To Crimp or Not to Crimp?

[FALex]

I'm running a JP-LRP 07 .260. I was messing around with some shoulder bumping the other day, seeing what would chamber, what wouldn't. I kicked a couple rounds back out where the bullet had been pushed in a few thousandths. I mentioned this to a friend and he said I should consider crimping my bullets. Mostly, from what I've been reading, it seems that crimping is not conducive to producing the most accurate and consistent results.

The die I ran these rounds through was a simple RCBS FL die. It appears the neck tension is right around .002 when using it.

Just curious if any of you running a gasser are crimping, and if not, what are you using in terms of dies?

In order to abstain from crimping, I was thinking about upgrading to a Redding Type S Full Bushing die and throwing maybe .003-.004 neck tension to see if that would do the trick.

As always, any help will be greatly appreciated.

 

[goldeneagle76]

I use RCBS SB dies for my DPMS and also a Lee factory crimp. Had regular FL size dies first but was having issues. Since going to SB dies, no issues. I pretty much use Lee FC dies on 90% of loads I do. Just gives me that warm fuzzy feeling.

 

[1MoreAR]

I always do the light crimp on the gas gun. I separated my .308 brass because I have one lot for bolt gun and one lot for gas gun. I just want to be safe.

 

[LRRPF52]

I've never crimped on gas guns, and have been loading for them since 2006.

I think your plan to add a little more neck tension makes the most sense.

For .260 Rem, I use RCBS full length sizing die, and have been using a lot of Winchester 7mm-08 brass necked down, as well as Lapua .260 Rem. brass. I have to size the Lapua brass because I have a tight neck in my GAP, with fired necks measuring .293".

I've never crimped, and have not seen any recoil or chambering-induced COL compression. I think .002" neck tension is too light for your chamber, obviously. The bushing dies seem to be a good solution to your problem. Let us know how it works out.

 

[lte82]

I shoot high master scores with uncrimped ammo in my service rifle, but I'm sure someone will chime in and say do the same with crimped. I honestly don't believe it makes a difference as long as you work up the load correctly.

 

[FALex]

I've never crimped on gas guns, and have been loading for them since 2006.

I think your plan to add a little more neck tension makes the most sense.

For .260 Rem, I use RCBS full length sizing die, and have been using a lot of Winchester 7mm-08 brass necked down, as well as Lapua .260 Rem. brass. I have to size the Lapua brass because I have a tight neck in my GAP, with fired necks measuring .293".

I've never crimped, and have not seen any recoil or chambering-induced COL compression. I think .002" neck tension is too light for your chamber, obviously. The bushing dies seem to be a good solution to your problem. Let us know how it works out.

Do you think doubling it up would be adequate, going from .002 to .004? Kind of a pain in the ass, but I figure it's a fine line between too much and not enough, right?

 

[Oryx]

If you are deciding between .002" and .004" you won't be crimping anyway. Crimping will definitely create much more tension.

.004 "is fine without crimping. The problem with .002" in a semi auto comes with variability in neck thickness. Without neck turned brass, you won't have consistent neck thickness and the neck tension will vary. When it varies on the lighter side you can run into problems.

Some may neck turn brass for a custom cut chamber, but most people don't with a gas gun as the chambers are typically cut on generous side for reliability. A tight chamber in a semi auto will usually require more attention to details when reloading.

I would also maybe measure your expander in your die to make sure it's not over sized and creating a looser than desired neck dimension.

Also, just out of curiosity, are you measuring your .002" neck tension based on your actual chamber neck or fired round dimensions?

 

[SWThomas]

I never crimp my 308 gas gun loads. I use a Lee die with the expander polished down to give me 0.003 neck tension. My GAP-10 shoots sub-MOA all day with these loads.

 

[Smcarroll]

I use a light crimp on my bulk ammo for plinking/run-n-gun and no crimp when I am loading match grade ammo. My theory is my gun is bagged and laid down for my precision work so the bullets don't bang around much.

