Expected accuracy of featherweight contour

[Litehiker]

I've posted photos of this 6.5 PRC Browning X-Bolt Pro several times on LRH to illustrate a good lightweight rifle.
It too has a skinny barrel made even "skinnier" with fluting, obviously to decrease weight (do ya think maybe for looks for marketing reasons as well? ;o).

For the first three shots within two minutes I get about a 3/4 MOA, with which I am very happy.
After that, as the barrel heats up, the groups open up to as much as 1 1/2 MOA and all this with Hornady Precision Hunter (ELD-X) ammo. Hey, if I can't get big game in three shots I need to take take up knitting.
SCOPE: Bushnell Elite LRTS 4.5 - 18 X 44 with G3 illuminated reticle, Cerakoted OD green.

 

[nksmfamjp]

Twist rate?

I would do a 3 bullet x 3 seat depths x 3 shots each at a low-mid range charge weight comparison and see what bullet groups best. Then develop the load for that bullet.

That said, I'm not following my own advice. I am trying a second bullet though. If I fail there, I will do 3 new bullets! Should only take me a year to get three boxes of different bullets!

 

[sobrbiker]

Beautiful rifle.
Your vertical dispersion (or lack of rather) would lead me to think it's perhaps more of a matter of consistent cheek weld. It's tough to get a perfectly repeatable position remounting rifle after letting barrel cool between shots.
I rarely see loads with that tight of vertical (and velocity) spreads being the culprit.

 

[slikmrc]

I see this as his most recent post (post #30 above) 5, 6, and 7 all print in the same area, which is the goal of OCW (good groups that print in the same area from charge to charge). There is one of the shots in group 6 that takes that to a 1" group, but I would check that node with seating depth. That's 44.0 to 44.8 grains printing in the same area…that's where I would start as well.

I agree with Oregonian, it looks like 2780/2790 shoots pretty good with both powders tried. I would run a couple clicks up and over also to give the scope a quick test to see if it tracking ok. Would look for a trend if cold bore or other shot is opening the groups as well.

 

[DoneNOut]

@markg208 Load developing for my first sporter/skinny barrel Kimber 84 Hunter in 7-08 required I adopt a whole new mindset to grouping. I am used to 3 shot groups to see any promise with a chosen powder, 5 shot groups to tweak charges, 10 shot groups to step away with a promise load. My Kimber I had to check 2 shot groups, because the 3rd was always off like clockwork. After two shots I can see mirage heat off the barrel.

So, I would fire two shot groups and choose the powder and charge it would print 2 shots touching. I would let the rifle cool 5-7 minutes in 30 F. temp and fire the third to get that 3rd shot touching the others. I'm cool with that. First two shots are the most realistic for hunting. (I typically make it one shot one drop)

Looks like you are having a blast with that beautiful rifle! Keep reporting!

 

[Willoughby]

id try adding a temporary pressure point ( double sided tape ) at end of stock, if it helps make it permanent by bedding a 1" area with a piece of .002 scotch tape under action with screws tightened - remove tape of course when bedding dry's and add a cheek riser - I use a piece of blueboard insulation and a elastic stock cartridge holder- trim blue board til eye lines up with scope instantly, hold it in place with a piece of painters tape , cover it all with cartridge holder - your cheek weld will always be the same - I have this on all my rifles,

 

[Mike Matteson]

From the looks of the targets your rifle/barrel is pretty much a 1 MOA rifle. I don't reckon that too bad for a feather weight barrel and that might be all your going to get out of the reloading components you're using.
I know IMR4064 has been a staple for the .308 Win for a long time. Not sure about the Bisley or what it is. I would try some more powders close to the range of IMR4064.
I had a stubborn .308 once, could not get it to shoot anything inside an inch and a half. It was a new factory barrel and I tried every powder I had and even bought a couple to try in it. Several different bullets and primer types later I decided to turn my attention to the rifle. I epoxy bedded the action and free floated the barrel, adjusted the trigger to 2lbs and that got it a little tighter, about a inch, but not what I had envisioned this heavy barreled, target rifle was supposed to do. I mean, come on, it's a dang .308. At this point I had spent close to a year troubleshooting this rifle.
In my searching the internet I came upon a gent who used a round headed, brass screw, valve grinding compound and a cordless drill to polish the crown. At first I was skeptical but then figured what the heck do I have to loose.
I polished the crown using the above mentioned items and wa-lah! the rifle thought it was a benchrest rifle! At 100yds it would put five in the same hole, or at least touching; using Varget, CCI BR2's and 175gn SMK's.
Sorry for being long winded but don't overlook the small things and don't be afraid to try something different. Good luck and let us know how it goes.

P.S. About a month after I finally got it shooting I pulled the barrel and installed a Shilen 6mmBR Norma. I still have the barrel and have considered putting it back on a couple of times.

I find that interesting, and I will add that to my info. I had a friend with a 243 that I couldn't settled down a great many year ago. Worked over the stock. Got to group better, but hadn't given any though about the muzzle.

