Building a benchrest rifle

[Lee Martin]

Problems
_________________________

I tested the setback barrel Saturday and wasn’t happy. The wind was bad, but even so the gun wouldn’t group (mid 3's). I ladder tested in 0.3 gr increments from 27.0 to 29.0 and couldn’t find consistent nodes. Basically, it would put three shots in a nice hole at 28.0 and 28.6. That was encouraging until I moved to five shot groups. Kept getting two’s and two’s plus a stray. I’m now thinking I may have a scope problem. So tomorrow I’ll head to the range with two scopes. On the gun now is my dad’s old 36x Leupold BR with fine crosshairs. I’ll also take my March to compare them side-by-side. If I can get it to shoot, I'll drive to Roanoke for the match. Otherwise, I’ll come home, install the old barrel which still shot, and repeat all this on Saturday. It becomes a game of “if-then”:

• If it shoots with the Leup but not the March, the March goes back to Japan for overhaul
• If it doesn’t shoot with either, the barrel may be toast, even after being setback. I have Lederer and Kreiger 13.5” twist blanks on the way. Shilen #1 will be assessed against Shilen #2
• I’ll load old, known brass, against the current lot. Differences between the two only complicates figuring root-cause. On the new batch, I turned some 0.0090” to see if it wants more neck clearance. Those shot about the same as the 0.0095”s.

Other variables I checked include torque on the pillar bolts, firing pin protrusion, and scope mounting (both rings and base). Borescoping the Shilen showed nothing to suggest the barrel is done. The new chamber also cut beautifully.

Here’s a photo of the bench from Saturday. Pretty much used everything I had to diagnose the miss.



Frustrating, but this is part of the sport. It reminds me a lot of drag racing. When the car won’t run the number or breaks, tools get pulled and the battle begins. I just hope my problem isn’t tied to $2,500 optics.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[cherokeetracker]

I hope you can get this ironed out. Good Luck.

Charles

[bradshaw]

Spoke with Lee last night on this subject. Fortunately, Lee has sensible mounts on his rifle, meaning he can swap scopes without removing scope from rings. A spilt ring which simultaneously clamps scope & base represents a stabile yet maddening design. Lee’s father Lee Martin, Sr., and I intuit the barrel going “soft,” headed south with accuracy falloff based on wear. Wind obviated dead nuts shooting, a buffeting wind plays spread even with great timing on the flags. An old Leopold 36x40mm AO (Adjustable Objective) scope is now on the rifle in place of the expensive March scope. If Lee lucks onto dead air today and shoots tight again, he can remount the March glass and shoot for a repeat. My advice was not to cocktail loads but shoot. Mind you, I have no credentials on the bench.

Some barrels from the same womb just don’t last as long as others. Perfectly capable of being wrong, but I don’t think it’s the March scope.
David Bradshaw

[cmillard]

Hopefully not for how expensive march scopes are

[Lee Martin]

Match #9 – NBRSA Virginia State Championship, Roanoke, VA
______________________________________________________________

I installed my dad’s Leupold 36X BR and went to the range early Friday. The first shot went off at 6:50 AM as the sun was rising. The wind was bad, but I had one goal. Get the gun to show signs of being competitive. I had no intention of shooting lots of groups. Instead, once it stuck bullets in the same hole, I was off to Roanoke. It took 4 rounds to reach the desired POI after bore sighting. I then put 3 in a tight cluster. That was followed by 5 under stiff conditions on sound flag reads. The group measured mid-2’s. Good enough to head south. I wasn’t confident in my equipment, but used any excuse to go.

Leupold 36X on home-made rings:



The motel I booked was interesting. I probably shouldn’t have expected much for $44/night. What I found would’ve made Norman Bates do a double take. No big deal, I’m current on my tetanus shot.











26 competitors registered for the match, 3 of which were Hall of Famers. The others were all names I recognized. Light varmint went in the morning, heavy in the afternoon.



Hall of Famer Smiley Hensley on the line.







The wailing wall:



I went to the line with three loads in the block for target #1. Taking two shot tests on the sighter, nothing looked good. I decided to run the load from the day before but the gun was wild. On flag reads I know I can manage, shots went everywhere. The wind was intense and switchy, however not enough to warrant what happened at 100. Over five records, I was in the 4’s and low 5’s. That’s worse than the horrible groups I’ve experienced for a month. I finished 24 out of 26 and was scratching my head. It seems the Friday test was a fluke. Perhaps I got lucky on those eight shots. Next steps:

• The March scope isn’t likely the cause. My dad’s Leup is a known entity
• At 800+ rounds, the barrel could be tired...really tired
• Barrel #1 is now on the action. It’ll be tried under both optics

That night I spoke with my friend Boyd Allen by phone. Boyd is one of the most knowledgeable guys I know in benchrest. He suggested I also check the bedding, which I’ll cover in a separate post. Among other things, he said to go through the front rest. Sensible enough, but something I wouldn’t have thought to do. I did and found the entire top to be loose. In fact, it was way loose. Here’s video of the problem.



