Question for you precision shooters

SuperCub

SuperCub

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I have a rifle here that I'm working with trying to get a load for.

It is a 700 in 375/338 with a new 21" King bbl. Gun has been bedded by Guntech as well as the trigger adjusted. Gun is very easy to shoot with a good pad and straight comb for recoil control. To date I have tried two different scopes and mounts on it, Three different powders (3031, RL15, Varget), Four different primers. Bullets have all been 270gr Hornadys and have been seated out as far as possible to the lands with almost 100rds down the tube.

I shoot three shot groups as the bbl heats up quick. Barrel is allowed to totally cool off between groups. Problem is that the gun fairly consistently gives two shots very close together with one off up to 2" or so.

I'm no trying to make this into a bench gun, but would like to see a bit more consistency that this. Any thoughts from the precision shooter crowd would be of interest. :)


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Try 260gr Nosler Partitions, they would shoot under an inch consistently in my old 375 H&H Ackley over RL-22. I never had much luck with the 270gr Hornadys.
 
If it is always the first two touching, then the barrel is overheating before the 3rd. Just work up loads by shooting 2- 2 shot groups on the same target. That way you have a 4 rd composite which is more indicative of a hunting situation anyways.

If the touching is random, then check your rests and shooting form. You need a solid bench and rests with both front and rear well supported. If you are using a bipod, stop and get a good quality pedestal front rest.

Although, recoil may not cause you to black out, something like this is going to boot. Maybe there is a slight flinch in there somewhere. Better yet, take long breaks between shooting groups.

Large kabooms do play with our nervous system whether we 'feel' it tangibly.

Of course, look at the scope, rings, bases, bedding, action screws, etc. Things do shift under this type of recoil and it is possible that something is loosening or bedding needs to be redone.

Did you check the stock for cracks?

Let us know..

Jerry
 
I've used IMR 4064 with good results in mine with 285gr GS and 300gr Hornady bullets. I doubt its your loads that are giving you grief.
Is your third shot consistant on where it goes or random?
Bedding full length including barrel? If so, try one thickness of electrical tape near the forend to apply slight upward pressure to the barrel.
Bevan's barrels are button rifled and overall very accurate. I've used at least six of his barrels with good results.
Keep us posted as to your results.
 
mysticplayer said:
If the touching is random, then check your rests and shooting form. You need a solid bench and rests with both front and rear well supported. If you are using a bipod, stop and get a good quality pedestal front rest.
Click to expand...
Touching is random. I use sand bags front and back.

mysticplayer said:
Although, recoil may not cause you to black out, something like this is going to boot. Maybe there is a slight flinch in there somewhere. Better yet, take long breaks between shooting groups.

Large kabooms do play with our nervous system whether we 'feel' it tangibly.
Click to expand...
Flinch is always a possibility. I wondered about that as well. I haven't owned a 375 for a couple years now, so am getting used to this one. It seems pretty easy to shoot, but ....?

mysticplayer said:
Did you check the stock for cracks?
Click to expand...
The stock is a B&C sythetic bedded at he action.


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mikeelliot said:
Try 260gr Nosler Partitions, they would shoot under an inch consistently in my old 375 H&H Ackley over RL-22. I never had much luck with the 270gr Hornadys.
Click to expand...
I have some Nosler ABs here as well. I'm gonna give the rifle another once over for screws and bedding and try these.



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Here's a couple of targets from today using Varget and 3031.

375targets001.jpg

375targets002.jpg


This target is from some sighter loads I used today to change to a Leupold 2x7 to start the day out.

375targets003.jpg
 
I like the 2rds that are marked sighter. Not sure what the rest of the holes are telling us.

I would say that stick to 2rd groups and do a composite of 2 to 3 groups if you are concerned.

The 1/2" spread in the 2 sighter rds is about the accuracy I would expect given the components and cartridge. A low mag scope likely has 1/8" in error all on its own.

