FrankenMauser
New member
1:7 twist is fast for 55 gr bullets. Don't expect peak performance.
You'd be better off getting some 69-77 gr projectiles.
You'd be better off getting some 69-77 gr projectiles.
Interesting link on the titanium firing pin, they call it titanium but in the description it’s made of stainless steel. So I wonder what is it.CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from using this information.
Mrappe,
Your IMR4198 should work well if you are not after maximum velocity. I read somewhere that Eugene Stoner used it early in AR development, but it was dropped because its maximum load fell short of his target velocity by a couple of hundred fps. Its maximum loads are about 9% lighter than the bottom end of the usual 223 powder charge range, as Shadow9mm pointed out, but it is also about 9% bulkier than IMR4895, so the light weight does not mean unacceptable case fill. The maximum listed Hodgdon load should be over 85% case fill. That will produce a bit more velocity variation than a higher case fill. Still, many have noted in the 222 Remington, where IMR4198 is more commonly used, that despite more velocity variation than some other powders, it often produced the best accuracy. Velocity variation and accuracy don't always coincide. Lower recoil, muzzle blast, and average barrel time can sometimes be the dominant accuracy terms.
Your primer dents are pretty pronounced. It leads me to ask, how deeply are you seating your primers? Many bolt rifle shooters are in the habit of seating only until they feel the primer anvil's feet touch the floor of the primer pocket. The military, however, will typically compress the anvil into the primer pellet to about -0.003" (what they call reconsolidating the primer, aka, setting the bridge). I've seen tests reported where this improved accuracy and tests reported where it reduced accuracy. The results are not consistent. However, it does move the back end of the primer cup further from the tip of your firing pin and may reduce the chambering indentation, so it's worth trying out.
You can also measure the length of your firing pin protrusion. This video is a good demonstration of how to do it. It should be between 0.028" and 0.036", with 0.032" right in the middle. If yours is on the long side, a different firing pin or a different bolt body can correct it.
Another path is to get a titanium firing pin, whose lower mass will mean it carries less kinetic energy when it hits the firing pin, and the pin metal has to apply less force to bring it to a stop. This thread at Brain Enos's forum includes a post by a fellow who had slamfires and stopped them by getting a titanium firing pin. I tried going to the source recommended in the video, but my browsers all refused because it was insecure and had tracking cookies, like Google.com.
Interesting link on the titanium firing pin, they call it titanium but in the description it’s made of stainless steel. So I wonder what is it.
Then they wouldn’t necessarily be any lighter than a standard steel pin, so no real advantage to being the lighter weight/less mass of a true titanium pin, thus minimizing the possibility of a slam fire.My guess would be a titanium nitrided coating like you can get om drill bits.
That is exactly what I was thinking too.Inserting a primed case and dropping the locked back bolt on to it is an "upper end test" and causes the primer to be struck harder than usual. IF you're ok there, you're very likely to be ok when feeding loaded rounds from the magazine.
The weight of a loaded round, and the force required to strip it from the magazine and push it into the chamber will slow down the bolt (slightly) so the firing pin won't bounce off the primer quite as hard.
The test for this is to use actual live ammo (Or dummies) where it is safe to do so, and fire a round or a few, then eject an unfired round from the chamber and examine the mark on the primer.
I would't think about throwing a way 500 bullets and I don't have another .223 gun to use them in. Besides I have shot plenty of 55 grn commercial ammo it the gun and never had bad accuracy with them. They might not be good for long range accuracy but they have been fine for plinking at 80 yds or so. In the future I plan on getting some heavier projectiles when loading with 5.56 brass and higher pressures for longer ranges.1:7 twist is fast for 55 gr bullets. Don't expect peak performance.
You'd be better off getting some 69-77 gr projectiles.
Ok, first off, 55s in a 1:7 should be totally fine.I would't think about throwing a way 500 bullets and I don't have another .223 gun to use them in. Besides I have shot plenty of 55 grn commercial ammo it the gun and never had bad accuracy with them. They might not be good for long range accuracy but they have been fine for plinking at 80 yds or so. In the future I plan on getting some heavier projectiles when loading with 5.56 brass and higher pressures for longer ranges.
Military 5.56 is used in a number firearms other than the AR15/16. Manufacturers make changes for the M249, that aren't needed in the other weapons.totaldla
That's depends on the primer in question.
Do you think it is a coincidence that when the military created its primer specification that it changed the anvil angle to reduce sensitivity?
Or that CCI recommends those primers for use in the AR, along with the 450, which has a thicker cup which also reduces sensitivity?
I would expect CCI knows their primers, feel free to call them and ask yourself like I did. Use the manufacturers product in ways the don't recommend at your own risk.
When I first started loading for my first AR15 about 20 years ago I had no clue about what a floating firing pin was or what a slam fire was. I had been shooting it some and worked up a pretty good load so I went ahead and loaded up a couple thousand rounds with CCI 400 SRP’s. Then I heard about the dreaded slam fire and went into panic mode. I pulled all 2000 rounds and managed to get a great deal from a friend on 5000 Tula primers that were more suitable and reloaded them for my stash. Since then though I’ve also gone back to using CCI400’s after more research and have shot a few thousand with absolutely no incident. The primers do get slightly dinged but haven’t caused any slam fires, the Tula primers show the same ding as well.Military 5.56 is used in a number firearms other than the AR15/16. Manufacturers make changes for the M249, that aren't needed in the other weapons.
The indent doesn't vary - I've tested this with pistol primers.
Primer seating depth matters. Primer height matters too (I read of too tall SRP). The point is that the speed the bolt carrier moves doesn't effect the indent - give it a try.
But
So-called "slam fires" happen so rarely that it is clear that the design is very robust. A bazzillion guys use CCI400, Fed205, and other "sensitive" primers with their AR15s - they might "blow" primers but they don't report slam fires.
Understanding the AR15 bolt design is helpful.