Seating depth

[Salchi Papa]

I don’t quite fully understand seating depth. I obviously know what it is but I never understand how to find optimal for accuracy changes. I typically find my magazine length and chamber length first then just start longer and work my way shorter in .010 increments but I honestly don’t see much if any changes in accuracy. I have also loaded to COAL from the books I have and experience similar or the same accuracy. I feel like either I’m missing something or doing it wrong. Just as an example I have a Remington 700 bdl from the late 60’s 24” barrel that wasn’t shooting well with several loads. I ended up using a knife stripping compound at 8000 grit with some kroil on patches to clean and smooth out the barrel. It helped cause I got better groups by a decent margin with 3 different loads. The load I’m looking to go within 270 win is REM cases rem 9.5 primers 54gr of H4350 powder and a 130gr Nosler BT seated at 3.32. I shot 2 3 shot groups of about an inch. The throat is long in this rifle but the 3.32 is about as far as I can go with the magazine length and I did a seating test of 3.28-3.34 in .001 increments and 3.32 shot the tightest but only about an inch. It is just a hunting rifle so I don’t need cloverleaf groups but it would be nice to see better than an inch if it’s possible. I’m not ruling out that I could be the issue as well but I do shoot other rifles better on a good day. If more info is needed please ask as I know this could be vague. Thanx boyz!

 

[RL338]

Scroll towards the bottom , this might help out.

Getting the Best Precision and Accuracy from VLD bullets in Your Rifle

VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifle.

bergerbullets.com

 

[Charlie-NY]

Testing at increments of .001" is much too small. Start by testing in increments of .015" and see if groups open or shrink. If groups shrink, then test in .005" increments on both sides of your previous good seating depth.

 

[wvbuckbuster]

The throat in your Remington 700 sounds familiar as I have couple with long throats as well. What is the overall cartridge length with the Nosler BT? Curious how much difference between col and magazine box length. Sometimes rifles like a lot of bullet jump, sometimes not. Depends on the rifle and bullet used. Have you tried this bullet with a different powder? Just a matter of finding which combination works best giving better results. As for cleaning, being your rifle is that old and what you did for a cleaning process, it's possible depending on the number of rounds down the bore it just might need a thorough cleaning. One inch group will kill all the deer you want but as you said it is always gratifying to get tight groups. Don't give up just try some different things.

 

[Salchi Papa]

The throat in your Remington 700 sounds familiar as I have couple with long throats as well. What is the overall cartridge length with the Nosler BT? Curious how much difference between col and magazine box length. Sometimes rifles like a lot of bullet jump, sometimes not. Depends on the rifle and bullet used. Have you tried this bullet with a different powder? Just a matter of finding which combination works best giving better results. As for cleaning, being your rifle is that old and what you did for a cleaning process, it's possible depending on the number of rounds down the bore it just might need a thorough cleaning. One inch group will kill all the deer you want but as you said it is always gratifying to get tight groups. Don't give up just try some different things.

I don’t remember off the top of my head what the chamber measurement is but the COL max is 3.34 to fit the magazine. The last 6 rounds I fired were 3.32. I did a thorough cleaning with the 8000 grit paste and kroil but also scrubbed the barrel with a bronze brush and MC7. I bought a bore scope yesterday so I’m waiting on it to arrive. The rifle shot much better after I cleaned it but I doubt I removed much copper but probably removed some and smoothed out the bore quite a bit even the brushes and patches went through easier.

 

[Salchi Papa]

Testing at increments of .001" is much too small. Start by testing in increments of .015" and see if groups open or shrink. If groups shrink, then test in .005" increments on both sides of your previous good seating depth.

I did make changes at .010 increments that’s what got me to 3.28-3.34 and then from there did .001

 

[Blkram]

If you have a long throat, you will have more jump to the rifling, and once you have hit max coal for your magazine, you may not be able to see as much improvement from seating depth changes as one would with a chamber with a shorter throat where fine tuning seating depth can show marked improvement (dependent upon the bullet you are using as monos behave differently than cup and core bullets when it comes their preference for the jump to the lands for enhanced accuracy).
(Unless of course, you are willing to single feed your cartridges in the rifle when shooting. Just may be impractical for hunting for you...but most who hunt with single shots do not feel handicapped by this! And if it improves the accuracy of your rifle/ammo combo...not necessarily a bad thing!) But only you can decide on whether this acceptable to you and your needs.

You could also check your concentricity of your loads as the straighter it is, the less negative impact on accuracy as the bullet isn't having to straighten out as it engages the rifling in the throat. This could improve things for you too.
When seating your bullets, do you do it one full stroke, or do you go half way, stop and twist your cartridge in the press 180 degrees, and then fully seat the bullet?
This was a method I was taught that seem to assist with straighter bullet seating...or at least is what I was taught long before I ever heard of a concentricity gauge, neck turning, etc. to check straightness.

 

[Salchi Papa]

If you have a long throat, you will have more jump to the rifling, and once you have hit max coal for your magazine, you may not be able to see as much improvement from seating depth changes as one would with a chamber with a shorter throat where fine tuning seating depth can show marked improvement (dependent upon the bullet you are using as monos behave differently than cup and core bullets when it comes their preference for the jump to the lands for enhanced accuracy).
(Unless of course, you are willing to single feed your cartridges in the rifle when shooting. Just may be impractical for hunting for you...but most who hunt with single shots do not feel handicapped by this! And if it improves the accuracy of your rifle/ammo combo...not necessarily a bad thing!) But only you can decide on whether this acceptable to you and your needs.

You could also check your concentricity of your loads as the straighter it is, the less negative impact on accuracy as the bullet isn't having to straighten out as it engages the rifling in the throat. This could improve things for you too.
When seating your bullets, do you do it one full stroke, or do you go half way, stop and twist your cartridge in the press 180 degrees, and then fully seat the bullet?
This was a method I was taught that seem to assist with straighter bullet seating...or at least is what I was taught long before I ever heard of a concentricity gauge, neck turning, etc. to check straightness.

In reference to the bold and italic section of this. I do seat half way and turn I wasn’t taught this, well I wasn’t taught anything about reloading I learned it myself, but I also just picked up a match seating die I think it’s a forrester die but it could be Redding and my intent was to get where I am with shooting a 1” group and then same load with the match dies and see the difference. I don’t have a concentricity guide but they are shooting an inch so I believe they’re at least close enough for that and any variance the match dies should remove some of it even if it’s a minor amount.