Savage LRPV 6mmBR has a very long throat is this normal????

[k80skeet]

My new Savage LRPV in 6mmBR 1 in 12 twist has a very long throat so it is impossible to touch the lands and keep the bullet in the case far enough to seat. This is the list of bullets that I tried
70gr Nosler Ballistic tip
70gr Sierra Match
68gr Barts
68gr Bruno's
68gr Berger Match
80gr Berger
The only (2) that would touch the lands and be in the case far enough to seat are the (2) Bergers and they aren't in the case as far as they should be. Is this normal for these Savage's ?? Is anyone else having this same type of problem?? It appears that Savage cut a real long throat this rifle. Are they all that way??

 

[CoverDog]

I have the 6BR F Class and with the 105-107 bullets this is not the case. I can jump with all of them, with plenty of bullet in the case. My gun does prefer to be jammed. I wonder if Savage has two different reamers for the different twists and yours was cut with the wrong reamer.

Sorry we could not be of more help.

 

[wooger]

I had a factory 8 twist barrel and could not reach the lands with Berger 105's.

 

[RonAKA]

I dug out my reloading records and did some calculations to get seating depths for bullets just to the lands in my 12 twist LRPV. I gave you some numbers earlier from memory. Ignore those. Memory not as good as it used to be!

Here are some realistic numbers in my specific gun. I base to the lands on the sized and slotted case chambered with a bullet and measured method. These are all flat base bullets.

Bullet - Seating Depth
Berger 69 - 0.080"
Berger 62 - 0.094"
Bart's Ultra 68 - 0.101"
Berger 68 - 0.159"
Berger 80 - 0.226"

I have some Sierra 75 Flat Base, and with a Hornady comparator they measure about 0.045" longer from base to comparator diameter than the Berger 68's. I've never loaded any, but expect they will seat around 0.205" into the neck.

These numbers are all just to touch the lands. I generally seat all bullets 0.010" into the lands, so unless they get pushed back when I chamber them, they are actually in the neck 0.010" less than the numbers above.

Hope that helps some.

 

[treeman]

k80skeet, Try seating the bullets about .100" off the lands you might be surprised. you might have to step up the powder charge a few tenths also.

 

[RonAKA]

German Salazar in another thread has provided a link to the CIP specifications for cartridges and chambers. Link below. If I am reading this drawing correctly it would appear Savage and other manufacturers are under the obligation to make the throat a minimum length (unlike a custom gun made by a gunsmith), which is represented by the dimension "s", 2.74 mm, or 0.108". The neck of the chamber also has a minimum length which gives an overall length of 1.570" or 10 thou more than the max length for cases. So if you measure throat from the mouth of the case then the minimum would be 0.118". And the throat is slightly larger than the nominal bullet body, and the lands only start there with a very slight taper of 1.5 degrees. A bullet which typically has a body size of a couple of tenths of a thou under nominal (0.243) will slip down the barrel past this point. My rather crude estimation of to the lands throat length comes out to be about 0.132", and right in the reasonable ballpark of 0.118" plus some slip down the taper of 0.024". That will obviously depend on the specific bullet taper near the ogive.

CIP Specs

While the throat in your gun seems longer than mine, I would say mine is probably built to these minimum CIP specs. The message in this may be that slow twist factory barrels get shafted by the safety oriented CIP specs, which do not consider twist, and probably have to allow for someone putting a 105 grain factory load in the 12 twist gun. It won't stabilize, and likely not hit the target, but it won't blow up either.

 

[k80skeet]

I want to thank all of the people that reaponded. And a special thanks to Ron AKA for all the tech information he supplied to me along with some great loads and pictures that worked in his rifle.

 

[Dodgedriver]

I am using the 80 gr. Berger in a Lapua case. The load is from the 6BR page using 31.8 gr of Varget. I am touching the lands and have just about a full neck of seating depth at an overall length of 2.210". This is my second Savage LRPV in this caliber and they both have had the same length with this load.

 

[k80skeet]

Yup, I would say that is about the same as mine. With 80gr bergers !! but the other weights are only that is in the case .100 or less I would like to see a full buller size in the case .243 with the 68gr's and the 70gr's, I think Ron AKA quote above is just about the same as mine. I am shipping out my barrel this morning to the gunsmith to have the chamber recut so I can get a full bullet size in the case with the 68&70 grain bullets. It may not shoot any better after doing this but I will like it better. Ron AKA's shoots awful good the way it is.

 

[RonAKA]

Russ, I'm not sure how much interest you have in shooting the Berger 80 grain. It is about the max you can put in a 12 twist. If you bring the throat back so that all the 68's (including the Bart's) are seated 0.243" then the 80 and possibly the Berger 68 will be back behind the shoulder junction. You can get an idea with my numbers posted earlier what will happen. This does not sound bad at first, but I can tell you I have a significant donut on the inside of the neck right at the shoulder. If you seat the 80 or 68 back past the shoulder junction then you will need to deal with that donut. I currently ignore it as I don't seat there.

If I had a choice in it, I would ask Savage that the throat be set back about 0.075" from where it is now in my gun. That would put the 80 near but not at the shoulder (I believe the neck is about 0.322" long). It would get the shortest bullet (Berger 69 High BC) 0.155" into the neck. I guess it depends on what bullet you want to optimize the chamber for.

The 80's have been consistent in group size but average second largest. The 68's have been the most inconsistent, and average the largest groups, but also have provided the smallest groups. They are the one hole and flyer pattern. Bart's overall have averaged the smallest groups, but are inconsistent with the flyer issue. One of my suspicions is that the flyer issue has something to do with insufficient seating depth, but it is not clear that is the case. Currently I would rate the Bart's and Berger 68's as having the best potential to shoot small one hole groups (if the flyer issue can be solved), and the Berger 69 High BC next best.

The other issue to think about is how much of the neck will you really use. I set my bushing to only size 2/3 of the neck. I believe others only size 1/2 the neck or 0.150" or so. If that is what you plan to do, then there is a point where seating deeper does not gain you anything in seating tension or alignment to avoid starting cant.

Hope that helps some,

 

[k80skeet]

Ron, That is some insite that I needed to hear and make sure I don't set that throat back too far. I think you are probably 100% right on .75-.100 much more I could be into th donut effect with the 80grs. I was thinking .200 but you are right that would be way too much. He has a .268 reamer that he suggests to use and just clean up the necks .002 of course I am going to have to buy a set of bushing dies. Ron thanks again for you knowledge before I went too far and I might have made things worse instead of better.


















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