Figuring out a load that will intersect a node for my 7mm Rem mag

[tazzman]

Hi everyone,

I've got a new rifle, a Tikka T3 Supervarmint w/set trigger in 7mm Rem mag.
Took it out to the range to run it in. I had new Winchester brass, cleaned up and checked for length.
Did a FL basic size and loaded up CCI 250 primers, H4350 (55Gr.) and Hornady Interlock 154 gr. FB bullets. COAL 3.245 in.
These were the safe loads I was going to use to fireform some brass for this new rifle.
Used the one shot-clean routine.
What surprised me was the groups I got.
Doing the one shot-clean-one shot routine, I ended up with 3 groups (3 shots each) at approx. 0.5 in. and 2 groups (3 shots each) with less than that.
The rifle is not too heavy, but was a pleasure to shoot all day long.
I understand that there are nodes to search for when doing load development, velocities where groups tend to shrink.
Is there a set velocity range to search for, in each caliber, where these nodes may be, to start load development?
I have this 7mm RM that seems to have potential. Is there a velocity target I should aim for to reduce my group size?

Thanks for your input,

Phil aka tazzman

 

[Tozguy]

Phil,
Doesn't look like you got much response for the 7mm. My T3 Super Varmint is in 222Rem so can't be of much help. May I ask how you like the set trigger and where you got it from? in Canada?

 

[deerhunter28]

Try 68 grains of IMR 4350 CCI BR Primer and Hornady 139 SP

 

[tazzman]

Try 68 grains of IMR 4350 CCI BR Primer and Hornady 139 SP

Hi deerhunter28,
Is this the load you are using? According to my research, it's a tad warm. Hodgdon lists a max of 62.8 gr (58,600 PSI @ 3045 fps) for a 140 gr pill and 64 gr(59,300 PSI @ 3131 fps) for a 130 gr. pill.
Is your rifle custom-chambered?

Not a criticism, just a way to keep this thread going.

Phil aka tazzman

 

[tazzman]

Hi Tozguy,

Wanted one for the longest time. Have a Remington Classic in 7mm Rem mag but wanted one with a heavy barrel. You're right, they are not listed for the North American market. My local guy got in touch with the wholesaler and heard they had one in Canada(no set trigger). The trigger was retrofitted prior at my request prior to the purchase. The set trigger is not new to me. I know the standard trigger is already excellent, but I wanted to have the option of doing serious benchwork.
Yours is in 222 Rem. What is the primary use for your rifle? Doing any 'varmint' favours for local farmers?

Let me know.

Phil aka tazzman

 

[BoydAllen]

Phil,
I have helped a friend work up loads for his custom 7mmWSMs and a couple of custom .338 lapuas. He shoots 175 Sierra MKs at around 2,950 in the seven. and 250s in the .338 at about the same, with good results. I work up loads the same for everything.... at the range, over a chronograph, with wind flags, on a day when the wind is easy. The first thing that I do is guess at a seating depth, based on experience with that or a similar bullet. A lot of the time, if there are no magazine issues it will be 5-10 thou longer than touch. I start the pressure series well below the point where I can expect any pressure. and step up, one shot per load. For your seven mag I would make the steps .5 grain, and stop when the bold got a little tighter than I like, using fire formed FL sized cases for every shot, shooting at a single target, carefully. After that, I analyze the target, looking for clusters where changes in powder did not seem to have much effect. Then I go back to the middle charge weight of one of these groups and start playing with seating depth, in small increments. It sounds to me like you have a fine rifle. A fellow that I know likes to stalk coyotes, and shoot them at long rang with a 7mag with the bullet and velocity that my friend with the WSM uses. He is aware that the mag. could be loaded quite a bit faster, but finds the accuracy at 2,950 to be excellent, and values that above what more speed would give him with less accuracy.
Boyd

 

[Tozguy]

Phil, sent you a PM of off topic info.

 

[tazzman]

Hi Boyd,

Thanks for your response. I also believe in doing detailed and well-documented work-ups when developing loads.
I read in your response that you prefer to jam the bullet in the lands. Is that primarily to ensure that the round is perfectly centered in the axis of the chamber/bore? What about an extraction scenario?
I also seem to detect that you use the OCW method of load development? Correct me if I'm wrong...
It's d%?n cold here today, -29C (-20F), so I, for one, will definitely stay indoors and dream of another opportunity for a day at the range.

Keep in touch,

Phil aka tazzman

 

[BoydAllen]

The reason for the seating depth is that it has worked in the past, with no bullet pulling with normal neck tension for field rifles. This is not to say that I know that it will work in all cases.

I am not familiar with the OCW method, but I am sure that there is more than one way to skin this particular feline. My method was a result of the cost of barrels and impatience. By finding my upper limit, and shooting the pressure series on one target, I begin with a lot of information in a few shots. The main lesson is the loading at the range, and doing the initial load testing, after the pressure series with two shot groups. Two shots, fired as rapidly as is possible, while maintaining good form, give the greatest likelihood of being fired in the same condition, if one is paying attention to the flags, and the wind is cooperating that day. I don't do workups on days when it isn't. I always tell folks, if two shots look ugly, more aren't going to make it better. Anyway, assuming that I find something that looks good for two, I expand the test, experimenting with seating depth, and at some point, thoroughly clean the barrel, and re-foul, with my best load, noting how many shots it takes to come to a stable condition. I also tell fellows that big calibers are generally for big targets (animals) and not to make a reloading and testing hobby out of their big game rifle, lest they wear it out. Generally, I believe that for a deer and elk rifle, that if one has three shots reliably within 3/4" that you are for all practical purposes there, and that if one simply cleans the rifle at the end of the hunt, and stores it for next year with a little oil in the bore, and checks the zero before each season, that such a rifle will last a lifetime. For playing at the range, I prefer something that has been built with that particular task in mind. I have a duce and a couple of PPC for that. One of the best moves that I made, in the past, was to separate my "range" guns from my field guns. I see friends wearing out field rifles that are perfectly OK for their intended use, trying to get them to shoot like target rifles. The stocks are wrong, as are the triggers and scopes. On the other hand, IMO, 2 oz. triggers and 36X fixed power scopes have no place in the field.

 

[tazzman]

Hi Boyd,

Here is Dasn Newberry's explanation of the OCW method: http://optimalchargeweight.embarqspace.com/#

And here is Chris Long's explanation on barrel resonance: http://www.the-long-family.com/optimal%20barrel%20time.htm

These are more methods of skinning the proverbial Cheshire feline.

Cheers,

Phil aka tazzman