Building a benchrest rifle

[Lee Martin]

Match #5 – Winter League, 200 Yards
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Saturday kicked off the 12th Annual IBS Winter League at Fairfax Rod & Gun Club. This was just the second time my PPC has seen 200 yards...and I was humbled. In August I placed well at 200 under mild conditions. Last weekend was anything but calm. Winds were consistently 10+ mph with gusts near 20. If you stay 49 – 50 with a few X’s in that mess, you’re in the running. Easier said than done.

I shot many sighters in warm-up and felt ‘ok’ about how much to hold. Record #1 mirrored the test target with a 49-2X in stiff air. Then disaster hit. The wind was unrelenting for record #2. I waited, hoping for flags I knew how to read. Six sighters later I had to move fast. Bull #1 was a 10, probably by way of luck. The streamers hung at 9:00 and I had two minutes to do the last 4. Bulls 2 - 4 all missed as 9’s. I just didn’t adjust my POA enough. I’m finding a 100-yard hold isn’t a simple 2X at 200. Up against the clock I sent #5 through big wind. I touched the trigger, crossed my fingers, and refocused my eyes on the reticle. Sure enough, it dodged the 9 ring by a hair. 45-0X early in a match puts you in a deep hole (the winter league attracts the die-hards; these guys rarely drop more than a point or two). I learned from #2, held accordingly, and went 50-50-49 on the last three. But the damage was done. That 45 booted me to 10th place.



Key takeaways:

1. Shoot a hotter load. The gun aggs best with 27.7 grs of LT-32, but that’s loafing. Velocity is only 3,100 fps. At 200 yards I need to find a node closer to 3,400 (check the chart below and you’ll see why)

2. I’ll start cleaning after every two groups instead of three. Following record #2, the first few patches were blacker than normal. Counting sighters, I pushed the barrel to 31 rounds.

3. A .30-caliber, like the BR or my soon-to-be Stingray, wouldn’t have made a difference. George Ulrich once told me a good 6mm at 3,300+ fps beats a short .30-cal bullet at 3,000 on drift. I ran the numbers and he was right.

How much does a 10 mph cross-wind move a 6mm bullet? Well, my 0.365 BC 67 gr gets shoved 3.5 inches at 200 when starting out at 3,100 fps. At 3,400 fps it's cut to 3.0”. That doesn’t sound like much, but 1/2” less drift helps when attempting to hit a 0.125” dot.



Of course we shoot short .30-calibers in benchrest; low volume cases pretty much mandate weights between 112 – 125 grains. Heavier .30-calibers at higher speeds and equivalent BCs are another story.

More learning curve to climb.

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

[bradshaw]

Lee.... we’ve talked about the drift multiplier distance represents. In handgun silhouette, I determined the pig @ 100 meters to access drift @ 150 meters/165 yds and 200m/220 yards. 3x is a light figure for judging wind drift between 100 and 200. Actual drift at distance in a full value wind (9 or 3 o’clock) usually is much worse. While it is entirely possible that silhouette championships have been determined by the diameter of a bullet----hit or miss----the overall accuracy requirement is crude in comparison with bench rest. Cave man crude. Which doesn’t mean you voluntarily give up anything to chance if your mission is to prevail.

I notice one Tim Menninger takes 4th @ 200 yards with 11x----eight more than the winner. This tells me that, despite the incredible drift consistency of a good bullet, the slightest juke in a breeze can queer the deal in bench rest. Things are so much lazier in silhouette. Somewhere in all this I have a feeling rhythm favors the bench rest shooter with a volume of trigger time under his or her belt. When it comes to stamina shooting, Time on the Mountain is big time.

Now it seems that these custom hunting rifles and match rifles, for which minuscule groups are reported, should immediately challenge you bench rest guys to a showdown. I’m afraid I must throw my meager funds on the boys & girls of Benchrest.
David Bradshaw

[Lee Martin]

Nov 16, 2016 19:28:20 GMT -5 bradshaw said:

Now it seems that these custom hunting rifles and match rifles, for which minuscule groups are reported, should immediate challenge you bench rest guys to a showdown.

I agree David. What’s the old adage? “Do it repeatedly in competition and we’ll talk”. Truth is, to hit the X in short-range BR your gun has to do mid-1’s. Wallet groups aside, that isn’t easy (a wallet group is when a guy unfolds a one hole target and says ‘see what my gun does’). A couple of those don’t impress me. Many bugholes laid down in a controlled environment, meaning backers, does.

But if folks can routinely cut 0’s and 1’s without windflags, or even with flags, they’re better than most. Hell, maybe they’ve found bullets that are immune to wind...but we all know those don’t exist. An IBS official once told me in registered competition, under 1% of the groups are less than 0.100”. And that includes the NBRSA and global sanctioning bodies.

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

[Lee Martin]

I just purchased a few thousand .30-caliber jackets; and that means I’m committing to swaging 30’s. It’s sort of like buying a set of reloading dies. The gun will soon follow.



