AR-15 Crimp vs. No Crimp

[Rock Knocker]

Ive found a load my AR likes better than the rest, 25.5gr Varget w/ 69gr SMK and BR-4 primers. The thing that i cant quite figure out is at some distances it shoots noticable better with a crimp and some better without a crimp. It will alternate from 100 better without a crimp then at 200 better with a crimp and 300 without a crimp and so on.

Ive heard if it likes the crimp it really just like the higher pressure so add an extra 3/10 gr of powder, but i end up with pressure issues.

How does any of this make sence?

These are the best of my groups 100-400 yards and they have if there was or was not a crimp on the rounds fired, this was all with a +/- 10mph tail wind and a backpack full of burlap as a rest.

 

[spclark]

Looking at your numbers, there's not a heck of a lot of difference between them accounting for the changes in distance: 0.535" @ 100 would be 1.08" @ 200, 1.605" @ 300, 2.14" @ 400 (The smallest squares on those grids is what, 1/4"?)

Whether you shoot bullets with a cannelure (fine for crimping) or those 69 SMK's without (crimp's gonna screw up the jacket & likely the ballistics too) you're better off doing an A vs. B test at the same distance.

69's aren't often counted upon to perform well out past 300 yards. That alone could account for the somewhat larger (mathematically) group at 400, along with a crimped jacket.

Most competitive AR (Service Rifle) shooters don't crimp at all. Maybe a little higher neck tension for mag-fed rounds than for 600-yard loads.

 

[Rock Knocker]

This was an A vs B test, i just kept the best groups. I also use a Lee Factory crimp die which shouldnt need a cannalure to effectively crimp the bullet.

I also regularly shoot out to 500 yards with these bullets and normally with less powder, the reason i believe for the slightly disportionatly larger group size at 400 was because the wind increase later in the day and i was shooting off of a relatively unstable backpack with a heavy factory trigger.

I was just wondering why a group would be better at 100 without a crimp then at 200 it would prefer the crimp, same with 300 and 400 yards.

 

[Killshot]

My bet is that the driver has more influence than whether
or not you crimp.

I don't know any AR match shooters who crimp.
Why introduce another variable? Full-length bushing dies
are the way to control neck tension.

 

[fdshuster]

Rock Knocker: I won't get into the crimp vs. no crimp debate, it's similar to the "best" cleaning methods and procedures discussions. That being said I've loaded many thousands of rounds for my AR's since 1995, and before that many 30-06 for my M1 Garand, and have never crimped a single round. In many CMP & NRA Hi Power match's I've never had to call an alibi for a cartridge or rifle malfunction in any stage of rapid fire. The 69 gr. Sierra #1380's are one of my favorites and without a crimping cannalure I would never even remotely consider crimping and damaging the bullet that Sierra so carefully made. Your load of 25.5 of Varget with the 69 SMK & BR4 is my standard load for my bolt guns, but for the AR's, I use 25 grs. of Varget. Have never had any pressure issues. Just looking at your targets and thinking: you might try seating the bullets out further, ( I like .020" off the lands), and single load.

 

[Rock Knocker]

Thats what ive heard from the begining, but.

When i first started to handload several months ago i did my ladder test with everything crimped, because i heard it was suggested with semiautos. 24.8g varget shot the best, around .75MOA, but i didnt work up to 25.5g because i was getting pressure signs with the origanal primers i was useing.

When i heard you didnt need to crimp with semi autos i was happy that i could stop crimping but my loads went to hell, 1+MOA. So i redid my ladder test and was using BR-4s that i liked much better and found that 25.5g varget was doing better, but i then tried crimping 20 and 20 w/o crimp and found mixed results.

Ether way, i have now handloaded almost 600 rounds for this AR and for the most part it likes the crimp but sometimes no crimp may beat it by +/-.10MOA.

 

[jonbearman]

Why not experiment with h335 and blc-2 as it works extremely well in the ar15.I have tried other powders adn I dont crimp at all and have settled on h335 for supreme accuracy with the 69 gr mk's. I have shot groups that are in the 3's regularly with a franken colt I built out of spare parts.At first it shot terrible and my brother owns a cryo system and I tried it.My groups prior were about 2 inches at 100 yds and now it shoots as good as mty friends custom.It pisses him off but a fact is a fact.And incidently he wont try ball powder which was designed for the ar in the sixties. Just my 2 cents.I also free floated the barrel.If you are using handguards,get rid of that system as it loads the barrel with stress.

 

[jonbearman]

Can you tell us everything you can about the rifle itself with respect too who's barrel,reciever,upper,handguards,muzzle device,stock etc?

 

[Rock Knocker]

I am going to get some H335 next time im out. i was about to totally give up on Varget untill i started getting this .5MOA and better.


BTW, this is a Model 1 Sales varminter i put together for $750. E.R. Shaw 24" bull, free floated, DPMS lower. No frills cheapy.

 

[fdshuster]

jon: A second vote for your choice of H335 in the AR. The only ball powder I will use, all the others I've tried are extremely dirty.

 

[mattt]

My mini 14 1 in 9 twist likes the 69 smk just fine at 600 yards with 25 grains of varget. I use the lee crimp die

 

[seanhagerty]

I crimp. I use the Lee FCD and this. It allows me to quantify the amount of crimp. I have been able to cut my group size from around an inch to about a half inch. Some of that may be the barrel break in, some may be the shooter getting better, but I am going to say its at least partly because of the Consistent crimp product.

 

[jonbearman]

The other beauty of h335 is it meters like sand.I still use a rcbs plain jane powder measure and then weigh a few during the process and they are right on the money.Varget has its uses but in an ar it really doesnt live up to its potential.The other powder I like is benchmark.It meters wonderfully and produces great groups and hasnt proved to be sensitive to temp variations with my loads.I use the benchmark in my remington VS with a 1 in 12 barrel with a 50 gr plhp(remmy bullet) and get in the 3's with a stock rifle with only trigger mods.I think that isnt bad at all.If you can afford it in the future,get a shilen replacement and you will be very happy with the results. Incidently you can get a good er shaw or one that isnt so good,its a roll of the dice.Do you clean it often? How do you clean it as alot of less expensive barrels really copper up fast and accuracy goes out the window.

 

[Rock Knocker]

I clean after i shoot it, and i never shoot more than 50 rounds in a trip. I have a bore guide that fits ARs and i usually use Butchs bore shine, but i just picked up a bottle of Sweets. The barrel is well broken in (must be around 1100 rounds through it) and copper fouling is pretty non existant.

What are some good loads to start out with for H335 and 69g smks?

 

[Killshot]

I found that 23.3gr of H335 with 69SMKs had an aggregate average of .629" of dozens of five-shot groups at 100yd from both 9twist 24" and an 8twist 26" barrels.
Chrono'd at ~2,700fps. Took a lot less powder in the case than Varget to get there.
(though Varget is my go-to powder for the 77/80 grainers)