accuracy crimp and lead coated bullets

[Quag]

not sure where this should be posted but I'm running a G34 Gen 4 MOS with adj rear sight a Dawson fiber optic. After terrible results at a local match I checked the zero and a bit off at 21 feet but at a silhouette USPSA target at 45 feet 8 of 10 total misses from a resting position. Most of my misses that day were long shots. I shoot my reloads which are low PF 9 mm 147 grn Bayou. I checked the rear sights and they were way off so I zeroed or attempted to at 30 to 40 feet and they were much better a lot more hits, at a local 3 gun match (targets at 30 feet or closer) 100% hits. So last night check the zero again at about 40 feet. Inconsistent results, 3 in bunch and 3 all over the place from a resting seated position. Very frustrating night shot about 100 rds and could not get it right. Could it be my Bayou's I have not had a problem with them before.

Read up on stuff and many posters said too tight a crimp affects accuracy. I've eliminated light powder loads as a factor because I'm using a micrometer on my Dillon and I get very consistent loads. I checked the crimp on the mouth and it was .373 to .375. That seemed vary tight compared to the cartridge, I adjusted crimp to .380 which is only about .003 to .005 tighter than cartridge. .380 is what I have measured on a lot of factory rounds.

I have not test fired yet. Any of you have any experience with this? of course my brass is all range brass that I have used several times.

Thx

Edited October 22, 2015 by Quag

[AzShooter]

If you can, pull one of your bullets and see if the coating is being cut. If so, that's your problem. Reduce your crimp until you are no longer cutting into the coating and that should solve your problem.

[dsa]

Too much crimp can also swage lead bullets resulting in accuracy issues like you described.

[GrumpyOne]

There is no crimp....Remove the flair/bell of the case. Measure the case wall thickness at the mouth, multiply that by two. Measure the diameter of your bullet (I'm assuming .355-.356 area)... Adjust your "crimp die to .355 + the case wall thickness x two...EG. Case wall thickness is .yy... multiply that by 2 (2 x .yy), add the diameter of the bullet (.355 -.356), total "crimp" is .355-.356 + (2 x .yy).

[Quag]

There is no crimp....Remove the flair/bell of the case. Measure the case wall thickness at the mouth, multiply that by two. Measure the diameter of your bullet (I'm assuming .355-.356 area)... Adjust your "crimp die to .355 + the case wall thickness x two...EG. Case wall thickness is .yy... multiply that by 2 (2 x .yy), add the diameter of the bullet (.355 -.356), total "crimp" is .355-.356 + (2 x .yy).

thx that equation is enough to make me grumpy, because I'm an engineer I will now obsess with how you came up with that equation, so I'm headed to my basement with my caliper, my reading glasses and a bright light for the next several days

BTW a lot of error in those caliper measurements depending on where you make the measurement on the bullet and the case.

[GrumpyOne]

Very simple really. The bullet is .355, right? The "crimp" die squeezes the outside of the case, right? So, if the bullet is .355, and the case wall is .012, then to straighten out the case, back to where it was before the bell/flair was put in the case at the powder drop, and not damage the bullet, you need to squeeze the case back down to .379 at the smallest point on the case where it meets the bullet.

Lead, plated, and coated bullets are much more prone to having issues with "crimp" than jacketed bullets.

[killab]

Whew.

[Hi-Power Jack]

You really need to address the accuracy issue before you go back out into the competitive

world.

Start with factory ammo ...

Shoot it at 20 yards, from a Very Solid rest - have the mag rested firmly on the table.

Measure your group size - Fire 15 shot groups - eliminate the 3-4 "flyers" and measure

the size of the remaining group.

It should be no more than 4" in size.

Fire 15 of your reloads from Solid Rest at 20 yards - if they are much larger than the

factory ammo group - you need to make more accurate ammo. Look at the bullet

you're using, the crimp and the powder charge (VELOCITY?), and OAL.

When you know your ammo is accurate, you need to look at your ability to hit

targets rapidly (start out slowly). Try an A-Zone at 15 yards.

You might find ( I have ) the Dot Torture Drill to be very helpful.

From what you've posted, it's tough to tell if it's your gun, your ammo, or

YOU.

Take them one at a time, and work on resolving all the problems.

Good luck with it.

