5 shot group opens up on 4th&5th shot

Jags19 · March 8, 2009, 07:45 PM

Shooting 44mag S&W 629 light hunter , Sierra 220grain bullet, 23.0gr H110 and Winchester brass. First three shots of a five shot group off solid rest less than .75 inch spread at 50 yards but last 2 shots open way up making total group 3.25inch spread. This is a repeatable problem. Advice please....

IllinoisCoyoteHunter · March 8, 2009, 07:53 PM

are you cleaning your bore in between the 5 shot groups? If so, are you shooting any fowling shots?

Jags19 · March 8, 2009, 07:58 PM

Not cleaning in between the 5 shots and I shoot one fouling shot.

SL1 · March 8, 2009, 08:28 PM

Some possibilities:

1. Are you shooting relatively fast, or letting the barrel cool between shots? If fast, then possibly barrel temperature is making the difference.

2. Are you shooting the 5-shot string starting with the same chamber in your cylinder each time? If so, it is not that uncommon for a revolver to have different chambers shoot to slightly different points of impact with the same aiming point. But, going from .75" to 3.25" at 50 yards in a little much for that particular issue. Still worth checking, though.

3. Since it is the LAST 2 shots that are fliers each time, there is a particular gun malfunction that will produce that. Your cylinder may not be latching for those shots. The problem occurs when the pawl that turns the cylinder does not QUITE get the cylinder to the point where the latch will engage. When the cylinder is pretty well balanced with ammo in all chambers, the cylinder turns far enough for the latch to finish turning the cylinder and drop into the notch. BUT, for the last shot or 2, the pawl is trying to lift bullets in the loaded chambers on one side that are not balanced by bullets in the already fired chambers on the other side, and the latch doesn't drop into the notch before gravity pulls the cylinder back a little. So, you fire with an unlatched cylinder and slightly misaligned chamber for ONLY those last two shots. I had a new revolver that did that because the pawl was machined slightly too thin. Once I realized that my gun was shaving brass from my bullets and leaving some in the forcing cone, I was able to find the cause.

4. Maybe it is YOU. Are you resting between shots, or do you get tired or lose focus by the 4th and 5th shots?

SL1

WESHOOT2 · March 10, 2009, 03:36 PM

Your bullets are 'jumping crimp'.
That's why the last rds are missing the group; their OAL has increased.

Firm crimp using the Redding Profile Crimp die......solved.

ThomasT · March 10, 2009, 08:46 PM

Weshoot is correct. I had the same problem with a new blackhawk and 240gr loads. Make sure your brass is new and the crimp is heavy. Make sure the expander ball is .004 smaller than your bullet.

I have more trouble with winchester brass being thinner the remington brass. I now use the rem for heavy loads and the win for lighter loads.

Ruger4570 · March 10, 2009, 11:48 PM

I had a Ruger 45 with a 4 5/8" barrel that shot very accurately... generally..
If I had your gun and wanted to try to figure out what is going on I would fire 5 or 6 shots from the same chamber. I would also fire one shot from each chamber, but only load that chamber and not the entire cylinder.
I made my 45 a lot more accurate and repeatable by having the chamber mouths reamed. I believe that most manufacturers ream all the chambers at the same time. With 6 different reamers it would not be unbelievable to think one or two may be spec'd different from the others.
Nevertheless, I sure would want to know the reason I got a 4 shot half inch group and then it opened up so much. Best of luck on your little quest.

RamSlammer · March 12, 2009, 12:06 AM

I'll join the chorus in guessing the bullets are jumping crimp. Had the same issue with some hot 158 LSWC-GC's in a .357 GP 100. Went a bit lighter on the expander die setting, added a bit more roll crimp and the problem disappeared.

To check just caliper all 5 rounds before loading the gun, shoot 3 then remove and measure the remaining 2.

bear300us · March 12, 2009, 01:53 AM

I have a 22 revolver an an couple cylinders shoot diffrent than the others,number the cylinders with a sharpie an see if its the same cylinders shooting like that.

