220 swift and seating depth

[jaytee]

Working up some loads for my 77R tang safety and just curious about the seating depth. Some say jamb 'em into the lands, others say back off 10 or 15 thousandths. Is it just a trial and error thing or? I like working up loads but with the scarcity of some items I want to keep the use as low as possible. Would you move 'em 5 thousandths at a time or less? Right now I've got a couple of pretty good loads worked up using 4064 and 50 grain Berger FB Varminter bullets seated 10 off the lands. I've shot one 5 shot group that measured .705 and 3 of those were .385 but I haven't been able to repeat that yet but have only tried it once and got just over an inch. Anyway, just trying to figure out where to go next. The load mentioned here was 39 grains of the 4064 and I also loaded 37 and 38.5 with nearly the same results.

 

[Mobuck]

For various reasons( mostly safety issues), I wouldn't recommend "jamming" bullets into the lands. I lean a bit to the conservative after surviving a catastrophic incident involving a firearm. It's not worth risking your life over an insignificant gain in accuracy.

 

[contender]

I generally have found that by dropping back from the lands is the better way to go. Yes,, competition guns, and match shooters often like to have the bullet kiss the lands,, but in general,, the better way is to back off about 10 thousands & start there. I do experiment with varying seating depths when chasing the final tiny bit of accuracy I'm seeking. But I never push a bullet into the lands of a hunting gun.
The idea is to allow the bullet to enter the bore while still being held securely in the case to assure a good alignment of the bullet.
There are all kinds of things a person can do to tweak accuracy,, but if you back off about 10 thousands,, you shouldn't have issues with a bullet stuck in the bore that you didn't fire,, and cause it to pull off the case. That's messy AND you have to push the bullet out before you can shoot the gun.
Your idea of backing off 10-15 thousands is a good place to start.

 

[kmoore]

I never bought into a chambered bullet touching the barrel will make it the best accurate load. It will certainly up the CUP. Years ago I read about bench rest guys doing that and they load single rounds not from a magazine. High power match, bolt guys I knew would get the 3006 or 308 as long as possible to feed 100% but not touching the lands and grooves. Weatherby Mark Vs are free bored and provide great accurate guns. My gunsmith friend and I were discussing the freebore in my 7mm wby. I have a aftermarket heavy barrel, freebored. It shoots most 3 shot groups in the 3/4 inch range at 100yd. I wanted him to remove the freebore and he had me read about rifles in 7mm wby and the 270 wby with aftermarket barrels built with no freebore over pressure and blow up. I understand a Weatherby mag. is different then a .220 swift just pointing out some possible side affects as Mobuck also mentioned. I read to many articles on bullet jump and frankly don't remember what guys found to work best in their rifles. I mainly want my hunting rifles to feed and cycle 100% and be as accurate as possible, Some are really accurate and all have some bullet jump.

 

[Mobuck]

"he had me read about rifles in 7mm wby and the 270 wby with aftermarket barrels built with no freebore over pressure and blow up."
This is basically what happened with my 257 WBY--not fun at all.

 

[sixshot]

Why not stay on the safe side & be just short of the lands, you will still get great accuracy with 37-38 grs of 4064 in your your Swift. I had several of them over the years & that was the sweet spot depending on bullet & case preparation. Also be very careful about thick necks on Swift brass because you can get pressure spikes very easy if you don't watch it. It's easy to get "brass flow" with a Swift, here's what happens, you fire a Swift case 3-4 times & then try pushing a bullet into an UNSZIED case, many times it won't go! So now you've got thick necks that you haven't even sized yet, that can easily lead to dangerous pressure spikes, beware!

Dick

 

[jaytee]

Gonna start by staying off the lands by 8 thou and go in and out in 3 thou increments and see what I get. I just bought the Sinclair chamber length inserts and measured the chambers on my 77R and 77V. The R was 2.240 and the V was 2.246. This would at least partially explain why I was having some issues with some rounds having a tougher bolt close then others in the R and why none of the rounds were tight in the Varmint barreled Swift. Looks like I'm gonna have to separate brass which I should've been doing all along I guess, it just seems like such a hassle.

 

[AZ10X]

After shooting benchrest for years with 3 guys that are in the benchrest hall of fame here are our general findings:
1- Neck tension is probably the single most important factor concerning consistent accuracy.
2- As it relates to seating into the lands we do not go beyond seeing a square mark on the ogive of the bullet that indicates being seated .05 into the lands.
3- As it relates to seating off of the lands we have found that the node does not exceed .06.
4- Our rifles are single shot and occasionally a shooter will seat bullets that we call jamb of .20 to .30 - however this is done with very little neck tension (.005) that actually allows the bullet to slide back into the case neck.

With all of this said I have seen or a very rare occasion when a .220 Swift would shoot a hummer group with a seating of .12 off of the lands but it is very rare to see super groups when seating exceeds (-) .06.

Here are some basic guidelines that we follow:

2 SHOTS AT 200 YARDS:
Vertical print (unless 12:00 or 6:00 wind) load is too light.
Horizontal wide print – load is too light

3 to 5 SHOTS AT 100:
4 + 1 = load is too hot (in other words 4 shots group 1 shot flyer)
3 + 2 = load is too hot
0 + 5 = load is way too hot. Sometimes this can be fixed with seating adjustment.

Vertical group – increase load

Horizontal group – seating depth or increase load

Diagonal group (string or cluster) – neck tension

Round group (regardless of group size) – all is good

Seating node is .06 maximum. Adjust in .02 increments.

Neck clearance – keep at no less than 2 to 3 thousandths.

As temperature goes up during the day, increase the load.

Bullet holes:
Dark ring on one side of hole – load is too light
Hole smaller than bullet caliber – load is too light
Dark ring completely around the hole is just right

Mirage:
Boiling straight up is no wind.
A small sine wave indicates fast wind.
Mirage is more accurate than wind flags

1st firing after initial fire forming – Brass in not yet at 100% volume. Use full load.

Trim to length is very important. Check at every reloading.

Primer pocket depth is very important. Check every reloading.