243 ai crush fit issue

[jaybic]

Hey fellas,

I am looking for some insight on something.

I just got my brand new Stiller/Hart .243 ai back from having it all put together at the gunsmiths and took it out to fire form some brass.

It is all brand new WW brass that was trimmed to length, pockets uniformed, flash holes deburred, necks chamfered, deburred and brushed. No cases were sized. I used 3 different loads(I realize that the cases may be different but I wanted to get a decent load worked up prior to fireforming 100 new Lapua cases.

1. 45gr H380 w/65gr vmax .10 off the rifling
2. 50gr Superformance w/65 gr vmax .10 off the rifling
3. 36gr RL15 w/87gr vmax .10 off the rifling

The results were ok at best and there is an issue I believe. I had about 12-15 misfires, most of which did go off on the second or third pull on them but 3 would not fire at all. I took them home, pulled them down and installed new primers and loaded them back up and shot them.

It was about then that I notice the primers backing out of about 6-10 of the cases. One of the primers was backed out 0.019(a lot IMO!)

I have since then pulled the firing pin assembly and put brand new Lapua brass in the rifle and the bolt closes like there is no case in there at all.

After some research on a few sights, I am inclined to the that my chamber did not end up with crush fit on standard brass that I often see mentioned and my headspace is still to long.

I have also had fellas suggest that I create a false shoulder and then size them down but in my mind that is just a bandaid on the root issue which is a chamber that is too long. Opinions on this are most welcome.

In my mind, the only real fix is to set the barrel back and get the headspace right rather than try "modify" the brass to fit a loose chamber.

The smith has been really good to me and fair and I don't want to drag him thru the mud or insult him or his work but honestly, what should I do here?

I have a 4000.00 dream rifle with a significant flaw...do I just live with it? Is it safe?.....Take it back and ask(insist?) that he redo it?

Sorry for the novel but this is my first real build and so far, not so good...

Advice??? Anyone????

Thanks for your time,

Jamie

 

[Gunpoor]

Jaybic, you mentioned a crush fit upon closing. Was this the way the chamber was supposed to be fitted? If so, what brass was used to check chamber dimensions with? I honestly believe the chamber will probably not close on a no-go gauge. I had a rifle built that had some generous proportions once and neck sized only and had no trouble with the brass. Once brass has been fired in your chamber it is a custom fit anyway, so I don't see the big issue with it. Chambers in a rifle are like any machine part and have tolerances, and it sounds like your rifle is within tolerance, therefore I think you would be out of line to make a complaint to the smith. Strictly my opinion.

 

[bigngreen]

I would check the head space just to see how much your working with, use scotch tape on the back of a new case, one layer is .002, stack it up till the bolt won't drop.

 

[LoneTraveler]

I would do a little experiment. Cut the powder load back to starting load and load 3 or 5 rounds with the bullet set out far enough to contact snug against the rifling and fire the rounds. If this stops the misfiring and primers backing out, should tell the story. The only cure may be set the barrel back one thread and rechamber the rifle. Good Luck

 

[buckfever]

You said you trimmed your brass that's why you didn't get a crush fit and that's where your problems came from.

 

[R.Morehouse]

I am using RL-15 and 85g sierras fire forming for my 243AI right now. My chamber is perfect and with 40g of the 15 so is the brass ( all Lapua ). Remember when you fireform you want a small bit of lube on your shells so they contact the bolt face before the shoulder blows out in order to get that perfect fireform. If your shoulder isn't contacting the front of the chamber tightly with the new brass be sure to be seating the bullets into the lands.....Best of luck.....GREAT choice of caliber.

 

[MNbogboy]

I totally agree with your assumptions...The chances of you getting two batches of brass totally out of SAAMI spec would be a rare thing.....And the case trim of course has nothing to do with the crush fit (the crush fit happens at the junction of the shoulder and neck).....If a primer backed out .019 then this is a very unsafe condition...That is why the crush fit was built into the AIs (usually about .004) in the first place is to hold the cartridge head back against the bolt face, if the cartridge slides forward as I believe yours is doing it not only can cause the misfires but also the protruding primers which now have a better chance of rupturing!.....The false shoulder and deep seating methods can prevent this during fire forming but your option of using factory ammo (in a pinch) is now out...If you have had good luck with your smith he will most likely see the error and correct....

