Tight neck advice

[tonedaddy]

I have a Nesika pistol in 6.5 Grendel. The chamber diameter is .292. A loaded case diameter at the neck is .290. I am able to reload the cases without having to resize just knock the primer out. After they are fired the outside diameter of the fired case is .290. Is this due to the case springing back after firing to .290 when the chamber is .292? Is this a near "perfect chamber"?
Thanks in advance for your help!

 

[BoydAllen]

Re: Tight neck advice

Yes, it is because of spring back. The perfection of the chamber would have to be determined by looking at targets. How does it shoot? What kind of load are you using? Some powders give more consistent results with more neck tension than you are reporting, but of course if you are getting what you want, I would not change a thing. What is the increase in neck diameter when you seat a bullet, and how are you measuring it?

 

[tonedaddy]

Re: Tight neck advice

Boyd, thanks for the response. I misspoke, the case springs back to .2895 after firing and after I seat the bullet it is .290.

 

[BoydAllen]

Re: Tight neck advice

I would probably want more neck tension than you have, but if there are no problems, and the accuracy is what you are looking for....
Typically, when I was running less neck clearance on my 6PPC I had a situation like what you have described, but testing showed that more neck tension gave better accuracy. This was with a relatively light short range match bullet, and the particular powder that I was using. It may be that with a heavier bullet, and a different powder that this would not be the same. Only testing will tell.

 

[kraky]

Re: Tight neck advice

Quick question for the experts. How much spring back is common for a case neck after firing in relation to chamber diameter.
In this case it appears about. 0025 which is about what I was thinking might be common?

 

[tonedaddy]

Re: Tight neck advice

Guys shot some new Lapua brass today not neck turned, fired case is .291 chamber is .292, bullet seats snug without resizing. Would you say I do not need to resize at all? Is this the infamous "perfect chamber"? Accuracy was right on as with the neck turned brass.

 

[BoydAllen]

Re: Tight neck advice Calling Boyd Allen again.

In short range benchrest, the trend is to more clearance than your rounds have. The best shooters that I know are using between .002 and .003. The reason given is more consistent bullet release that mostly shows at 200 yards. For my 6PPC I have found that more neck tension than you have discussed shoots smaller groups. This is easy to verify with bushing dies and loading at the range. Let's see some targets. Do a test or two. (or three or four.....)

 

[284driver]

Re: Tight neck advice Calling Boyd Allen again.

I would like to see a picture of this pistol if you don't mind.

 

[chuckbuster243]

Re: Tight neck advice Calling Boyd Allen again.

Both of my Grendels spring back .001" on Lapua cases... I have a .295 chamber in my boltgun and .300 in my ar or at least till I rechamber with my boltgun reamer. My loaded rounds are .291-292 with the older lots of Lapua brass I have. The Hornady and reformed 7.62X39 mics at .289 loaded if I remember right. I think that the .295 chamber is just right for my needs and is a slip fit with bullets on the fired case. I think the .003-.004 neck clearance is just right, but thats just me. I will have to check but I think I am running 1.5-2 thou neck tension. Both my Grendel's are not finicky at all as long as with the 123"s the load is between 28.0-28.5 IMR 8208 xbr. Jumped or jammed depending on the bullet. Matt

 

[CatShooter]

Re: Tight neck advice Calling Boyd Allen again.

In short range benchrest, the trend is to more clearance than your rounds have. The best shooters that I know are using between .002 and .003. The reason given is more consistent bullet release that mostly shows at 200 yards. For my 6PPC I have found that more neck tension than you have discussed shoots smaller groups. This is easy to verify with bushing dies and loading at the range. Let's see some targets. Do a test or two. (or three or four.....)

I found the same thing - I first cut the necks of my 6mmBR for a total clearance of 0.00075" (not a typo - less than a thou).

It would shoot well for 15 or 20 rounds and then open up - it was a real "Princess with an attitude", and it needed cleaning all the time. It turned out that the slightest ash would cause the necks to be grabbed erratically, and the groups went down hell.

I re-cut the necks for a 2-3/4 thou total clearance, and the rifle is a joy to own.

 

[tonedaddy]

Re: Tight neck advice Calling Boyd Allen again.

Photo here. Built by Gre Tan rifles. Krieger barrel, Dewey trigger, Poulsboro action.

 

[284driver]

Nice looking iron. Do you hunt with it? If not, have you considered losing the pistol scope for a higher mag rifle scope? I don't think the Grendel would give you any problems with scope eye if done right. I shoot a 243 encore with a rifle scope. My 6.5/284 will have a rifle scope as well. It's a rear grip xp in a McMillan bench rest stock.

 

[BoydAllen]

Nice looking rig. Thanks for the picture. I have a couple of questions. I am not familiar with the action. Can you tell me about it? Also, does the barrel have a nut?

 

[tonedaddy]

The barrel has no nut. The Nesika action is the same size as an XP100 and uses the same trigger. The threads on the Nesika are not the same as the XP so barrels are not interchangeable. I also have an exact duplicate of that barrel in 6PPC which I have yet to shoot. I use the gun for IHMSA silhouette matches, I'll bet a lot of you are cringing now because I shoot silhouette with it. The gun has shot several groups in the 4's with the 8 power scope, no doubt it would probably do better with a rifle scope. The gun has shot these groups with 26.0gr H4895 with a 140 Hornady SP and the same with 24.0 gr H322. Velocity for both is just over 2100 fps. ES on both loads were under 9. In fact the 4895 load was like 4.

 

[tonedaddy]

Another photo added