260 lrp Lapua brass pressures

[tizzy]

I've been lurking for awhile and need advice/help. New (factory) model 12 .260, virgin Lapua brass 39 gr. of H4350 cci br2 and a 139 Lapua, .020 off and it almost blows the case head off. Headspace is good with a ptg and Forster go gauge. Same components with 34.5 Varget and it shoots about 1/2 moa, but really slow and leaves a ring near the case head.
Kinda reluctant to buy another batch of Lapua. I did buy some Federal fusion 140g at it shot a 6" at 100. Yeah, 6" at 100. I tried that brass with the 4350 load and neck sizing between the brass stayed together.
So, is the Lapua brass generally an issue with saami reamed chambers? I had this rig over 2 years and I'm beginning to become frustrated. Any help is greatly appreciated.

edit: my goal here is to find a combination of components that work, not to place blame on a component company or the rifle maker.

[Robinhood]

I don't think it is pressure causing your problem. The problem is more than likely your brass expanding excessively lengthwise. It is possible that you don't have your sizing die set up correctly. I would bet that you are bumping your shoulder back too far..... or maybe you need to recheck your head space. You did not mention the use of a no-go, It might be long.


How are you checking your case head space?

[tizzy]

It's virgin Lapua brass. I'm neck sizing with a Redding comp bushing die on the Federal and Lapua/varget load. My Forster no-go won't chamber. Headspace is checked with the bolt head stripped and the firing pin removed.

[darkker]

Need to know the velocities being run at those charges. Assuming that you don't have a fat chamber, Lapua brass is typically a smaller volume than others. So that can speed-up the burning rates and you will have higher pressures.

[schnyd112]

39 g of h4350 is not anywhere close to a max load and if lapua put out a bad lot of brass, there would be more than one person having problems. Have you taken measurements before and after sizing? Before and after firing? All the data is in front of you, we just need to find out what is changing.

As an aside, I fully prep virgin lapua brass before loading. Full length size, trim and neck turn.

[Robinhood]

Have you measured the base of a new case and a fired case to see if the chamber is oversized?

Are the primers backed out?

If you have the tools, check fired Case head space against you go/no-go gauges.

Have you called Savage?

Just throwing things out there to get more data.

[tizzy]

I have not called Savage, yet. I'm away for the weekend but I'll have the data Sunday afternoon. Bear with me, and thanks.

[LoneWolf]

I would also want to know the loaded and fired neck diameter of cases. You may have a tight neck or short throats chamber. Savage has had a number of chamber issues in the last few years


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[tizzy]

Ok here it goes...
new brass mouth .291, mouth loaded .2935, mouth fired .298
new brass shoulder 1.5565, shoulder fired 1.5625
new brass base o.d. .464, fired .471
new brass length 2.022, fired 2.032
primer is flattened and backed out of case ~.002
Separation occurs about .280 up from base of case and .o.d is .4705 at that point.
Go gauge measures 1.549 No-go measures 1.554 (in my comparator)
Tools used: RCBS digital caliper, Sinclair comparator body and Sinclair "bump" insert #20A and Forster go (1.630) and no-go (1.634).

[cowtownup]

Dang.. IM anxious to hear what is causing it... Could it have a super tight bore?

[schnyd112]

It looks like a very loose chamber. Your brass is growing a lot, especially length and necks. Mine grow less than .003 in length each firing. I would change bushing size so your loaded necks are .295 to work the brass less. Aside from that, I don't see anything off unless maybe there is a bulge in your chamber. My base-shoulder measurement on fired brass is 1.626, but that is probably just different comparators.

Are you using imr 4350 instead of h4350? The varget load seems very low too but I never messed with it shooting heavies. I used 36.5g in a .220 swift to push 55 gr bullets.

maybe change powders? Rl17 or h4831sc are both pretty easy to get and great options in .260.

[Zero333]

Measure the brass in question with the headspace comparator, and compare this measurement with the go-gauge measurement. This will tell you everything you need to know.

If the brass is indeed sized to far (shoulders bumped too much causing excessive working headspace) there is a way to salvage the brass. But it requires a fireforming technique with the bullets jammed hard in the lands. And preferably a faster burning powder like Varget or Benchmark and a load near the middle between the starting and max load, maybe more like 1/3rd of the way from minimum book recommendation just to be unquestionably safe.
This will form the brass with out thinning the brass above the case head.
Sometimes it requires fireforming more than once to get the shoulders as far as the chamber if the load is too mild.

Also a picture or link to one would be helpful for us to judge the brass in question.

[LoneWolf]

I think at this point I would either have the chamber inspected by a competent Gunsmith or contact Savage and see if they will inspect it. The other option would be to rebarrel with an after market barrel and start fresh. Also are you measuring distance from the lands to a specific jump or jam for seating depth?

[tizzy]

https://instagram.com/p/BVhxvNig19y/

https://instagram.com/p/BVhx3ftgnWT/

[tizzy]

I used a Hornady oal tool, modified case, and comparator to "find" the lands.

[LoneWolf]

Very well. Same method I use. I believe this may be beyond an internet diagnosis at this point.

[bigedp51]

Why was the tread "260 lrp Lapua brass pressures" locked out?

