Saubier.com  



Go Back   Saubier.com > Saubier.com Forums > Small Caliber Discussion Board

Reply
 
Thread Tools Display Modes
  #21  
Old 08-24-2015, 03:26 PM
Dean2 Dean2 is offline
Supporting Member
 
Join Date: Jan 2010
Location: Alberta
Posts: 2,497
Default

Quote:
Originally Posted by Bayou City Boy View Post
A properly cut AI chamber is actually SHORTER than the factor SAAMI chamber. Dimensions may vary slightly from reamer to reamer, but the general difference is ~4 thousandths of an inch shorter distance from the case head to the case/shoulder juncture which stops the case in the chamber for the AI chamber. This should cause a slight crush fit for factory brass or ammo when the bolt is closed, holding it in place properly against the bolt head.

To get a properly cut AI chamber its necessary to set the shoulder back approximately 1 or more threads thread on the factory chambered barrel and re-chamber with the AI reamer properly head spaced. If your smith simply ran an AI reamer into the existing barrel to get the 40 degrees shoulder, you definitely have a chamber that is too long for factory ammunition which is not a good situation for someone like a potential future buyer who has no clue about how the chamber was created..

If that is the case, factory brass is about your only option. You can create a false shoulder on a case with maybe a 25 caliber shoulder on the case neck to fire form properly and then neck down most of the neck with a 243 die, leaving the slight larger case neck near the case body juncture to hold the case properly against a bolt face. This is a fix and not a solution, just like seating bullets into the lands is a fix and not a solution to the problem.

As Kenny stated, it sounds like you have a head space issue that needs to be addressed by a properly reamed AI chamber that will be slightly shorter than the factory chamber dimensions. Each one of the brass that has a backed out primer also has some stretching that has occurred in the web area of the case upon fire forming. Contrary to what has been stated, this is not a normal occurrence when firing factory ammo in a properly cut and head spaced AI chamber. Unless your smith left you with an AI chamber that is longer than factory/SAAMI spec which is not a good thing.

To add further: if you "fix" your problem and then resize the cases using an AI die that is adjusted properly, you have the very easy potential to recreate your issue every time you reload the cases. Eventual premature case head separation will result. Getting the rifle repaired is the proper solution versus any of the proposed "hide the real problem one more time fixes".

-BCB
While I agree that AI chambers are supposed to be 4 thou shorter than the factory chambering for the same round my experience has been that either there are a lot of over long AI chambers being cut or there is a pile of short factory ammo.

Primers backing out a thou or so when firing factory ammo in an AI chamber maybe shouldn't happen but I have seen it happen a lot, and in quite a few different guns. As long as you don't bump the shoulder back on the next sizing, either only neck size or properly adjust the FL die, those brass with the backed off primer work just fine from there on out.

KB

Your subsequent shooting results would indicate the Hornady ammo is short. It would probably lift primers even further in a 243 if your AI chamber is correctly cut..
Reply With Quote
  #22  
Old 08-24-2015, 04:13 PM
csterner csterner is offline
Administrator
 
Join Date: Apr 2008
Location: Gettysburg, PA
Posts: 1,904
Default

Quote:
Originally Posted by kenbro View Post
Alex, I don't have anything to accurately measure from base to shoulder. Thanks.
I bet you do Ken...here's a 38 spl case and mic measuring base to shoulder on a case of mine.

Reply With Quote
  #23  
Old 08-24-2015, 04:27 PM
Daryl Daryl is offline
Senior Member
 
Join Date: Sep 2006
Location: Prince George, B.C. Canada
Posts: 4,273
Default

Quote:
Originally Posted by kenbro View Post
Alex, I don't have anything to accurately measure from base to shoulder. Thanks.
What I did today.
Pulled bullets and emptied powder from 2 Superformance carts. Reloaded with Hodgdon's Max load of H414 for Win 243 and put in 70 grain bullets. Speeds were, 3410 and 3392. One primer was level, the other backed about 2 thou.

