tuning this varmint rifle-wide open for suggestions

[wildcat westerner]

I have a varmint rifle which should be an ideal weapon for prairie dogs and coyotes and it is not!
A single shot Model 70 action in a Mcmillan hunter benchrest stock with a Hart barrel: 3/4" muzzle, 26 inches long, fired less than 150 rounds-all from me! The twist is 1-12 and chambered in .244 with a Saami neck. Originally the neck was tight, but since I have had a variety of 6mm-.244's I have about 500 rounds of brass that should fit this rifle so I had the tight neck specs removed by a thoroughly competent gunsmith.
Despite a background of benchrest shooting and worlds' records I cannot get this rifle to shoot precisely. The barrel is a fast one. it likes lightweight bullets and velocities to 3,600 fps are relatively easy to reach with safe pressures. It does not group well despite a wide variety of bullets and powders being used.
At this point I am wide open as to bullets for this twist. I know my bullets for my 6PPC are incredibly fast in this barrel, but nowhere near as accurate as they once were in my competition rifles. I am ready to give this rifle one last try and maybe someone out there has a similar rifle and load with a wide range of tolerance that may work well in mine.
Thank you,
Gene So

 

[just country]

morning, what bullets, powders, brass and primers? did u have
this custom built? since u had the neck size changed.
what r the dimensions of the cartridge neck now? justme gbot tum

 

[Jud96]

Personally, if you're willing to take the time and start from scratch. I would start with 10-20 pieces of once fired brass. Prep it the best way you can with the equipment you have. Find a suitable powder for the .244, I would personally use H4350 or RL16 with the lighter weight bullets in that cartridge. Then I would pick a good bullet. I know you said you have bullets designed and used in the PPC, but maybe try like a 70-75gr Sierra, Berger, or Hornady.

I would find your lands, hopefully it has a short freebore for the light bullets. I'd start about 0.010 off the rifling and then go right to finding your powder node. I'd start 3gr below book max and load up one round each in 0.2gr increments. Shoot all of those over the chronograph. Find the charge weights that produce the smallest change in velocity, also known as "flat spots" or nodes. From there, I would start experimenting with seating depth. Shoot 3 each starting at 0.010 off the rifling and going to 0.080 off the rifling in 0.010 increments. Take the seat length with tightest group and you can further fine tune it in and out in 0.002 increments until you get it as small as you can.

I would also look over the rifle before wasting anymore time and components. I would look over your bedding job. Check if your barrel is touching the stock or if there's any binds or unwanted pressure points affecting the barrel or action. I would also double check the torque on your action screws. Check scope bases and rings. You can even try another scope if you have an extra sitting around. Also clean the barrel thoroughly and shoot 2-3 fouling shots through it before proceeding to test accuracy. Measure the outside diameter on your fired case necks and compare it to the O.D. on your loaded case necks. Ideally you want 0.004-0.006 clearance between your loaded rounds and chamber.

 

[wildcat westerner]

Jerry, your insights are exactly what I needed. I like your approach and will use it. I have never in my life had a rifle with so much potential and so little return up to this point. I have won competitions with 307 other shooters and set two long distance worlds records, but this rifle makes me seem like a rookie.
Thank You
WW

 

[Jud96]

Jerry, your insights are exactly what I needed. I like your approach and will use it. I have never in my life had a rifle with so much potential and so little return up to this point. I have won competitions with 307 other shooters and set two long distance worlds records, but this rifle makes me seem like a rookie.
Thank You
WW

I'm not a record holder and don't do any high power rifle competitive shooting yet, maybe one day haha, but I do have experience loading and tuning rifles. Recently I went through this exact problem with my Dad's 7mm Rem Mag and my custom .284 Winchester. By using the above techniques, we were able to get both rifles shooting sub 1/2 MOA. I had to change bullets, and his ended up just needing the seating length to be further off the lands than we have previously ever found accuracy at. Sometimes good rifles make you go crazy. Using the above methods have really helped us narrow down accurate, consistent, and repeatable loads and is one of the most efficient and affective methods to finding the sweet spots in your rifle, bullet, powder, primer, brass combo.

