I have an A-bolt in 300 rum with a VXII that shoots pretty well, but I can't get it to consistantly group under an inch with a good hunting bullet. I have a sneaking suspicion that she's holding back on me.

Tonight I measured my chamber length, and found it to be 3.224" from head to lands. My magazine will only allow me to load a round out to 3.615" OAL, which amounts to 2.974" with a 200grn Accubond or 3.025" with a 180grn Partition when measured to the ogive of the bullet. I can't get partitions to shoot under 1.5", so I'd like to find another hunting bullet. Ballistic Tips (180) group around an inch. I haven't had a chance to shoot the Accubonds. Anyhow, this amounts to the AB sitting .25" off the lands and the Partition .19" away.

Not having very much experience with cartridge length experimenting, I'm wondering how much affect this is having on my accuracy.

My options, as this is primarily a hunting rifle in which I would like to have multiple rounds, seem to be:
1. Find a hunting bullet that has an ogive further out.
2. Modify my magazine to allow for more length.

On the first option, I would appreciate some feedback. Any ideas, short of RN pills? I've never tried Barnes pills, as I'm afraid of petals breaking off at the velocities involved. Might this be a good option in a heavier size (200grn+)?

Concerning the second, I am in a bit of a quandry. I can cut out the front of the magazine and then modify the outer chamber area to feed a round. As it sits, the round is ramped up by the front of the magazine and the outer chamber bottom is quite square--I could modify this to ramp up and then seat all the way to the inner-action wall with some epoxy work to smooth the front of the magazine area (so the bullets would actually stick out of the magazine by perhaps 1/100"). However, this will only buy me about .05", leaving the bullet far from the lands in any event. And it will involve my making modifications I'm not too thrilled about.

I know that these over-bores have alot of free bore. Is this something I must live with? Will I risk a possible catastrophic pressure spike if I try to seat closer to the lands? How much is this bullet jump hurting my accuracy? Are there bullets that will seat closer and give better accuracy as a result? Is the magazine modification worth the effort and risk (with me, any such modification does involve a certain level of risk!)?

I'm not trying to make a match rifle, I would just like to see it shoot around 3/4" consistantly with a hunting bullet. Any help will be received greatfully. Thanks.

Mike

yea, bad things can happen that close to the lands. Short of going to a roundnose, there is not much you are going to be able to do.

But after 2 years of working with this round, here is what I found. Long COL's touching the lands isn't critical. In fact, try for grins pushing that bullet in the case even farther like 3.56". I got surprising results. Good results. Here is how I came to this. I shot a 180 Nosler Partitions with H1000 from 92gr to 96gr. I found 94gr to be the most accurate with the bullet set up to where it barely fit in my magizine. I then consentrated on seating depth. I tried different depths from 3.55" to 3.635". I found very accurate results at 3.56" and they were consistent. I got good results loaded out real far, but alway got this pesky flyer. I rarely see that now.

There is people that had custom made throats where they hit the lands at 3.6" with a Nosler Partition. They basically had to throw out all the manual data and do there own.

Not jumping in on your post here but ihave had good luck with loading the 10 thou off the land and then trying some 178 A-max at factory spec with just as good results with the plus of being able to laod more than one bullet in the mag.

I would be intrested in what you find witht he ACCU Bond as I have not be able to buy them local.

Big Country,

I had an indication that I might be worried about nothing when my BT's shot so much better than both partitions and game kings, which both have an ogive further out towards the lands. And I have read the posts of those with custom chambers--this is much of what got me thinking about mine.

Steve,

Jon A posted a long thread about AB in his 300 rum. His results looked great. If you do a search you won't have any trouble finding it, as it wasn't very long ago. Now if only they were making them in 180...I can't believe that the only size they are produced is in 200 for .308's. Anyhow, I just read an article in which the author tested several bonded bullets and had better retention with Hornady's Interbonds (something like 85% vs 50%), but, though he didn't make much of it, he tested the different bullets with different rifles--I think a 308 and a 300wm--a fact that could easily make up for the discrepency.

Anybody else fighting the free bore? So far it looks like a moot point.

Edit:
How long are your chambers? Are yours (Steve and Big Country) as long as mine--not trying to start a contest here or anything!!

[ 09-09-2003, 19:08: Message edited by: mikea ]

For me to touch the lands with a 200gr Accubond, I have to have a COL fo 3.85". For me to touch the lands with a 180gr Nosler Partition, I have to have a COL of 3.81" Pretty long. I was pretty bummed out when I had this rifle rebarreled, and saw how long the throat is. Since the other barrel had a throat 3.74" with the Nosler 180gr Partition.

But even though its long, I get subMOA groups at 200 yards with just about anything. And the other factory barrel didn't. So I really can't complain too much to the gunsmith. Then I started seeing people haveing troubles out of their 300Weatherby's and RUM when customizing the throat to be able to hit the lands with a 3.6" COL.

I just did the math, for me to touch the lands with an Accubond it calls for 3.859" COL, so we are in the same boat. I think I'll drop the whole idea of getting near the lands with this gun and just play with seating depth within my magazine restrictions.

That sounds right. When I talked to clymer about it, who makes the reamer, they said, "thats the factory specs" for that long a throat.

I had the same problem, 2.835" or something to reach the lands with the 200gr AB. Rest assured, and try this load, 90gr Retumbo at 3.660", 215M. I'm curious to see how it shoots in others rifles too. So far it's been under .7 MOA at 200yards every time. I haven't worked up any higher to see what it will do there yet, although in my rifle it's a grain or three away from max and only running 3015 fps. This was the first load I seated deep to fit in the mag, just to hit the trail and hunt with. Wow did I get lucky. If you all try it please post what you find.

mikea,
You might want to try the barnes especially the tripple shock. I have a 300wsm A-bolt and cartridge size to magazine size is a problem. Barnes seem to shoot better at .05 or further away from the lands. Which helps with the magazine problem. Also because they penetrate so well you can use a smaller wt. bullet which also helps with the small magazine problem. Don't worry about Barnes abd velocity, they seem to have better terminal performance at higher velocities.