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Best bullet design for long throat/freebore?

 
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Old 09-02-2013, 08:32 AM
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Join Date: Aug 2008
Location: Kansas City
Posts: 100
Best bullet design for long throat/freebore?

I decided to start a new thread with this specific question.

I have currently two guns with very long freebore. A 270 win with about 400 thou and a Weatherby 340 with easily 600 thou.

I cannot come anywhere close to the rifling on either rifle, and whats more, I observe that in the case of the 340 Wby, the bullet has LEFT the case neck before it has engaged the rifling, with both my recently acquired 250 gr Bergers and Nosler 225 Accubonds.

I have read that this latter scenario is a real NO-NO. The bullet is truly allowed to "skew" in the throat, potentially even allowing hot gasses to pass around the bullet till it seats into the rifling.

Interestingly, the 340 Wby shoots factory 225 Barnes TSX bullets BADLY, with 3" groups. When sent back to WBY, they shot it with 200 gr spirepoints and got a 1.5" group. Told us it was within factory spec, and we should use 200 SP bullets. Nevermind they are no longer in production.... The 340 shoots the 225 Accubonds very poorly as well. The 250 Bergers have not yet been tried.

We did shoot some factory 250gr Partitions (flat base) in the Wby. They shot under 1.5" as well

Another observation, perhaps unrelated to throw into the mix, is that my long throated 6.5x55 also prefers flat base bullets. I never bothered to measure the throat on the old swede, cause I know its a long way out there, and I have to keep COAL short for the magazine. But, now, in retrospect, I am suspicious that my troubles with the swede and boattail bullets may be related to the same problem I am seeing with the Wby -- a very long throat.

So here is my theory: When working with a long throated gun, it is VERY important to make sure that the bearing surface of the projectile is still in the case neck when it contacts the rifling, and since boat tail bullets have reduced bearing surface, they may be a poor choice for accuracy.

Moreover, if the gun has sufficient magazine length, or you are willing to hand feed, a flat base bullet can be seated further out than a boat tail of similar weight, getting your ogive closer to the rifling and potentially reducing some of the negative effect of the long freebore on accuracy.

Could I be right?
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Old 09-02-2013, 08:45 AM
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Join Date: Feb 2007
Location: Townsend, Montana.
Posts: 7,900
Re: Best bullet design for long throat/freebore?

I have shot both solids and lead jacketed bullets in many rifles with free bore. For years the only factory ammo available for Weatherby's was jacketed bullets. I have owned many Accumarks in 30-378 and some in 337-378 they all shot Berger's well. My primary rifle for a long time was a 30-378 with a 210 Berger seated at 3.800" and I took truck loads of game with it at all distances. One example is the Bull in my signature holding my 30-378 Accumark.

There are scads of members on here that shoot Remington Ultra Mags. Many use Bergers. All RUMs have freebore.

Here is some pretty good proof to support my statement. This is from another member with a factory barreled 300 RUM with freebore. I think it is always nice to support statements when possible. Watch the video and then draw your own conclusion about jacketed bullets and free bore

Impressed with the sendero results

In the end, there will be one bullet your rifle will shoot better than others. Or you will find the reason your rifle is giving you some fits. But my advice is to do your own research and don't limit yourself to one type of bullet. There are many out there to choose from. Do your own testing and ignore the key board warriors with no proof of statements.

Jeff

Ps: in the old days I also found good accuracy with flat based bullets in Weatherby's. But the long range accuracy was poor and the BC of the boat tails were much better. I never felt I gave up any accuracy with boat tails in free bore rifles. But if you want to try a good bullet for your 340 with a flat base look at the 250 gr Nossler partition. Just realize this would not be my choice for long range hunting.

I have also found a sweet spot in my factory barreled 340 with 250's at 2900 fps. This load has worked in several 340's.
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