Ocw seating depth question

[doctordoctor]

Okay just need some clarification on starting seating depth.* *

It is my understanding that to safely work up any reload it is best to start. 010" jammed. Reason being this will be relatively the max seating depth and therefore be the highest pressure state. You then work down from here as far as seating depth goes once you find your max powder charge.

So should I start* . 010" jammed conduct my test finding my ideal powder charge?

I have read else where to just start at COL. Since the goldstandard FGMM is not jammed anyways and it's results speak for themselves, thus the benefits of "jamming" are largely overstated.

I could see the advantage of starting jammed is finding max pressure load.*

Anyone have their 2 cents?

Fyi: factory stock Remington 700 xcr long range tactical 26" barrel. I know these are notorious for having long throats so maybe starting jammed is not even feasible. Can't recall what my OAL is right now, I plan on remeasuring soon.* Thanks guys

 

[Dan Newberry]

I would load the cartridges to whatever length they'll magazine feed at. With most Remington 700's that's going to be no longer than 2.800", maybe 2.810". If you make them too long, they will not magazine feed reliably--if at all.

Some folks say they're not interested in magazine feeding. That honestly makes me wonder why they hang out in a tactical oriented forum, rather than on BR Central or some such target shooting forum. The genre is totally different... a rifle that won't mag feed is a single shot.

I'll use Federal Gold Medal Match ammo to demonstrate a point: It is 2.800" in .308 Winchester... it magazine feeds well, and shoots better than good enough to accomplish anything that truly needs doing with a .308. If you have a good rifle, good factory match ammo will shoot 1/2 to 3/4 MOA groups on demand. Actual distance to the lands will vary widely from one rifle to another, of course... but it all shoots well. Hmmm...

We often see folks jamming their bullets into the lands who are simultaneously using very light neck tension through Redding or similar bushing dies. Tactical ammo should NEVER have light neck tension, in my opinion. If you're just gaming, then that's fine... but field ammo should have strong neck tension to keep bullets from shifting seating depth under recoil (as regards cartridges in the magazine), or during aggressive working of the bolt. And if the cartridge box gets dropped, rolled over onto... stepped on... whatever... with light neck tension you're possibly going to see runout numbers go up, and seating depths shift.

Trying to jam the lands the same amount each time is a hard game to play. You might be .005" of jam on one shot, and the other .005" is nothing more that "push back" into the case... the next shot, as the barrel heats, does jam the full .010" into the lands; it doesn't get pressed back into the case... then the next is some mixture of the two. If you're going to try to jam, I believe firm neck tension is needed to get any modicum of consistency. But again, seating to jam the lands for a tactical rifle cartridge is asking for trouble in the field...

My opinion. Others may vary.

Dan

 

[damoncali]

Don't jam the bullet or you'll get a bullet stuck in the chamber and powder all over the inside of your action when you try to unload. It doesn't take much. Jammed is for benchrest.

 

[Ultraman550]

Dan I have a question. I love feeding through a magazine by the way, lol. I have a chamber OAL of 2.300. Barrel only has 60 rounds through it, new Stiller action so lets call it brand new. I've been loading my bullets from bullet ogive to case base and using 2.285 (I read where Bryan Litz said to start .015 off the lands) and I'm comparing it to a loaded case that is 2.225 so I'm not really jamming but getting close to the lands and I'm giving it enough jump where the COAL is pretty much what you'll find with the FGMM of 2.800 give or take .005. I'm loading 10 rounds of each to compare MV and accuracy. I'm using SMK bullets and when I measured bullet base to ogive I had some that were .650 ranging to .690+ so the variance was pretty huge. Both COAL's load easily from the magazine (Im using Alpha mags which actually allow 2.920 COAL but at that length the bullet wouldn't only be seated in the neck and not enough neck tension). Is there anything I could do differently, you would do differently etc...? I haven't been measuring from the tip of the bullet to the case head because my measurements are always fluctuating due to that shitty copper tip and bullet length inconsistency. Also, I'm using a Magneto Speed V2 to check.

 

[Dan Newberry]

I would let the target be the judge--if things are working well, then just continue as you're doing. I had not heard before of that much bullet base to ogive variation, but to be honest I rarely check that.

Try marking some of the cartridges where the ogive variance is highest, and see how they end up grouping. Some folks do measure and weigh bullets, segregating them to be as uniform as possible. This may not be necessary, depending on your accuracy needs.

I had done an OAL test on a load I was working on last year, and when finished, I had about 7 or 8 cartridges which varied in bullet seating depth by probably .020", if I remember right... just for trigger time, I shot them all onto the 600 yard target plate, and was pretty amazed at the size of the group. It was well under MOA, probably had I measured it it would have been no larger than 4 inches.

So just see how the load shoots, and go from there.

 

[rw496]

[MENTION=83425]Dan[/MENTION]
What neck tension are you recommending?

 

[Dan Newberry]

I use near exclusively FL dies and the Lee Collet die to neck size. If you're using Redding... I would stay away from the lighter bushings, preferring something that would give me enough neck tension to be sure bullets won't easily shift. I can't honestly tell you which Redding bushing dies would give stronger neck tension as I don't use those. I did have a client recently that was experiencing bullet shift on the mag loaded cartridges during recoil. I thought that might have been the case as he was only using a couple thousandths of neck tension on the bullets. I had him measure the OAL's off all the cartridges in the magazine after firing a shot, and lo and behold... they all shifted longer. Going to .004 tension seemed to solve the problem.

 

[bruddah]

Good thread. I can't help but wonder though. If you are jamming the bullet into the lands, you are limiting the powder charge right off the bat since the pressure will be higher jammed. I would think .005" to .010" would be as good of a start as any, and you won't have to worry about a spike in pressure from the lands.

Staying off the lands would allow you to use a few higher charges than into the lands would no?