SL1 · March 12, 2009, 09:35 AM

Maybe we could turn this into a lottery

Hopefully, Jags19 will solve his problem and tell us what was actually causing it in HIS gun.

SL1

James R. Burke · March 13, 2009, 08:13 PM

I am betting WESHOOT 2 got it right.

Slamfire · March 14, 2009, 09:36 AM

3.25 inch group at 50 yards seems pretty good to me.

Jags19 · March 14, 2009, 10:19 AM

Sorry for not getting back sooner but work has me traveling. Crimp not heavy enough. OAL increased by .003-.004 on last two shots. Still trying to find the right amount of crimp. What does it look like if you over crimp? Using Lee's Factory Crimp die plus I might be over expanding the case mouth. Will check that today.

Thanks for everyone's suggestions to a newbe loader. Jags

SL1 · March 15, 2009, 01:02 PM

If you were using a roll-crimp, then a COL increase of 0.003" to 0.004" doesn't sound like a classic situation of "jumping crimp." Unless the crimp is actually straightened out enough to substantially affect bullet pull, I doubt that would change pressures significantly in a .44 Magnum.

Did you try shooting those slightly longer cartridges and verify that they indeed shot outside your initial group?

SL1

Jags19 · March 22, 2009, 11:06 AM

Just want to show that the crimp adjustment paid off. Thanks again. Jags

March 8, 2009, 07:45 PM	#1
Jags19 Junior Member Join Date: January 25, 2009 Location: Iowa Posts: 4	5 shot group opens up on 4th&5th shot Shooting 44mag S&W 629 light hunter , Sierra 220grain bullet, 23.0gr H110 and Winchester brass. First three shots of a five shot group off solid rest less than .75 inch spread at 50 yards but last 2 shots open way up making total group 3.25inch spread. This is a repeatable problem. Advice please....

March 8, 2009, 07:53 PM	#2
IllinoisCoyoteHunter Senior Member Join Date: December 23, 2008 Location: Southern Illinois Posts: 1,527	are you cleaning your bore in between the 5 shot groups? If so, are you shooting any fowling shots? __________________ ~~IllinoisCoyoteHunter~~ ~NRA LIFE MEMBER~ ~NRA CERTIFIED INSTRUCTOR~

March 8, 2009, 07:58 PM	#3
Jags19 Junior Member Join Date: January 25, 2009 Location: Iowa Posts: 4	Not cleaning in between the 5 shots and I shoot one fouling shot. Last edited by Jags19; March 8, 2009 at 08:22 PM.

March 10, 2009, 03:36 PM	#5
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	better guess? Your bullets are 'jumping crimp'. That's why the last rds are missing the group; their OAL has increased. Firm crimp using the Redding Profile Crimp die......solved.

March 14, 2009, 10:19 AM	#13
Jags19 Junior Member Join Date: January 25, 2009 Location: Iowa Posts: 4	Solved, I hope! Sorry for not getting back sooner but work has me traveling. Crimp not heavy enough. OAL increased by .003-.004 on last two shots. Still trying to find the right amount of crimp. What does it look like if you over crimp? Using Lee's Factory Crimp die plus I might be over expanding the case mouth. Will check that today. Thanks for everyone's suggestions to a newbe loader. Jags