 

[just country]

morning, some rifles like flat base short ogive bullets. some rifles
like the long ogive bullets. justme gbot tum

 

[357Mag]

Gene -

Howdy !

Just out of curiosity..... how much trigger "pull" does your rifle's trigger have ?
If somewhat heavy, there's not a whole bunch of after market triggers for M-70's.

Have you tried Sierra 6mm 85BTHPs ? They are super consistent on wt, when checked over several boxes. And, can be made to shoot into tight groups ( IMHO ).

And also, did you happen to say how much "jump" you've been using w/ your bullets ?
I've had good success using .002" jump, for all 6mm bullets I have shot in my
"Deep 6 " wildcat ( 29" SS 1-8 5-groove ). My gun, my loads... I realize.
Fred Sinclair advised I start about .002" off the lands many years ago.
I wildcat some, and .002" has worked ( for me ) for a whole host of various varmint/target rifles. It's a starting point.


With regards,
357Mag

 

[wildcat westerner]

Hello 357 Mag,
I have dealt with 1.5 and 2. oz. Jewell triggers for 30 years and while this Winchester trigger is not of that quality, its very good.
.002 in OAL is pretty finite and I look forward to trying to set a OAL to that finite degree. With other peoples help", and yours, I feel I can finally reach a decision as to just what to do with this rifle. I have several custom target weapons with custom actions so am well aware of what true accuracy can be. This weapon with its Hart barrel, unfired when I bought it, should be capable of some pretty special accuracy. An early 3/16" group in windy conditions has never been duplicated, no matter what I have tried.
Thanks for your input.
W.W.

 

[Quackshot]

If it don't shoot 75 grain Sierra with a case full of 4831 trade it off. Life is too short to pee into the wind with a bad barrel. Some barrels just don't work

 

[357Mag]

W.W. -

Howdy, again! Thanx for you response.

A couple more questions....if I might ?

What is your M-70's barrel profile ?
Straight bull, #7, Palma ?
In particular..... how long is the straight section of barrel @ the chamber end ?

I'll tell you why I asked, once I read your response.


With regards,
357Mag

 

[aushunter1]

How does one give advice to a world record holder?

Still you haven't informed us what the actual combinations you have even tried in the components.

Im interested to know what projectile you are actually using to you 1:12 twist rate!

 

[aushunter1]

How does one give advice to a world record holder?

Still you haven't informed us what the actual combinations you have even tried in the components.

Im interested to know what projectile you are actually using to you 1:12 twist rate!

 

[wildcat westerner]

OK,
Here goes specifics:
Hart barrel is match grade 26" long with a 3/4" muzzle
Bullets: many in the 80-85 grain range, I am at 6,500 altitude and real winds blow here in the Rockies, which is why I concentrated on heavier weight bullets.
80 gr.- h4350-45 to 47 varget-38-41 win 760-40-46
85 gr. h4831sc 45-49.5 h4350 42-46 Varget 36-39 Mrp-40-52'
90 gr. Mrp-43-46 h4831sc 43 to 45, h4350 40-43, v160 43-45, 760-40-46
Berger 80 gr. bullet
Vit 140- 40-41 gr.=.194 group at 100-never duplicated-extremely hot
dropped to 39.5- accuracy mediocre.
I have virtually not touched this rifle in over two years, because or relocation to New Mexico and concentration on hunting rifles with flat trajectory and heavier, wind bucking, high BC bullets for big game.
WW

 

[357Mag]

WW -

Howdy, again !

Thanx for the info !

Please stick w/ me. and I'll get around to " the point " further down the text......

Perhaps outside the box, but since your monicker included the word " wildcat ";
I felt compelled to share:

I shoot a wildcat of my own design, which I call " DEEP 6 " .
My idea was to come-up w/ a 6mm wildcat that would be useful for 1,000yd shooting; whether that be for target or varmint use ( groundhog @ the time of design ).

