Belted Magnums

Thefabulousfink · May 14, 2012

I was told by someone who owns and shoots several belted magnums, that they are less accurate than non-belted catridges. He explained that this was because the rounds headspaced off the belt, and there was usually a bit more tolerance up by the bullet.

My question is would it be feasable to trim the chamber until the round it resting on the shoulder like a non-belted round? And if that is possible why don't all the belted magnums do that?

essentially, what are the issues with accurizing large belted magnums?

Horsemany · May 14, 2012

Do you handload? If so you simply neck size or lightly bump the shoulder back so you are then headspacing the same way a non-belted cartridge does. You will find several belted cartridges that are very accurate. In the 60 and 70 the 7mmRM was used in 1000yd matches. 300Win mag has been used by police and military for long range shooting for decades.

jmr40 · May 14, 2012

As long as the tolerences are right belted magnums can be as accurate as anything else. It is just one more thing that must be done right and it is less work to get non belted magnums to shoot accurately. The 300 win mag is belted and it set many long range shooting records. But as good as it is the non belted 300 WSM is proving to be slightly better and is now setting new records. In theory the person who told you this is correct, but for most shooters the difference is pretty small and likely undetectable.

Instead of trying to modify existing rounds it is just much easier to buy and use a rifle and cartridges designed without belts.

1948CJ2A · May 14, 2012

Yea - I've seen this debated on other forums before. Head-spacing off the belt doesn't make a cartridge less accurate than on those which space off the shoulder (assuming the rifle's tolerances are correct). Plus there are some belted mags that are purely cosmetic like the 240 WBY that spaces off the shoulder.

MachIVshooter · May 14, 2012

Non-belted factory ammo, new brass of FL resized brass doesn't really headspace off the shoulder, either. It pretty much lies on the bottom of the chamber and is held by the extractor.

If you want accuracy from any centerfire rifle, the first place to start is keeping the brass fired from that rifle for that rifle and neck-size only. Then it will actually fir the chamber and headspace on the shoulder, belted or not.

Loosedhorse · May 14, 2012

A least two of the belted magnums (.458 Lott and .470 Capstick) utilize a "ghost shoulder", in which the last part of the case near the mouth is actually straight-walled. That should allow the round, even when there is "play" from the taper and belt, to line up consistently concentric when the bolt is closed. (It also provides better retention of the bullet if the cartridge is subjected to heavy recoil.)

I don't think it is difficult to run across a .375 H&H that is better than MOA.

Thefabulousfink · May 14, 2012

Interesting, So the main difference between an accurate belted and non-belted round is the belted cartridge takes a little more work to acheive the same level of tolerance as a non-belted round?

adelbridge · May 14, 2012

I was under the impression that the 7mm rem mag head spaces off the shoulder and the belt is a cosmetic carry over from the parent cartridge.

Lloyd Smale · May 15, 2012

probably the two most accurate bolt rifles ive ever owned were my 700 rem 7mm stw. and one that foolishly i let get away. i model 70 super grade 300 win mag. Anyone that says mag rifles are less accurate are smoking crack. Go to a 1000 yard match some day and see what they can do.

303tom · May 15, 2012

MachIVshooter said:
Non-belted factory ammo, new brass of FL resized brass doesn't really headspace off the shoulder, either. It pretty much lies on the bottom of the chamber and is held by the extractor.

If you want accuracy from any centerfire rifle, the first place to start is keeping the brass fired from that rifle for that rifle and neck-size only. Then it will actually fir the chamber and headspace on the shoulder, belted or not.

This is the correct answer..............

SaxonPig · May 15, 2012

Most belted magnums are intended for hunting, not match shooting (although the 300 W is used for long range shooting) so pinpoint accuracy really isn't a mandate. I'm not an engineer but I would think the belt would make better head spacing because it doesn't change with each firing like the shoulder does. Wouldn't it be more consistent?

jmr40 · May 15, 2012

Maybe, but almost all belts are purely cosmetic. The first belted magnums were designed to be fired from double rifles and the belts served the same purpose as older rimmed cartridges. Positive extraction. Mainly for marketing purposes for many years anything with magnum in the name had to have a belt, even though it was actually just in the way with bolt action rifles.

Shooters and gunmakers are finally figuring out that the belt is a useless addition to the cartridge and newer magnum rounds are all beltless.

Does not mean they cannot be accurate, it is just one more thing to consider and go wrong.

H&Hhunter · May 15, 2012

that they are less accurate than non-belted catridges

I don't think it is difficult to run across a .375 H&H that is better than MOA.

I've seen very few .375H&H's that weren't MOA rifles many that are better. the .375H&H is one of those "inherently" accurate cartridges. Mine will regularly shoot sub 1/2" groups and so do the majority of them that I've played with. Belts do not negatively affect accuracy. Shooters do.

Here is a 100 yard group from my 20" .375H&H M-70. It'll do this with boring regularity when I am up to the task.

---------------------------------------------------------------------------------------------------------------------------------------------------------

The first belted magnums were designed to be fired from double rifles and the belts served the same purpose as older rimmed cartridges.

WHAAATTT?? ^^^^^^^????? I have to take historical exception to this comment.

