Seating Depth and Engraving on 7mm

[iplaywithnoshoes]

I just got some 145-SILH from Montana Bullet Works and loaded got a few rounds loaded for the Encore Pistol in 7mm-08. I am getting an interesting problem though: I've seated the bullets as deep as I could get them; the gas check is a little bit under the case neck and the nose is already engraving. There is some resistance when closing the action but not as much as there would be with a jacketed round seated too shallow. Is this considered safe? Note: I'm starting with 12.0gr of Unique (load range is 11.5-16gr) and the bullet is straight Linotype with a gas check.

Left one is unchambered, and the right has some engraving on the nose if you look closely:

233943

shoe

[coloraydo]

Looks like two different length cases and different diameter boolits.

[MT Gianni]

I think the photo differences is camera angle. If you can extract the cartridge without changing OAL I am OK with a mild start load worked up. I am not sure where 12 gr Unique fits in there. I topped out at 10 in the 30-30 but that was for accuracy. If 16 gr is max you're probably OK. If 12 is max you might be pushing it. I can't tell but the case looks like 7mm-08?

[iplaywithnoshoes]

Looks like two different length cases and different diameter boolits.

Yeah, it really does but it's the camera angle.


I think the photo differences is camera angle. If you can extract the cartridge without changing OAL I am OK with a mild start load worked up. I am not sure where 12 gr Unique fits in there. I topped out at 10 in the 30-30 but that was for accuracy. If 16 gr is max you're probably OK. If 12 is max you might be pushing it. I can't tell but the case looks like 7mm-08?

Yes, this is 7mm-08. Lyman 4th edition specifies a load range between 11.5 and 16gr of Unique with similar bullets. I was going to do a workup but it looks like I'm going to be testing if the pressures are safe at the bottom of the load range.

[waksupi]

Don't worry about the gas check being inside the case. Seat the bullets ot just clear the lands.

[Wm Cook]

1) With a no primer, no powder full length sized case seat your Bullet as you show in the picture. With your calipers measure OAL of the cartridge before chambering.

2) Chamber the round and remove it from the chamber.

3) Measure the cartridge now. That’ll give you a “kind of” jam depth. “Kind of” because how far you are able to jam the bullet into the lands depends on the neck tension and the wear the chamber throat has on it.

4) Knock the Bullet out and resize the case.

5) Seat a different Bullet in the chamber to the OAL length of the cartridge you measured as it was pushed back in step 3.

6) Using fine steel wool wipe down the exposed bullet to polish it. Chamber that round, remove and look for engravings from the lands.

7) Repeat step 4, 5, 6 but seat the bullet.005 deeper each time.

Repeat steps 4, 5, 6 and 7 until you see no lands. That puts you at “just off the lands”. Be careful about shooting cartridges with the bullet jammed in the lands. If you have a hot load worked up with the bullet .010 “off” the lands, then use that same charge with the OAL extended and with the lands pushing the bullet into the case (jam depth) you will have excessive pressure. That is dangerous.

When you get that “just off the lands” measure one of your bullets OAL and substact the exposed portion of your bullet to see how far into the case the gas check is located.

As a rule of thumb, for accuracy I try .005, .010 off the lands and so on until I find the sweet spot. The over all length of cartridge your firearm allows plays into this as well. Good luck, Bill.

[iplaywithnoshoes]

Well, I got my answer. Despite the action closing with some resistance, the rounds shot fine with no pressure signs on the primer or case. These rounds were actually quite consistent at 100 yards and a lot quieter with significantly less muzzle blast than an equivalent load of H4895. As Bill up above mentioned, do not try this at home unless you know what you are doing. Your rifle may not need to jam into the lands like they do in my Encore, which has an extremely short throat.