Possible Seating Depth Problem

[South Pender]

I'm loading, for the first time, for a new-to-me Sako 6 PPC repeater. FWIW, I'm using Norma 6 PPC cases, and I'd like to try some Bart's 68-gr. 6 mm. bullets. After taking some measurements using the Sinclair seating depth gauge, I find that I have a longer throat than I had expected. The Bart's 68-grainer is .828" long, and the OAL with the bullet just touching the lands is 2.207". The upshot is that the bullet is seated a mere .121" in the case neck.

Is this going to be problematic (i.e., too little bullet/neck contact)? I would have preferred to have more of the bullet in the case neck, but, of course, can't do this without seating this particular bullet well off the lands. The rifle has a 1-14 twist, so can't really go to much-heavier bullets to solve this.

Again FWIW, I'm using Wilson chamber-type dies for both resizing and seating.

Any suggestions and advice would be much appreciated.

 

[T-shooter]

I'm loading, for the first time, for a new-to-me Sako 6 PPC repeater. FWIW, I'm using Norma 6 PPC cases, and I'd like to try some Bart's 68-gr. 6 mm. bullets. After taking some measurements using the Sinclair seating depth gauge, I find that I have a longer throat than I had expected. The Bart's 68-grainer is .828" long, and the OAL with the bullet just touching the lands is 2.207". The upshot is that the bullet is seated a mere .121" in the case neck.

Is this going to be problematic (i.e., too little bullet/neck contact)? I would have preferred to have more of the bullet in the case neck, but, of course, can't do this without seating this particular bullet well off the lands. The rifle has a 1-14 twist, so can't really go to much-heavier bullets to solve this.

Again FWIW, I'm using Wilson chamber-type dies for both resizing and seating.

Any suggestions and advice would be much appreciated.

Doesn't sound like enough. I read someplace that the bullet should be into the neck the diameter of the bullet not including the boat tail. Is your .121" just on the bearing surface?

 

[seymour fish]

Doesn't sound like enough. I read someplace that the bullet should be into the neck the diameter of the bullet not including the boat tail. Is your .121" just on the bearing surface?

Run with it

 

[South Pender]

Doesn't sound like enough. I read someplace that the bullet should be into the neck the diameter of the bullet not including the boat tail. Is your .121" just on the bearing surface?

Yes, the .121" is just on the bearing surface. FWIW, the Wilson chamber-type neck sizer sizes only about .1875" down the neck, so there's no way I could get a full caliber neck contact with this die, no matter how long the bullet was.

Would a solution to this (if it is indeed a problem) just be to size the brass down another .001", say, so that the neck tension was greater? Or is there more to it than that?

 

[wholman]

What fish said

 

[DOGCAPPER]

what fish said. more shooting less thinking.

 

[rifleman3]

When you see too much smoke on the shoulder then you don't have enough bearing surface in the neck

 

[spclark]

0.121" is plenty as long as you have enough neck tension to avoid having bullets in rounds still in the magazine move under recoil. That could potentially lead to misfeed issues, among others.

I started messing with a 7mm variant using 308 cases last year that have all of about 0.070" neck. But it's single-load only, never imagined trying to feed 'em from a magazine.

Did the prior owner run this rifle much from the mag or did they single-load mostly? You get any user experiences related to you or just the hardware?

Too, you just might find those Bart's'll shoot bugholes jumped 0.060"-0.100" too if you try 'em that way.

 

[Mikemci]

In my 6mm Rem. my most accurate load is .071" off the lands. As spclark said, you may be good seating deeper.

 

[South Pender]

Thanks a lot, guys. I agree with more shooting and less thinking, but I'm just starting out with this rifle and am really ignorant about the cartridge, so felt that a little "thinking" might not be a bad idea before I start with the "shooting."

I got no information from the previous owner about any handloading details (if he indeed handloaded for it), but I could try to get in touch with him for more info. However, I plan to shoot this rifle single-loading only, so that seating to fit the magazine is not a factor. What I'm hearing you guys say is that this amount of bullet-neck contact (.121") is sufficient if single-loading and shouldn't present problems (like excessive run-out).

To get information on a couple of other bullets, I performed the same measurements with (a) the 70-gr. Nosler Ballistic Tip and (b) the 68-gr. Watson--in each case with the bullet touching (but not jammed hard into) the lands. With the Nosler, the bullet sits more deeply in the case, but the boat-tail looks to be about .05" long, so that I'm getting even less bullet-neck contact (about .101") than with the Bart's. With the Watson, it seats slightly deeper than the Bart's, and gives me about .140" of bullet-neck contact.

 

[spclark]

Whichever you choose to start with, and at whatever seating depths you try, let us know what you see as a result please!

We ALL learn stuff from the efforts of others, as long as we can talk about it afterwards!

 

[Zero333]

I think you'll be just fine as long as you have close to 0.002" neck tension, no less than 0.0015"

With Freshly annealed cases your bullet pull tension will be less, so closer to 0.003" Neck tension would be best if that's the case.

Several years ago I took my calipers to the range to see if bullets were moving in the necks under recoil of a 8 lb 300 winmag hunting rifle. I remember the bullets were seated a tad more than 1/2 way in the neck. Under recoil none of them moved. If I had to guess how much bearing surface was in the neck I'd guess around 0.180"ish.

 

[boltfluter]

I would start at least .010 into the lands as this will let the bullet self center, so to speak. Now, get out there and shoot some bug holes. Good luck and keep us posted.

Paul

www.boltfluting.com

 

[South Pender]

Out of interest, I just tried the shallow-seated Bart's (touching the lands) and was surprised to find that they (just) fit into the magazine. I didn't think they would. However, I suppose that if I filled the magazine, the shallow seating might result in the bullets being pushed further into the case from recoil with repeated firing. On the other hand, Zero333's results with his 300 Win. Mag. might suggest otherwise.

 

[T-shooter]

Thanks a lot, guys. I agree with more shooting and less thinking, but I'm just starting out with this rifle and am really ignorant about the cartridge, so felt that a little "thinking" might not be a bad idea before I start with the "shooting."

I got no information from the previous owner about any handloading details (if he indeed handloaded for it), but I could try to get in touch with him for more info. However, I plan to shoot this rifle single-loading only, so that seating to fit the magazine is not a factor. What I'm hearing you guys say is that this amount of bullet-neck contact (.121") is sufficient if single-loading and shouldn't present problems (like excessive run-out).

To get information on a couple of other bullets, I performed the same measurements with (a) the 70-gr. Nosler Ballistic Tip and (b) the 68-gr. Watson--in each case with the bullet touching (but not jammed hard into) the lands. With the Nosler, the bullet sits more deeply in the case, but the boat-tail looks to be about .05" long, so that I'm getting even less bullet-neck contact (about .101") than with the Bart's. With the Watson, it seats slightly deeper than the Bart's, and gives me about .140" of bullet-neck contact.

Try loading a dummy round (no powder or primer) with each of the bullets. Check the runout before and then chamber several times and check again. When you extract, do it very gently and catch the round in your hand. If the bullet isn't getting pushed sideways or bending the end of the neck, then it's probably ok. With only that much neck contact, it won't take much side force to egg out the neck and make the bullet loose.