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Post by Richard on Jul 10, 2016 20:38:13 GMT -5
with a smooth sized muzzle loader bullet should you deduct the land dimension or the groove dimension? This was discussed at another location and my opinion was not in favor. My contention is that a smooth sized bullet hardly if anything, get into the rifling and hence do not take on the groove dimension. Here is what led me to this conclusion: Two weeks ago when I got done shooting, I only ran one wet and one dry patch down the bore. Just a little while ago I did the same thing to lightly clean the bore from last Tuesdays shooting. Curious to see if there was any fouling I broke out the Hawkeye bore scope.................Clean as a whistle! I would think that after some 40 shots there should be some semblance of copper fouling (as one wet and one dry patch in succession will not remove much of anything ) There was nothing in the groves or on the lands. Next, I went to some of my old targets with clearly defined holes and EVERY one of them produced perfectly round holes. As I looked over my center fire targets, there is always the outline of the rifling imprinted on the paper! Next I took and very carefully measured, under good lighting and with a magnifying glass the outside dimension of the holes and could not come up with any that measured over .450". This leads me to believe that when I measure my groups, .450" is the number to subtract (.45 cal. smooth sized) from the outside to outside dimension to get real size of the group. If you use .458 you will get a smaller group I know its only .008" but when you shoot and score BR targets, .008 is a lot! Since things are slow, I threw this up in case anyone wanted to offer other opinions.
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Post by doug136 on Jul 10, 2016 22:08:32 GMT -5
Is there a way to capture a bullet ? Like shooting your gun in water at a very long range ? Also wouldn't the bullet have to obratate into the rifling some in order to get the bullet to spin ? I have know idea Richard I'm asking . So how exactly are you suppose to measure a group ? I thought it was center to center or furthest outside to furthest inside ? Again I'm asking .
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mtj555
Junior Member
Posts: 68
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Post by mtj555 on Jul 10, 2016 22:30:27 GMT -5
You can measure center to center or outside to outside. If you measure center to center than you don't subtract the bullet diameter. If you measure outside to outside, you subtract the bullet diameter. That's what Richards post is about. With a 452 land 458 groove barrel most subtract 458 because thats how you measure with a centerfire cartridge. The debate is whether a smooth form fully obturates out to the groove dimension of the barrel and Richard was stating when he measured the holes they were not 458.
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Post by deadeye on Jul 11, 2016 7:28:46 GMT -5
years ago I run some into a 55 gal barrel for obturation check, I say in reality really don't know exact & could vary with each gun/load etc. could actually be .458,457,456 etc
they appeared fully obturated & measured approx. .458 so I have always deducted .458 .
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Post by schunter on Jul 11, 2016 12:19:31 GMT -5
I just deduct .450 to keep the math simple for my little pea brain...
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Post by Richard on Jul 11, 2016 12:54:31 GMT -5
Just look at bullet holes produced by a cf rifle and you will see they look like a clover leaf only all around the perimeter. Then look at the bullet holes from your .45 smooth sized and tell me if you can see any evidence of the rifling marks? I just looked at my 6mm cf 600 yard targets from Saturdays match and I can see and count all eight groves? But, I can see nothing resembling a rifling mark on the .45 cal holes and when measuring, I can not come up with any measurement other than .450?
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Deleted
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Post by Deleted on Jul 11, 2016 13:04:53 GMT -5
I measure my groups with how many critters are on the ground!!
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Deleted
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Post by Deleted on Jul 11, 2016 15:31:11 GMT -5
I measure my groups with how many critters are on the ground!! +1
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Post by itneverends22 on Jul 11, 2016 17:47:47 GMT -5
I measure my groups with how many critters are on the ground!! +2
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beans
Full Member
Posts: 248
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Post by beans on Jul 11, 2016 18:27:16 GMT -5
In my limited sabotless in the .50 I barely got scratches from the rifling on my bullets that I recovered. And these were from bullets that actually made the target in stable flight cutting round holes. I was shooting Barnes coppers.
I never thought that obturation was nearly as effective in filling the bore as is forcing a bullet into the land from a cartridge gun. I'm not even sure that much obturation even takes place.
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Post by Hank on Jul 11, 2016 19:12:32 GMT -5
Some obturation must happen or we would not be shooting the groups that we shoot.. Exactly how much we don't really know.. Perhaps we can try and capture some bullets shot into a box is wet newspaper at 450 yards at the next challenge and examin then to see if we can get any good answers..
