Author Topic: Advice for accurizing a problem 308 Win  (Read 1813 times)

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Offline cpileri

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Advice for accurizing a problem 308 Win
« on: July 23, 2011, 06:05:57 AM »
Dear Sir,
Given the below situation/informatio, can i implore your expertise on helping fix a 308 WInchester chambered gun that throws 6-8" groups at 100yds?  and for use of any of your products that might help.  I am not sure if its the ammo or the barrel, but I suspect the barrel since its inconsistent with so many brands of ammo; and for the below reasons:
 
This rifle is a saiga-308, and since it is a semi-auto and the Russian ammo is ~150gr; I try to stick with 150-ish gr ammo. (*) I have tested ~20 brands of 150gr 308 (**).  On a fair number, but not all, of the brass I noticed:
 
The case necks had expanded concentrically to ~.314 Internal diameter!  a new .311 bullet coudl be dropped in easily.  Other cases were back to .308-9.  OK, seems to me the only way these casenecks could get to expand is if the chamber throat is that big.  The other cases must have 'rebounded' back to 308. So if the chamber is so generous, and the projectile is .308, I will have gas blowby, maybe "cutting" or whatever throwing off my accuracy?
I have not done a chamber cast, but I might do just that so I can post all the info?
At this point I see no reason to post any more information, as you have identified a major problem in the greatly oversized chamber neck.  Probably the throat is as greatly oversize and the combination allows the short bullets to lean before they get into the rifling.  If you handload using jacketed bullets, let us know here, and I'll post the most effective solution to the problem.  If this is the problem, which you'll know for sure once you receive the LBT slugs which you say you ordered later in this post.
 
also,
 
On slugging the bore, the final measurements came out: lands .301, grooves .308.  So that at least is OK.
 
But, and I really need some advice here, here is how the slugging "felt": I used a .312 pure lead ball and rod/small hammer.  just out of the chamber, it was tight as expected since the ball had to swage down to size.  then it tapped down about as snugly as usual, then hit a tight spot, then slid again.  Makes me think my bore is actually too LARGE for most of its lenght, then has a constriction down to .301/308; then widens again to some unknown diameter.
 
could that constriction be just a snag?   It's the real thing, and a snag is about the same thing as saying constriction.  A tight spot of any shape or size is a constriction and will leave the bullet loose after passing through.  Lapping will fix this problem
Could I be looking at a bore that begs to be.311? and therefore I need to lap out the tight spot to make a uniform .311 bore?  Of course, that might leave me with a semi-wildcat .311/308 chambered rifle.  But I can cross that bridge later.  You will throughly enjoy being able to provide all the answers to these questions by yourself, once the slugging supplies arrive.  YOU will be the expert then!
 
So...
In preparation for accuracy improvement, if possible, i just dropped a check in the mail for a LBT lapping kit, and bought some .311 cast 165gr bullets to use.  According to this article: www.surplusrifle.com/articles2008/trailbosskiss/index.asp
9gr of Trail Boss should be (just barely) subsonic.
But I am wondering if I may need something else.  Again, any advice you have would certainly be appreciated.
 
Most sincerely,
cpileri
 
(*): I am not married to the idea of 150gr loads, just thought to stay with what she was manufactured to fire. But some on the saigaforums report better accuracy with 168gr loads, so I do have some to test (barnes TSX, as that is the bullet I want the most to use, if possible).
 
(**) to include: Wolf, WInchester Supreme Partition and XP3, Hornady TAP 155gr, Nosler Custon, Barnes VorTX, Federal Premium TSX's, relaods w/ barnes MRX, Prvi Partisan, Sellier and Bellot, and others: as you can see I am looking for a hunting load, suitable for Texas WHitetail/feral pigs. So I have not tested any match loads as the are not the hunting projectile I would prefer.  I also have still to test Remington Core-loks and a handload of 150gr Partitions with H4198 as I just read in Handloader a tip that .308 bullets accasionally fire well in .311 bore 303British guns when a faster powder is used to belp 'bump up' the rear of the bullet. We'll see, i suppose. You've answered one of my first questions here, about whether you would be reloading, so I'll give the information right now.  First, regarding the use of 308 bullets in larger bores.  If the throat is large, as I suspect you can also go the other way.  Use .312 bullets in a 308 bore, without pressure problems,   IF the bullets are seated to jump a little before hitting the rifling.  Also, again, if the throat is oversize, long loose, use only flat base bullets, not boat tail, as you need all the bearing length possible.  Seat them out close to the rifling, if possible, and crimp using the Lee Factory Crimp die.  Crush the crimp in deep enough so that the remaining crimp in  a fired case will drag against a bullet when inserted with the fingers.  This will provide a pilot for the back of the bullet while the nose is getting engraved by the rifling.  Plan on lapping out the constriction also, and you should have  a VERY accurate hunting rifle.