 

[Tommo64]

From the looks of the targets your rifle/barrel is pretty much a 1 MOA rifle. I don't reckon that too bad for a feather weight barrel and that might be all your going to get out of the reloading components you're using.
I know IMR4064 has been a staple for the .308 Win for a long time. Not sure about the Bisley or what it is. I would try some more powders close to the range of IMR4064.
I had a stubborn .308 once, could not get it to shoot anything inside an inch and a half. It was a new factory barrel and I tried every powder I had and even bought a couple to try in it. Several different bullets and primer types later I decided to turn my attention to the rifle. I epoxy bedded the action and free floated the barrel, adjusted the trigger to 2lbs and that got it a little tighter, about a inch, but not what I had envisioned this heavy barreled, target rifle was supposed to do. I mean, come on, it's a dang .308. At this point I had spent close to a year troubleshooting this rifle.
In my searching the internet I came upon a gent who used a round headed, brass screw, valve grinding compound and a cordless drill to polish the crown. At first I was skeptical but then figured what the heck do I have to loose.
I polished the crown using the above mentioned items and wa-lah! the rifle thought it was a benchrest rifle! At 100yds it would put five in the same hole, or at least touching; using Varget, CCI BR2's and 175gn SMK's.
Sorry for being long winded but don't overlook the small things and don't be afraid to try something different. Good luck and let us know how it goes.

P.S. About a month after I finally got it shooting I pulled the barrel and installed a Shilen 6mmBR Norma. I still have the barrel and have considered putting it back on a couple of times.

Do you have a link to the crown polishing article?

 

[D$tring]

id try adding a temporary pressure point ( double sided tape ) at end of stock, if it helps make it permanent by bedding a 1" area with a piece of .002 scotch tape under action with screws tightened - remove tape of course when bedding dry's and add a cheek riser - I use a piece of blueboard insulation and a elastic stock cartridge holder- trim blue board til eye lines up with scope instantly, hold it in place with a piece of painters tape , cover it all with cartridge holder - your cheek weld will always be the same - I have this on all my rifles,

This seems interring but I can't imagine it in my mind. Do you have pictures?

 

[DoneNOut]

The oval cut piece of credit card under the barrel near the front of the handguard was popular years back.

 

[bamban]

Sometimes luck is on your side.

I bought this 300 Win Mag Weatherby Vanguard prior to Weatherby putting Sub Moa floor plates and upgraded stocks on barreled receivers from Japan that came with sub moa targets. Four years ago I tried to sell it, no takers though it only had maybe 10 rounds through it. I never like the recoil of the 300WM, thus the reason for the low count. Fast forward to 2019 when I decided to thread it for a brake. I ran across a video from APA highlighting the Micro B on a magnum

The muzzle is so skinny
9/16x24 is all I could thread it for. Bought the MicroB in 9/16x24. The only other things done to the rifle were; bedding job, and replaced stock trigger with Timney trigger

In preparation for our trip on the 3rd season in CO I loaned this rifle to a friend while I carried my other 300WM. During one of the zeroing days at a TX Guard base off a bipod and sock rear bag, he fired this 3 shot group at 500 yards, the longest yardage on the KD range. Target is a SR3 with 3 inch X ring. Ammo used, issue MK248 MOD0, 190 SMKs were coming out 2950 FPS average.

 

[nksmfamjp]

Also, do you have other primers you can try. Sometimes certain primers won't shoot for poo in an otherwise good load.

 

[Swiftkill]

Nice rifle. Nice looking bedding job. I can't read everybody's post. All I can tell you is consistency is the key. Your #1 and #6 groups look good.
Do you test shoot off a front pedestal rest?
Will you shoot off a bi-pod?
You need to keep your fulcrum point consistent from shot to shot and this will probably change in the field unless you are shooting off a bench . I cannot make you a benchrest shooter unless you are already? If you can shoot .25" groups or better with any other gunb then you probably know how to shoot.

Again, I believe that harmonics consistency is the most important part of repeatability. Where that bullet leaves the barrel in the harmonics node is almost everything.
I find for hunting loads almost everytime... .005 to .015 off the lands works best. You should start at .010 and go .002 up and .002 down.

Choose your powder and bullet first. I try to get the maximum velocity at the best accuracy. The lyman and Nosler books are a great place to start. I find usually a little less than max velocity gives best accuracy. Sometimes you'll get max accuracy at max velocity, this happens with my 300 Win Mag and 44 Magnums, but that's me.
If a powder is not looking good reasonably close to max vel. Ill change powders.

EXCEPTIONS: lead free bullets. I am loading for 243 with Nosler 55 gr Ballistic tips.. I have Three 243s but only tested two. I have a Heavy barrel 26" Custom Remington with a JP 3 port brake meant to be shot off a bench and a Howa 1500 - 22" meant for carry for coyote hunting. By some miracle the distance to the lands is EXACTLY the same to within .001 between the two guns, I don't know how this happened, but the Remington shoots SUB 1/4" groups seated .050 off the lands with a long OAL of 2.691 which is .081 longer than the max of 2.610 recommended SAAMI specs, BUT at that length it functions through my internal box magazine so I am ok. This gave me Sub quarter inch groups at 4200 fps. Also using H414 powder which is old school, but **** if it doesn't work.!!

And the Howa did NOT like the .050 Jump so I seated to OAL of 2.610, for hunting that is the max OAL length but That is .131 Off the lands!!!. This seems like a Looong jump but I can get 3/4" groups from a light 22" barrel without a brake and using 16X magnification. I have the trigger set to 1.25#. This gun is for well inside 300 yards. Most shots will be 20- 150 yards while calling in coyotes.
NOTE: I did shoot off an accubag and using a separate rear bag for this testing. But still, consistency was key. My friend shoots long range prairie dogs and rock chucks so he develops his load shooting off a Harris bipod because that is the way he hunts. That adds weight and some possible bounce to the recoil.
But, I digress. Don't be afraid try something Unconventional, you'd be surprised that it might work.

 

[Zorack]

So you never tried any other powder?

Handloading is all about finding the combination that best works for your rifle. You cannot be discouraged just because you cannot get the accuracy goal out of 1 powder (IMR 4064).

What cartridge are you loading?