Reloading for ar-10

[steve4102]

Originally Posted by reynolds357

Thanks Steve. I will take Barts word for it. With a bushing change I can put as much neck tension as I want on the bullet. I know for a fact crimping a match grade bullet will kill its accuracy. I accidentally did it on one batch of ammo. 1/4 minute rifle shot over a minute. Thought I had a bad scope.

The thing you need to understand about Bart's word in regards to crimping is, it is an opinion. An opinion based on years of experience, but with zero hands on testing.

Yes, that is correct, with everything you have read from Bart in regards to crimping he has Never tried it. He has an opinion on why it is Bad, but he has no personal data to back it up. Opinions are great and we all have them, but facts are what counts in my "Opinion" he has none.

Several years ago I did a test with my Browning BAR 300 WSM. I don't have the test result anymore so I'm gong from memory here, sorry.
I loaded up several rounds using my Redding Bushing die. I started at .002 neck tension/bullet pull and increased it to .006.

What I found was that no matter the neck tension the amount of bullet creep when cycling the action was basically unchanged. Meaning even at .006 neck tension the bullet still move forward. So, IMO "opinion" based on my actual test results, neck tension alone will not stop bullet creep in a 180gr .308 billet in a Browning BAR.

I also tested these rounds for accuracy. If I recall correctly accuracy was basically unchanged from .002 to .003. Accuracy started to drop off at .004 and was down right horrible at .006. So, In my "opinion" based on my actual range testing, the increasing neck tension can decrease accuracy and should be avoided.

I also tested this load with .002 neck tension and a medium light crimp with the Lee Factory Crimp Die. Although bullet creep was not totally eliminated it was reduce to almost nonexistent levels. It is my "opinion" based on my actual tests that the Lee Factory Crimp will indeed help secure the bullet and increase accuracy.

I still shoot that same "Crimped" load in my 300WSM BAR. Took it out of moth ball this last fall to give it a go at some MN Whitetails. Still shot pretty darn good for a Semi-Auto with a Lee Factory Crimp.

This is three at 100 yards.

[reynolds357]

Steve, I have a few reasons to doubt crimp is necessary in my semi auto.
1. Armalite guarantees the accuracy of the rifle with 168gr Federal Gold medal match ammo. It is un-crimped ammo. They factory tested the rifle and recommend ammo that just happens to be un-crimped. The second ammo they recommend is 168 Black Hills match. It is also un-crimped.

2. The Rifle is designed to shoot the 168 Sierra Match king. Sierra says do not crimp that bullet.

3. I am shooting a compressed charge of Varget. If the bullet does get moved in a bit, it still cant hurt anything. You cant pack that powder tight enough with a reloading press, let alone bumping in a magazine, to cause a pressure problem. If I was using a 80% case capacity charge, I might worry about a bullet getting seated deeper.

4. I also do not know what Barts experience is with an AR-10. I bet he has plenty. If not, I am quite sure he has "seen it all." He probably knows some of the most accurate ar-10 shooters in the world. He might even be one of them.

I will add that I am not dead set against crimping a bullet with a cannelure, but crimping a bullet without one defies all logic. I used to make jacketed bullets. You start crimping grooves in them and you deform the entire bullet.
Sierra's info is their opinion as well. Its not fact because Sierra said it. Go back and read some of their old manuals and there is just some flat out backwards ways of doing things stated in them that are really quite laughable by todays standards.

[steve4102]

Measure the OAL of a few of your rounds from the Ogive. Record the measurements of these rounds.

Load the magazine and fire a round letting the next round chamber automatically.

Do not shoot this round, Eject the round by hand and re-measure. If it grew in length, by how much. If it did not grow in length, then you are GTG.

By doing this test you are testing your rifle and your handloads for yourself and you do not need me or Bart or Sierra to tell you what will or will not work with your rifle/ammo combo.

Once you have tested for bullet creep, you can move on to doing your own accuracy tests with and without Crimping with the Lee Factory Crimp die. No opinions, no theories, just you and your rifle at the bench.

Carry on.

[zeke]

Good discussions on tailoring the case neck tension to specific bullets and brass being used. If you're going for accuracy potential, would add that have found a Redding comp seater die to be very useful, especially when using increased case neck tension.

As has been pointed out, increasing case neck tension can be overdone. If you only decrease shoulder setback .003 inch, you need to ensure your case is still adequately sized at base. Using a shell holder from same company that made the sizing die may be helpful in this regard. If you use fired brass from another rifle, you ay need to adapt a little.

Personally am using a LFC die with Sierra 168 hpbt's, but use it extremely lightly to ensure case mouth uniformity after bullet seating. This for best accuracy.

When loading surplus 147 fmj for FAL, they get crimped into cannelure with standard crimping die.

