Building a benchrest rifle

[Lee Martin]

Barrel #2 - Chambered

I finished chambering the new blank and it went well. Headspace is dead-on to the first. Bolt clearance is gapped at 0.004”. Here’s a shot of the shank. Forgive the oil and chips...it hadn’t been cleaned yet.



The muzzle was indicated and cut to 21.5”, which is the same as #1:



Notice how true it runs when properly centered:



The old barrel was marked and stored in a cardboard tube. It may see work again someday.



I repainted the stock last weekend and it came out better than expected. After 6 coats of clear, it glistens and adds more than enough protection. I’ll post photos once I get it reassembled.

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

[cmillard]

lee, is that new one also a Shilen?

[Lee Martin]

Sept 29, 2016 19:49:08 GMT -5 cmillard said:

lee, is that new one also a Shilen?

Yep, same as the first. Shilen 7 contour, 13.5 twist.

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

[Lee Martin]

The gun is back together and was shot last Saturday. Pretty tough day to tune a new barrel. We had brutal wind and heavy rain. I believe I found a load that’ll work for this weekend’s IBS Virginia State Championship. It’s a two day event with 100 yards Day 1, 200 yards Day 2.

Here’s a picture of the new paint job. Sprayed it myself and the color and clear laid down well. I went with 6 heavy coats of clear for plenty of protection. It shines more than the single-stage urethane and is glass smooth.



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

[cmillard]

very nice!

[2 Dogs]

There's a ton of shop time in that rig....

[Lee Martin]

Match #4 – IBS Virginia State Championship
___________________________________________

Last Saturday I shot the 100-yard VFS leg of the Virginia State Championship. Heavy rain started around 9:30 and never let up. The air was calm yet soaked flags made it tough to read small changes. I took a chance and went pre-loaded with a combination that worked OK the week prior. Remember, I only had one day to test and that was under intense wind. Regrettably, I missed on the load. Judging by the amount of vertical I was way out of tune. It hung in there for records #1 and #2 but had some close calls on the 10 ring. Then on #3 I dropped a point. It wasn’t by much and with a .30-cal I would’ve caught the edge. Return a 9 at a competition like this and you go to the bottom fourth; 100 yards, mild air, and there's no bouncing back. The next two targets were frustrating 50’s. They kept landing a hair above or below the X. I tried compensating by holding off but the tune was too erratic. On a node I think the gun could’ve done a 250 15 – 17X. The 10-0x’s were that close to the dot.



Due to a commitment I wasn’t able to shoot day 2 at 200 yards. Sorry I missed it...remnants of Hurricane Matthew delivered 30 mph gusts.

So to recap, I didn’t place as high as I would’ve liked. But that’s on me. I simply didn’t have the right set-up. Mediocre alongside great competitors still beats the hell out of tearing bug holes alone.

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

[cherokeetracker]

Mediocre alongside great competitors still beats the hell out of tearing bug holes alone.

Lee I agree. Shooting any competition is better than shooting alone always. Shooting with great competitors, you will learn something from them. You have already shared some of their knowledge here on the board.

Charles

[Lee Martin]

Reloading Error
________________________

Boy did I ever screw-up. Ten loaded cartridges were left after the last match. On a whim I mic’d their base to ogive. Glad I did because all were 0.005 – 0.017” too long. Jam + 0.005” is how I dialed the seater, which equals 2.362” on the gauge. These ran 2.367” to 2.379”. Did the stem move? Nope. Were my bullets off? Can’t be, I spot check bearing surface as I swage. They’re always dead nuts. It had to be in the seater or FL sizing. The brass was correct at 0.200” and around the shoulder. Then I shined a light into the seating body and voila. I found granules of LT-32 stuck on the shoulder junction. Earlier I spilled a charged case in the die while adding a bullet. A mild film of lubricant used to ease extraction must've trapped it. I should have noticed die wobble in the arbor press since it wasn’t flush. However, I missed that too. It doesn’t take much to throw all this out of whack. A sized PPC is only 0.001” smaller than the chamber at the shoulder. Back at the 0.200” mark it gets squeezed a miniscule 0.0006”. Dirt and foreign particles have nowhere to hide when you pull the lever.

