun), there was a minor ad war between Lee and Redding about the assertion that crimping improved accuracy. In the very limited comparison data I have seen, the data was not statistically compelling. Even if there is a slight improvement in combustion consistency, or lower SD of muzzle velocity etc due to crimping, I will not be crimping my Sierra or Hornady match bullets any time soon, and its one extra step I don't need. I get plenty of neck tension and consistency in them. Maybe a more compelling case can be made for crimping .223, but either way, my reloads in .223 are sufficiently sub MOA as meets my needs. I do sometimes crimp lighter FMJ bullets with cannelure, and the Lee FCD is an excellent tool for that purpose. YMMV as always.

[Bruce_in_Oz]

It is more important in semi-auto types than general bolt guns.

Neck tension alone will often not be enough to stop bullets "sloshing around" in their necks whilst in a magazine. FAL/M1A/HK etc. owners take note.