The AR-10 style .308 rifles can also be touchy on powder burning rate, even within the usually recommended burning rates. Has to do with the timing of the action.

[Bart B.]

Would a test for bullet creep from several magazine front wall impacts on ammo in it from recoil in M14's and M1A's be good? For example, a magazine loaded with 10 rounds of uncrimped ammo being shot semiauto then checking them for bullet shift after chambering. The bottom round gets its bullet tip bumped 9 times before firing.

Note the bolt speed chambering the first round from a magazine will be slower than what the last round gets.

What about checking bullet creep in a 7.62 NATO chambered Garand single-round loading uncrimped ammo with 190's in their necks?

[Bart B.]

If you only decrease shoulder setback .003 inch, you need to ensure your case is still adequately sized at base. Using a shell holder from same company that made the sizing die may be helpful in this regard.

Aren't standard shell holders .125" in height so all standard full length sizing dies headspace will be correct with them?

[JMP]

I have the LR-308 and do not crimp. I've had great luck with 180gr Nosler BTs, better in my gun than SMKs.

When I first started loading for it I too wondered about crimping. The first magazine I shot, I only loaded five rounds and looked at each before I shot to see if it looked like the bullet was moving. Never did that I could see but I wasn't actually measuring them. Next time I went to the range I marked five rounds with a sharpie and loaded those same five rounds in the bottom of a magazine, shot 14 times, then removed them and measured. I did this with those same five rounds in three magazines. Those rounds were in the bottom for 42 shots. After all three were done, three of them had no change, one was setback .002, and one was set back .003. I now have well over 3,000 rounds through that rifle and have never had a problem that had anything to do with the bullets sliding back in their cases.

[steve4102]

Originally Posted by JMP

Next time I went to the range I marked five rounds with a sharpie and loaded those same five rounds in the bottom of a magazine, shot 14 times, then removed them and measured. I did this with those same five rounds in three magazines. Those rounds were in the bottom for 42 shots. After all three were done, three of them had no change, one was setback .002, and one was set back .003. I now have well over 3,000 rounds through that rifle and have never had a problem that had anything to do with the bullets sliding back in their cases.

If you read the link to Sierra provided above you will note that they were talking about the bullet moving after it entered the chamber, not from recoil while the round is still in the mag.

Test your rounds the way Sierra did and see if the bullet moves.

[JMP]

Test your rounds the way Sierra did and see if the bullet moves.

I will try to remember to do that and post the results. Could end up scaring me though! Ten inches of new snow is kind of hampering me today but I'll try to get to it soon if I can.

[reynolds357]

I will do the test tomorrow or Tuesday. Considering the rifle is shooting multiple consistent 5 shot sub 1/2" groups at 100 yards, I seriously doubt the bullets are moving in the necks. Considering the fact I am only using a 10 power scope I am probably causing over 1/4" of that 1/2". (I usually shoot 36 to 48 power scopes)
I had one called flyer that was 1" away from the group. I saw the orange appear under the dot before the rifle went boom. The hammer fall dry firing the rifle on bags (not mechanical rest) is over 1/4" of movement.

[Bart B.]

Most of that movement of the reticule when dry firing is its tube inside the scope bouncing off of the adjustment flats it slides on. The shock to the scope does that. The springs opposite each adjustment flat press that tube back to the same place each time; hopefully.

[zeke]

"Aren't standard shell holders .125" in height so all standard full length sizing dies headspace will be correct with them?"

No. Learned that lesson by helping someone who couldn't get his full length sized 7 wsm reload to chamber in custom rifle, and by resizing 308 brass fired from excessive headspace gun. in both cases using the same brand sh as the die worked.

Redding #1 308 sh = .127
RCBS # 3 308 sh = .119

And wouldn't exactly call the machining precision. Am guessing the different brands have differing tolerances.

Not an original thought, if memory holds learned that from a reloading manual, although which one escapes me at the moment.

[Bart B.]

Zeke, I'd send that .119" high RCBS shell holder back asking for a replacement that's .125" I've got 6 or 7 RCBS #3 shell holders and they're all .125" +/- .001"; normal for their specs. Same for my several #4 magnum ones from RCBS.

[reynolds357]

The uncrimped ammo is not changing length in my rifle.

[steve4102]

The uncrimped ammo is not changing length in my rifle.

There ya go, thanks for the report.

Now you can do an accuracy test when you are bored and have nuttin better to do. A work up crimped vs no crimp.

[Bart B.]

Reynolds, how many shots will each load type's test group have?

I hope it's enough to be at least 90% statistically significant.

[reynolds357]

So far I have shot 25 of my new load of Varget. 1/2" at 100 with 2 flyers that I am 100% confident I pulled. I seriously doubt I will crimp any match kings to perform a test with. The un-crimped is not broke, so I aint a going to "fix it."