Read this, belts were specifically designed to ease feeding issues in magazine rifle.

http://www.huntnetwork.net/modules/wfsection/html/Ahclassic African Cartridge Pt10.pdf

"The addition of a belt to a rimless cartridge design provided the advantage of allowing for correct headspacing of highly tapered cartridges (an advantage of flanged cartridges) and smooth feeding through magazine rifles (the advantage of rimless cartridges)"

The first commercially successful belted round was the .375H&H designed specifically for a bolt action rifle and is now the parent case for ALL other belted cases except for the .378,416 and .460 Weatherby cases which are based on a belt added (By ole Roy) version of the .416 Rigby.

The .375 version of the H&H that was used in double rifles is the .375 Flanged Nitro Magnum which is a non belted rimmed version of the H&H belted case. Belted rimless cases are shunned by double rifle makers due to the extreme problems they can face with extraction issues. Rims are the preferred case for a double rifle though some belted and non belted cases have been chambered in carious doubles over the years. Rimmed cases are by far and away the most popular in double rifles.

MCMXI · May 15, 2012

Thefabulousfink said:
I was told by someone who owns and shoots several belted magnums, that they are less accurate than non-belted catridges.

More internet BS!! Two five-shot groups shot with my Krieger barreled Remington 700 chambered in .300 Win Mag and shot prone off a bipod at 100 yards and not off some fancy bench rest. Clearly I ruined the first group but the second group is more than respectable.

LoonWulf · May 15, 2012

Achieving accurate results with a belted magnum is no harder then with any other cartridge design.
The issue that I personally have is that usually on first firing shoulders move forward enough to cause excessive stretching at the web. This has been an issue with a couple of factory rifles Ive had. After first firing it wasnt hard to get any of my belted mags to shoot at or under 1". My new procedure is to neck up then back down for a slight crush fit on first firing, as of this week im using cases on the 8th firing of hot 7mm loads. I also anneal every other firing as the only real ware i see is work hardening of the neck and shoulder.

H&Hhunter · May 15, 2012

The issue that I personally have is that usually on first firing shoulders move forward enough to cause excessive stretching at the web.

This is a very real issue and if you full length resize setting your shoulder back with every reloading you will get case head separations at about 6 to 8 reloading due to web stretch.

Hizzie · May 15, 2012

"My _____belted magnum isn't very accurate."

Translation

"I cannot tolerate the recoil and flinch terribly when I shoot my magnum."

LoonWulf · May 16, 2012

I just realized my post was a bit confusing.

I should have clarified that using NEW cases i neck up to a cal or so larger then back down. This provides an small shoulder to hold the case against the bolt face during initial forming.
After first firing they are all neck sized. Ive been cutting one or two up after each firing, and so far ive seen little stretching at the web.

Kachok · May 16, 2012

Belts are just one more big marketing ploy from way back when, they never were good for anything and are just one more thing that can go wrong with accuracy, but we have gotten really good about getting around that hence several professional long range shooters still use belted mags. Why would they when there are all these nefangle WSMs now? Because they already have a wealth of good data and the longer cases give more room to seat long VLD style bullets. I still give a slight edge to the WSMs but for hunting accuracy you would never notice the difference and I do mean NEVER. We are talking a fraction of an inch difference at 1,000yd.

MtnCreek · May 16, 2012

and the longer cases give more room to seat long VLD style bullets.

My biggest gripe w/ the 300wm: Long bullets, short neck & not enough mag length. I wish it was made for a longer mag action that would allow seating the bullet further out.

CAUTION: The following post includes information NOT consistent with currently published load data and is NOT intended to be used. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

A couple of things the belt is good for: Couple of months ago, a guy here posted where he mistakenly used 300wm ammo in a RUM (non-belted). The belt gave enough dia where the case set in the chamber where it would fire. Just for a little risky fun, I’ve loaded 7mm rm w/ with a 308 bullet and fired it in a 300wm. Cartridge spaced off the belt and fired fine. It blew the shoulder out to fit the wm chamber. No head separation.

MachIVshooter · May 16, 2012

My biggest gripe w/ the 300wm: Long bullets, short neck & not enough mag length. I wish it was made for a longer mag action that would allow seating the bullet further out.

Solution: Remington 700 action. The long action is the magnum action.

MCMXI · May 16, 2012

MtnCreek said:
My biggest gripe w/ the 300wm: Long bullets, short neck & not enough mag length. I wish it was made for a longer mag action that would allow seating the bullet further out.

When I had Krieger put a barrel on THIS rifle, I made sure that both the 208gr A-MAX and 220gr SMK would be well into the lands when loaded to AICS magazine length.

MtnCreek · May 16, 2012

Very nice!!! Mine's the plain-jane 700P; stock barrel, xmark and stock. Maybe mine will look like that when it grows up.

Did you send them a dummy rd or give them specs to lands?

Thanks.

MCMXI · May 16, 2012

MtnCreek said:
Did you send them a dummy rd or give them specs to lands?

I measured the internal length of the five AICS magazines that I have and subtracted 0.050" from the shortest magazine to get a maximum C.O.L. for a 208gr A-MAX. I told Krieger that I wanted the 208gr A-MAX ogive (at a minimum) to touch the lands when loaded to the max C.O.L. I knew that if it worked for the 208gr A-MAX it would definitely work for the shorter and "fatter" 220gr SMK. Krieger did the rest ... and did it very well.

CountryUgly · May 16, 2012

Hizzie said:
"My _____belted magnum isn't very accurate."

Translation

"I cannot tolerate the recoil and flinch terribly when I shoot my magnum."

Just from my personal experiences that I have personally witnessed this has been the case more often than not....the one time it couldn't be blamed on the shooter it turned out to be the cheap scope couldn't hold a zero.

Belted Magnums

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