Next I fired 4 Superformance rounds, 3472/3402/3427 and 3401. All primers backed out.

Next, I collet neck sized 3, once fired Superformance cases and loaded them with 48 grains of H414 and 69 grain bullets. 3401/3454 and3463. Primers didn't back out.

I then fired 4 rounds of Winchester 100 grain Super X ammo.2892/2855/2892 and 2842.
Primers didn't back out.
Opinions please.
Thanks again for all replies,Ken.
If the pressures are high enough, the cases stretch back against the bolt face, which re-seats the primers.
__________________
Daryl
Reply With Quote
  #24  
Old 08-24-2015, 04:32 PM
Daryl Daryl is offline
Senior Member
 
Join Date: Sep 2006
Location: Prince George, B.C. Canada
Posts: 4,273
Default

Quote:
Originally Posted by csterner View Post
I bet you do Ken...here's a 38 spl case and mic measuring base to shoulder on a case of mine.

Good idea, but must use the same case for measuring all cases, else a case with larger or smaller ID will seat at different locations on the shoulder, giving different total measurements. Still a good idea.

I think the datum line, with is the shoulder location for headspace measurement on all standard cases, is supposed to be .375" on the shoulder.

This should be easily produced with a ctg. or tube having exactly a .375" ID.
__________________
Daryl
Reply With Quote
  #25  
Old 08-24-2015, 04:35 PM
LT17 LT17 is offline
Senior Member
 
Join Date: Nov 2006
Location: England
Posts: 363
Default

For what its worth Ken when I worked in a gunshop a couple of customers came in with faulty "super performance" ammo. One I recall was 7mm rem mag and the primers had backed out and in one round ruptured. Quite why you would carry on firing after getting results like that escapes me, but he assured me he had never had problems with other factory fodder. I must admit I don't use the stuff as it seems to me to be pushing the envelope.
Reply With Quote
  #26  
Old 08-24-2015, 04:48 PM
Daryl Daryl is offline
Senior Member
 
Join Date: Sep 2006
Location: Prince George, B.C. Canada
Posts: 4,273
Default

Primers do not back out due to excessive pressure, but due to excessive headspace coupled with low to moderate pressure. with low to low-moderate pressure, there is not enough pressure to stretch the case (at the web) and re-seat the primer against the bolt face.
__________________
Daryl
Reply With Quote
  #27  
Old 08-24-2015, 05:11 PM
Bayou City Boy Bayou City Boy is offline
Supporting Member
 
Join Date: Sep 2006
Location: Tomball/Klein, Texas
Posts: 3,989
Default

Quote:
Originally Posted by Dean2 View Post
While I agree that AI chambers are supposed to be 4 thou shorter than the factory chambering for the same round my experience has been that either there are a lot of over long AI chambers being cut or there is a pile of short factory ammo.

Primers backing out a thou or so when firing factory ammo in an AI chamber maybe shouldn't happen but I have seen it happen a lot, and in quite a few different guns. As long as you don't bump the shoulder back on the next sizing, either only neck size or properly adjust the FL die, those brass with the backed off primer work just fine from there on out.

KB

Your subsequent shooting results would indicate the Hornady ammo is short. It would probably lift primers even further in a 243 if your AI chamber is correctly cut..
If you will notice, the first words in my oroginal post were "a properly cut AI chamber"............

I don't argue with your logic above at all. It simply shows that a lot or rifles, regular chamber or AI, are cut long for head space. But if I pay to have a rifle AI'd, I hope the smith is smart enough to do it right so I don't have to go to special steps just to make it all work. Ackley's concept has always called for a crush fit on factory ammo that can be verified by a head space gauge and not a box or two of ammunition and a neck sizing die after the gun is "finished" and in the customer's hands.

If I'm going to get a rifle AI'd and I pay good money to have it done, I'm not going to use a smith that can't get it right and live with his ineptness like a lot of people do. Those smiths aren't worth walking through their door with a job you want done, and unfortunately there are a lot of them out there.

