Contacting the Rifling

[El Chivo]

35 Rem loads have always worked pretty well for me, Remington factory and my own with Sierra bullets were accurate. I tried the Hornady bullets and noticed they sit farther forward than the Sierras if I crimp to the mark. This increases the overall length, leaving more room in the case and also the tip of the bullet just touches the rifling, so the lever is a little hard to close.

I use a pleasant load of 36 gr H4895 which is two or three grains under the max. WOW it was more accurate than before, which I attribute to touching the rifling. What kind of pressure increase is there with two identical loads, one that touches the rifling and one that doesn't?

[wolfdog]

It can make a big difference in pressure. Look for signs. Also if you are talking about the flex tip bullets, in most loads Hornady shortens the case a bit.

[Griff]

What you've described is a situation that may have no effect on pressure. If the two bullets (projectiles) are the same length, and you set one out to touch the rifling and the other normally, the increased space in the case mayactually cause a reduction in pressure. One fairly sure way to know is to measure the velocity of the two rounds. Generally speaking, two rounds of equal powder charges and equal bullet weights will give equal velocities, if there is a difference, the lower velocity can be attributed to lower pressure. I.E., the increasef space in the case from a shallower seated bullet may exhibit lower pressures and lower velocities.

Now... the actual contact with the lads could increase pressures as it will take more pressure for the powder charge to overcome the bullet's lack of inertia. You have both the neck tension AND the lands holding the bullet in position. Under this scenario the case must expand 'x' amount to release neck tension, and an infintessimal moment later the bullet has jumped forward to begun it's trip thru the rifling. That initial jump seems as tho' it would require less pressure to keep the bullet moving, than the amount of pressure needed to start it moving.

So, to me the question is whether the decrease in pressure due to larger case volume is offset or even overcome by the increase needed to overcome the bullet's inertia and rifling resistence? A chronograph will begin to give you the answer you seek.

[Sixgun]

Griff saved me a lot of typing----thanks partner! Well said.

Lead bullets offer little to no resistance when they are slightly engaged in the rifling. Problems come in with pressure spikes when jamming jacketed bullets in the rifling using loads that are already on the hot side.

Whole chapters have been written on cast bullets concerning seating depths.---------------Sixgun

[El Chivo]

Well, the bullets in question are jacketed, they are the 35 Rem 200 grain jacketed, with the long blunt nose. Still it sounds like I'm ok, as I'm about 3 grains under the max, that's almost ten percent. If the extra space in the case is considered, there's even more room to play with. Also consider 35 Rem loads are not that hot to begin with. The rifle is a 336 which should take 40,000 at least. Pressure for my load without touching the rifling is around 27,000 cup.

If this thing increases the pressure wildly then maybe I should back off, but if it's moderate then maybe I can continue. In the other thread someone mentioned it raises pressure by 6,000 cup, but what was the pressure to start with, 50,000? And those are factory loads, and near top pressure anyway, so any variable will increase the pressure a lot more? So I'm betting I'm in the low 30,000's at most. But even if it's high 30,000's my rifle is ok.

A while ago someone posted that looking for pressure signs only works with bolt guns; by the time pressure signs appear, your levergun is wrought iron latticework.

I may try out the next loading with the bullet pushed in just a hair and see what it does for accuracy. But it was a kick to see this splotchy yellow green hole in my Shoot'n'See after five rounds.


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ran a search and found this observations from another gun forum:

When Oehler came out with its pressure testing stuff, a friend used it to measure the difference between bullet's seated to just touch the lands and backed off with a .025-inch jump. Those touching the lands were about 2,500 psi higher. Cutting the 45 grain charge in his .308 Win. by about 1/2 grain for loads with land-touching bullets made pressure the same for both loads.

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[Sixgun]

El Chivo,
Ok, I had a good nights rest. Last night I had a "cast bullet on the brain" thingy. It must have come from that "Cast Bullets and Leverguns" post by C Cash.

I reread your question and yes, jacketed bullets touching or slightly engraving the rifling will raise pressures, but in your case, its nothing to be concerned with as pressures are not even close to borderline high. Its still nice to seat the jacketed bullet about .005-015 shy of the rifling because in addition to having the rifle operate smoothly, eventually your going to seat one out too far and then instead of shooting it, your going to extract it, only to find the bullet stuck in the throat and an action full of powder.

Like Griff says, a chronograph can tell a lot.----------------------6