We did subtract grove diameter at the shoots in the past just to keep the same for everyone... .458, .416, .400 ect. ect.
Anyine have access to a lot of newspaper... ?
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Post by Richard on Jul 11, 2016 20:14:48 GMT -5
Hank.......there is no problem using .458 at the shoot since everyones group will be measured and that amount subtracted from the outside to outside dimension. But, in reality, if your bullet is only producing a .450 hole and want to know the real size of your group, then using .458 will give you "not as accurate" group size. What one can do is to measure, as closely and accurately as possible a very clean hole. Then use that dimension to subtract from their group. On the other hand, if there is enough separation in the widest shots then just measure the far side of one hole to the inside of the other hole and not worry about any dimension? I personally believe these bullets........some more than others, depending on the jacket thickness and/or material, do not expand or obturate into the groves.......maybe just slightly? But not enough to put a footprint on the bullet.............BUT, just enough to grab and spin the bullet Heavy friction on the lands (IMHO) will spin the bullet. Somehow, I just can't see a bullet, being pushed from the base, is going to expand and impress itself into the rifling? Maybe a bullet with a skirt (Hornady fpb) or a very hollow base might engrave some rifling .......in the base area? Like beans said, some slight scraping marks might be all you will see?
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Post by hillbill on Jul 11, 2016 21:02:44 GMT -5
way back on the old board Rich this was a topic of discussion, when Blakely did his water barrel test I distinctly remember seeing pictures of the bullets and they appeared to be fully engraved and I also remember him doing measurements of close to .458, I don't recall the exact dimension but it was close if not.458.
I too have recovered bullets in dirt banks that appeared to be fully engraved, by fully engraved I mean being able to see smear marks from barrel contact in both the lands and grooves similar to a FF bullet, yes I fully believe we have .458 bullets upon firing or very close to it.
using the same 70 grn load with a 300 MH in a .458 build and a 310 APB in the same gun /load, smooth/ FF the speeds have been very very close. If the bullets were not fully filling the bore the smooth form bullets would have a much lower speed due to pressure blowing by the bullet, I have done this test from a couple different guns with similar results...JMO though for what it's worth..
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Post by Richard on Jul 11, 2016 21:16:05 GMT -5
That may very well be Bill but dang, I measured pretty meticulously and got .450" on the bullet holes I measured and no sign of rifling marks on the paper?
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Post by Kyle on Jul 11, 2016 21:24:35 GMT -5
Ok... Where is the popcorn eating critter at?
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Post by bestill458 on Jul 11, 2016 21:38:25 GMT -5
I have a little off topic question but we all know how quickly gas cutting happens on a front sealing plug. If a bullet only rides lands upon ignition wouldn't it flame cut the bullet and barrel very quickly also? This concern recently came to my mind shooting smooth form without a wad
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Post by bestill458 on Jul 11, 2016 22:21:54 GMT -5
327 match hunter recovered from buck Shot in 2014 at 267 yds with blackhorn powder. Smooth form with20 lb loading pressure in a 1-20 twist brux. Cant measure o.d. but rifling is fully engaged the full length of bearing surface and .458 groove area clearly scuffed bullet between rifling.
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Post by buckdoehunter on Jul 12, 2016 11:46:36 GMT -5
Here's a Barnes 290gr TEZ I shot this morning with 5gr Clays Internal./60gr IMR 4198 at 100yds. The back stop at the range consists of small rocks, gravel, and dirt. You can see where I knurled the bullet and the knurling is mostly smoothed away at the base of the bullet, about 1/8" total all the way around.
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Deleted
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Post by Deleted on Jul 12, 2016 11:47:55 GMT -5
Here's a Barnes 290gr TEZ I shot this morning with 5gr Clays Internal./60gr IMR 4198 at 100yds. The back stop at the range consists of small rocks, gravel, and dirt. You can see where I knurled the bullet and the knurling is mostly smoothed away at the base of the bullet, about 1/8" total all the way around. I'm gonna go out on a limb here and say that bullet has some engraving going on
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Post by Richard on Jul 12, 2016 16:01:58 GMT -5
That was smooth sized? or Full Formed? If smooth sized, I stand corrected. I was thinking of a way to capture a bullet with out destroying it. Thanks for showing! That is what this board is about, learning and sharing.
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