Consistent seating depth is key, even when jamming the bullet. The amount of land engraving effects point-of-impact. If it changes, so can POI. I can’t say for sure this caused the vertical I fought at the Virginia States, but it didn't help. I plan to run 3-shot tests this Saturday on the new barrel. That’ll involve seating from 0.005” ahead of jam back to 0.015” off in 5-thou increments. Charge weights will be 27.7, 28.0, 28.3, and 28.6. I’m curious to see what it’ll do without user error.







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

[ProGun]

Gosh almighty that's a tough break. Thanks for sharing the lesson.

[Lee Martin]

Introducing the .30 Stingray
___________________________________

I've decided to add a .30-caliber barrel to this action. It only makes sense since I'm shooting a fair amount of score. 0.065" less diameter sounds trivial, but it isn't when you're trying to hit 0.0625" dots. I've lost quite a few X's with the smaller 6mm.

There are a number of cartridges to choose from; the .30 BR being a favorite among competitors. However, my bolt face was tightly machined for the PPC. There's no way it'll accept the BR's 0.473" base. Turning the rims and deepening the extractor groove is a workaround. A lot of guys do just that. I won’t. Instead I'll leverage the 6.5 Grendel for a wildcat. Grendels are PPC headed and the datum line is a mere 0.070" longer. Lapua produces it, which means super high quality specs out of the box. Parent 6.5 Grendel is used a little in benchrest, such is the case with the .30 Major. The Major is a straight neck-up to 308 with no other changes. Powder capacity is a grain or two below the .30 BR. My goal is to match the BR on speed so I'll improve the shoulder to 40 degrees, remove a few thousandths of body taper, and retain the stock neck length. It should duplicate the volume of the shorter and fatter BR. I named this one the ".30 Stingray".



The reamer specs:



Neck diameter will be set at 0.331" with zero free bore. Expand the 6.5 Grendel on a .30-cal mandrel, neck turn, load, fire form, and out pops the .30 Stingray. More to come.

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

[gunzo]

I'll admit, I first thought "why would Lee want to use something other than the proven 30 BR". Then you mentioned being able to use Lapua brass & what little you have to do to it, & I'm on board. I'm a huge believer in Lapua rifle brass, & think anytime you can take advantage of it is a good thing.

BTW, dimension E & F are confusing me, which is easily done, but are they backwards?

[Lee Martin]

Good catch Gunzo. Even after proof reading it twice, I got those numbers swapped. The above print is now correct. I also should clarify that Grendel brass isn't 0.070" longer in total length. The datum line however is moved ahead by that amount.

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

[Lee Martin]

Tuning Barrel #2
________________________________

Every barrel is unique unto itself. That’s probably true, but Shilen #2 acts just like Shilen #1. Two Saturdays ago I did 3-shot tests with four weights of LT-32: 27.7, 28.0, 28.3, and 28.6. Four seating depths were tried with each. As before, defined nodes appeared at 27.7 & 28.3, while 28.0 and 28.6 showed mild vertical. The tightest groups were 0.005” ahead of jam.

Barrel #1 always performed best with 27.7 and jam +5. That combination in the new tube:



At the end of the day I had four bullets left and shot another group with that tune:



I packed up feeling pretty good about what #2 wants. This past Saturday I re-tested 27.7 and 28.3 at jam +5. Conditions were 60 degrees, 55% humidity, and the wind was very switchy. The first group, done with 27.7, measured 0.156”:



I was hoping the 28.3 gr node would shoot as tight. I’m entering a 200-yard Winter League this weekend and the extra 100 fps helps with drift. But the rifle prefers the lower speed and that’s what it’ll get. Four targets were done per charge:

27.7, jam+5 – 0.156”, 0.177”, 0.215”, 0.182” Average = 0.182”
28.3, jam +5 – 0.234”, 0.195”, 0.226”, 0.208” Average = 0.215”

Close, but I’ll take the slight edge shown by 27.7.

And a quick side note about new brass. After fire-forming, always true the mouths; even if you trimmed prior to neck turning. Often they become uneven when the shoulder sets. Below is a case I trimmed to 1.490" final length post fire-forming. The shiny edge was a hair longer than the dull side (which was already 1.490”):



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

[cmillard]

very nice shooting!!