Bullets touching rifling, How much should I reduce powder charge?

[rickt300]

For all you guys that load your bullets out to touch the rifling how much do you reduce your powder charge? Does this practice raise pressures appreciably?

[myronman3]

first,  i dont know of anyone that seats bullets to actually touch the rifling.   the idea is to set the bullet just off of the rifling.  setting it to touch the rifling would be begging for trouble in regards to chambering a round.   
    why would you think this would raise pressure?  i use the same charge that i would if it were spec o.a.l..   if anything, seating the bullet out further should in theory REDUCE pressure a bit.  that is splitting hairs, though.

[Questor]

My limited understanding of this contains two facts:
1) Touching the rifling like that is usually reserved for fire forming cases, and in that case the wildcatter or proprietary cartridge supplier gives load data for doing the fire forming.

2) Touching the rifling like that does affect the "pressure curve". For example, Weatherby has long throats on their rifles because they are managing the pressure curve. I do not know if full power loads touching the rifling lead to dangerously high pressures, but the pressure curve will be more spiked than the same load seated farther from the rifling. I can see where it would cause unusually high pressures, and would be wary of using this technique.  In the cases where I have had to fire form cases, the loads have been quite hot to ensure a fully formed case (as opposed to a case with rounded shoulders that doesn't fill the chamber.

Perhaps there is some confusion about this. It is a common technique during load development to adjust OAL until the bullet touches the rifling and then seating the bullet a bit deeper (say a hundredth of an inch.) I haven't found that technique to make a difference when I've tried it, so I just stick to published OAL figures now.

[mjbgalt]

i had a browning a-bolt in .243 that, when i loaded to C.O.L., with copper HP's left rifling marks on the bullet if i ejected a loaded shell. apparently it was touching and i couldn't do anything about it. it also shot extremely well...like under 1/4" most of the time. VERY accurate rifle...maybe BECAUSE it was touching?

-Matt

[ranger 76]

Cast bullet shooters like to set there bullets on or in the rifling if you are using jacket bullets and set them on the rifling it will increase the pressure and will not help accuracy I would back off the lands 0.050 hope this helps. Lorne

[myronman3]

call me a monkey,  i seem to recall  that when fire forming one didnt need maximum velocity.  i am going strictly off of memory here,  so i could be wrong. 

    it is just another varible that one should be aware of.  sometimes it can be adjusted one way or another for better accuracy.  some rifles it doesnt make a difference, others it makes a dramatic difference.

[LaOtto222]

I have one gun that shoots better into the lands, but the majority of them shoot better off the lands and some I can not get to the lands no matter what I do. I do not have pressure equipment to measure the difference, but have read that the pressure is increased in the 7000 psi range when touching. I do not know from personal experience. I start at the recommended minimums and work my way up in small increments. Usually .5 grains at a time. If it is 22 Hornet, I only go .2 grains at a time. When I reach any kind of pressure signs, I back off that load about 5% and call it good. You will not find this in any reloading manuals. All of their testing is done with standard OAL length or close to it. This is for good reason, every gun is a thing onto itself and the companies that develop loading manuals would be guessing where your bullets touch the rifling. If you are loading for a hunting gun, you are kidding yourself with trying to reach the lands in most cases, you do not need to, believe me. The gun that it will help is one that is custom built, single shot with lapped barrels and you are trying to squeeze out the last .1" or .2" out of it. Those same people take GREAT care with case consistency, neck thickness, flash hole uniformity, bullet/case run out and many other little factors that most do not even think about. In most guns except the very best built guns, you will not see any gain by touching the lands, maybe even worse accuracy. I had a stock 222 Remington 700 BLD VS and it would shoot .25" 3 shots groups @ 100 yards and the bullets were .020" off the lands. Into the lands I was lucky to get .75". I also have a 223 Savage that I have built up into the custom range and it shoots best into the lands about .005", but still shoots .5" off of the lands. In the field where I will be shooting the 223, the little difference in accuracy will not mean a thing within the 300 yards I will be shooting it at (varmints); beyond 300 yards the wind, distance estimation, bullet drop etc will mean more than the little accuracy you can gain. It also give me peace of mind (even though I take great care at the loading bench) that I have a little room for error if some thing is not exactly right. Just my 2 cents

[millwright]

Whenever you make any change in your loading technique it is a good idea to go back to minimum load and work up SLOWLY

[stimpylu32]

rickt300

The pressure curve is designed to work with the bullet drag as the bullet slides from the case neck , if you seat the bullet into the lands you are loosing drag in the case neck but increasing Resistance by the bullet being pushed against the rifling and will increase pressure at a diffrent level , so as millwright has said drop back to the starting load and work back up slowly .

stimpy

[rks1949]

The rule of thumb,in benchrest shooting is: Reduce charge weight by 10-15% when seating the bullet into the lands. Ron

[Luckyducker]

The only cartridge I have loaded up against the lands was a 243Win.  I used full power loads but as someone said before reduce and shoot, look for signs of excess pressure and work up the load until you get the results you want or not but stop when the primers start to flatten or the bolt lift gets sticky, etc.   I would not want to try encroaching the rifling on some high capacity cases but a lot of cartridges operate at high pressures so be very careful. 

[rickt300]

I am in fact fireforming cases in a 30-30 that has .010 excess headspace. I want the case to stretch at the shoulder end and not in front of the web. Anyway I used a relatively slow powder, IMR 4320 and 170 gr. corelokts. I started at 30.0 grains and worked up to 32.0 grains till the primers ended up being flush with the face of the case. I never saw any signs of high pressure and it worked as far as the fireforming goes.

[stimpylu32]

rickt300

What type gun are you shooting ? The 30/30 headspaces on the rim so fire forming is only a temp fix for a bigger problem in this case .

stimpy

[hoggunner]

the way it was explained to me was, if you take your truck and start out two feet from the curb you can bounce that curb easily. if you put the front tires against the curb you need to push harder on the gas to get the truck to bounce the curb. more pressure builds if you touch the lands.
Hoggunner

[rickt300]

Interestingly in this Contender carbine loading to firmly touch the rifling gives outstanding accuracy using the above mentioned load. Using your truck analysis don't you think you could cause more damage by hitting the curb from a short run easier than if you eased over it?

[jhalcott]

  .010 in a contender SOUNDS like a stretched frame !! If this is the case you are going to wind up with a damaged gun and possibly a few injured bystanders also. I'd have T/C check the gun and frame for safety sake.

[rickt300]

Industry standard headspace tolerance allows for .006. This action is brand new and was ordered as a 22 rimfire rifle. No loads have been fired in it that come closer than 1 grain to max using 748 and 4320, both on the slow end for the 30-30.  However the barrel does have a slight noticable gap between it and the action face, a condition I have seen with several barrels and several contender frames. If the action is in good working condition and steps are taken to reduce/eliminate case stretching then .004 excessive headspace means nothing other than possibly reduced case life.