Loading for an auto loader

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Morrey

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I have loaded .30-06 and .308 Win for years for my various bolt action rifles. I now have on order a new Ruger SR-762 so this is my first foray into an autoloader to reload for.

The SR-762 (.308 Win) has a two stage gas piston cycling system, and reports are that it is a very soft shooter which is leading me to my question about bullet crimping.

Realizing loading for bolts and autoloaders have some differences, I read Sierra's section on hand loading for auto loaders. While I got some good information from this, I also came away with a question about bullet crimping. I think they are talking about crimping for hard cycling mil-spec service rifles that may be very much different than my new Ruger. But, I honestly don't know hence my thread.

I have never crimped .308 rounds for my bolts, and I have always maintained good neck tension with no bullet movement once seated and in the magazines. I use bullets that have no crimp ring so that is the second concern. I will load Sierra 150 gr flat based spitzers for hog hunting.

To crimp or not to crimp? With an extremely soft shooting (adjustable) two stage gas piston system, does this have an impact? Can I load w/o a crimp if maintaining good neck tension with well prepped casings ? THANKS!!
 
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I never have crimped a rifle round & stopped crimping my revolver rounds years ago. I have a few revolver rounds in stock that are really heavy recoil from the days I did crimp & they probably need it but most round don't.
 
I load 308 to feed my PTR 91 and use RCBS AR series taper crimp dies. I dont try to overcrimp with them, just snug. Ive had only positive results so far. I havent attempted to reload any due to the deformation of the fired cases. I was told that the taper crimp dies would eliminate some feeding issues that are non issue with other types of actions. My PTR eats them like a hungry kid without issue so far. The only drawback is the factory warranty is voided by handloads.
 
Competitive rifle shooters learned decades ago that any crimp degrades accuracy. Bullet companies making the best match bullets don't crimp them for accuracy tests. Commercial match 308 Win ammo is not crimped.

That said, sometimes crimped in bullets fixes poor reloading stuff. Accuracy will be better. Do all the right stuff with reloading tools, techniques and components then crimping won't be needed; accuracy will then be best.

All those semiauto service rifles shooting 308 Win ammo testing sub 3/4 MOA through 600 yards (under 1/2 MOA at 100) did so with brand new unprepped cases; either hand loads or commercial match ammo. Nobody used reloaded fired cases from these rifles for best results as accuracy wasn't as good as new cases produced.
 
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I load 30-06 for an auto-loading Garand. I have never crimped and have no issues. Even without a crimp, the neck tension is so tight on the projectile that intentionally trying to pull same is very difficult without severely damaging the projectile, at least...

Bayou
 
7.62 NATO M118 and M852 match ammo has bullet "release force" specs of 20 pounds minimum. That's how "neck tension" is correctly measured. It's the force on the bullet needed to move it out if the case neck. It's easy to measure at your home with a bullet puller, shell holder and a set of weights. 30 caliber bullets in them are three times heavier than 22 caliber ones in .223 Rem's and have twice the grip area on them compared to 22's. Both are chambered at about 9 to 10 feet per second speed. Calculate the energy in ft-lbs both bullets have as they come to a stop when chambered.

The interference fit between case throat and bullet based on their diameter differences is only part of the equation. Surface friction and mating force between bullet and case are part of it. Mating force varies with case neck elasticity

Sierra's article would have been better and more meaningful had they measured those 22 caliber bullet's release forces then stated them. Sierra makes one 22 caliber 77 grain match bullet with a knurled in cannelure for crimping because of customer demands for them. They're tested for accuracy in quality tests without being crimped in case necks; better accuracy that way.
 
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Bayou52 said:
I load 30-06 for an auto-loading Garand. I have never crimped and have no issues. Even without a crimp, the neck tension is so tight on the projectile that intentionally trying to pull same is very difficult without severely damaging the projectile, at least...

Bayou
Click to expand...


Yeah, Bayou, I follow you on the neck tension. When I load for Bolt Actions, of course we make mistakes meaning the bullet puller comes out to play. I use a Midway impact puller and pop it on a block of wood sitting on the concrete floor. I have whacked the darn fire out of the bullet, then took it out of the puller to measure what the COAL is after a huge whack like that. Very little change, so it typically takes several healthy whacks with the impact puller to unseat the bullet. I figure I am putting good neck tension on this round to stand up in a semi-auto especially with a gas piston to buffer the setback. Yeah, like Bart says, I want to avoid crimping at all costs to maintain accuracy. Even tho its only a hog hunting gun, I'd still like to shoot under 1.5 MOA for effective shot placement. We shall see.

Bart, I just saw your second post. May I ask how to measure neck tension as you described? Interesting. Bart, I also have a press mounted RCBS collet bullet puller and I expect this is what you'll describe.
 
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I measure neck tension by feel when seating. Not very scientific, but it works for me. You can always measure it in pounds if you want to.

Size the cases to fit a case gauge or move the shoulders back an average .003 from fired cases and you'll get good case life with good function. I would suggest the RCBS or Redding bushing style FL sizers. Throw in a Forster, Redding, or RCBS match/competition seater, use match bullets, and those Sierras will likely out shoot you. (Heck, they'll likely do that with a standard seater too. :)
 
Walkalong said:
I measure neck tension by feel when seating. Not very scientific, but it works for me. You can always measure it in pounds if you want to.

Size the cases to fit a case gauge or move the shoulders back an average .003 from fired cases and you'll get good case life with good function. I would suggest the RCBS or Redding bushing style FL sizers. Throw in a Forster, Redding, or RCBS match/competition seater, use match bullets, and those Sierras will likely out shoot you. (Heck, they'll likely do that with a standard seater too. :)
Click to expand...

I know this may sound a bit overdone, but I am pretty detailed with my process when I load. Every case gets inspected checked with my Wilson headspace gauge plus I can use same gauge to check for length when it needs trimming. I take my time with a Forster micrometer seating die after using an RCBS full length sizing die. All in all, my slowwww process is making some rounds that group nicely for me given some load development time on the bench for each individual gun. With my process loading for this new .308 Win gun, I am hoping to create a 1.5 MOA group (or less) with the Sierra Pro Hunter 150 gr flat based spitzer. This will be my hog hunting round for the new Ruger SR-762. I just hope the semi-auto won't disappoint me when the grouping results start coming in. I have a ready supply of IMR 4064 so will see how a "mid-velocity" load will work, then adjust from there.
 
First I wouldn't rely on "reports" of a "soft shooting" rifle. That gun may be easy shooting for one shooter, but painful for another, so that description is just an opinion at best. Perhaps a report from the manufacturer on foot pounds of recoil would help (if such a report exists).

I have been reloading for my Garand in 30-06 for 6 years and when I started I listened to all the fellers in the "crimp camp" and crimped all my reloads. Not used to crimping rifle rounds I forgot to crimp 20 or so rounds so I tested them. I loaded up a clip and shot 7 rounds then ejected and measured the OAL of the 8th round. Did this for about 5 clips full and none exhibited any bullet movement. My 7.62x39 SKS ammo is not crimped either...
 
Thanks Bart, now I have real numbers to apply to "neck tension". I believe I'll give that a try for my 308 bolt gun...
 
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