I collect milsurp rifles and had many .303 British Enfield rifles that have "LONGER" military headspace. And there are many reasons for case head separations, defective brass, thin case wall thickness and excessive head clearance.

Below is a animated image of firing a thin commercial .303 British case in a Enfield military chamber.

http://i.imgur.com/sHgqVJR.gif

This factory loaded Winchester .303 case started to seperate after being reloaded just once.

http://i.imgur.com/DVy4C4T.jpg

Please do not take this question the wrong way, and I'm not claiming a expert but after discussing reloading methods in Enfield reloading forums my .303 case life improved greatly.

My wild ass guess is the new Lupua brass had excessive head clearance on the first firing and stretch and thinned.

I bought a RCBS case mastering gauge below as my $100.00 bent paper clip to check for stretching and thinning in the base web area. And with moderate loads have gotten over 30 reloads from thicker Prvi Partizan .303 brass with case walls .010 thicker than Winchester .303 British cases.

http://i.imgur.com/jDCS39v.jpg

The Winchester case below stretched .009 on the first firing and had .009 head clearance.

http://i.imgur.com/YoV80b4.jpg

A .303 British Enfield Rifle at max military headspace of .074 and a case with a rim thickness of .058 will have .016 head clearance. And these cases must be properly fire formed to prevent them from stretching when first fired.

Below the properly fire formed .303 case below is now headspacing on its shoulder with "zero" head clearance and will not stretch and thin when fired.

http://i.imgur.com/AQEQ9Vw.jpg

The .308 cases below were fired in a Savage rifle and full length resized over and over until they failed. These cases were sized per the dies instructions with the die making hard contact with the shell holder, meaning not adjusted for minimum shoulder bump.

http://i.imgur.com/TDwPD1Q.jpg

http://i.imgur.com/XEuny9C.jpg

Again no offense but I have had brand new Winchester .243 cases over .012 shorter than chamber headspace. And if not fire formed properly they will separate after very few reloadings.

A reloading forum is where experience and knowledge can be shared, and with modern rifle with a good venting system a case head separation is not the end of the world.

The Enfield rifle below has had the headspace adjusted from .004 "under" minimum headspace and .010 "over" maximum headspace. And any escaping gas from case head separations excaped from the vent hole in the receiver.

http://i.imgur.com/v1GFvaK.jpg

On the Enfield rifle below paper was wrapped around the receiver with a cartridge chambered that was going to separate on its next firing.

http://i40.tinypic.com/29fw5ft.jpg

After firing and a full case head separation "NO" rips or holes were in the paper.

http://i42.tinypic.com/11ayg6q.jpg

And Savage rifles have two vent holes on both sides of the receiver, and a Remington 700 only has one vent hole on the right side.

http://www.shootingtimes.com/files/2010/09/ststevens200_041106b.jpg

[tizzy]

If I may..I was just curious if European brass didn't work well with Saami chambers. SAAMI vs CIP. The indication (that I got) from the other thread is Lapua should work fine in my chamber. My original plan was to buy a reamer from Dave Kiff to accommodate the Lapua brass if the opposite was true.
I've been hand loading for almost 10 years for a variety of other rifles (Savage included) and never had an issue. I do understand speculation, especially when it comes to diagnosing a potential problem with a firearm, can be extremely dangerous when ones experience is questionable. I am not a smith, but I am more mechanical than most. You have offered some great information here that may help me when I call Savage. I haven't called yet only because I wanted to understand better what might be causing my problem so I can better communicate it to them. I also understand my first post questioning the manufacturers (Savage and Lapua), probably the two most highly regarded companies on the site, could draw the conclusion I was trolling. This could not be farther from the truth. I'm here to contribute and learn when I can. No offense and none taken.
Moving forward I'm going to cut a few cases apart and take a look. Ultimately, as LoneWolf indicated, either a smith or Savage needs to inspect things.
Thanks

[bigedp51]

tizzy

If it was my rifle I would measure a fired case with a Hornady cartridge case headspace gauge or RCBS precision mic. Then measure new unfired cases and see how much shorter they are than the fired case and chamber.

Case head separations are cause by the case stretching to meet the bolt face when fired. Head clearance is the air space between the bolt face and the rear of the case and the distance the case can stretch and thin. A case with .002 shoulder bump will have approximately .002 head clearance which is well within the elastic limits of the brass.

http://i.imgur.com/HK76WCp.jpg

Below I'm measuring a fired Lake City 5.56 case fired in my AR15 carbine, after taking this measurement I set up the sizing die for .003 shoulder bump.

http://i.imgur.com/OJqNmQH.jpg

And again my WAG is the new Lupua cases had excessive head clearance when fired and caused the case head separation. Meaning the new cases were far shorter than the chamber and stretched excessively and separated. Another clue is the primer backed out .002, meaning the base of the case never made contact with the bolt face when fired. And this normally happens at "lower" chamber pressures well below max pressure.

Bottom line, you either had excessive head clearance with the new Lapua brass or the cases were defective. And this WAG is only if you only neck sized the cases, if these cases were ever full length resized then the case head separation could have been caused by excessive shoulder setback.

[tizzy]

I may know a little more today when I cut some open. Thanks