ELD M 178gr OAL /Varget Load

[JGC]

My load
178Gr ELD M
42.5gr Varget
Hornady Brass
CCi Primer
2.890 OAL
Remington 700 .308 Varmint 26 inch Heavy Barrel
1/4@100 cloverleafs
Magneeto velocity average 2630

* Wasn't concerned single feeding but want to go hog hunting and now want to try and load these to mag length. I worked them up to 43gr and settled for 42.5 most accurate of all test. my concern is If I seat those long eld rounds at 2.800 will the pressure increase be substantial? after all those eld x precision hunters iam sure are loaded around 2600 with same hornady brass..

[Unclenick]

The SAAMI maximum length, unlike the military maximum for 7.62 ammo, is 2.810", so you have a little more room than you thought. Also, while the 2.810" limit is official for fitting into and feeding from all magazines manufactured to SAAMI standards, most actual product will tolerate a little more. I would not be surprised if your magazine actually tolerated 2.830" to 2.850" or so before it didn't work. You can test this by making up a dummy round at 2.890" and putting it in the mag with some snap caps or standard length dummies over it to get it to the bottom, and try feeding all the way through the magazine. When you find the maximum length that still feeds, knock another 0.020" off to allow for bullet and case variation and go with the resulting new length.

As to whether pressure will go up or down when you seat deeper, it depends how close to the lands you are seating now. A bullet jammed in the lands will usually have about 20% higher pressure than one seated to factory recommendations. As you seat deeper, the pressure drops until you are around 0.030" off the lands with most bullets, but some shapes, like a round nose, have to go deeper to reach a pressure minimum (see plot for a round nose bullet, below). After that, seating deeper still will raise the pressure again. So I can't answer your question very specifically. As a starting point, when you change the seating depth, adjust the powder to produce the same velocity the gun did with the previous seating depth. This does not produce an exact pressure match or barrel time match (important to super tight groups), but its a good first approximation for further tweaking.

[T. O'Heir]

42.5 grains of Varget is very close to the start load(so is 43.0) for either a 175 or a 180(only place you'll see a 178 grain bullet is in a Hornady manual) so you can just load 'em to 2.800" and you'll be fine.
Loading to the off-the-lands length is done after you have worked up a load anyway. It's a load tweaking technique that is not necessary.
Like Nick says, try the 2.890" in the mag. It might just fit, but not likely. Remember that OAL is measured from the pointy bit of the bullet to the flat part of the case. Ogives do not apply.

[JGC]

2.890 with 42.5 varget is my 178 ELD Match load. I want to shorten to mag length just was curious if pressure could be a problem. My velocity average is 2630 with hornady brass and they are grouping real nice at 100yards 3 shots 1/4 inch.

[Unclenick]

The Hornady manual shows a maximum of 42.4 grains with that bullet at 2.800" COL. They were getting 2450 fps from a 22" barrel. Your's should be about 85 fps faster, but it is more than that, so I am thinking your gun is tighter than their Winchester model 70 was and may be experiencing higher pressure.

I would seat the bullet to 2.810" and leave your load alone. Whether the pressure will go up or down, as you can see from the graph, is not really knowable without putting a strain gauge on your gun and measuring it. Your gun's pressure vs. seating depth curve will have a trough in it like that one does, but where that will fall depends on your chamber and the bullet shapes. Whether you go up or down depends which side of the trough you are on now.