A few opinions please

[Dougfir]

So, I'd appreciate a few other perspectives. I'm in the process of working up a load for my new hunting rifle (Tikka T3x lite in 7mm-08). I've been working with the 140 grain E-tip and found a promising load that I'd like to play with more. The load is:

140 E-tip, 41.5 grains varget @2.775" (Fed case, WLR)

I've shot two groups with it now, they measured 1" and 15/16" velocity is right around 2790. Barrel is 22.4" The primers look fine, flattened a bit, but fine, and the bolt lift feels ok. Still, the available load data and the velocity make me think I must be right up near max. Nosler lists 42 as max, but I think that's really for the ballistic tips, accubonds, etc. They definitely hint that you won't neccessarily get to the same charges with the e-tip.

So, if those MOA groups held out to 200 and 300 yards, I'd call that a pretty good load and be fine with it. But, normally, at this point, before I did that, I'd shorten the OAL a bit and see if that tightened things up. The pressure signs tell me I could probably do that. The data and velocity tells me maybe that's pushing it. What do you think? Also, anyone ever lengthen a load and get better accuracy? I suppose I could increase OAL a tad and reduce pressure and see what the group looked like... Maybe I'm being a bit ridiculous here, in terms of caution, but what would you do?

 

[HAWKEYESATX]

Well.....let me tell you something that happened to me several years ago.
I was shooting an old 6.5x55 M96 Swedish Mauser. I had, at that time, PMC 140 gr SP bullets, and when I shot like 5 of them, I saw pressure signs. Flattened primers, and the metal on the primers flowed a little bit.
I was scratching my head, because military Swedish Mausers tended to have long throats. I checked the ammo oal, and it was within oal. I was really puzzled. Then I ran 2 rounds through without firing, and pulled them out. I saw land marks on both, exactly the same place. AHA! This particular Mauser didn't have an excessive long throat. It had a throat that was like a commercial throat. So I quickly got my dies out, and seated them an 1/8 of an inch deeper. Voila! That did the trick! No more pressure signs!
Now, with your situation.
I think the ogive for your e-tips is completely different from a Ballistic Tip, or a Partition. The e-tips are a harder material due to being all copper alloy. Plus there is a longer bearing surface on them.
I would honestly try another bullet with your powder charge, or reduce your powder charge with the E-Tip.
I've seen in some reloading manuals that when the e-tips are used, the powder charges are reduce an extra 5%, due to longer bearing surface making pressures spike.
I would try that as well.
Just my 2 cents worth.

Hawk

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[mjcmichigan]

If you shorten the OAL, you might get less primer flattening. Monos sometimes behave better short than long. If I was shooting a cup and core I’d try to make them 0.002-0.005 off the lands. I would not go longer than OAL with a mono. You might want to look at RL26. I don’t have a 7-08, but used it in 243win, similar case, and got amazing speed and no pressure signs.


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[Dougfir]

If you shorten the OAL, you might get less primer flattening. Monos sometimes behave better short than long. If I was shooting a cup and core I’d try to make them 0.002-0.005 off the lands. I would not go longer than OAL with a mono. You might want to look at RL26. I don’t have a 7-08, but used it in 243win, similar case, and got amazing speed and no pressure signs.


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Wouldn't shortening OAL increase pressure though?

 

[mjcmichigan]

There is a weird dynamic there. Case volume vs Jump.

You do have a long-ish skinny bullet in a smaller case. (7mm-08)

The Shorter OAL, will let more gas bleed through the barrel until the bullet completes the jump.

To be safe, drop back a bit and shorten the OAL to Sami.


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[D21ALASKA]

Do you have an OAL gauge to verify your distance off the lands?

Where did you start working up from and what were your speeds at lower charge weights? If you have a good node a grain or so back without appreciable loss of speed, 100fps or less, that may be a good idea.

Also, I don't have experience with it personally but I've heard a number of times that federal cases can have less powder capacity since they're thicker and thusly increase pressure signs at less than max loads.

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[grifmXC]

I’ve never played with etips but I use barnes TTSXs almost exclusively. From what I have read etips like a bit of a jump.

From what I have seen with TTSXs the pressure curve for a given charge seems to be shaped like a bathtub. As you change seating depths off the lands. Really close it spikes and then it reduces/smooths out and then spikes back up once you start really eating into case capacity. Barnes recommends starting with a .05 jump. I like to start there because the. I only have one way to go as far as seating depth. My 30-06 loves .083 jump with 168 TTSXs. When I started working on a load for my 308 with the same bullet I started with the .05 recommended jump and hit pressure in the middle of the Barnes load data. I did another ladder with a .1 jump and was able to go up above the max Barnes data without any signs of pressure.

It would be great to know how far you currently are from the lands to know which direction would be best. But, as long as you keep your changes small (.01) steps, I don’t think you would run into any major issues with seating the bullets a little deeper. I probably wouldn’t go longer until I had a good measurement of the current jump.

-Matt



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[ShadeTree]

You gotta be close to peak pressure, but if you say cases and bolt lift is fine, then it's fine. Just make changes incrementally without doing anything brash, and your not going to blow your gun up, but watch for those pressure signs showing up, and it might not take much.

1 thing to pay attention to in load data is what length barrel was used. Nosler's online data shows they used a 26" for a velocity of 2850 with 42 gr's of Varget. You didn't mention barrel length but in a Tikka Lite I'm assuming 22"? If so using a conservative estimate of 25fps per inch, you should be running roughly 100 fps behind Nosler's top load. You're within 60 fps, and with a 1/2 gr less powder.

I'm not saying you're overpressure, but the velocity signs with everything else considered, especially with a mono, are pointing to proceed slowly. Which you are wisely considering.

 

[Guy Miner]

You're looking at 1" groups, nearly 2800 fps velocity, and a great bullet.

Me? I'd load up a bunch of them, practice, then during hunting season, go kill things.

But, I'm a simple man.

Regards, Guy

 

[DrMike]

In our pursuit of velocity and accuracy that allows us to brag, we often forget (or ignore) that our purpose is to ensure that the bullet is delivered to the target (usually of rather large size during hunting) with sufficient energy to disrupt vital systems. I taught my grandson that if he could hit a paper plate nine out of ten times at a given distance, he would kill his animal (whether moose, elk, black bear, deer, caribou, sheep or goat). I do enjoy accuracy as much as the next person, but I do attempt to remind myself on a regular basis that the end product is meat in the freezer and not accolades for a picture posted on a web site. Load up some cartridges using the recipe you've worked out and go kill some deer.

 

[ShadeTree]

Agreed Dr Mike. Although there certainly would be some degree of accuracy differences required when comparing a moose to a deer or sheep.

With a moose you're looking at an animal at 100 yds that is the size of a utility shed. The old adage hitting the broadside of a barn door comes to mind. :lol: