I had a rifle rechambered to 6-284. It started life as a Rem 700 VSSF 220 Swift. I ordered a LILja 30" barrel w/ a 1-8 twist for lrange accuracy. I told my gunsmith when he chambered my rifle to make sure the throat was long enough so I could seat the Sierra 107 gr MK and not give up so much powder capacity.
Here's the problem. Accuracy hasn't been what I was expecting. 200 yards groups usually stay around 1.5 ". I've got one group at 3/4", but the norm is 1.5- 2". I've racked my brain to the problem. Runout number are ok. I've tried fireformed brass in which runout is .002 or under-doesn't make a difference. I ususally play w/ seating depth after I get the powder/bullet combo figured out- problem is I can't seat those MK's to reach the lands. With the boattail part of the bullet so long, I just barely seat the bullet far enough so it doesn't move. The bottom of the bullet is even w/ the case shoulder.
Shouldn't I be able to reach the lands? I always thought the seating out right around the lands yields best accuracy. Either right at the lands, sometimes into them a fuzz, or maybe just off a little. Any ideas....
I was thinking about sending the barreled action back to him and have him set the barrel back 1/2" or so and rechamber. I only need about.050 closer to the lands.

First and formost.

If no other causes can be found, have you contacted the smith?

Later....

carverelli--

If the base of the bullet is even with the base of the neck and you need another .050 why don't you seat the bullet out another .050?? All you need is .100 of bullet in the neck to hold it.

Have your 'smith pour a chamber cast and LOOK at the throat to see how long it is.

JBelk, the base of the bullet is a boattail, therefore it will not touch the case. The problem is I can't seat the bullet pout far enough to reach the lands - I run out of bullet first
Mauser kid, no I haven't contacted the smith yet. I was confirming my suspicions before talking to him. This is my first wildcat, so you could say a real novice at this sort of thing. I have read several places(this board and others) where the best accuracy is achieved reight aroung the lands of the rifling-sometimes even into the lands a little. In either case, I can't reach them as it is right now. I can pull the bullet out of the case w/ my fingers if I wiggle it a little. My chamber has a .268 neck, so I turned the necks on my cases and have only .002 neck tension.
Thanks for the help

1. Try another bullet like a Berger VLD that is long enough to reach the lands when seated out. a VLD bullet should actually contact the lands for best accuracy.
Do a chamber cast and see what you actually have before contacting your smith
your case neck dimension should be .002 less than the neck dimension of the chamber.
You need a cartridge neck sizer that will provde decent neck tension, you should not be able to move a seated bullet by hand at all! If the case neck is turned to.266, then try a .264 or .263 neck sizing bushing.
2. With all of the above not occuring it's amazing your sub MOA at all.-Rob

carverelli,

I can't imagine requesting a smith long throat a barrel in such a hot-rock caliber, given that you'll have to accommodate the increasing throat erosion over time. Why pre-wear the barrel?

Are those 107s mollied or bare? I've found in another "lengthy" 6mm throat that the moly bullets like to be 35 - 50 thou off the rifling. Maybe it'll work in your rifle too. Sounds like a neat rig!

Redial

redial, they are mollied. After breaking in the barrel, I mollied the rest of the 100pack, then boughjt a 500 pack already mollied from Sinclair.
I thihnk I'll call the gunsmith tomorrow and ask him what he thinks about it. From everything I've heard Rl 22 is THE powder for this application. I've tried every charge from 53 to 57 grains. 57 grains gave me 3650fps but the bullet broke up. I backed down to 56.5 when I got 3550 and the 3/4" 5-shot group at 200 yards. So I stopped. Maybe I should keep backing down a 1/2 grain at a time. I'm just sure like robgunbuilder mentioned VLD bullets are best suited seatred into the lands.

When a customer wants a specific throat length it can be accomplished two different ways.
The first way is to seat a bullet as he wants and give the dummy cartridge to the smith who will then cut the throat seperately to the appropriate length.
The second is to send a dummy cartridge with the correct bullet seating to the reamer maker and have a reamer made with integral throater to cut the correct throat.
The second way is the most expensive but will give the most consistent throat length in subsequent chambers. When cutting seperately it is sometimes difficult to get precisely the same length with each chamber and throat length may vary by .005" or so. In the real world this means little to nothing since a minor adjustment to seating depth is not uncommon anyway.
The thing is with the integral throater the gunsmith is stuck with the length provided by the reamer maker. This is why the use of a dummy cartridge is so important.
Concentricity is not an issue if the setup is good. If the bore is running true it would be difficult to cut an eccentric throat. If the setup is not good then the gunsmith is possibly incapable of doing good work by any method!
I have had reamers which cut throats longer than I expected and in these cases I cursed myself for not checking the reamer before using it, then altered the reamer and corrected the job. I prefer to cut throats as a seperate operation just because it offers versatility and gives the throat configuration I want. By the way, I have found a long throat to not be too detrimental to accuracy provided the throat is no more than .0005 over bullet diameter. Regards, Bill.

carverelli

I would say that the smith isn�t that good if you have told what you intended to use the rifle for. If a shooter/hunter comes to me for a chamber job and tell me that he will use the rifle for long range shooting I ask him right away what bullet he vill use and how the throat should be made!

A 6/284 with a 1-8" Lilja barrel indicate that the customer are serious about his goal! If the smith know his job he start to ask questions about anything that involves neck dimentions, short or long throat etc.

In a big case like a 6/284 it could be a good idea to try a bit more neck tention to get a good ignition of the slow powders involved. The coated bullets also like some more tntion compared to bullets in the "nude".

I hope you will get your rig going carverelli!! Long range shooting is really fun and put the shooters skills on tuff tests!

Stefan.

You gave a blanket request to the smith and assumed he would cut the throat as you thought it should be done. You erred,in that he had no idea what you wanted. The only way to do it is to give him the cartridge/bullet combination you intend to use and let him match the chamber to that. Take it back to him and ask him how much he would charge to re-do it. Do not expect him to do it for free, as he already used his best judgement on it, albeit the wrong one. It will probably only cost you a few 16th's in length of barrel.

Well, I talked to my guy this morning. He seemed surprised that I couldn't reach the rifling w/ my seated bullet. Then it got confusing. He thought all the talk about reaching the lands and seating into the lands was overrated. He also mentioned his 6/284 reamer was built to have that much freebore. I thought "what would he have done w/ a 1-12 twist 6/284". Mine is a 30" 1-8. I got the twist to stabilize the vld bullets and the length to make the velocity.
Oh something else I forgot to mention. When I eject a loaded round from the chamber, I have to release the bolt so the bullet tip wil clear the ejection port.
I told him I would seat the bullet a little deeper w/ more neck tension. I have been using right at .002 neck tension so far, but someone here mentioned more might be better. My smith told me he would have to alter his reamer to give me a shallow throat. I understood most smiths use a seperate neck reamer, but I guess he doesn't. My chamber has a .268 neck if this makes any difference.
Thanks for the help guys. The barrel is a 3-groove Lija. There may be better barrels available but not many. I almost opted for a Kreiger cut-rifled barrel because my 1-13 24" Kreiger AR15 barrel shoots better than most good bolt guns.

Of course you have to release the bolt before you can eject a loaded cartridge. You built your 6x284 on a short length action, and are loading it with cartridges longer than it was designed for. When you get your throat length issue resolved, your cartridges will likely have a shorter OAL, and will no longer require you to release the bolt before they will eject.

I bet they currently don't fit into the magazine well either.

Regards,
Scott

[ 05-25-2003, 16:10: Message edited by: Scott Thornley ]

I have a Bushmaster V-match heavy barrel AR15 from the factory.
The throat is out so far I have never reached it with any bullet with any seating depth. period. It can't be reached.

The best that rifle has done is 1.05", and averages 1.4" with the best load.

If I want a barrel with a SAAMI chamber from Bushmaster, that is extra.

It sounds like the guy used the reamer he had. If you want to rechamber, there has to be enough barrel left.
For a project like that, go to the Clymer web site reamer design function and nail down all the dimentions on the reamer drawing.

[ 05-26-2003, 08:28: Message edited by: Clark ]

If you are able to pull the bullet by hand... you don't have .002" neck tension on them. If the reamer was designed to cut the throat too, the smith has no way to keep it shorter than it's designed to cut already. If you didn't specify the throat length and tell him ahead of time, it's on you now, just the way it goes. It is a major consideration in designing a reamer if the throat is cut with it too, if not, no big deal, he can go as deep as you like, so long as you tell him first.

I'd find a different bullet and/or seat them out farther and find a good load, I doubt you have a bummer barrel at all though. Live and learn...