Home Forums Hunting & Shooting Ask The Gunwriters Mule Deer - Article on Bullet Seating Depth?

Have you ever or have you considered doing an article on bullet seating depth? This is one part of my reloading that still remains a bit of a mystery to me and I was wondering if there were any detailed articles on it.

Would be interesting read.

Good suggestion.

I think it would be a difficult article to do because of all the variables. Some bullets prefer a jump. Some guns are more accurate with a jump. Others prefer being right up against the lands. Ultimately the article would probably tell us we simply have to experiment.

centershot,

Actually I'm working on an article primarily about that very subject for November's issue of RIFLE LOONY NEWS.

Great what I would like to know is can you determine anything about group shape and bullet seating? Some people claim they can and it seems to work for them but for me it's like trying to read tea leaves. Is there any other way other than trial and error to figure out optimal seating depth? I start out at maximum magazine length and work backwards usually if three to five increment depths don't work I figure it is the load.

Looking forward to it MD. I remain mystified about the best approach.

I look forward to that article too JB.

Currently working with a 7x57, economy A&B 21" bbl ( I was gifted several vz-24 recievers, A&B bbls in various chamberings, reamers, go/nogo gages, Timney triggers, sporter stocks, & so forth). Dyna coated the bore due to the A&B bore is very prone to copper foul.

Anyhow, worked w/ Hornady 139 IL & Nosler 150 BT. Goal is to get some background w/ Nosler BT, then work with 150 Nosler Accubonds for the final load.

Seated the Hornady to 3" oal, per Hornady book. I did the slit case neck, start bullet, push case in chamber until case shoulder butts chamber shoulder. OAL =3.080". Hornady 139IL jump is ~0.080". 2700 fps per crono, makes 1 3/4" @ 100.

Nosler 150 BT seated to 3.070" (SAMII max is 3.065" per Nosler book). I did the slit case neck, start bullet, push case in chamber until case shoulder butts chamber shoulder. OAL =3.150".

I conclude that the Nosler 150 BT is jumping ~0.080". This shoots ~1.00-1.25" @ 100 yard. W/49gr IMR 4350 makes 2815 fps per crono.

Intuition tells me to jump the Nosler BT a bit less, say 0.050" using same powder weight. Given I'm working with an A&B barrel, could be that 1" 3-5 shot groups could be all I can expect.

I've always approached seating depth (bullet jump) as trial & error. I'll say it again, looking forward to that article JB.

Pat

Ya know......the 'fire seems to have such good timing for you. Are you sure this isn't a set-up?........

If anybody wants to keep it really simple (which is the primary reason any shooter looks for simple solutions on the Internet), start with the bullet seated as far out as possible, whether limited by the magazine or chamber throat. Then if the accuracy isn't all you expect, seat 'em deeper and see what happens. Unless rifle bullets are seated REALLY deeply (which isn't what occurs most of the time), then pressures are lower with deeper seating.

The article will go into a little more, uh, depth.

I had an A&B barrel that would consistently average 3/4" at 100 yds with its favorite load. It was also on a Vz-24 ,but was a .458 winchester . I liked the barrel and it only fouled about like most factory barrels. A 150 gr Accubond at 2800 and grouping an inch would be fine killing medicine in my book........

Is there a rule of thumb that is close but ensures that variances in the bullets does not create an issue? .020, .030, .040 or so just to be safe but still typically gives good results?

Looking forward to article.

Aha! I see what you did there JB!

Centershot,

I haven't found any rule-of-thumb to work consistently, probably because bullet construction and shape varies too much these days. Chamber throats are another factor, whether custom or factory.

Centershot,

Perhaps you are asking, "How far out (how close to the lands), when not limited by magazine length, can one seat the bullet so as not to create an issue (pressure issue), considering variances from bullet to bullet?

If that is your question, then you realize that touching or jamming into the lands causes a significant rise in pressure as opposed to being somewhat short of the lands, and you are concerned with bullet variance. You wouldn't want one bullet out of ten to hit firm against the lands and have a higher pressure and velocity than the other nine rounds.

Today's bullets don't vary a whole bunch. I remember some old manuals suggesting as much as .030" for hunting loads. With today's bullets I am comfortable with .010" to .015" off the lands to start with, then work shorter (more jump) from there looking for best accuracy. That should keep all bullets in a batch from actually hitting the lands. And just as important, preclude having a random bullet stick in the lands and stay there when you extract a loaded round.

Barnes has always suggested seating their all-copper bullets at .050" off the lands for accuracy and pressure reasons. This was more important with their older non-grooved bullets, I believe, but many people find good results at that seating depth with their bullets.

Others may have their own thoughts on this. If I correctly interpreted your question, I hope this helped. Good luck.

nifty, that is exactly what I'm asking/concerned about. I like to get all the accuracy I can but am not interested in blowing up my rifle for 1/8" better groups.

One other question I have - Is a bullet comparator the way to go or is measuring OAL with a good un-marred bullet good enough?

I like a comparator. The Sinclair "nut" is a good way to go, and relatively inexpensive.

https://www.sinclairintl.com/reload...-style-bullet-comparators-prod83792.aspx

Another fan of the Sinclair nut. I've been using one for thirty years.

A bullet comparator. I use the Stoney Point/Hornady comparator but the Sinclair nut MM mentions is less expensive.

I used the Stoney Pt comparator for several years, but only with cartridges for competition rifles. For military surplus and hunting rifles, I never noticed any difference, so I quit using it.

With improvements to both bullet mfging and rifles, I don't see a need. Load. Shoot. Smile.