Deep 6 uses a frustrum off the 6mm Remington base-shoulder-sidewalls " cone ".
The chamber is cut by running a 6mm Remington chamber reamer in " short ",
for a nominal .466" base diam. * NO custom reamers to $$$ !

I use 7X64 Brenneke for the parent brass, as it features the .466" base diam I need.
7 X 64 is one of a handful of Euro-spec cases SAAMI maintains specs on.
It is .308 bolt compatible, and rimless .470" .

Quality brass is available from Norma and RWS ( I use the former ). Case taper is highly compatible w/ the 6mm Rem's taper rate. Since DEEP 6 is formed from the lower portion of the 7 X 64 case, its upper case sidewalls and shoulder are thicker than what is typically encountered. I have cases that have 30+ firings on them.
I bias my loads more towards accuracy first, and useful velocity; second.

Deep 6 has a case capacity of 51.2gr H2O. It has the same long neck the 6mm Remington has, and the same easy-to-form 26* shoulder angle.
These 2 features serve to keep the powder combustion " turbulence point " within the case' neck. That long neck results in DEEP 6 being just skosh longer on case
oal than a .243Win, even though its case capacity is around 2.8gr H2O less.

I prefer to shoot high load density, and have concentrated on accuracy loads that feature cases full or very nearly full of powder... along w/ safe pressures.

My initial loads were with IMR7828/7828SC, and RL-22. I can completely fill the case w/ 7828, and shoot it under 6mm bullets of 88-108gr (mostly VLDs ).
With RL-22, the case is very, very near full; and accuracy w/ 105s -108s is great.
Since reading RL-22 burns comparatively "hot", I went wholly over to trying temp insensitive powders, first RL-23; and more recently RL-26.
I believe 43.7gr I7828 was what I shot under Sierra 85 BTHPs, and had nice small groups. With RL-22, the charges ran in the 42.5-42.7gr range, to propel 6mm bullets of 88-108gr. 42.5gr shot well under all weights, but tailoring each load to the .1gr level helped to tighten groups to their bet potential.

For my application, I'm shooting Sierra 95 T-MK, as their 95BTHPs ( and Berger's too ) shot so well. It appears that RL-23 charge weights will run just under
those for RL-22 ( my loads, my gun ). This was the result of my mic'ing fired cases; and wanting to avoid undue case expansion. And, while I have not had a whole bunch of range time yet w/ RL-23, I have even less w/ RL-26. But once again, it looks like I should be able to fill the case; when using RL-26.
( For all loads I mentioned, I used FED Large Magnum Rifle Match primers. )

I load/ reload DEEP 6 using stock 6mm Remington dies.
* NO custom reloading dies to $$$ !

For case forming, I use a stock ( LEE ) 6.5 X 55 Swedish FL die, that has its internals removed; to make the die open-topped. I use a " perch" made from a .308 shell holder, a 1/4-20 flat head machine screw w/ head diam <.466" ; and a 1/4-20 nylon insert lock nut. In use, the perch is snapped in-place on the reload press' arbor.

For case forming..... brass to be sized is placed atop the perch, and press handle operated to advance the case up-into the form die. As the shoulder is shoved downward on the cases, excess brass extrudes pit the top of the open-topped die.
I do anneal the cases prior-to running through the form die.

Cases emerge from the form die in near-net shape. Cases are first rough cutoff for length, then detail trimmed to final oal desired. I inside neck ream and outside neck turn to arrive @ final 6mm caliber desired.

My point:
IF your barrel had a sufficiently long straight section @ the chamber end, the
existing .244 barrel could have its chamber shortened and some external threads added to give you a DEEP 6 wildcat chamber.

I shoot DEEP 6 in my WICHITA WBR 1375 single shot action ( s/n 15 ).
My Wichita and your M-70 both operate from a flat bolt face, and have 1-16 threads.
So...how far off could I be, comparing the possibilities of the 2 ? Hmmmm.....

My thought is that you could significantly shift selected charge wt of H4350 compared to your 6mm Rem loads, or take things down town; and shoot the slower stuff like RL-23 / RL-26.

And no.... I don't have a bunch of chrono data to