These are 0.925” by Hines which I’ll turn into a 114 grain pill. I spoke with George Ulrich this week and placed an order for carbide dies. On his recommendation I chose a 7-ogive. He’ll also send new presses so I won’t have to swap out my 6mm’s. George reworks the toggle system for 30-caliber on the Lee Classic Cast for added leverage. Looks like they’ll ship in the March timeframe. That should coincide with my .30 Stingray.

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

[Lee Martin]

.30 Stingray Case Forming
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6.5 Grendel necks are expanded to .30-cal using a K&M mandrel. A generous amount of Imperial die wax is applied inside the mouth and on the mandrel body.



A shot of the mandrel, which is matched to the neck turning pilot. Also shown is the tube micrometer used to measure wall thickness.



Our chambering reamer will have a 0.331” neck. Lapua 6.5 brass averages 0.0143” up top. Knowing the neck clearance and bullet diameter, we derive the turned thickness:

Desired neck clearance = 0.0020” (used by many .30 BR shooters)
Bullet diameter = 0.3084” +/- a tenth or two
Chamber neck = 0.3310”

0.3310” – 0.0020” = 0.3290”
0.3290” – 0.3084” = 0.0206”
0.0206”/ 2 = 0.0103”

The K&M pilot was lubed and the carbide cutter slowly dialed in until 0.0103” was reached. Remember to lube the inside of the neck before turning.



Left to right - Lapua 6.5 Grendel, Grendel expanded to .30-caliber, and neck turned to 0.3290”.



Fire-forming will improve the shoulder to 40 degrees, move the datum line ahead 0.030”, and expand the body.

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

[kings6]

Okay Lee, I got to ask. Besides a slighlty bigger bullet, what is the benefits of the .30 Stingray over the parent case? May be no reason other than because you can but any theory shared is appreciated.

[Lee Martin]

Nov 22, 2016 20:35:42 GMT -5 kings6 said:

Okay Lee, I got to ask. Besides a slighlty bigger bullet, what is the benefits of the .30 Stingray over the parent case? May be no reason other than because you can but any theory shared is appreciated.

Robb - in benchrest score competition, we're trying to hit a 0.0625" dot at 100 yards (0.125" at 200 yards). 30-caliber offers a 0.044" advantage over 6.5mm. The other reason is there are match grade jackets available for .30-cal. 6.5 is limited to lengths too long for the weights we shoot in small volume BR cases; though J-4 and Hines now produce some outstanding 6.5 cups for heavier bullets.

The plan is to shoot the .30 Stingray in score and my 6 PPC barrel in group.

-Lee
www.singleactions.com

[kings6]

Thanks Lee, that makes sense when you look at purely diameters versus the set size target dot.

[Lee Martin]

Practice Screamer
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I killed some PTO today and practiced for a match this Saturday. After 1 1/2 years of shooting a PPC, I finally broke this out:



Chrono results, all seating at jam + 0.005” with LT-32.

27.7 = 3,180 fps
28.3 = 3,285 fps
28.6 = 3,359 fps
28.9 = 3,443 fps

Around 8:30 I laid down group #1 under dead calm. The flags and streamers weren’t even flickering. Two foulers and then:



I measured it from every angle and came up with 0.078”. The specifics:

Bullet – Martin 67 gr FB
Powder – 27.7, LT-32
Seating – Jam + 0.005”
Barrel – Shilen 13.5 twist, 350 rounds on it
Primer – CCI BR4
Temperature – 38 degrees
Humidity – 79%

While this was tight, I’ll go with 28.3 grs for this weekend’s match. At 200 yards, I’ll take the added 105 fps. Plus 28.3 is on a node. Notice how little vertical there is on this 0.189” group. The hole to the right edge is likely wind push.



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

[kings6]

I would hate to be a fly on y our target stand if you got mad at me! Sheesh Lee, that looks like what I would imagine the term bug hole was based on.

[cmillard]

very fine shooting lee!!!

[Rimfire69]

Absolutely incredible, always a pleasure to follow this thread.

[Lee Martin]

Match #6 - 200 Yard VFS, Winter League Round 2
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I shot the second leg of the Winter League last Saturday. All around a tough day for weather. When I arrived it was only 26 degrees. Winds were equally bad. Not heavy in the way of gusts, but very switchy. Up and down the line the flags showed bi-directional flow. Stuff like orange, orange, green, orange, green, and orange again (orange is right to left, green is left to right).

In spite of a poor first record target, I finished fourth overall. Wayne France, who took first, just won the IBS Score Shooter of the year award. I'd say he had a productive week.



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

[cmillard]

fine job lee!! have you thought about crossing over into the mid/long range game?

[mhblaw]

Back in the day I shot a Remington 40 XBR in 6 x 47 for BR competition, so was interesting to read about your matches and quest for the best load. Currently have a Kimber single shot in 6 x 45, but more of a varmint gun than BR.