custom 300 mag shooting like crap

[JoeJen]

Hi all, I have a question that maybe someone here can help with. I have a rifle I bought that was built in 300 mag.

It has a Manners stock, Rock Creek Barrel, Remington 700 action and a Holland muzzle brake. it was new when I bought it. I have been shooting the gun and have put about 60 rounds through it. It shoots like crap averaging 1.5 inches. The best group I was able to achieve measured .976. This is with Handloads shooting 208 A-max and factory Winchester Supreme.

It has been glass bedded and has an oversized recoil lug. Everything looks good and I cannot figure out why it shoots so bad. Any ideas or what I can do?

 

[ZLBubba]

Re: custom 300 mag shooting like crap

A couple things come to mind:

1. Glass: are you positive your scope is properly torqued down and there's nothing wrong with it? Something loose, externally or internally, will make repeatability very difficult.

2. Flinching: 300 mags, even with brakes, take time to get used to shooting. I don't know your background, and I'm not saying this is it, but realize that shooting a heavy recoiling round requires most people to spend more time behind the gun to get comfortable with recoil.

3. Rifle: Despite being a custom rig, sometimes rifles leave gunsmiths not properly tested or with defects. Most smiths stand behind their work and will fix what's broken. Return customers are a key part of the gun business, so give the smith a chance to make this right.

 

[tpr564]

Re: custom 300 mag shooting like crap

Try a variety of factory match loads or more combinations of bullet/powder/C.O.L. Maybe it just doesn't like what you're feeding it.

Are YOU capable of shooting sub MOA or a new shooter?

 

[kraigWY]

Re: custom 300 mag shooting like crap

For what its worth, in the early 80s I built a Model 70 Winchester in 300 WM for 1000 yard shooting.

Over the years I've tried about every bullet you can stick in a 30 cal case.

The only bullets my rifle likes is the 200 grn SMK. Don't know why but thats the way it is. I can't complain though, its an excellent shooter with those 200s.

Maybe you should try a bunch of different bullets and see what happens.

 

[LRI]

Re: custom 300 mag shooting like crap

Magnums. A few things to consider.

Little bullets often respond well to being shoved into the ass of the barrel. (meaning the throat)

Magnums are often a little different. I'll offer my explanation.

You have quite a bit of powder behind this bullet. The projectile, even the VLD types have quite a bit more surface area when compared to a little 6mm. All this surface area, added weight, and powder means that Newton's little rule needs to be observed.

It's been my experience that when a Magnum is jammed up tight the gun sort of "sneezes" the bullet down the bore. What your after is more like a "cough". It's a nice steady/linear rise in pressure that holds at the peak and then peters out.

A sneeze tends to be more violent/abrupt/inconsistent.

I'd offer to consider backing your bullets about .02" from the lands. Then work forward. If you have a chronograph run some over it with them jammed tight and some with them backed off. Watch your standard deviation.

Weighing charges tends to work better than throwing. Especially when stretching your legs with a rifle. (meaning beyond 600)

On that note a SD of less than 10 means your doing exceptionally well at the reloading bench. It takes diligent reloading to get this, but its very possible to do.

If your groups are stringing vertical it can be the load, or a parallax issue in your glass. Can also be that you just aren't holding well on the tgt. You said the gun is bedded so we'll assume for now it's not that. (bedding does this too if its bad or not there)

A round group in a magnum often gets resolved by gassing up the load a bit. This works really well with my 300-338 Lapua Magnum shooting 110 grain Horn. Vmax bullets (Mr. Mister

)

Last: 100 yards with a magnum isn't always the best way to test. A rifle like this shooting a 1/2 minute at 100 doesn't always mean it'll shoot 3" at 600 yards or 5" at 1000. Often they get better. Just one of the little quirks with boat tail bullets.

If you want, try a flat base at 100 and see if it improves. BR guys swear by em for bag gun stuff.

Hope this helps and good luck.

C

 

[blonz]

Re: custom 300 mag shooting like crap

@JoeJen: at what range did you shot, 100yards? Have others the same experienced with your rifle? Magunm bullets need some more range until they are stabilized.

 

[Raven 6]

Re: custom 300 mag shooting like crap

Just something no one else has talked about. Have you checked your action screws? I normally torque to 55in lbs and try for groups working up to the max of 65in lbs to see which groups the best. Just thinking your bolts may have worked loose, also note I said inch pounds not foot pounds.

 

[LRI]

Re: custom 300 mag shooting like crap

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: triple 6</div><div class="ubbcode-body">Just something no one else has talked about. Have you checked your action screws? I normally torque to 55in lbs and try for groups working up to the max of 65in lbs to see which groups the best. Just thinking your bolts may have worked loose, also note I said inch pounds not foot pounds. </div></div>


It's easy to disregard most of this and whittle it down to saying "it's just a fricken deer rifle." Thankfully that position isn't taken by engineers who design stuff most of us take for granted when flying commercial or cruising around under the arctic circle.