A check with a .243 go gage should be a no go in the AI chamber....The smith may have received an errant or mislabeled gauge...

Good Luck,
Randy

 

[westcliffe01]

Call Mansonreamers.com they have "proper" 243 AI headspacing gauges that are machined with the same angle as the ackley chamber than that will give you the correct preload on a virgin 243 Win case for headspacing.

I bought just the "GO" gauge and put a thin piece of paper behind it to verify "NO GO" when I built my savage and my install has worked out perfect.

I never cease to be amazed how people will not spend $30 on the CORRECT gauge to check their rifle. Once you have the gauge, it will tell you how much the headspace is off. You will just have to keep shimming until it just closes and add up the thickness of the shims to tell the error.

More than likely, it would not need more than 1 turn added on the thread, shoulder set back and then adjusted with the reamer to a perfect fit. If the chamber is not milled for an extractor, then of course it may be a lot simpler than that.

 

[jaybic]

Thanks for the help fellas.

I think I have things resolved. I talked to my smith and let him know that I have tried brand new Lapua brass, new and FL resized WW as well as FL resized RP and Fed brass and other than the odd case that measures long, all of that brass is nearly all the same size case head to datum and NONE of it will crush fit. The bolt has the firing pin assembly removed and still just flops shut like there is no case in there at all.

After this he thought maybe we should set the tube back and rechamber to the brand new Lapua cases that I am taking to him along with the rifle which I believe is a very stand up thing for him to do. I have to drive 2 hrs each way, once to drop off and once to pick up but he is gonna get it fit right and I am gonna spend some gas money and in my mind that is MORE than fair of both of us and I can chalk it up to a positive experience with his services overall because otherwise, the work and the speed in which he did it were top notch IMO.

When I first dropped it off, I asked him if I should bring some of my new cases and he didn't think he would need them so I kinda feel like I did tell him what I was after because we had the "crush fit" conversation but in any case, as long is I am shooting a safe rifle and its not a negative experience, I feel I can still have him do work for me and recommend him to others.

Now I just gotta get this fire forming thing under control and I hopefully will be all good.

Any one got any load data to share, I am all ears.

I have 65 and 87gr Vmax bullets
70gr Sierra HPBT match bullets

pretty much every LR primer out there and the following powders:

IMR 4350, IMR 4064, IMR 4831, IMR 4198
WIN 760 and 748
Hodgdon superformance, Varget, Blc2 H335 H322
RL 12 and 15..

Thanks for the help fellas and have great day,

Jamie

 

[westcliffe01]

Your smith got you into this by not using the right gauge and now he is going to get you out by using a cartridge as a gauge ? Shadetree engineering, is all I can say.

 

[bigngreen]

It's always a good idea to have the case one intends to use on hand when chambering, especially if your intending on a cartridge that will require fire forming, I've found it ensures a more harmonious out come.

 

[westcliffe01]

Agreed, but nothing is a substitute for using the CORRECT headspace gauge. Even Lapua brass has a tolerance, whereas the tolerance on a headspace gauge is substantially smaller.

 

[Freebore]

I agree the 'smith obviously did not set the head space correctly or he would not be recutting things to fix it.

I do also agree to use the case you intend to shoot to check the fit.

I have a switch barrel Savage (mostly all are) with 3 different barrels and that's what I use to set head space...a fired case.

Red Dot, Cream of Wheat and a TP patch to fireform standard cases or max book load for a standard 243 to fireform with a bullet.

BUT you have to have a good snug bolt fit on a factory case to begin with.

jaybic you never mentioned your twist rate if your looking for loads.

 

[jaybic]

oops, sorry....

Its a 10 twist....25.5 inches....long range coyote wacker..

BTW, should there be a good mirror like finish on the chamber walls or should it show a crosshatch pattern? I have what appears to be a ridge or ring about 1/4 inch into the chamber. not sure if it goes 360 degrees around the chamber walls but the brass I have fire formed in earlier in the process shows some scratches that I can catch with my finger nail almost like there was grit or a burr in there or something.....I just noticed it tonight and I can catch the edge of that ring with a brass rod thingy that I have. Its kinda like a dental pick. Is this normal?

Jamie