Jamming into the lands

[supercorndogs]

I have some 6.5 Grendel Hornady brass. When firing it is growing around .01 at the shoulder. This extra head space is causing ejector marks, and I am sure stretching at the web. I have some 1x brass I bought from another member and it measure the same as my fired brass, so I think its the brass and not the chamber. I have already run down gas and timing and don't think it the issue. Primers are still very tight, so I don't think its pressure. It did from 26.5 to 28 g of 8208 with a 123 ELD. MV at 28 was 2450. OAL is 2.24.

I want to jam into the lands to fire form the rest of brass. How far should I back my loads off to keep the pressure spike in the safe range?

 

[Steel head]

Jam them hard with a mild charge.
If they aren’t jammed hard you don’t get the full benefits of the case head being held firmly on the bolt face.
Usually starting data and then a bit more will still be mild pressure on a hard jam.

 

[47guy]

I shot a BRX for a few years and fire forming was a PITA!

if you are going to jam I’d suggest you set neck tension at .005-.006...light neck tension when FF will let the bullets push into the case...and jam at least .030...I starting going .050 jam.

as far as charge I’d go 26-27g if your running 28g normally...to light a charge is a waste of time and to high can ruin brass.

 

[sig2009]

As far as jamming into the lands I have never had a rifle that liked it.

 

[spife7980]

If you were going 26.5 to start then thats what I would do and stick the bullet in the lands hard based on bolt feel. Go as deep as you can stand to have resistance in the bolt.

When forming my dasher that .1 I had the false shoulder and was initially jamming .2 into the lands and could stand it. A lot, I know, but that batch of 100 cases is the best formed stuff. I just couldnt stand to run the bolt after awhile, it was actually hurting my hand so I backed it down to .1 of jam and it was perfeclty tolerable so llong as you could stan do feel it jamming for a few hundred more rounds. With only .020 of jam I could barely feel it was jamming up.


Then again I think this boils down to whether people consider jam a "hard jam" or "anything from actually touching the lands". I use anything from actually touching the lands. And from there .1 of jam wasnt bad so, again, I would say to go based on bolt feel.

But crap, youre on an AR. With that in mind and the carrier doing the work for you I would see if .1 of jam can be sent home by the bolt carrier reliably.

 

[47guy]

As far as jamming into the lands I have never had a rifle that liked it.

he is jamming to fire form his brass not looking for an accurate load.

 

[MtnCreek]

I'm not sure you're going to be successful jaming enough to resist the firing pin and chamber in an autoloader. You might cheat a little out of them with a fl die, staying off the shoulders. More extreme you could expand up with 7mm(?) and size that back down for a false shoulder.

 

[supercorndogs]

I don't have any dies for it. I am seating with a 6.5 Creedmore seating die.

 

[MtnCreek]

Then seating long shouldn't be a problem LOL. Surprised it adj enough for that short case.

 

[supercorndogs]

I think the 6.5 Creed and 6.5 Grendel seater are the same die for Hornady. Maybe they make a shorter one for the smaller cases. My Horandy 300wm seater is about 1/4" longer than my 6.5 Creed seater.

 

[MtnCreek]

Interesting. I think I have RCBS creed and Grendel seaters; may compare to see on these.

I loaded 06 for years using a 308 neck and seater.

 

[supercorndogs]

RCBS seaters are a little bit different than Hornady.

 

[918v]

Your bolt carrier slamming into battery may bump the shoulder, unless maybe if you single feed and close the bolt gently.