Take it for what its worth, but this is what I learned:

I'm fortunate to have some pretty smart fellers for friends. One in particular lives in the Seattle area and makes a very comfortable living designing, developing, and evaluating fasteners for aerospace and nuclear submarine applications.

About 8 years ago I asked for his help on this very question. First, there isn't a "blanket answer" that covers everything. For the sake of this discussion we'll use a particular screw.

1/4-28 made from 300 series stainless. Popular now with many of the custom actions.

With this particular fastener you don't exceed 40 inch pounds. Period. If you do the fastener will yield because it exceeds the tensile loading capacity of the threads and you end up only chasing problems that really don't exist.

Different materials have varying degrees of lubricity, tensile strength, and surface hardness. All of which play into this.

You also must take into consideration the thread pitch. This is where friction coefficients, flank surface area, and shear angles also become important. Not to mention root diameters vs major diameter and the torsional/shear loading applied to the cylinder/shaft portion of the fastener.

Be that as it may if you sit and do the math the numbers are pretty close. One does not clearly outshine the other.

Don't forget also that the threads in the receiver are just as capable of being influenced. A kryptonite fastener is only as effective as what its being screwed into.

Excessive screw torque is attempting to mask a larger underlying problem: Poor bedding and/or incompatibility of components.

If your building a spaghetti M700 in a boomer with a barrel that resembles the axle out of an excavator in a featherweight sporter stock, then its likely the gun will perform poorly no matter how much tension is put on the guard screws.


Hope this helped.

C

 

[Raven 6]

Re: custom 300 mag shooting like crap

Maybe you could put that in plane english for us dumb ole country boys.
http://www.futek.com/boltcalc.aspx

 

[Black-X]

Re: custom 300 mag shooting like crap

My .300wm wouldn't shoot the 208 AMAX until I loaded them way out there next to the lands.

 

[Tactical30]

Re: custom 300 mag shooting like crap

Try a box of Black Hills 190gr. SMK's factory ammo.Triad usually has them in stock for the best price i have seen around. I have a "custom" built .300WM also. It shoots these factory loads pretty accurate. If it doesnt hold atleast a 1" group with these i would say there is a problem somewhere.

 

[Tactical30]

Re: custom 300 mag shooting like crap

Try a box of Black Hills 190gr. SMK's factory ammo.Triad usually has them in stock for the best price i have seen around. I have a "custom" built .300WM also. It shoots these factory loads pretty accurate. If it doesnt hold atleast a 1" group with these i would say there is a problem somewhere.

This problem could be numerous different things. I would start with the factory loads. There is aslo the FGMM 190gr. Factory ammo but it is almost twice as much as the Black Hills and it shoots the same out if my rifle.

 

[seanh]

Re: custom 300 mag shooting like crap

I'd get some Federl gold medal match for starters. In general this is a consistent round that shoots well out of many guns. It will give you a good baseline to start with.

Also, have someone else shot the rifle. You'd hate to have to go through a lot of frustration only to find out it's you.

Back when I used to work as an RO I'd test fire/sight-in many guns that "were all F'd up". Most were fine, the shooter was flinching, not breathing right, didn't have NPA. In a majority of the cases all it took was seeing that the gun would shoot and magically, that person started shrining their groups.

 

[wildcats]

Re: custom 300 mag shooting like crap

The key to accuracy is BBB (Bullet Barrel and Bedding).
At least thats what all the old timer gunsmith that i've dealt with in the past always told me,and they have been quite a few.
I've had more then a handful of 300 win. built by the best in the business and they all shot sub 1/2 min. 5 shot groups @ 100 and hold that at 600 when i did my part.
That being said,you need to go back to basics, and everything Chad said is correct including,
( Excessive screw torque is attempting to mask a larger underlying problem: Poor bedding and/or incompatibility of components.

If your building a spaghetti M700 in a boomer with a barrel that resembles the axle out of an excavator in a featherweight sporter stock, then its likely the gun will perform poorly no matter how much tension is put on the guard screws.

Loading components,brass,powder charges
barrel twist
scope paralax (had this problem with one)
bedding quality

hope this helps.

 

[hamr56]

Re: custom 300 mag shooting like crap

I would like to know how you have been shooting the rifle? Are you shooting from a bench, or prone? Off a bipod or bags? What is your rear support? I have seen rifles shoot quite different depending on the setup. I have a custom 300 RUM that likes to have forend pressure. Once I figured this out it shrunk my groups dramaticaly.