Bullet Seating Depth - learning something new

[elpac3]

Just picked up a new favorite rifle, a 1957 vintage Remington 722 in .222 cal.

Made up some hand loads using Nosler 40 grain Ballistic Tips with 22.5 of H322. Loads shot well - but after reading thought I could do better.

Bought Hornady comparator so I could measure ogive to land seating depth. Went to work and made some loads .040, .030 and .020 off the lands. The .040 off the lands are really close to the OAL in the manual of 2.130. The .040 loads again shot well, same as the week before. Hoping to see things get tighter the .030 loads were a real letdown: mad: as the group opened up. The .020 loads tightened up significantly, producing all rounds touching.

Moving onto the Hornady 50 grain Vmax, again the OAL of 2.130 and 22.5 of H322 produced a load that was .040 off the lands. Shot it and had good results. Made up a batch of .040, .030 and.020 loads and back to the range. Shooting the .040 loads produced and identical target to the one from the week before.


Being anxious to try the .020 load I fired them next and was totally disappointed, having hoped for results similar to the Nosler.

Not sure what to expect from the .030 loads I was pleasantly surprised when they turned in the best group of the day. Could have been a one hole group had I done my part with a called flyer.

Lesson learned: Even though shapes are similar and seating depths are close, you never really know what each individual gun will like until you test under controlled conditions changing only one variable at a time.

 

[JohnK]

I think that the most important variable, in rifle loading, is loading to favorable barrel harmonics.

It may have nothing to do with distance to the lands, but the seating depth, that gives barrel exit, at the "sweet spot" of barrel vibration.

Manufacturers that developed adjustable barrel weights, "accurizers" so to speak, knew this. They worked splendidly.

 

[H Richard]

Have you tried 4198 powder? That is the powder developed for the .222 and used for many years in Benchrest competitions. Also, my Sako .222 really likes the 52 gr. Speer HP. Another trick for accuracy is neck turning. A lot of brass is not really concentric as it comes from the factory. Turning it one time will make a difference.

 

[elpac3]

Have not tried 4198 yet. Was debating when I selected the powder and it was a toss up between H322 and 4198.

I am collet sizing necks and rotating cases 1/3 turn then resizing again.

Have not yet tried the 52 grainers but that is on the to-do list

 

[Nevada Ed]

If you go to removing brass;
You can ream the inside of the case neck, shave to outside of the case neck or maybe, even both...............
but just make sure minimum copper is removed. You can always do it again but you can't put the material back !!

Don't inside ream after sizing the brass...... It takes too much material off. I always use the first fired case for the inside reaming, and I always run a new case that is not round at the neck into my die to fix this problem. Even new factory cases can be out of round or have a dent.

The "Triple deuce" is a very accurate rifle..............enjoy.

 

[MichiganScott]

Most reloaders get to hung up on being close to the lands. I've got a couple of rifles that are sub-MOA with bullets seated over 0.1" off the lands. My military Swedish Mauser actually likes 0.125" off with 140 gr spitzers. Good thing. It was throated for 160gr round nose bullets. I don't have a single rifle that prefers less than 0.020" off.

If you don't have the Hornady Lock-n-Load overall length gauge set, you need it.

 

[elpac3]

Most reloaders get to hung up on being close to the lands. I've got a couple of rifles that are sub-MOA with bullets seated over 0.1" off the lands. My military Swedish Mauser actually likes 0.125" off with 140 gr spitzers. Good thing. It was throated for 160gr round nose bullets. I don't have a single rifle that prefers less than 0.020" off.

If you don't have the Hornady Lock-n-Load overall length gauge set, you need it.

The Hornady Lock-n-load OAL gage has been getting a work out with these new loads. opens up a whole new aspect of rifle loading for me.

 

[rockquarry]

After using a 722 Remington and several Sakos, I've found the .222 cartridge to be one of very few that is usually most accurate with the bullet seated to approximately the book recommended OAL. I have run across a few exceptions and it's still best to try different OALs.