And with the information now supplied by the Op, I agree that the problem is likely faulty ammunition. That's why I recommended a different ammo brand. Other solutions that have been offered work too to determine if this is the problem, but firing live ammo is the bottom line anyway so why not use it........ One or two rounds fired will give a quick answer.

-BCB
__________________


I miss mean Tweets, competence, and $1.79 per gallon gasoline.

Yo no creo en santos que orinan.

Women and cats will do as they please. Men and dogs should relax and just get used to the idea.

Going keyboard postal over something that you read on the internet is like seeing a pile of dog crap on the sidewalk and choosing to step in it rather than stepping around it.

If You're Afraid To Offend, You Can't Be Honest - Thomas Paine

Last edited by Bayou City Boy; 08-24-2015 at 05:21 PM.
Reply With Quote
  #28  
Old 08-24-2015, 05:47 PM
Dean2 Dean2 is offline
Supporting Member
 
Join Date: Jan 2010
Location: Alberta
Posts: 2,497
Default

Quote:
Originally Posted by Bayou City Boy View Post
If you will notice, the first words in my oroginal post were "a properly cut AI chamber"............

I don't argue with your logic above at all. It simply shows that a lot or rifles, regular chamber or AI, are cut long for head space. But if I pay to have a rifle AI'd, I hope the smith is smart enough to do it right so I don't have to go to special steps just to make it all work. Ackley's concept has always called for a crush fit on factory ammo that can be verified by a head space gauge and not a box or two of ammunition and a neck sizing die after the gun is "finished" and in the customer's hands.

If I'm going to get a rifle AI'd and I pay good money to have it done, I'm not going to use a smith that can't get it right and live with his ineptness like a lot of people do. Those smiths aren't worth walking through their door with a job you want done, and unfortunately there are a lot of them out there.

And with the information now supplied by the Op, I agree that the problem is likely faulty ammunition. That's why I recommended a different ammo brand. Other solutions that have been offered work too to determine if this is the problem, but firing live ammo is the bottom line anyway so why not use it........ One or two rounds fired will give a quick answer.

-BCB
I agree with what you have said, and I was not arguing with what you posted at all. I also agree there are a pile of bad smiths out there. I have seen so many cocked up custom rifles, some AIed very many more not, that I won't buy guns that have been customised unless I know the gun well or personally know the smith and his work that did it. I have also seen quite a lot of messed up factory guns. so that is no guarantee of superior quality either.

I further agree that more people should be sending back poor work and making darn sure it is done right. Should also stop using bad smiths but the problem is there is a very high demand for gunsmith work and so few places to get good accurate info on the quality of work a smith does, unless the smith is really famous. Unfortunately the really famous ones have prices and wait times that mean we often need to go looking for ones working their way up the success ladder.

It is why I have found a couple of good ones and stick to them like glue. I have one that is about to retire so I will be on the hunt for another one to replace him. I hate trying out new smiths.
Reply With Quote
  #29  
Old 08-24-2015, 06:20 PM
kenbro kenbro is offline
Senior Member
 
Join Date: Feb 2009
Location: Lancashire UK
Posts: 3,294
Default

Forgot to say, I also did as trotterlg suggested, and fire two Superformance rounds with just the primer in. The primers backed out 24 thou!

csterner, I might find something that will do, although I don't have a big selection of different cases. Thanks for the idea.
Ken.
__________________
" Pay it forward buddy"
Get up each morning and don’t let the old man in.
(Clint Eastwood).

Last edited by kenbro; 08-24-2015 at 08:04 PM. Reason: Correction.
Reply With Quote
  #30  
Old 08-24-2015, 06:36 PM
trotterlg trotterlg is offline
Senior Member
 
Join Date: Nov 2007
Posts: 3,108
Default

Holy $hit Batman, .024 is really a lot!
__________________
A gun is just like a parachute, if you really need one, nothing else will do.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 01:01 AM.


Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.