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Post by Kyle on Jan 24, 2016 10:03:29 GMT -5
Looking at Dons thread in Banging Steel with the AccuMax 275's we can start to get an idea on BC of the Pittman AccuMax .275. I have sent Don a message to see if he can retrieve the atmospherics, direction, elevation, scope height and velocity for his load to get a BC estimate for that fps range.
Although I don't have these variables yet from Don, here is some "guesstimate" using drop data alone: If we plug in 3000 fps and 1.75" scope height with a zero at 100 of 0.0 MOA and 6.5 MOA at 400 since it looks like his group was centered about 1/4 MOA high at 400 or 1 inch, I estimate real world BC at .345 - .347 for Don's setup.
Scope Height calculation is a big variable in estimating BC with these ballistic programs. BC estimation can vary greatly with 1/4 inch of scope height. Nothing beats real world shooting in the field to gather data on your particular setup to determine a BC for your setup. BC changes with velocity and other variables, so the BC of a particular Bullet at 3000 fps will not be the same at 2300 fps.
I will get out soon to shoot drop data with the 275, 300 and 325's. I have found a place to shoot 40 minutes from my house, 10 minutes from my work that I can shoot a max of 588 yards. I'm on a waiting list for a range that I will be able to shoot 1250 yards that is laid out due north to due south. I should be able to shoot there in July. Just a guesstimate for now using Don's data alone. More to come with more real world testing in the field. Kyle
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Post by Kyle on Jan 24, 2016 10:19:16 GMT -5
Don just replied about some of the variables. Temp was 24, elevation 956 and humidity 87%. Taking into account these conditions, the BC may be higher than predicted. Further range testing will help determine BC. Ultimately though, accuracy is what counts.
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Post by deadeyedon89 on Jan 24, 2016 10:33:19 GMT -5
Thanks Kyle, I will send the info over to you..... I am the kind of guy that all of this really doesn't matter to me.... Because I know every gun and conditions are different. So I go out and shoot "my" weapons(bow/gun/xbow) with different components to get the best possible combination for "that weapon". My Hankins SPML LOVES your Accumax 275's so well that I have shot some of my best groups in my life with this gun/bullet combo. But a lot of times a bullet that you find that shoots great groups on paper might not perform well in a animal, but the Accumax does both superbly..... I am not a scientific kind of guy but I have been shooting for for close to 40 yrs now and having the best times of my life with these SML's. Jeff Hankins and yourself have a lot to do with that and I appreciate it very much!!
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Post by keith on Jan 24, 2016 11:05:53 GMT -5
I'd use barometric pressure instead of elevation.
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Post by deadeyedon89 on Jan 24, 2016 11:35:15 GMT -5
I'd use barometric pressure instead of elevation. Barometric Pressure..... 30.12 |
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Post by Richard on Jan 24, 2016 12:00:09 GMT -5
I like the way you think deadeydon! Got to test yourself to get the real results! When I tested Kyle's 275 with the 78 gr. single powder load out of my gun on that day with the way I had them sized, they wanted to group but would throw one shot out of the group.....When I switched to a duplex?.........Five shots grouped under and inch! You just don't know until you test the combination out of your gun. Maybe if I had them sized a b it tighter, with my .028" bushing, Arrowhead plug and Win. 209's the results would have been different? Maybe a longer bearing surface would have changed the results. I think Hillbill mentioned that the 300 AccuMax will have a longer bearing surface?.........Kyle? It was obvious immediately that the 275 BE which has .100" more bearing surface, shot small with the straight 78 gr. IMR-4198 load. Mag primers might have helped but in my case, they always stick on the bolt nose where the Win.209's do not?
Anyway, it is evident that Kyle's bullets can and do shoot.
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Post by Kyle on Jan 24, 2016 12:07:45 GMT -5
I like the way you think deadeydon! Got to test yourself to get the real results! When I tested Kyle's 275 with the 78 gr. single powder load out of my gun on that day with the way I had them sized, they wanted to group but would throw one shot out of the group.....When I switched to a duplex?.........Five shots grouped under and inch! You just don't know until you test the combination out of your gun. Maybe if I had them sized a b it tighter, with my .028" bushing, Arrowhead plug and Win. 209's the results would have been different? Maybe a longer bearing surface would have changed the results. I think Hillbill mentioned that the 300 AccuMax will have a longer bearing surface?.........Kyle? It was obvious immediately that the 275 BE which has .100" more bearing surface, shot small with the straight 78 gr. IMR-4198 load. Mag primers might have helped but in my case, they always stick on the bolt nose where the Win.209's do not? Anyway, it is evident that Kyle's bullets can and do shoot. Bearing surface will increase approximately .060" per 25 grain in weight increase. |
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Post by hillbill on Jan 24, 2016 12:56:06 GMT -5
Regardless of BC accuracy is priority #1, obviously these bullets are going to be accurate and I think in part because of very consistent weight and the lack of air voids inside. I have only sized 50 so far but I have yet to have inconsistent sizing issues like I have had in the past with other bullets, again I believe due to lack of air voids.
Obviously they are going to have a decent BC, will they be the BC king? No, likely not but what Kyle wanted to do is design a very accurate consistent bullet, I believe he has indeed succeeded in doing that..
the heavier weights are what I'm really interested in trying out, especially at distance...
