Losing accuracy after 20ish rounds?

[GetReal]

So, I've tested this 3 times and its held true each time....

Rds 1-10 groups about 1.25" (@ 100 yd, 5-shot grps)

Rds 10-20 groups 0.3 - 0.5" ( 2 grps of 5 rds)

Rds 20-25+ groups about 1.25"

Details:

6 Dasher F-class gun ... 32.0 +/- gr Varget... CCI 450 primers ... 2980-3000 fps... 105 Berger H.T.... Douglas 28" bbl 1: 7.5

I fl size, with neck bushings, anneal brass each time, careful brass prep, careful powder measure, LE Wilson chamber type seater dies etc etc etc

I don't understand how my "window" for accurate fire is only 10 rds wide. Is that typical?

I get "seasoning" a cold clean barrel. I get a fouled bbl loses accuracy. But I only get 10 rds accurate fire? With my other bolt guns its 30-50 rounds, and even suprpessed semi autos are 30+ rounds.

What gives? Do match shooters clean after every 10 rounds, typically?

Thanx.

 

[Frankm]

How many rounds down the tube? Building copper?

 

[Dusty Stevens]

Thats a strange one. Is the barrel getting unusually dirty?

 

[ballisticdaddy]

Curious if this started with a clean bore and if you kept shooting would it get small again? I have a .284 Win that takes about 30 rounds after a deep cleaning to settle in but will then go for almost 200 rounds before it would start to open back up.

 

[GetReal]

Thats a strange one. Is the barrel getting unusually dirty?

Compared to other bolt guns and my suppressed semis....no.

 

[GetReal]

How many rounds down the tube? Building copper?

Less than 500. And I use copper cleaner every 100 rounds or so, or every 3rd or 4th cleaning.

 

[GetReal]

Curious if this started with a clean bore and if you kept shooting would it get small again? I have a .284 Win that takes about 30 rounds after a deep cleaning to settle in but will then go for almost 200 rounds before it would start to open back up.

Yes, all 3 tests started with a cold clean bore.

I guess I didn't wanna wait "waste" all the components waiting for it to settle back down a second time.

 

[Dave M.]

So, I've tested this 3 times and its held true each time....

Rds 1-10 groups about 1.25" (@ 100 yd, 5-shot grps)

Rds 10-20 groups 0.3 - 0.5" ( 2 grps of 5 rds)

Rds 20-25+ groups about 1.25"

Details:

6 Dasher F-class gun ... 32.0 +/- gr Varget... CCI 450 primers ... 2980-3000 fps... 105 Berger H.T.... Douglas 28" bbl 1: 7.5

I fl size, with neck bushings, anneal brass each time, careful brass prep, careful powder measure, LE Wilson chamber type seater dies etc etc etc

I don't understand how my "window" for accurate fire is only 10 rds wide. Is that typical?

I get "seasoning" a cold clean barrel. I get a fouled bbl loses accuracy. But I only get 10 rds accurate fire? With my other bolt guns its 30-50 rounds, and even suprpessed semi autos are 30+ rounds.

What gives? Do match shooters clean after every 10 rounds, typically?

Thanx.

This is not normal at all. Most F class shooters will shoot the entire day without cleaning (3 relays of 20 shots for record plus unlimited sighters can easily push 100 rounds)
Something is not right with what you are seeing.
Curious what your seating depth is in relation to the lands??

 

[GetReal]

Curious what your seating depth is in relation to the lands??

30 off.

Had some ppl tell me to get right on the lands. Even jammed. Then others came and told me that was foolish and dangerous.

I'm wondering if I slowed velicity to 2850ish.... I had a good accuracy node there, also. In theory, slower bullets copper up the bbl slower.

Your comment that "this is not normal" helps... that I should expect different.

 

[Mark W]

@GetReal 1.25” at 100 yards is pretty terrible. What’s your rate of fire? I’m wondering if it could be heat related. I’ve had skinny barrel rifles that got squirrelly as they heated up due to inadequate barrel to stock clearance. With only 500 rounds on it now, I’m assuming that this build has never performed to your expectations?

I’ve never had the problem, but I did have a trusted BR gunsmith tell me that he had saw rifles do funny stuff as they heated up because the barrel wasn’t torqued enough.

I would check all of the usual suspects barrel clearance, barrel torque, bedding, action screw torque, scope mounting, and the scope itself. Of course, a look with a bore scope wouldn’t hurt if you haven’t done that yet.

If all that checks out, I would definitely be talking with the builder and barrel maker.

 

[GetReal]

@GetReal 1.25” at 100 yards is pretty terrible. What’s your rate of fire? I’m wondering if it could be heat related. I’ve had skinny barrel rifles that got squirrelly as they heated up due to inadequate barrel to stock clearance. With only 500 rounds on it now, I’m assuming that this build has never performed to your expectations?