If you can be consistently 2rds 1/2" at 100yds, what more do you want with a bruiser?

I would also repeat test load #4 of your varget target. If it will repeat, you are set.

Nice stuff....

Jerry
 
mysticplayer said:
I like the 2rds that are marked sighter. Not sure what the rest of the holes are telling us.
Click to expand...

The two "sighters" were the first two fired at 100yds after boresighting in at 25yds. The bore was allowed to completely cool after.

The next two fired are the ones in the green after the scope was adjusted. The bore was cooled again.

The last three were fired together. The first of these three is the one between the red and green dot and the last two are the ones together left of the green. No adjustment was done to the scope after the "sighters" were fired.

375targets003.jpg
 
My 340 Weatherby Mark V Stainless shot patterns like this when I first bought it. I think I was lucky with the problem because the factory bedding job in my rifle was horrible. It was spongy and I could pick it out with my fingernail. Rebedding it helped quite alot. One thing I would look for in this case is whether there is a tight spot anywhere along the barrel channel where the barrel touches or is close to touching. Easy to test with a dollar bill. If all else fails, I might reverse things and try a 120 degree, 10 to 15 lb. pressure point near the front of the forend. Good luck. Fred
 
I gave the rifle the once over last night. All mount screws were tight and in order. The bbl is totally free floating, even up to the recoil lug. The bedding looks OK and there are no cracks in the stock. I think I may bed the bbl channel a bit, about 3" out from the recoil lug and then skim bed the receiver.


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Hey SC,

All mechanical things being fine, you should consider the nut behind the trigger.

I have found, and any target rifle shooter will tell you, that a consistent position is critical for good group shooting. This applies to everything, right down to where you put your feet on the ground under the bench.

My head position caused me some problems, and some parralax error may have compounded it until I started placing my head in exactly the same place on the stock every time. I do this by getting into my position, then pointing my chin at the target and rolling my head down into position. If you extend your neck as far as you can like this every time, your head position will be consistent and you can set your scope's eye relief to suit. If you rely on the fuzzy edges around the scope, your position can vary quite a bit without fuzzing the sight picture.

Apologies for preaching to the choir SC, but it helped me! :D

V7
 
I can't speak from first hand experience with that cartridge, but My first impression was that RL15 and Varget were WAY too fast for that size cartridge and those bullet weights. I'd have thought 4350, 4831 or N160 would be the way to go.
 
It sure looks like a barrel heating issue to me. To get that 3rd shot more consistent, you might consider bedding a pressure point in the barrel channel.

I'd start with card stock to see if it works. If so, you could make it permanent with a little bedding compound.
 
375/338

Bedding the barrel does work with some rifles.

Before doing that I would check the float of your barrel again. One "bill" clearance is a way too tight for me - I like a five or six bill clearance. The worst thing is if the stock just kisses the barrel during recoil interfereing with its natural harmonics. If this is happening it will never shoot consistently. Open it up the barrel channel and give it lots of room.

If that doesn't fix it then a full length bed with a few lbs upward pressure at the forend may be in order.
 
I would

Obtunded said:
I can't speak from first hand experience with that cartridge, but My first impression was that RL15 and Varget were WAY too fast for that size cartridge and those bullet weights. I'd have thought 4350, 4831 or N160 would be the way to go.
Click to expand...

tend to agree with Obtunded. My first thoughts were wrong powder choices when I saw what powders you were trying. I would have tried 4350, RL19 or RL22, 4831. Look more at the powders recommended for a 338 with heavy bullets.
 
Sorry, disagree. This is a 375/338 Win mag I believe. That is a huge bore size for the case.

Looked up the 375 H&H and H4350 is very much on the SLOW side. The Win mag wildcat is considerably smaller in case volume.

Given the case size, 70ish grains of powder would be the volume I would expect to use.

Opening the forend is most likely the solution here.

Jerry
 
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