Possible Muzzle Crown Problem

[brinkhdlow]

Hello, need some help. The gun I am having problems with is a DPMS LR-308 and it is a 24” bull Barrel with a NightForce NXS 5.5X22-50 as the optic system and a Geissele designated Marksman Trigger. Before I sent the barrel it to the gunsmith, the barrel was not fluted and did not have a brake on it. My grouping was minute to sub-minute at 100 yards with Hornady TAP 168 A-Max. I sent off the barrel to a local gunsmith to have him flute the barrel and install a brake to help improve accuracy. When I got the barrel back I started shooting and the groups had become worst. I struggle to get 1 inch groups at 100 yards and the groups a unpredictable. I have used several different types of ammunition such as: Federal Sierra Matchking 168, Hornady TAP A-Max in 155 and 168, and HSM Berger VLD 168. The Hornady TAP 168 is still the best grouping, but again my 5 shot groups are anywhere between .0800 inches to 3.750 inches! I have shot it clean and fouled. The groups get a little better with a fouled barrel, but not much. I have checked all my scope rings and mounts to verify they were tight, which they were. The only thing I can think of is the crown is the problem. I can see some pitting and some dings on the outside, but I wouldn’t think that would cause my shot to be off by approximately 3 inches, or could it? Should I recut the crown and if so should I got with an 11 degree target crown or another recessed target crown? Any suggestion would be great. Thanks

 

[problemchild]

Re: Possible Muzzle Crown Problem

Try shooting with the brake off. If no joy try to cryo the barrel. If no joy recrown. If no joy then maybe Joy doesn't like to party with you. Maybe Joy like man with bigger stick.

 

[Zebra644]

Re: Possible Muzzle Crown Problem

Whats your round count down the barrel? Mine shoots sub-moa with 168 FGGM but I had to get right around 260 rnds through it before it started to shoot like that and I have not touched the barrel. A FUBAR'd crown can casue that. My dad had a S&W 629 classic, chambered in .44 Mag. He shot it from a bench with a pistol rest, 25 yds. 1st round dead nuts on, from then on it looked like a shotgun pattern. We both shot it with differnt loads, and we cleared the pistol and gave it a real good look over, felt like a burr on on the crown of the barrel. Sent it back to Smith with a target and a letter got it back with a note stating it was a problem with the crown. After that shot like a champ.I would also look at the barrel to make sure there is no play. I am not sure that by fluting the barrel and adding the break caused enough change in your barrel harmonics to cause it to shoot like that. If it were me I would see take it back to him with the target and say here, and then go from there, also I would make sure it was done free of charge.

 

[brinkhdlow]

Re: Possible Muzzle Crown Problem

I already tried to take the break off and she no worky and no joy. I will try the Recrown first and them maybe the Cryo. What does somthing like that cost? Here are some inmages of the crown.

 

[brinkhdlow]

Re: Possible Muzzle Crown Problem

I an right at 700 to 1000 rounds and I have checked and recheck for play in the rifle, from the scope all the way to the barrel and she does not have any play at all. I also posted some pictures of the muzzle crown. I did not go through a proper break-in because I was a dumby, but the gun was shooting sub-minute be for the work I had done to it, but the crown does not look that bad, I Think.

 

[BOLTRIPPER]

Re: Possible Muzzle Crown Problem

crowns are best checked with a borescope....from the inside

if this barrel don't shoot its because there is throat erosion

 

[Jumper]

Re: Possible Muzzle Crown Problem

Fluting could have introduced stress into the barrel. Anytime metal is machined stress is created somewhere in it. Thats why reputable barrel makers final step after all machining is done is to heat the barrels up to a certain temp, hold that temp and cool them down slowly. This stress-relieves the barel. And from what I've read, fluting introduces a lot of stress to a barrel and cryogenic treatment is ineffective. Here's a good article on what makes a barrel accurate. Stress is addressed in about the last 1/3 of the article. http://www.riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htm