As for powders, one can hardly go wrong with H322 or IMR4198. However, Reloder 7 usually provides accuracy at least on the same level, though velocities are slightly lower.

I've tried many bullets from 40 - 60 grains. A lot of them are quite accurate, but one long-time favorite is the Sierra 50 grain Blitz (medium velocity version). In most .222s, it will shoot about as accurately as any target bullet and works well on varmints.

 

[ggibson511960]

Fun to Explore, but Take Care

My experience with comparator gauges is that a reasonable seating depth, about 0.020 in. off the lands, doesn't make a great deal of difference in accuracy in my standard configuration rifles. This makes sense, as a longish rifle bullet is still in the grip of the case neck when it encounters the lands, even if seated to extreme depths requiring a longer throat jump to the lands.

What can happen is that seating depth can affect the pressure curve. I made the mistake of seating some 130 gr. .270 bullets out to 0.010 in. gap, thinking I was safe with a decades old recipe of 59 grains of 4831, well under the maximum 63 grain load in one current manual. I tried other seating depths, starting at 0.040 in. and decreasing in 0.010 in. increments. I pressed on below 0.020 in. because I wasn't seeing the dramatic increase in accuracy I thought I deserved for taking so much trouble with my carefully loaded rounds. The rifle, a Winchester M70 Featherweight, was grouping just under 1 MOA, but I wanted more. The 0.010 in. gapped loads flattened and cratered primers to a frightening degree. I backed off to 0.020 in. loads and counted myself lucky. Rifle probably has a tight bore. It groups well with almost anything. In any case I learned a valuable lesson to not just squeeze down the bullet jump without watching for signs of excessive pressure. There is a good reason Roy Weatherby free-bored his rifles. There is a lot going on in those microseconds as the charge lights off, builds pressure, un-sticks the bullet which jumps the gap against neck friction, and encounters rifling.

 

[elpac3]

My experience with comparator gauges is that a reasonable seating depth, about 0.020 in. off the lands, doesn't make a great deal of difference in accuracy in my standard configuration rifles. This makes sense, as a longish rifle bullet is still in the grip of the case neck when it encounters the lands, even if seated to extreme depths requiring a longer throat jump to the lands.

What can happen is that seating depth can affect the pressure curve. I made the mistake of seating some 130 gr. .270 bullets out to 0.010 in. gap, thinking I was safe with a decades old recipe of 59 grains of 4831, well under the maximum 63 grain load in one current manual. I tried other seating depths, starting at 0.040 in. and decreasing in 0.010 in. increments. I pressed on below 0.020 in. because I wasn't seeing the dramatic increase in accuracy I thought I deserved for taking so much trouble with my carefully loaded rounds. The rifle, a Winchester M70 Featherweight, was grouping just under 1 MOA, but I wanted more. The 0.010 in. gapped loads flattened and cratered primers to a frightening degree. I backed off to 0.020 in. loads and counted myself lucky. Rifle probably has a tight bore. It groups well with almost anything. In any case I learned a valuable lesson to not just squeeze down the bullet jump without watching for signs of excessive pressure. There is a good reason Roy Weatherby free-bored his rifles. There is a lot going on in those microseconds as the charge lights off, builds pressure, un-sticks the bullet which jumps the gap against neck friction, and encounters rifling.

Absolutely correct. So far the primers are all looking good, no signs of pressure. It was interesting the different weight bullets (40 gr vs 50 gr) peak accuracy came at different points. In the case of the 50's, accuracy was good at .040peaked at .030 off then opened up at .020 looking almost like a nodal point - which would go along with barrel harmonic vibrations. Accuracy is good enough that I do not trust myself to get any closer than .02 off the lands.

Love the .270. Been shooting one, a Parker Hale 1200 40+ years now. Rifle shot really well out of the box with manual recommended OAL - being abel to get .75" @100 yds. Never fiddled with the seating depth - 55 grains IMR 4350 with a Nosler 130 ballistic tip or Speer 130 BT.