7/338 lapua magnum

[12valvetater]

With all the talk about the 195 gr berger I put a big 7mm together to try and take advantage of it. It's nothing wild or crazy just a straight 338 lapua taken down to 7mm with a .319 neck and throated so the pressure ring of the bullet is about 3/4 of the way into the neck. The rifle is a bat hr action with a Bartlien 8.3 twist 4 groove 32 inch barrel and a t2 brake.at In total I have about 75 shots out of it so far. I've settled at 95.7 grains of H50BMG which is moving those 195s along at 3245 fps and producing groups less than 3/4 of an inch at 400 yards. Now after about 7 shots it is copper fouling to the point of over pressure and the group blows up to over 3 inches. I know I'm driving a bullet with a long bearing surface relatively fast into a fairly fast twist barrel but is this normal? This is my first high horse power 7 and I really like it so far I'd just like to hear from some of the guys who have been playing in these waters longer.

 

[valleyloader]

Hopefully Kirby Allen will chime in on this one, I know he has the experience and expertise you are looking for.

 

[PackersFanboy]

Turn it down or moly coat the bullets. Try alco bullets

 

[12valvetater]

I've never heard of alco bullets so I looked them up. It looks like they are a non expanding bullet? Correct me if I am wrong. This is a long range hunting rifle which is what the whole idea behind building around the berger. I considered molying the bullets but again this is a hunting barrel and I typically don't moly hunting bullets due to needing to clean the barrel pretty much right after the shooting session. I also don't want to turn the speed down. It shoots good where it is and less speed will just limit my range. I am ok with having to clean the copper out after 7 or so shots since this is for hunting and 6 shots will be more than I'll be able to take at any one time. I was mainly just seeing if other people were experiencin the same amount of fouling out of similar cases.

 

[PackersFanboy]

195 berger 2950-3000 I shoot. I stop testing for a while wasn't happy with the accuracy. Jumping back on them testing during the spring.

 

[kyron]

Try HBN instead of Molly.

 

[RockyMtnMT]

I agree with the HBN idea. It may just take care of it.

It may be worth a call to Berger to see if they have any ideas as well as to Bartlein.

I am interested to follow your results. We have this same reamer on the shelf but with a 40* shoulder that we have not tried yet.

Steve

 

[12valvetater]

Forgive me for not knowing but what is HBN? I can't seem to get the search function to work.

 

[HammerB1]

Hexagonal Boron Nitride.

 

[RockyMtnMT]

Check this out.

http://www.longrangehunting.com/forums/f19/hexagonal-boron-nitride-151457/

Steve

 

[bigngreen]

With this type of chambering you have to absalutely keep the throat smooth, the 195 may not be able to hack that much of a case for very long, I've seen a number of similar chamberings that guys just can't shoot these kind of bullets in because they went too aggressive and are having to shoot Accubond or monos just to keep things going. I've seen guys not getting them nearly as clean as they think also and they won't last long before plugging up and causing issues. The HBN will help keep the friction heat down as well but you need to have it all the way clean before running it.