Building a benchrest rifle

[Lee Martin]

Match #8 - 200 Yard VFS, Winter League Final Round
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Saturday was the last match of the 2016 – 2017 Winter League. Conditions were tough. When we started the air temp was 26 degrees, rising to only 35 by day’s end. Wind chill dropped both another 10 degrees. The real challenge however was the wind itself. We fought a steady 10 – 15 mph with gusts over 20. Direction and intensity never held long. It’s what we call ‘switchy’.

The gun shot well but I struggled to stay in the 10-ring. Then on target #4 I made a big mistake. When I got to the upper left bulleye, the flags changed rapidly and didn’t return to the previous read. Wind was a hard right to left, probably 15 mph+. I wanted to test the condition and came down to the sighter fast; at least I thought I did. The only problem was I neglected to also dial windage to the bottom right corner. I fired a center hold and as expected the bullet went way left into the black. The only problem was I shot on the first bull for the second time.



Want to guess which hole they scored? But this target shows how hard it is to shoot in strong wind. A 67 grain 6mm at 3,250 fps is moved 3” at 200 yards in 15 mph crosswind. Your ability to hold off is what keeps you competitive, but it takes getting used to. Putting the POA fours rings out from the desired POI becomes a leap of faith.

This brought the winter league to a close. I finished in 5th place overall.



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

[ProGun]

Good job Lee. I admire that you posted this even though you didn't shoot impeccably and win. In today's Facebook world, seems everyone has to look perfect all the time.

[bradshaw]

“... flags changed rapidly and didn’t return... probably 15 mph+... came down to the sighter fast; at least I thought I did... The only problem was I shot on the first bull for the second time.

-Lee
www.singleactions.com
"Chasing perfection five shots at a time"[/quote]
*****

It is so easy to crossfire. All it takes is to think it isn’t going to happen. Some range conditions, crowded targets for instance, the play of shadow & wind. Now add a high powered scope. Wondering, whether at that moment your in-breath came in a bit shallow?

Love this story. Including the part about the extra bullet hole on a bull which only has room for one bullet. We must respect the fabric from which sharpshooting is made.
David Bradshaw

[Lee Martin]

One thing I forgot to mention. Notice where the left shot went? The wind was straight right-to-left according to the flags. I held dead center. The bullet landed UP and to the left; and that too was expected with a right twist barrel. This chart illustrates the point.



If I were going to hold off on that exact condition, my POI would be 4 o'clock relative to the mothball (~3 inches to the right, 1 inch down). Another quick rule of thumb. Flag vanes are typically orange for right to left and green for left to right wind. If you see orange all the way down the line, the shot will rise. Green and the shot will drop. Again, that assumes right-hand twist.

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

[Markbo]

Lee I have seen that graph many times. I suppose the actual spread or distance can vary dramatically depending on wind speed and distance. Is that your experience using it?

[Lee Martin]

Mar 16, 2017 14:56:58 GMT -5 Markbo said:

Lee I have seen that graph many times. I suppose the actual spread or distance can vary dramatically depending on wind speed and distance. Is that your experience using it?

Is it. Distance, wind speed, BC, and velocity all play into how hard you hold off relative to the graph.

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

[Lee Martin]

Brass Management
__________________________

Arbor presses and inline dies are a good way to meter bullet seating. For all their mechanical advantage, arbor presses convey a lot through the handle. Round to round you can feel slight differences in resistance. Conversely, uniform feel indicates even pull. When felt resistance differs, it may point to a change in neck tension. Such is the case with my current lot of PPC brass. I tube mic'd the necks and wall thickness runs 0.0095". Not bad after 14 firings, as they were turned 0.0095". The bullets’ pressure rings are 0.2433" and never vary. A 0.261” sizing button puts neck tension at 0.0015”. That's light and exactly where LT-32 wants it. Dimensionally these check out, so I suspect they’re work hardening up front. I’m surprised because my first batch went 38 firings before consistency lapsed.

The NBRSA Virginia States (group varmint) are April 8th & 9th in Roanoke and I won’t go with questionable brass. Annealing may revive the necks, but I’m short on time. It can take 1 - 2 firings before annealed cases settle in. And if they don’t, I’m back to square one. Instead, I turned new brass from Lapua .220 Russian and fire-formed them Saturday.

Left: unformed 6 PCC, Right: fire-formed case.



I process 50 at a time. The numbers on the inside of the box reference the case weights. These were batched within 0.3 grs of one other.