I would check all of the usual suspects barrel clearance, barrel torque, bedding, action screw torque, scope mounting, and the scope itself. Of course, a look with a bore scope wouldn’t hurt if you haven’t done that yet.

If all that checks out, I would definitely be talking with the builder and barrel maker.

12 shot every 30 seconds. Barrel got barely warm.... in 60 degrees.

I bore scoped it... nuthin jumped out at me. A littte darker near the chamber than down near the muzzle. The fact it groups decent at rds 10 - 20 but then turns to crap suggests to me its barrel fouling....right?

Unfortunately Stan Taylor died (Douglas, the barrel maker. They guy knew his stuff)

 

[JMayo]

At the least a wet patch followed by dry ones after every card. My ppc goes down at 20 +- shots.
On my match barrel copper killer is a waste of time & effort.
I use kg1 & #9 on a patch then Dry with 4+h- patches. I've got to get it done fast.

 

[beemanjohn]

Unless you are really bad at loading, or real bad at shooting, I bet you just got a bad barrel. (it happens) Heck, I have ADL Remingtons I bought at Walmart that shoot way better than that.

 

[scissorhands]

out of the 3 times you tested, did you get the same exact results, where shots 10-20 were .5 moa?

 

[rwj]

Have to admit that after about 20 rounds/5groups my focus/concentration/interest starts to fade…

 

[K22]

Based on what has been posted I would suspect one or more of the following in the following order:

1. Over cleaning with copper solvents.

2. Overheated barrel

3. Shooter fatigue, trying to shoot too much, too fast.

4. Rifle (barrel) capable of only 1 1/2 moa

You may want to try this - I've used this before myself and with fellow shooters, and it can be helpful to diagnose your problem.

First put the bore scope in closet. Second, clean the barrel with whatever carbon remover you have and a bronze brush. Any carbon remover will do, Hoppe's 9 for example is fine but no harsh / intense copper solvents.

Don't crazy with this, just a normal clean, a few solvent-soaked patches, let sit, then about 10 brush strokes, 3 more solvent soaked patches then dry patch. Finally run a patch with three small drops of Hoppe's gun oil or mineral oil down the bore. Before you go to the range, run a dry patch down the bore.

Take your time and shoot several 3 shot groups allowing the barrel to cold between the groups. Shoot the 3 shot groups slowly. It may take about 10 to 20 shots before the barrel starts shooting consistently so be patient. You don't have to do all of this in one range session, if fact I would advise against it.

What we are trying to achieve is an aggregate record of three shot groups over time to discern if cleaning is the culprit, and / or the shooting method, and / or the shooter, and what the barrel is capable of shooting. Shoot 20 - 3 shot groups (60 rounds) and do not clean until this is sequence is completed. Label the group in the sequence shot, i.e., 1, 2, 3 etc.

Study the groups and see what they tell you. If this works as it has for me in the past, you should start to see some consistency in group size after about 10 - 20 shots. Note I said consistency, not necessarily small groups.

If consistency is achieved, clean with carbon remover only every 50 rounds or so.

 

[GetReal]

out of the 3 times you tested, did you get the same exact results, where shots 10-20 were .5 moa?

Yes.

 

[GetReal]

UPDATE:

After talking to both Berger (shoot well in all my guns but this 6 Dasher ) and Compass Lake (built guns / spun bbls for my two others guns consistently under half moa) the consensus of both was either:


1. A tomato stake bbl, replace it or

2. Clean / lap bbl with JB bore paste. At this point....NOTHING to lose.

 

[Texas Solo]

My barrel starts shooting 1" low after 15 rds. I've never figured it out. It's a well floated heavy Shilling bull barrel. After 15, I have to hold top of 10 ring.

I don't think you have a cleaning issue.
And if all your ammo is identical, that eliminates an ammo issue.

For a barrel to go from bad to good to bad again is really weird. I'd suspect a barrel issue. Harmonics?

 

[DShortt]

UPDATE:

After talking to both Berger (shoot well in all my guns but this 6 Dasher ) and Compass Lake (built guns / spun bbls for my two others guns consistently under half moa) the consensus of both was either:


1. A tomato stake bbl, replace it or

2. Clean / lap bbl with JB bore paste. At this point....NOTHING to lose.

You said you have access to a bore scope. If you really want to get to the bottom of this I'd keep careful notes including bore images and repeat your experiment another 3x. You'll find a pattern in there somewhere. Scope between all shot groups. Yes, it will take some time but if you REALLY want to know that's what you need to do.

Or you can swap barrels and if it doesn't repeat then it's an unknown barrel issue and you can forget about it.