With the center post screws locked, the top shouldn’t move. Mine did and any canting can wreak havoc on paper. The smaller screw to the right had backed out.



Did this cause the erratic performance? Maybe, maybe not. It’s now fixed and Saturday I’ll shoot barrel #1 with the March and Leupold. Barrel #2 will also be tested.

Benchrest is like an orchestra. When one instrument out of many goes awry, you’re off the rails.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[cherokeetracker]

For some reason I have not been able to get any of the Videos lately. None of David's, and now this one. So I am not fully understanding. I see the photo of the screws and you state that the right one, is backed off. I do not have an absolute of what I am looking at. But this sounds like you are going to get things back on track.
Charles.
BTW: I have had to stay at a few of the Bates Motel chains... A few times it was a battle with the bed bugs. And the pungent smell of Curry chicken seemed to permeate everything I took inside there. And then again it saddens me so to see a sign that says American owned and Operated, and upon the entrance to the room, the greeting is stranger than the twilight zone. Lee you and I are tightwads when it comes to some things. LOL

[ProGun]

Wow! $44 hotel room AND Old Crow?! Thousands of dollars in fine shooting equipment though. Guess we know where the man's priorities lie...
Hope that rest was the problem.

[cmillard]

hope you didn't take some bed bugs home with you!

[Lee Martin]

Charles – sorry to hear the video won’t play for you. In a nutshell, the top plate which attaches the front bag to the center post came loose. The smaller of the two screws backed way out. Prior to retightening, the top would rotate from 12 o’clock to 11 o’clock. I shoot free recoil, so between rear push to resetting on the stop, it could tweak. That’ll throw shots all over the place.

I suspect that plus high mileage barrels are causing the problem. We’ll see on Saturday. I checked my notes on barrel #1 and at 1,800 rounds it still cut mid-2’s in mild air. Definitely lost some edge because in similar conditions it used to agg high 1’s to low 2’s. Pains me to miss a 200 yard score match this weekend, but I won’t compete until this is ironed out. If neither barrel shoots, I’ll screw a Bartlein in right away. Chris Harris had a HV gain twist in stock and it’ll arrive tomorrow (13.85 to 13.75 progressive). I’m also expecting two Lederers and a Kreiger any day now. Never again will I be without an inventory of blanks.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[mtngun]

Lee, I am enjoying and learning from your experiences.  And we learn as much from our failures as from our successes.   Thanks so much for sharing.   

The loose rest could indeed be the culprit.   Or the aging barrel.

"If you see me or Faye at a big match shooting a barrel that has 300 rounds on it, then you will know we are struggling to find good barrels.  

Our normal process for the big matches is to have no more than 100 rounds on the barrel when we start.
...
Very few barrels Faye and I have used over the years had 1,200 rounds on them, even when we went to small matches."  ~ Tony Boyer, The Book of Rifle Accuracy, p. 182.

[Lee Martin]

The gun did fine with the first barrel re-installed. Five-shot groups were in the 2's across swirling wind. Both the March and Leupold got used and performed the same. I’m confident I don't have a scope problem.

A typical group from last Saturday:



Below – potential screamer had one not landed low. Still, it measures high 1’s.

]

The barrel now has nearly 1,900 rounds on it. I could keep shooting it but won’t run the risk of more drop off in a match. As respectable as #1 did, it has lost a few hundredths in the agg department. The second Shilen will see work Saturday on a stable rest. If it groups tight, the rest may have been the problem. Anything close to how it did in Roanoke points to the barrel. A Bartlein blank waits in the wings.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[cmillard]

Lee, have you thought about getting a barrel salt bath nitrided to get more life out of them?

[Lee Martin]

Apr 19, 2017 7:28:42 GMT -5 cmillard said:

Lee, have you thought about getting a barrel salt bath nitrided to get more life out of them?

Salt nitride has been tried on benchrest barrels with less than satisfactory results. The level of precision we're trying attain allows for no loss in performance, no matter how small. John Kreiger summed it up pretty well:

kriegerbarrels.com/faq#salt

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[Lee Martin]

After a month of diagnosis, the problem was a loose rest. I screwed Shilen #2 back into the action and shot Saturday; and the conditions were miserable. Heavy rain, near 100% humidity, and moderate wind made for a tough session. But my first 3-shot test went into one hole (27.7 of LT-32, jam + 0.005”)



That was backed-up with another tight 3-shot cluster, same load:



Two 5-shot groups followed which were impressive.





Looks like the Bartlein will stay in the tube for a while.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[ProGun]

The little foxes spoil the vine.