I also just opened a new jug of LT-32. The tag is 4 lots and 1 1/2 years newer than the previous. I’ll spend the next two Saturday’s dialing it in. I hear there isn’t much lot variation with LT, but that’ll have to be verified on paper.



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

[cmillard]

Lee, have you tried sorting brass by internal volume?

[Lee Martin]

Mar 23, 2017 4:33:42 GMT -5 cmillard said:

Lee, have you tried sorting brass by internal volume?

Ran the test on weight vs. CC's of water (volume). Lapua brass is so consistent on thickness top to bottom, the two are almost identically correlated.

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

[cmillard]

Lapua is great stuff!

[Lee Martin]

Barrel Setback
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I fired 3-shot practice groups last Saturday with a new lot of LT-32. The conditions were ideal. Low humidity, a light breeze, and 70 degrees is where the guns shines. But sadly, it didn’t. I tried 5 powder weights and 4 seating depths per and couldn’t dial a tune. Quite frustrating because it would stick two bullets in the same hole, then walk one out 1/4” plus. The groups were a combination of vertical and drift, in other words erratic. LT-32 shows nodes every 0.6 grains so I should've found at least one between 27.7 and 29.0. Mechanically, everything checked out. Firing pin protrusion was 0.055”, the pillar bolts torqued 32 in-lbs, and the scope was tight. Pair that with new brass and I suspect the barrel was at fault (round count = 730).

Sunday I bore-scoped the Shilen and found spotless rifling. No signs of carbon or copper fouling. There was a bit of erosion at the front edge of the lead. Not bad, but noticeable enough. With only one weekend before the NBRSA match in Roanoke, I decided to set the barrel back. That entailed lathing off the tenon and rechambering. The crown was also recut. While the gun was apart, I also serviced the Bix N Andy trigger. The guts were void of any residue or dust.

Out of curiosity I slugged the barrel for dimensional inconsistencies. This is done by taking a 22 LR bullet, which is pure lead, and inserting it in the bore. Two rods hold it in place, then one is smacked with a hammer. This upsizes the bullet to fill the rifling. The bore is lightly oiled. Next, the bullet is pushed with a rod from the breach end through the muzzle. If there were loose or tight spots, I’d feel them in the rod. Not surprisingly, there were none.



The barrel was chucked in a lathe and the old tenon was chopped off.



Indicating the bore on all six grooves. Total runout over 360 degrees was 0.0000”. The same was done at the muzzle end.



Machining the new tenon.



Testing the action on the threaded and chambered barrel. They were firm and headspace was confirmed with a depth mic at 0.132”.



The rifle is now 1.0” shorter than before. Barrel length equals 20.5”. With a fresh chamber, meaning a clean lead and throat, it should shoot better. I’ll find out Saturday when I retune across six weights. Initial seating will have engraving marks half as long as they are wide (~jam + 0.005”). Once a node or two are found, I’ll bump seating depth back in 0.005” increments.



If I get it tuned, I’ll shoot at Roanoke the week after. Otherwise, I’ll fiddle with it one more time. With any luck it’ll return to its previous performance level of high 1/low 2 aggs. Otherwise it gets relegated to fire-form duty. I have a Lederer 13.5 twist HV coming soon. I also placed an order for the same twist and contour from Krieger. I’m really eager to try James Lederer’s barrel. His stuff is hot right now. Durward Wooford just won the Cactus Classic LV class with a 0.170 agg shooting a Lederer.

Here’s the link to the Cactus light-varmint results. Earlier I touched on how hard it is to shoot a zero-something group (<0.1”). There were 118 competitors in LV, each shooting five matches. That’s 590 targets from some of the most talented precision shooters in the US. Only two were scored under a tenth, or 0.3%. Putting five shots through a tiny, concentric hole isn’t easy.

azbrs.com/downloads/results/2017-Cactus_Classic-Light_Varmint_100yd.pdf

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

[Rimfire69]

Fantastic stuff.

[cmillard]

Never heard of lederer barrels. How long have they been around?

[Lee Martin]

Mar 29, 2017 15:57:26 GMT -5 cmillard said:

Never heard of lederer barrels. How long have they been around?

About 3 years. James worked at Rock Creek barrels for quite a while. His blanks are quickly finding their way into precision shooting circles. Wayne France, who I compete against every month, won the IBS Score Shooter of the Year with a Lederer.

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

[cmillard]

nice. figured he worked for someone big in the business. its great to have another name out there for barrels!