March 8, 2009, 08:28 PM	#4
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Some possibilities: 1. Are you shooting relatively fast, or letting the barrel cool between shots? If fast, then possibly barrel temperature is making the difference. 2. Are you shooting the 5-shot string starting with the same chamber in your cylinder each time? If so, it is not that uncommon for a revolver to have different chambers shoot to slightly different points of impact with the same aiming point. But, going from .75" to 3.25" at 50 yards in a little much for that particular issue. Still worth checking, though. 3. Since it is the LAST 2 shots that are fliers each time, there is a particular gun malfunction that will produce that. Your cylinder may not be latching for those shots. The problem occurs when the pawl that turns the cylinder does not QUITE get the cylinder to the point where the latch will engage. When the cylinder is pretty well balanced with ammo in all chambers, the cylinder turns far enough for the latch to finish turning the cylinder and drop into the notch. BUT, for the last shot or 2, the pawl is trying to lift bullets in the loaded chambers on one side that are not balanced by bullets in the already fired chambers on the other side, and the latch doesn't drop into the notch before gravity pulls the cylinder back a little. So, you fire with an unlatched cylinder and slightly misaligned chamber for ONLY those last two shots. I had a new revolver that did that because the pawl was machined slightly too thin. Once I realized that my gun was shaving brass from my bullets and leaving some in the forcing cone, I was able to find the cause. 4. Maybe it is YOU. Are you resting between shots, or do you get tired or lose focus by the 4th and 5th shots? SL1

March 10, 2009, 08:46 PM	#6
ThomasT Senior Member Join Date: January 22, 2009 Location: Texas Posts: 2,773	Weshoot is correct. I had the same problem with a new blackhawk and 240gr loads. Make sure your brass is new and the crimp is heavy. Make sure the expander ball is .004 smaller than your bullet. I have more trouble with winchester brass being thinner the remington brass. I now use the rem for heavy loads and the win for lighter loads.

March 10, 2009, 11:48 PM	#7
Ruger4570 Senior Member Join Date: April 3, 2005 Location: Rochester, New York Posts: 2,136	I had a Ruger 45 with a 4 5/8" barrel that shot very accurately... generally.. If I had your gun and wanted to try to figure out what is going on I would fire 5 or 6 shots from the same chamber. I would also fire one shot from each chamber, but only load that chamber and not the entire cylinder. I made my 45 a lot more accurate and repeatable by having the chamber mouths reamed. I believe that most manufacturers ream all the chambers at the same time. With 6 different reamers it would not be unbelievable to think one or two may be spec'd different from the others. Nevertheless, I sure would want to know the reason I got a 4 shot half inch group and then it opened up so much. Best of luck on your little quest.

March 12, 2009, 12:06 AM	#8
RamSlammer Senior Member Join Date: November 5, 2008 Location: Arkansas Posts: 722	I'll join the chorus in guessing the bullets are jumping crimp. Had the same issue with some hot 158 LSWC-GC's in a .357 GP 100. Went a bit lighter on the expander die setting, added a bit more roll crimp and the problem disappeared. To check just caliper all 5 rounds before loading the gun, shoot 3 then remove and measure the remaining 2.

March 12, 2009, 01:53 AM	#9
bear300us Member Join Date: May 26, 2008 Location: metro detroit Posts: 49	I have a 22 revolver an an couple cylinders shoot diffrent than the others,number the cylinders with a sharpie an see if its the same cylinders shooting like that.

March 12, 2009, 09:35 AM	#10
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Maybe we could turn this into a lottery Hopefully, Jags19 will solve his problem and tell us what was actually causing it in HIS gun. SL1

March 13, 2009, 08:13 PM	#11
James R. Burke Senior Member Join Date: January 3, 2009 Location: U.P. of Mich/Quinnesec Posts: 1,897	I am betting WESHOOT 2 got it right.

March 14, 2009, 09:36 AM	#12
Slamfire Senior Member Join Date: May 27, 2007 Posts: 5,261	3.25 inch group at 50 yards seems pretty good to me.

March 15, 2009, 01:02 PM	#14
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	If you were using a roll-crimp, then a COL increase of 0.003" to 0.004" doesn't sound like a classic situation of "jumping crimp." Unless the crimp is actually straightened out enough to substantially affect bullet pull, I doubt that would change pressures significantly in a .44 Magnum. Did you try shooting those slightly longer cartridges and verify that they indeed shot outside your initial group? SL1