 

[FALex]

If you are deciding between .002" and .004" you won't be crimping anyway. Crimping will definitely create much more tension.

.004 "is fine without crimping. The problem with .002" in a semi auto comes with variability in neck thickness. Without neck turned brass, you won't have consistent neck thickness and the neck tension will vary. When it varies on the lighter side you can run into problems.

Some may neck turn brass for a custom cut chamber, but most people don't with a gas gun as the chambers are typically cut on generous side for reliability. A tight chamber in a semi auto will usually require more attention to details when reloading.

I would also maybe measure your expander in your die to make sure it's not over sized and creating a looser than desired neck dimension.

Also, just out of curiosity, are you measuring your .002" neck tension based on your actual chamber neck or fired round dimensions?

Great question, and no, I got the .002" number confused with a spent case from my bolt gun (also in .260). This is something I still need to figure out...next time out I'll throw a few rounds down range to get some numbers on the spent case from the gasser. Thanks for the info and sorry for the confusion!

 

[Grand]

I never use it crimp until I had a 168g SMK from factory GMM stick in the throat of my GAP 10 when I tried to extract a loaded round.

 

[corym468]

I don't own a 260, but I do crimp for my 5.56 and Grendel.

When developing a load, I want to find a precise load that I can bulk load and store loosely in an ammo can and not worry about handling affecting my COL. Maybe I don't need the crimp, but I'd rather be safe than sorry.

If you're only going to load what you need for the next range trip and store them safely in a nice ammo case, then I don't see the need. Unless you have a rifle that likes crimped ammo better.

 

[smschulz]

I always do the light crimp on the gas gun. I separated my .308 brass because I have one lot for bolt gun and one lot for gas gun. I just want to be safe.

Same here, light crimp on gas gun loads.

 

[Emerson0311]

I didn't crimp for bolt guns until I had a 375 Ruger that moved the bullets under recoil. Now I crimp most reloads. Haven't seen an accuracy change, but I can only get down to about 0.7MOA with my hunting rifles, so perhaps hard to tell the difference.

 

[lizzardking308]

Whoa... holy necropost.... that being said, I polished the expander ball down so I have 0.003 neck tension. Works just fine for me.

 

[bigjake83]

FALex i don't crimp at all, I adjust mine via neck tension, going .004 smaller bushing is a good place to start. Load a couple rounds, then chamber them by releasing the BCG like you normally would do to load a mag. Do this 4-6 times with the same round and then measure the OAL if the bullet hasn't moved you're GTG.

 

[Greg Langelius *]

I don't crimp, although I did at one time (to try it out). I was using the Lee Factory Crimp for .223 ammunition and .30-'06 ammunition. I could see no evidence of any accuracy improvement, which was the basis for the experiment; so I discontinued the practice. I suppose I am still doing some sort of crimping in a way, whatever crimp the seater die (RCBS for all but .260 Rem) applies in the regular course.

Neither do I find any undiagnosed accuracy loss from ignoring the crimp step. The only bullet setbacks I have observed were due to misfeeds.

I distrust crimping for applications where a cannelure is not present, and wonder whether crimping bullets without the cannelure may be distorting the bullet. Doubly so for the Factory Crimp.

Greg

 

[Velocity Chad]

I shoot more autos than bolts anymore and I don't crimp any of them. Everything from 458 socom to 243 win and a bunch in between. Never had an issue, so never bothered to crimp. AS far as dies, I use RCBS and Hornady depending on the caliber. I just run all full length standard dies for all my autos except my 300blk. It is small base just because the old lady picked it up for me and the guy at the shop told her "I had to have small base for AR's". I guess nobody ever told my other calibers...

 

[Rudy Gonsior]

No crimping here, I've been running Hornady FL dies for 5.56 and 7.62 gas guns for 5-6 years and I can't say out of the tens of thousands of rounds I've never really seen any issues. As others have suggested, I'd try switching out expander balls and see if you can come up with one that produces a little more neck tension.