Group opening up after about 15 rounds

[lisagrantb]

Trying to get the kinks worked out of a new gun and having problems with this one. Here's what's happening, cold bore shot .2 mills high then the next 3 to 5 shots form a nice .5" group. After the barrel cools a bit I fire the next 8 to 10 shots at various ranges, not getting the barrel too hot. If I go back to 100 yards for group testing I find that it's hitting about an inch high and the group has opened up to 1.5 inches. I can clean the barrel and the process starts all over again. I have tried letting the barrel cool down totally and no difference, it's not until I clean the barrel that the groups tighten up.. This is my first 7WSM, can it be fouling that bad in only 15 shots

The action is Defiance and has a 27" Brux barrel. Nightforce scope meticulously mounted, I don't suspect the workmanship or components because everything is first class and I have rechecked everything. I went through the barrel break-in process and have 138 rounds down the tube, so I would think the barrel has settled-in by now. I'm pushing 180 Burger hybrid's .015" off the lands at 3000 FPS using Reloader 25. And no pressure signs at all, during load development I went to 3130 before showing pressure signs.

Any ideas

 

[Coyboy]

what are you cleaning with?

are you pulling lots of "blue" out of the barrel while cleaning?

How long ago was the barrel made by Brux, or do you know the barrels lot number?

 

[WildRose]

Trying to get the kinks worked out of a new gun and having problems with this one. Here's what's happening, cold bore shot .2 mills high then the next 3 to 5 shots form a nice .5" group. After the barrel cools a bit I fire the next 8 to 10 shots at various ranges, not getting the barrel too hot. If I go back to 100 yards for group testing I find that it's hitting about an inch high and the group has opened up to 1.5 inches. I can clean the barrel and the process starts all over again. I have tried letting the barrel cool down totally and no difference, it's not until I clean the barrel that the groups tighten up.. This is my first 7WSM, can it be fouling that bad in only 15 shots

The action is Defiance and has a 27" Brux barrel. Nightforce scope meticulously mounted, I don't suspect the workmanship or components because everything is first class and I have rechecked everything. I went through the barrel break-in process and have 138 rounds down the tube, so I would think the barrel has settled-in by now. I'm pushing 180 Burger hybrid's .015" off the lands at 3000 FPS using Reloader 25. And no pressure signs at all, during load development I went to 3130 before showing pressure signs.

Any ideas

Well it sounds to me like you really did your homework and put together what should be a killer one-holer of a rig.

Is it fully free floated?

Are you sure you are not flinching/jerking?

Pull your bolt out and look at the frong and rear surfaces of the lugs. Are they showing completely even wear on both front and back?

It is possible that it's still fouling badly if it was rough when you started but it sounds like you have a nice custom rig and therefore it should have been hand lapped pretty smooth.

 

[lisagrantb]

I clean with Butches and the break-in was typical for a high quality barrel. When I clean it now after about 20 rounds I remove a small amount of copper, nothing out of the ordinary.
I purchased the barrel from Brux in April of this year, it wasn't a standard contour or twist rate so I would doubt it would have been sitting on their rack for a while, why do you ask this, is there a question about their older barrels.
The barrel is totally free floated and I blue checked the locking lugs and they have 95%+ contact. I won't totally rule me out as the problem, but I have shot this gun for 10 rounds then switched to another gun and constantly shot .5" groups then switched back to the 7WSM and still have the same problem. I know a couple of good marksman; I will get them to shoot it just to make sure it's not me. From what I can see the bore is very smooth but I want to get it borescoped so I can see the entire bore.


Thanks for the input guys

 

[J E Custom]

Trying to get the kinks worked out of a new gun and having problems with this one. Here's what's happening, cold bore shot .2 mills high then the next 3 to 5 shots form a nice .5" group. After the barrel cools a bit I fire the next 8 to 10 shots at various ranges, not getting the barrel too hot. If I go back to 100 yards for group testing I find that it's hitting about an inch high and the group has opened up to 1.5 inches. I can clean the barrel and the process starts all over again. I have tried letting the barrel cool down totally and no difference, it's not until I clean the barrel that the groups tighten up.. This is my first 7WSM, can it be fouling that bad in only 15 shots

The action is Defiance and has a 27" Brux barrel. Nightforce scope meticulously mounted, I don't suspect the workmanship or components because everything is first class and I have rechecked everything. I went through the barrel break-in process and have 138 rounds down the tube, so I would think the barrel has settled-in by now. I'm pushing 180 Burger hybrid's .015" off the lands at 3000 FPS using Reloader 25. And no pressure signs at all, during load development I went to 3130 before showing pressure signs.

Any ideas

Most all barrels do this at some point or another (Reach there fouling point) and there are a
few things you can do.

First; If you need to shoot 15 or 20 shots without cleaning (Like in a match) you need to work
up a load that will shoot in a fouled barrel. I found that backing off the lands and reducing
the powder charge improved the groups in a fouled barrel. (It reduces the pressure and
smoothes out the pressure curve. This load may not shoot quite as well as the clean barrel
load but if the rifle is shooting 1/2 MOA with a clean barrel it should be close to a 1/2 MOA.

Some shooters like 50 or 60 rounds through there barrels before cleaning because they have
a good load for a fouled barrel.

The next thing if the rifle is for hunting only, Be happy with what you have and just get in
a cleaning regiment that maintains the best accuracy. (I have hunting rifles that loose
accuracy between 7 and 9 shots and some that will go as many as 15+ before accuracy
falls off).

The match rifles that I have may have to shoot up to 100 rounds without cleaning and they
have loads that will stay under 1/2 MOA through the entire match.

I hope this has helped you.

J E CUSTOM

 

[ken snyder]

Lisagrantb you have stuck yourself between 3 worlds in your testing. LR testing at 100yds. is no information at all and is counter productive! Hunting conditions probably will never occur in the shot sequences you have described. Decide whether you want a cold shot hunting rifle or a target rifle. If shooting as a Target rifle the barrel does not want to be cleaned as often as you want to clean it and the loads you are shooting have been worked up for the wrong barrel condition. Go to 300yd. minimum, for LR testing it is close enough that the wind wont be impossible to deal with and far enough away that you are actually dealing with relevant Data. Getting to look down a barrel with a bore scope is fun and everyone should get the opportunity to do it at least once. Although in general pushing a patched tight fitting jag down the barrel and hunting for a tight spot ( generally copper fouling ) or a loose spot followed by a hang up ( Blown out rifleing) will suffice, particularly if you need to pay for the time and use of the scope! About the only thing I use a bore scope for is to check the first couple of inches ahead of the freebore including carbon rings that can be hard to remove!

 

[Coyboy]

If that barrel came out of the shop before or during april of 2011 it would have been lot ss15, this was one of the best lots of steel they have run off of. My records indicate I had used over 30 barrels from this lot and all were impressivly accurate, many on f-class guns.

I would ditch the reloader 25 it is too slow for a 7wsm and is likly leaving lots of carbon in the barrel, thus impacting your extended grouping ability. try h4831sc

 

[lisagrantb]

Thanks guys, you have given me some things to work with. I checked my records and I purchased the barrel from Brux on March 15th so maybe it's from the ss15 lot you spoke highly of. The barrel does feel smooth and consistent when I use a tight patch; I have access to a borescope but its 50 miles away so maybe I'll have a look when I'm going that way some day. Again, thanks, and now I have to start eliminating one thing at a time, and that's what I need more of (time).