.308 Workup Question

[jwrowland77]

I was working in my workup for the range this weekend and I came across something I haven't come across yet in the 1 and a half years I've been reloading.

Gun I'm using is a Savage Axis .308. I'm loading Sierra MK 155gr Palma.

I used my Hornady OAL gauge and came up with a ogive measurement of 2.289 which barely put the bullet in the case. From what I read, you should have at least the bullet width in the case, in this case it should be .308. At the measurement to ogive of 2.289, there was not .308 left in the case, once I moved the measurement to ogive back to like 2.250, then there was .310 of the bullet in the case.

After coloring the top of a bullet I finally settled on a OAL of 2.900 with an ogive measurement of 2.241 which as you can see from above, is quite a bit away from the lands. I ran the dummy round I made that had the bullet colored and everything ran through fine, no lands marks on the bullet. Even for the magazine just fine with plenty of room to spare. Plus with an OAL of 2.900, there's just over .308 in the neck.

Well I got to looking in the Sierra manual, and they have a OAL for this bullet of 2.775.

I've never had an OAL this much over a book published OAL.

Should I recheck my measurements even though everything ran through fine, and none of the marker got scratched off from the lands? Can I move it out longer or should I keep at least .308 in the case like I've read?

I'm thinking that this rifle just has a generous throat between where the shoulders catch and where the lands are.

Thoughts?

 

[243winxb]

Start with the bullet base at the neck/shoulder junction. Full diameter of the bullet, not the boatail.

 

[gamestalker]

I have an Axis in .270 win and they are pretty deep throated, and it seems to have a bit more gradual tapered lands. Although I have been able to seat up to the lands, the rounds barely fit the magazine, and shank depth with 130 gr. Ballistic tips @ .174" - .185" in the neck. The .011" inconsistencies are due to olgive variations from bullet, to bullet. I'm not having any problems though, and accuracy has been very good.

My advice would be to seat as far out as you want, while making sure you have adequate neck tension, and the rounds fit the magazine. Check neck tension by pulling on a seated bullet as hard as you can, I bet you can't budge it, even if you have only half of .308" in the neck, or .154". But do realize that you could get a bullet with a longer olgive stuck in the throat when trying to eject a live round. It's never happened to me personally, but it can happen when seating up close to the lands.

GS

 

[Robert101]

As a matter of practical application....... I'd also chamber a dummy round at the same OAL you mentioned above and see if you have any scaring of the bullet from the lands. I prefer to have some bullet setback off of the lands rather than a compressed condition.

 

[jwrowland77]

I did make a dummy round of the one with the OAL of 2.900, and none of the market came off.

 

[cowtownup]

I've noticed this same variation from the OAL the manual gives and the OAL I use. I'm glad you ask the question because I was curious also... However, I have a Stevens Model 200 in .308 Win and I use an OAL of 2.810".. Based on my calculations that should set me back .025" from the lands...

 

[Jim Watson]

If you are single loading the old rule of thumb of one caliber of bullet in the case neck goes out the window. Any seating depth that won't lose the bullet in normal handling can be worth trying. I'd go ahead and shoot some 2.90s.

If you want to load the magazine, you are just gong to have more jump to the lands, no way around it.

 

[Muddydogs]

My 308, 243 and 7mm Rem all have long throats, way longer then mag length. I have been working up loads for all of them and started with bullets seated to mag length. What I found is that all 3 calibers like a little jump as to get a decent group I had to seat the bullet even deeper into the case. I'm not sure about all this ogive measurement and only having the bullet a hairs width off the lands since it seems that most hunting rifles have long throats. When checking my 223 Ruger heavy barrel with the Hornady OAL gauge the bullet falls out of the case the throat is so long but this rifle likes rounds loaded to just under mag length.

A lot of good all this load work up did. The only thing that is going to see action again this year is my muzzy. Dang big game draw.

 

[jwrowland77]

@Jim: even at the 2.900 OAL, I actually still have a lot of room in the magazine that I could easily go to 3.0 plus if I had enough bullet to hold it in. When I was using my Hornady OAL gauge, the ogive measurement was at 2.899. LOL

@Muddy: yeah when I was using my Hornady OAL gauge, the bullets were falling out due to there being so much room to the lands. I measured it probably 15-20 times because I thought I was doing something wrong. LOL. Came up with same measurement every time though.

I loaded up a ladder work up going from 40-45.5 in .5 increments. Results to follow tomorrow after some range time.