Brake Installation Accuracy Problems

[james]

I have a BAT action 6BR in a Shehane ST1000 stock with a Brux barrel that I just had a Harrell brake installed on. The gunsmith did an excellent job on the installation however using the same loads that I had previously used the accuracy has fallen off. I have tried several different loads that I used before and the accuracy with the brake installed is not as good as before. I understand point of impact maybe being different however not a loss in accuracy? I realize it may be coincidence and something else is my problem such as scope issue etc. I'm checking now to ensure everything is secure such as rings, scope base etc.

Just wanting confirmation that accuracy with/without a brake should be the same.

Thanks

 

[BRGUY]

IF the brake was installed properly, accuracy should be as good as or better than what it was before!

IF the brake is just screwed on hand tight, that can cause issues, because it can very easily shift, causing a change in vibration and harmonics, which can and will have an adverse effect on accuracy.

 

[james]

I only hand tighten my brake - how should it be tightened? I failed to mention I did perform a search on this forum and there were several threads regarding brake installation and accuracy issues. Several posts noted the extra weight of the brake has altered the barrel harmonics and one would need to change load combinations.

 

[BartsBullets]

Re-Tune your gun.

Bart

 

[johara1]

What was the thread size? .... A small thread diameter can alter the bore size..... jim

 

[MClark]

How does the crown look?

 

[james]

The Harrell brake specs for my 1.25" Brux barrel - 1" x 32 thread.

 

[james]

My gunsmith re-crowned the barrel when he installed the brake.

 

[BoydAllen]

As usual, Bart nailed it. You need to do a start from scratch retune. Adding the weight of a tuner, or anything else for that matter, changes the way that a barrel vibrates.

Some time back, a friend who builds rifles ran into the same issue. In his case he wanted to keep the powder charge, so he worked with seating depth to see if he could reclaim the previous accuracy that way. His bullet hole cutting bullet hole seating depth went from a firm touch to an .080 jump for one powder, and when I gave him some LT30 to try he found his best accuracy (with the tuner) at about .060 off the lands. I probably would have given up long before getting that far off of the lands, but he is a real out of the box, not afraid to try anything guy and he stayed with it, and kept going. He did his testing in .010 intervals, shooting two shot tests (to start). This has worked very well for him.

 

[james]

Thanks for all the tips - I like the idea of really experimenting with seating depth. I have a good supply of Varget and Berger 105 Hybrids so I would like to stay with these for now. I think I'll try starting at firm touch then .010 off, going up to .020 off and so on using 2 shot tests. Hopefully I can find a sweet spot with Varget/Berger 105's.

 

[BoydAllen]

Have you read what the Berger manual has to say on finding a seating depth? It is also on their web site. Before you start your tests I would recommend reading it carefully.

 

[johara1]

The Harrell brake specs for my 1.25" Brux barrel - 1" x 32 thread.

Good thats not an issue then, I never had an issue with or without a brake, except for the cost and the noise. One other thing take it off and see if it still shoots. Never had to retune, it may shoot a different spot but it would group the same. That was over 10 or 12 barrels one more thing, make sure there are no burrs sticking out of the holes, seen that before and I used a 3/16 rod to tighten it, you need a little more than by hand and make sure the surfaces are clean...... jim

 

[james]

Thanks again for all the great advice! I have a follow-up question regarding determining the cartridge overall length where it is touching the lands. I have a Sinclair gauge that I use to identify COAL where the bullet is touching the lands - it is straight forward to use. I have also used the dummy round method to determine COAL where the bullet touches the land. In this method I resize a fired case then just seat the bullet. I then chamber this dummy round and close the bolt. I extract the round and measure it's overall length - thought being this should be the COAL where the bullet is just touching the lands.

My confusion is the measurements using the two methods above is always different the COAL is never the same? The dummy round method yields a COAL that is always longer that that of using the Sinclair gauge. Would appreciate thoughts on what I'm doing wrong!

 

[LRPV]

Thanks again for all the great advice! I have a follow-up question regarding determining the cartridge overall length where it is touching the lands. I have a Sinclair gauge that I use to identify COAL where the bullet is touching the lands - it is straight forward to use. I have also used the dummy round method to determine COAL where the bullet touches the land. In this method I resize a fired case then just seat the bullet. I then chamber this dummy round and close the bolt. I extract the round and measure it's overall length - thought being this should be the COAL where the bullet is just touching the lands.

My confusion is the measurements using the two methods above is always different the COAL is never the same? The dummy round method yields a COAL that is always longer that that of using the Sinclair gauge. Would appreciate thoughts on what I'm doing wrong!

Not really anything wrong just two different methods. You need to pick one that is easy for you to repeat the same every time and stick with it. It's not the actual distance of jump/jam it's the relationship between YOUR measurement and the seating depth you determine through testing that works best. Whatever method you choose needs to be repeatable though.

And to add, when you had your barrel threaded it reduced weight, you screwed the brake on and it increased weight which effectively you added a 4oz ish tuner on the end of the barrel that was not part of your initial load tune. Tuners work and this could very well be the culprit. If the smith re crowned the barrel in my mind that would also be suspect. Remove the brake and shoot without it. Cheap and easy test. If the brake was not bored to the correct size, it will let you know as well. Hand tight is fine as long as it doesn't come loose while shooting.

 

[johara1]

Thanks again for all the great advice! I have a follow-up question regarding determining the cartridge overall length where it is touching the lands. I have a Sinclair gauge that I use to identify COAL where the bullet is touching the lands - it is straight forward to use. I have also used the dummy round method to determine COAL where the bullet touches the land. In this method I resize a fired case then just seat the bullet. I then chamber this dummy round and close the bolt. I extract the round and measure it's overall length - thought being this should be the COAL where the bullet is just touching the lands.

My confusion is the measurements using the two methods above is always different the COAL is never the same? The dummy round method yields a COAL that is always longer that that of using the Sinclair gauge. Would appreciate thoughts on what I'm doing wrong!

.

When you say measure over all length what do you mean? tfrom the meoplat to base of the case? you should be measuring from the ogive to the base the case ..... jim

 

[Shooter13]

You installed a tuner without knowing it, will require load development again. Good luck!