on the subject of bullet seating depth, aka jump

[cali_tz]

so I have been seating my 308 bullet depth on my Rem 700 Police to about 20 thou off lands. Given some very good results with much deeper seating on my 338 Lapua, I decided to try the same with my Rem 700 308 rounds.

I was seating about 0.020", and then today tried 0.100" and my ES (was like 60-70) went down to 30, and my SD (was in high teens) went down to 7. Accuracy at least on vertical disperson seemed to tighten up measurably, to 1/2MOA. My horizontal dispersion was messier than normal (about 1MOA) but wind was gusting at 90deg to my shooting direction 5-10mph.

Seating at 0.020 and 0.030 jump has previously provided ES and SD much less than desireable. I thought it was the chon maybe, but today at 0.100 the chron all of a sudden was like reporting speeds right next to each other.

Anyway, I don't offer any explanation, just what I observed today.

 

[Fuzzball]

Re: on the subject of bullet seating depth, aka jump

Soooo..once again the firmly held idea, a near religious conviction of many, that 'best accuracy' is always going to be at or very near the lands takes a reality hit.

 

[Tripwire]

Re: on the subject of bullet seating depth, aka jump

Dare I mention the bone stock M700 BDL in .270 win that the best load it ever shot was with Sierra 90 grain flatbase HP's that would put 5 into one little ragged hole barely discernable from a single bullet hole?

To get .277" worth of bullet contact with the neck that short fat bullet had to be seated .250" from the lands.....more than one Myth busted by that rifle.

 

[cali_tz]

Re: on the subject of bullet seating depth, aka jump

and btw, Fed 175 GMM2 is seated even deeper, significantly deeper than even my new deeper seating. And it shoots pretty darn good. Though I did test some Fed 168 GMM and it's speeds were not as consistent as you'd hope... ES of like 80. That's what the chron reported after 10 rounds.