[nwhpfan]

I shoot coated 147 and get very good accuracy. As for knocking out the bell... I just straighten it out. If I take a part a bullet, there is just a slight ring around the coating. It's not cut, just a simple ring. Measurement at the case mouth is .378-.379. Bullet diameter is pretty consistent at .3565

[rooster]

What GrumpyOne said. I've been doing it that way for years never a mark on the bullet when pulled. Very consistent results. You won't experience set back because of the taper. If you have to pull a round maybe 2 whacks, I've pulled range pickups where I've had as much as 30 whacks to pull. I'm glad I'm not running that stuff in my gun.

[rancher5]

What GrumpyOne said. I've been doing it that way for years never a mark on the bullet when pulled. Very consistent results. You won't experience set back because of the taper. If you have to pull a round maybe 2 whacks, I've pulled range pickups where I've had as much as 30 whacks to pull. I'm glad I'm not running that stuff in my gun.

Tried Acme and Blue Bullets, B&B'S have a rougher surface found No crimp was best,since case sizes very as much as .10-.15 thousands, Acme glossy smooth finish required a slight crimp ,harder to set up being brass is different sizes,Yes I could sort my brass 9mn, tho that ain't going to happen IMOP

not sure where this should be posted but I'm running a G34 Gen 4 MOS with adj rear sight a Dawson fiber optic. After terrible results at a local match I checked the zero and a bit off at 21 feet but at a silhouette USPSA target at 45 feet 8 of 10 total misses from a resting position. Most of my misses that day were long shots. I shoot my reloads which are low PF 9 mm 147 grn Bayou. I checked the rear sights and they were way off so I zeroed or attempted to at 30 to 40 feet and they were much better a lot more hits, at a local 3 gun match (targets at 30 feet or closer) 100% hits. So last night check the zero again at about 40 feet. Inconsistent results, 3 in bunch and 3 all over the place from a resting seated position. Very frustrating night shot about 100 rds and could not get it right. Could it be my Bayou's I have not had a problem with them before.

Read up on stuff and many posters said too tight a crimp affects accuracy. I've eliminated light powder loads as a factor because I'm using a micrometer on my Dillon and I get very consistent loads. I checked the crimp on the mouth and it was .373 to .375. That seemed vary tight compared to the cartridge, I adjusted crimp to .380 which is only about .003 to .005 tighter than cartridge. .380 is what I have measured on a lot of factory rounds.

I have not test fired yet. Any of you have any experience with this? of course my brass is all range brass that I have used several times.

Thx

There is no crimp....Remove the flair/bell of the case. Measure the case wall thickness at the mouth, multiply that by two. Measure the diameter of your bullet (I'm assuming .355-.356 area)... Adjust your "crimp die to .355 + the case wall thickness x two...EG. Case wall thickness is .yy... multiply that by 2 (2 x .yy), add the diameter of the bullet (.355 -.356), total "crimp" is .355-.356 + (2 x .yy).

You really need to address the accuracy issue before you go back out into the competitive

world.

Start with factory ammo ...

Shoot it at 20 yards, from a Very Solid rest - have the mag rested firmly on the table.

Measure your group size - Fire 15 shot groups - eliminate the 3-4 "flyers" and measure

the size of the remaining group.

It should be no more than 4" in size.

Fire 15 of your reloads from Solid Rest at 20 yards - if they are much larger than the

factory ammo group - you need to make more accurate ammo. Look at the bullet

you're using, the crimp and the powder charge (VELOCITY?), and OAL.

When you know your ammo is accurate, you need to look at your ability to hit

targets rapidly (start out slowly). Try an A-Zone at 15 yards.

You might find ( I have ) the Dot Torture Drill to be very helpful.

From what you've posted, it's tough to tell if it's your gun, your ammo, or

YOU.

Take them one at a time, and work on resolving all the problems.

Good luck with it.

Sent from my SM-G920V using Tapatalk

[Quag]

Original OP here, thx guys: I took out two batches to the range to zero 1) 9mm Bayou 147 FN 3.4 gr tite with the old crimp .373 to .375 (when I pulled these there was a slight ring imprint on the coated lead bullet and it took about 4-5 whacks to get the bullet out). Groups for the .373 crimps were about 4 to 5 inches at 21 feet resting position. Next batch .379 to .380 crimp all the rest the same. Results 3 inch group 6 shoots with one flyer. Repeated it with another 6 and pretty much the same results. So it appears to be the crimp.

Lesson learned never apply a plated bullet crimp to a lead/lead coated crimp. I'm still going to obsesses over Grumpie's equation and I like the 2 whacks rule. Also good idea to get some factory ammo and use that as a test group. BTW I case gauge every round.

The reason I got into this was I did not like the accuracy at 35 to 45 feet. Still working on that but my sights now have a pretty good zero at 21 feet with my reloads so at least I'm back in the game.

