SPR Loads....Crimp or no?

[nksmfamjp]

Should I use my Lee Factory crimp....collet type...for best accuracy?

Looking for SPR accuracy ....sub 1 MOA at 100 yds.

Build is WOA barrel, Geissele hi speed, 2-8x quality optic....

[jaholder]

Most precision loads don't require a crimp, bullet deformation may degrade accuracy.

With that said, I've got a Mk262 clone using TAC that I got better groups from my 16" carbine by crimping the Sierra 77's with the Lee FCD. My other AR's had no difference in accuracy between the crimped and uncrimped bullets, so I crimp.

I also crimp (with the FCD) my 55 grain Sierra HPBT but the Nosler 55 grain BT's get none.

[bp7178]

Sub MOA is sub MOA regardless of distance.

I applied a light taper crimp, but not to the point where it would deform the bullet. IMO, good neck tension is more important.

[gunnerblue]

I believe that neck tension is more important than crimping in a precision load. I control tension by using Redding Type-S sizing dies which use interchangeable bushings. Typically for an auto loader I will go for about 0.003” worth of tension. This is subtracted from the outside diameter of the neck of a loaded cartridge. I haven’t used the Lee product but a lot of people seem to like them.

[markm]

Buy the die and try it out. There's no correct answer since it depends on dozens of variables in your specific set up. I crimp everything.223. In my set up, I lose gobbs of accuracy without the crimp. I tested it once, and it was dramatic.

[Vegas]

markm, what is the amount you crimp?

Thanks.

[5.56 Bonded SP]

I apply a light taper crimp to all my loads. Some of them shoot submoa. I mainly do it because I feel safer doing so. YMMV

[HKGuns]

I use the Lee factory crimp for all of my 556 and 762 loads. They all shoot sub moa.

[markm]

markm, what is the amount you crimp?

Thanks.

I set the die so that I can just start to see crimp marks on the neck.

[Vegas]

Thanks. You had asked me in another thread a while back about whether I crimped. Think I am going to get motivated to order a LFCD and give it a try.

[markm]

Thanks. You had asked me in another thread a while back about whether I crimped. Think I am going to get motivated to order a LFCD and give it a try.

I think the reason it helps me is that I don't anneal. So the FCD gives some neck consistency improvement.

Sinister, another experienced loader here, does almost the opposite process that I use and gets great results. He anneals with no crimp if I remember correctly. So the FCD alone is only part of the total process.

[Coal Dragger]

I don’t anneal my brass either and use a light taper crimp on my .223/5.56. I have plenty of loads in bullet weights from 55gr to 77gr that can hold MOA or better for 10 shot groups. The crimp helps as markm says to provide consistent tension. I also suspect that in my AR’s the crimp helps maintain consistent seating depth where a non crimped round may experience bullet setback during feeding in a semi-auto. I don’t have any experience with .223/5.56 in a bolt gun, but my .308’s over the years, and my .280 Ackley don’t seem to benefit measurably from a crimp. However those all use the same lot and headstamp of brass, so there is more inherent consistency in neck tension than my mixed 5.56 brass. I’m also not cycling the rounds into the chamber as hard as an AR would over a barrel extension and feedramps with sharp edges etc.

[Vegas]

I think the reason it helps me is that I don't anneal. So the FCD gives some neck consistency improvement.

Sinister, another experienced loader here, does almost the opposite process that I use and gets great results. He anneals with no crimp if I remember correctly. So the FCD alone is only part of the total process.

I don't anneal 223 brass, only my 308 and 7mm brass for bolt guns. So basically crimping in lieu of annealing gives that consistency to neck tension. Makes sense.

Thanks.

[markm]

So basically crimping in lieu of annealing gives that consistency to neck tension. Makes sense.

Thanks.

That's my guess. I tested the same loads with the crimp as the only variable, and the non crimped ammo wouldn't even hold MOA.

[Vegas]

That's my guess. I tested the same loads with the crimp as the only variable, and the non crimped ammo wouldn't even hold MOA.

So after a little testing with the Lee FCD, I'm seeing more consistent velocity, lower ES and group sizes. I consider myself converted. I shot my smallest 5 round group with the WOA barrel today. Thanks.

[Eurodriver]

I use a Lyman m die to expand and don’t crimp.

I’m not gonna play with it as my SPR load shoots really freaking good, but part of me wonders what crimping would do.

Interesting to see so many folks that do.

[gunnerblue]

What do you use for sizing and seating, out of curiosity?

[Vegas]

I use a Lyman m die to expand and don’t crimp.

I’m not gonna play with it as my SPR load shoots really freaking good, but part of me wonders what crimping would do.

Interesting to see so many folks that do.Never hurts to do a side by side. The Lee die is cheap enough that you won't care if it doesn't work out. What I am now curious about is going back to some of my other loads that shoot well to see if I get a similar improvement.

[user]

That's my guess. I tested the same loads with the crimp as the only variable, and the non crimped ammo wouldn't even hold MOA.

If you google shot start pressure and crimping you will find a lot of discussion about crimping raising the shot start pressure and helping accuracy. Particularly with mixed brass and un-annealed brass. Good luck.

[markm]

So after a little testing with the Lee FCD, I'm seeing more consistent velocity, lower ES and group sizes. I consider myself converted. I shot my smallest 5 round group with the WOA barrel today. Thanks.

That's awesome.


If you google shot start pressure and crimping you will find a lot of discussion about crimping raising the shot start pressure and helping accuracy. Particularly with mixed brass and un-annealed brass. Good luck.

Makes sense.