Over All Cartridge Length

[PA BEN]

I'm working up some loads for my 7mm rem. mag. How close to the rifling should I start w/the bullet? Some say anywhere from .015 to .030 I didn't take my time w/my first loads, I seated them close to spec and they shot good enough for hunting. I want to take my time and work up a good load for this rifle.

[GoldTip]

I like to set them up as close to the lands of the rifling as possible without contacting the lands thats just how I was taught to load them.  So I guess my answer would be this, somewhere between .015 and .030.  Watching when you shoot for any pressure sign on the case of course.

[demontang]

It all depends on the rifle/ bullet. I have some loads that like to just kiss the rifling and some that  or .035 off the lands. Its just something you have to play with. If you are hunting with that load just make sure it cycles everytime without a hitch.

[cwuwildcat]

I've got a question on these lines.  What do you do if the workup for it says to have the oal at 3.17, but having measured the chamber with Hornady's oal gauge and comparitor, and taking into account the ogive, the oal should be closer to 3.25?  Do you try to stay closer to what the book calls for, or what your rifle calls for?  If you don't seat it as deep at the recipe calls for, will it effect the pressures much?

[JackOfAllTrades]

As long as the bullet is not 'touching' the lands or shoved into the rifling, then you're not going to see much difference between pressures from what the book lists. Remember, in most cases the books are showing data from a fixed test barrel, seldom from a real gun. You can get more pressure differences by having a different amount of crimp than they did when testing, but they don't tell you how much crimp was applied. Pressure spikes happen when the bullet is not allowed it's initial movement at time of propelant ignition. A good rule of thumb is to keep the bullet off the lands the distances that have already been mentioned. The OAL listed in manuals is considered a base point for all cartridges with SAAMI specs. They also list the OAL as tested so you know if that loaded cartridge should feed through an auto/repeating firearm. A bullet seated too deep may compress the powder resulting in a pressure difference. Seating a bit longer, but not so much to touch the lands could actually change/ or even drop pressure a bit, but certainly not enough to be noticeable to the shooter or ever be outside the SAAMI spec's. What you're looking for when extending the OAL is to find the sweet spot for a chambering that allows the most stable entry of the bullet into the rifling. If the bullet is vibrating less, it will have less harmonics when traveling down the barrel, thus be more stable when it exists the muzzle. Some barrel and bullet combinations will never see better accuracy by seating the bullet out just shy of the lands. But in many instances there is an improvement.

-Steve

[cwuwildcat]

all right, make sense Steve.

As always, thanks for the advise, Dave

[PA BEN]

.02 seemed to work real will. The widest group out of 6 rounds is 1"1/4 to bullets touching at 90yds.

[JackOfAllTrades]

PA BEN,

What's the trigger weight of that rifle? Still factory stock with no work on the trigger? And, have you moved forward with any glass bedding of the action as was posted in another one of your threads?

-Steve

[PA BEN]

I did float the barrel, factory stock. And no trigger work. Don't know the trigger wt. I would like it a little lighter but it's not to bad.

[C-Money]

I have always made mine just under the books max length. I've had good resultes with a wide range of cartridges. My Dad talks about being close to the lands. He colors a bullet with a marker and puts it in a dumby round and slides it in the rifle and looks for marks on the bullet and makes his length according to those marks.  I just follow the book and have done fine.

[JackOfAllTrades]

If you have this trigger, it is sweet and very adjustable. http://www.varminthunters.com/tech/ruger77trigger.html

If you don't have that trigger, then I have installed these. They are just as sweet if not better.

http://timneytriggers.com/sunshop/index.php?l=product_list&c=8

Or there there used to be a company called Trapper, that made a three spring kit for the Ruger77 MKII. (can't remember which rifle you have) I've installed them a time or two in Rugers. Trapper springs are listed at Natchez.com, but not for your rifle anymore. I think Trapper is out of manufacturing business now, but you might be able to find some new/old stock with a distributor somewhere.

For the 77 MKII, Clipping coils on the factory spring is a tricky proposition as there's tight coil at both ends so you have to clip VERY small amounts from both ends. 1/4 coil at a time, but you can go too far and ruin the over-all length. This won't affect travel length. Just a little weight of pull.

A little fine stone to the sear and trigger sear notch will make your trigger a bit nicer too. A fine stone won't change angles or reduce travel, you're just looking to smooth things up a bit for a slightly lighter pull.

I'll suspect that with your current groups approaching MOA, then glass/pillar bedding and a trigger job will most likely get you there. Like I said in a previous thread, Pillar/Glass bedding won't make a 2" gun shoot moa, but a stock 1 1/4" gun probably has a little tighter groups left to be found. There might be some brass prepararation in your reloading process that'll help too. The easiest thing to do for the trigger is buy a drop in unit like the Timney, Jard or other brand. Not to discount the skills of a gun smith to pillar/glass bed the action, but that task is not really all that difficult.

Just like building horsepower in a race engine, balance and weight reduction in the rotating mass builds a little more power. A polish in the intake and exhaust ports builds more, bigger intake valve, more lift from the cam, three angle valve job, each allow for more efficiency of the engine. The same holds true with rifles/pistols for accuracy. There's not one single thing that will make a gun accurate, it's the little things added up that produces results.

I am not a gun smith! But I give this advice based on my experience. 

-Steve

[PA BEN]

My Gun is the m77 markII. My trigger has no creep. Just pull. I've talked to a gun smith about trigger work and he said my gun is the hardest to do. BTW, these groups I shot aren't w/ the best rest in the world.

[carpsniperg2]

I like to set them up as close to the lands of the rifling as possible without contacting the lands thats just how I was taught to load them.  So I guess my answer would be this, somewhere between .015 and .030.  Watching when you shoot for any pressure sign on the case of course.

same as me we must of had good teachers   seat a bullet close but still over load manuals coal and then put the round into the the gun and chamber it then take that shell out and set my die to that length and then put it a tiny tiny bit deeper so it is not sitting the lands but there is nothing of a jump. always had great luck

[KillBilly]

My Gun is the m77 markII. My trigger has no creep. Just pull. I've talked to a gun smith about trigger work and he said my gun is the hardest to do. BTW, these groups I shot aren't w/ the best rest in the world.

Check this link:  http://www.riflebasix.com/index.php?main_page=product_info&cPath=65&selectOpts=1&products_id=205

Rifle Basix makes some awesome replacement triggers. I installed one of these for a site member on their Ruger and it made a world of difference. They come with good instructions and you can probably do it yourself.

[PA BEN]

My Gun is the m77 markII. My trigger has no creep. Just pull. I've talked to a gun smith about trigger work and he said my gun is the hardest to do. BTW, these groups I shot aren't w/ the best rest in the world.

I guess I should post the group. 6 shot group.