Edited October 24, 2015 by Quag

[rooster]

Take average wall thickness. I've found that most 9mm brass is .011 to .012 my bullet is .355 so I set my crimp to be .379. If the finished round comes out to .378 to .380 I'm good. You know what your bullet is so just give yourself a little leway on the brass. If your round comes out to .376 you got a problem. If your out to .383 it probably won't chamber. Most mistakes are from too much crimp. Sammi spec is .380 so now if your running a lead bullet at .356 and your brass is .013 your going to have a ring arround the bullet if you hold .380. So now you've got to pay attention to headstamps and cull any brass more than .012. This is why in 9mm I run only jacketed bullets. 9mm is a high pressure cartridge upwards of 30,000 psi in some cases. You don't want to be screwing around with a tight crimp and unsupported chambers.

[IDescribe]

A couple of things:

1 -- What headstamp are you using? Case walls start to thicken as you move from case mouth to case head. With most 9mm brass, the walls start thickening around .300 from the case mouth. If the base of your bullet is being loaded deeper than that (you get a bit extra over .300 for bullets with beveled bases), you're going to swage the bullet base in loading. As I said, most 9mm brass that wall thickening starts .300 from the case mouth, but some brass it starts as early as .250 from the case mouth. Make sure that's not swaging the bullet base.

2 -- The bell can cause problems with lead and coated lead. You might need to bell the case a bit more.

3 -- As to crimp, everything I load in 9mm is .377 or .378. BUT MAKE SURE you're measuring crimp correctly. If you center the case mouth on the thick part of the caliper jaws, you're doing it wrong. Make sure you measure with the bladed tips right at the case mouth:

CORRECT:

NOT CORRECT:

The reason I would suggest you measure with the thin tips is that when you measure further into the caliper's "mouth" where the jaws are thicker, and what you're measuring is tapered, that extra thickness of the jaws can cause your measurement to be taken behind the case mouth instead of right at it. Remember that by the time the taper crimp die gets the case mouth to the measurement you want it that it has tapered the cartridge just behind the case mouth, as well. I know that 3/16ths of an inch jaw thickness doesn't seem like it would matter, but on the .45ACP in the photos, the difference between measuring crimp at the case mouth and 3/16ths behind the case mouth is .005. Even if I get the case mouth nearly centered on the jaws, I'm still actually measuring 3/32nds behind the case mouth, which might be a difference of .02 or .03. And if I'm shooting for a crimp of .469, which is perfect, but I'm measuring at the thick part of the jaws and centering the case mouth on the jaws, by the time my calipers show me .469, my actual crimp might be .466 or .467, which is significantly over-crimped. Over crimping isn't good for any kind of bullet, but for bare lead, coated lead, or plated, it can ruin accuracy.

Another, perhaps simpler, way to measure crimp accurately is to set your calipers to the desired crimp, turn down the locking screw to lock the calipers at that measurement, then keep adjusting crimp down on the press until you can pass the case mouth a hair into the caliper jaws.

4 -- And one final note: if you're loading on a progressive, make sure you recheck the bell and crimp measurements AFTER all stations are full and you're producing ammo. The stations can drift a thousandth or so from where you set them as you continue to set up consecutive stations.

[KustomHolsters]

I use alot of flair for coated bullets. I then pull my barrel or case gauge and gradually decrease flair with the crimping die until it will drop in and out freely. Then pull a bullet to make sure the coating is not cut. On some bullets, i see a faint line where case mouth was, but never more than a faint line or you will have problems.

[Quag]

And one final note: if you're loading on a progressive, make sure you recheck the bell and crimp measurements AFTER all stations are full and you're producing ammo. The stations can drift a thousandth or so from where you set them as you continue to set up consecutive stations.

All very good suggestions and I was using the calipers correctly as you suggested. The crimp that I ended up with is .377 to .378 so its the same as you. When I pull a coated bullet I cannot see a mark on it. This shooting season I was using a .373 crimp and having a lot of accuracy problems (so now I have a new excuse to blame my terrible results, it can't be me!).

As far as brass I'm using range brass, out of 20 pieces the wall thickness was .010 there was only one .012. If I really get into this I may start sorting by head stamp but I really don't want to get into that (yet).

Thx for the suggestions

[bowenbuilt]

At .373 it probably was not you this time.

[9x45]

Here is a much easier method, called the wipe test. With all stations full, black mark a case at the mouth after the seating station, and run it thru. Should "wipe" about .005" from the case. Again, just enough to remove the bell.