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Post by keith on Jan 24, 2016 15:43:22 GMT -5
What is the supposition with air voids? Air voids where?
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Post by deadeyedon89 on Jan 24, 2016 16:30:46 GMT -5
What is the supposition with air voids? Air voids where? Facts, not supposition!! 300 MH Cross section  |
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Post by keith on Jan 24, 2016 17:09:24 GMT -5
Read more carefully. The supposition is with voids not that there are air voids. You cannot discuss with regard to something that is not. That's why I asked where. What are we supposing the effect of the void is? I think what I'm to understand it affects sizing as written thus far.
So, having established there are voids, that void is a function of how the core seat punch works. It is probably just longer than the actual male portion of the tip that seats in the core when it goes through the pointing die. My guess would be that it is there to minimize lead flow that would occur without it. If you look at the top of the lead core it is not 100% flat/even and it would be exacerbated without that female cavity to accept stem. So long as it is concentric and of consistent depth it should not create a center of mass vice center of form issue. I can't say how it affects sizing since lead doesn't really spring back, it flows.
If Kyle's bullet does not have this issue I would think it is because he uses a greater mass of lead for a given jacket volume than the other design. I do not have any of Kyle's bullets but base this supposition upon the fact that from the pictures I have seen it appears that the lead core has a very minor bleed at the mouth of the jacket where it meets the swaged tip.
The reason I asked where there is a void is because without a punch that introduces a void (aforementioned)there should be no voids in a core that is swaged. Lead wire is extruded not cast. It is compressed in a die with a bleed hole to bring it to desired weight. It is compressed again as it is seated in the jacket. Then it is compressed again as it is pointed. I'm not saying the void there is good or bad but I bet Parker knows about it.
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Post by Kyle on Jan 24, 2016 17:24:23 GMT -5
Read more carefully. The supposition is with voids not that there are air voids. You cannot discuss with regard to something that is not. That's why I asked where. What are we supposing the effect of the void is? I think what I'm to understand it affects sizing as written thus far. So, having established there are voids, that void is a function of how the core seat punch works. It is probably just longer than the actual male portion of the tip that seats in the core when it goes through the pointing die. My guess would be that it is there to minimize lead flow that would occur without it. If you look at the top of the lead core it is not 100% flat/even and it would be exacerbated without that female cavity to accept stem. So long as it is concentric and of consistent depth it should not create a center of mass vice center of form issue. I can't say how it affects sizing since lead doesn't really spring back, it flows. If Kyle's bullet does not have this issue I would think it is because he uses a greater mass of lead for a given jacket volume than the other design. I do not have any of Kyle's bullets but base this supposition upon the fact that from the pictures I have seen it appears that the lead core has a very minor bleed at the mouth of the jacket where it meets the swaged tip. The reason I asked where there is a void is because without a punch that introduces a void (aforementioned)there should be no voids in a core that is swaged. Lead wire is extruded not cast. It is compressed in a die with a bleed hole to bring it to desired weight. It is compressed again as it is seated in the jacket. Then it is compressed again as it is pointed. I'm not saying the void there is good or bad but I bet Parker knows about it. I agree with Keith, The air void at the top is not 100% flat and even. If the air void is not flat and even, can the bullet be gyroscopically stable? |
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Post by keith on Jan 24, 2016 17:49:18 GMT -5
No bullet has 100% uniformity. I promise Berger, Lapua, JLK, etc do not have perfectly flat and even tops on their cores. They also don't have perfectly even meplat or Whidden wouldn't make money on uniformers or pointing dies.
Everything you can do to minimize imbalance and runout helps but their are limits. I tried to control it by using a mass of lead with enough volume to fill to the meplat. Most of the time it would be as flush as I could observe through a 10x loupe but it only takes a fraction of a grain to bleed like what you see on Kyle's bullet. It doesn't affect performance any more than a minor imperfection just under the tip does.
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Post by Deleted on Jan 24, 2016 18:58:40 GMT -5
The absolute minimal to non-existent void in the Accumax is further proof of Kyle's attention to detail in making a superior product. Kudos Kyle
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Post by shane on Jan 24, 2016 22:12:23 GMT -5
I have a BS and A Doctorate, but
This thread gave me a headache.
Geeez
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Post by Hank on Jan 24, 2016 22:45:17 GMT -5
Let's try to keep the threads on topic so no one gets a headache.
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Post by Kyle on Jan 24, 2016 22:59:11 GMT -5
I have a BS and A Doctorate, but This thread gave me a headache. Geeez Shane, we'll keep sectional density out of the equation so as not to give you a headache. Lol! Glad to have you here on the board. |
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Post by keith on Jan 25, 2016 7:45:22 GMT -5
Let's try to keep the threads on topic so no one gets a headache. Where did it go off topic? |
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Post by shane on Jan 25, 2016 14:06:15 GMT -5
It didnt go off topic.
I realized there are some VERY SMART
guys on here!!!
I wasnt trying to be sarcastic.
Actually very Impressed by the Knowledge
On this Site.
Stands to Reason why SMLs have come so far
In the Last 10-15 years. Its because of
Guys like Ya'll.
Carry On. Keep up the Great Work!
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