  With a big smirk I'll say I'm not authorized to write about jacketed bullets on this 'cast bullet' forum, but understand that understanding all one can about jacketed will broaden his base of understanding about cast, and vice versa.  Thanks for 'intruding' with your questions!
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that we received it from them,
and that without them
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Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #1 on: July 23, 2011, 09:00:50 AM »
Made it through 28 pages of this forum!  Reading this ( http://www.gboreloaded.com/forums/index.php/topic,98059.msg1098250425.html#msg1098250425 ) thread, looks like I need to forget my lead round ball measurements and purchase some of your slugs, both for slugging the bore and for firelapping.
Would you prefer me to call or email, or PM to discuss the particulars of this purchase?  If you still sell lapping bullets and slugging ...uh... slugs, that is.
C-
____________
"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline Veral

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Re: Advice for accurizing a problem 308 Win
« Reply #2 on: July 26, 2011, 09:23:58 PM »
  You have a length bunch of questions which would be hard to answer without confusion, yet should be of interest to many readers.  So, for clarity, I'll answer in bold and underlined type under your questions.
Veral Smith

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #3 on: July 27, 2011, 01:41:46 AM »
Thank you, Sir! Please accept my apologies for asking about jacketed bullets on a cast bullet forum. I appreciate your kindness in answering, since I have been just about everywhere else without success.  For what its worth, my next step was to proceed to using cast bullets in the thing; and working up a hunting load from there after the problems with the rifle were fixed.  Does that count?  :)
Since I am a big planning person, my plan is
 
1. wait for your lapping compounds and lapping slugs (need to order .312 diam)
2. lap
3. test fire with ammo of choice
4. if that doesnt work, begin to handload (or use factory loaded?) the longest flat-based bullets I can chamber; with a tight crimp, seated just off the rifling
5. test for accuracy
6. if still no good, go to .312 cast bullets and begin working out a hunting load
 
Did I miss any important points?
 
Very Sincerely,
C-
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"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline Veral

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Re: Advice for accurizing a problem 308 Win
« Reply #4 on: July 27, 2011, 06:43:50 PM »
  Don't be sorry for intruding with  jacketed bullet questions!  I think the questions are held by many, and the answers will be usable.

  You understood my answers fully.  I hope you ordered some push through slugs also, as they are the only way I know of to 'feel out' a barrels straightness and know what bullets are going to encounter on their passage through it.
Veral Smith

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #5 on: July 28, 2011, 01:49:36 AM »
Well, I have now!
The check is in the mail.   ;D   (It actually is).
 
Should i post any results (with pictures if possible) here?  I will if the info willbe useful/interesting to others.
 
I plan to take this beast to the range Tuesday to try the aforementioned handloads with Partitions and H-4895. 
 
If your stuff arrives by then, I will also use them.  If not, i'll head back out soon as I can.
 
C-
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"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #6 on: July 29, 2011, 08:12:23 AM »
Dear Mr. Smith,
Can i impose on you again: regarding the Flat Base recommendation?
Is the flat base simply to make the bearing surface the longest possible? such that the support from the case mouth on the rear of the bullet is maintained long enough for the front of the bullet to engage the rifling squarely?
or is there another reason for the flat base?
 
reason i ask is because the limiting factor in my bullet search seems to be the flat base characteristic.  So i am wondering if i can find a boattailed projectile with a bearing surface long enough to have both the casemouth and the rifling suportinng the bullet at the same time during the firing cycle, would that be meetinng the goal?
Or, as above, is there some other reason for the flat base?  the way the powder pushes against the bullet?  bumping up the "skirt" perhaps?
 
thanks, again, Sir!
C-
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"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #7 on: July 29, 2011, 09:32:09 AM »
More info:
So I went ahead and made a chambercast anyway to check how far the rifling was away from the casemouth (0.17", btw).  But I also measured the diameter of the casting at the case neck/mouth; measured .345-.346.
Where my unfired 308 loaded cartridges measure .338 on average. 
The picture on the loaddata site says that area is .343, so is .348 within spec?  or is it my problem?
 
the bore ahead of the case/chamber was .309-.3095 lnads, and .301-.302 grooves. (oops: well, it should be reversed since it was a cast: grooves being deeper than the lands!  So grooves .309, lands .301-2)
the bore up to the 'constriction was the same.
the bore AFTER the constriction was grooves .3095, but lands .300-.301.  I figure lapping will fix that.
 
Any thoughts or analysis appreciated!
 
C-
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"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #8 on: August 02, 2011, 02:48:52 PM »
what a lousy range trip.
 
OK, the worst day at the range is better than almost any other day.  But in-and-of itself, no love with several new bullets.
 
Tried the rem core-loks: first shot: BULLSEYE!  OK! Maybe we're getting somewhere. 2nd shot 5 inches down, 3rd shot 5 inches in high. Well, at least they are straight up-and-down...
 
OK, maybe something heavier (i.e. longer): Hornady TAP 168's: 5-6 in pattern (I wouldnt call it a group) x3 shots. 168 barnes TSX factory load: same.
 
How about some handloads: 150 Nosler partitions w/ 44.5gr H4198: first shot 3 in off center, 2nd and 3rd shots 5 inches at 5 oclock position, but right next to each other: so maybe some promise there.  same bullet w/ H4895: pattern.
 
Surplus and practice FMJ: Aussie ball, German MEN, Prvi FMJ: all shot inconsistent patterns.
 
scope mount was solid, rest was solid, day was sunny and little wind.  Oh, well. will wait for the lapping kit and use these cases to load the lapping slugs.
 
 
 
 
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"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther

Offline cpileri

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Re: Advice for accurizing a problem 308 Win
« Reply #9 on: August 11, 2011, 03:41:44 AM »
Just thought of something:  how would you recommend crimping the 310 bullets in the "fireformed" 308/310 cases?
 
thanks,
C-
____________
"We are compelled to concede to the Papists
that they have the Word of God,
that we received it from them,
and that without them
we should have no knowledge of it at all."
~ Martin Luther