Overall length question

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civilian75
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Re: Overall length question

Post by civilian75 »

Feeding issues are more magazine related than COAL. I'm now using strictly Magpul. No more USGI. I believe anti-tilt followers are of great help, especially true for 300BKL cartridges with COALs not close to max. Makes rounds less sensitive to differences in COAL. Here is why:

On 5.56, the rib appears to help keep the rounds in place. Maybe not a big deal considering most cartridges are loaded close to max COAL, when compared to 300BKL! In 5.56 the rib holds back the case shoulder, keep rounds in place when BCG strips the top round, as a result of recoil, or just by firearm handling. Without the rib, if 5.56 shift forward and the bullet tip were to hit the mag front inner wall, IMO, they could tilt the follower and jam. Not good! Rib saves the day.

It could be said the rib is located at the wrong place for 300 BKL. It could be relocated to touch the 300BKL diminutive case shoulder. But given the almost non-existent 300BKL case shoulder, it could well be of little use. What's worst, we'd end up with a 300BKL specific mag.

Nevertheless, even in the current location, the rib can still serve he same purpose, sort of, and with a caveat. The bullets should touch the rib. If COAL is too long, rib will yaw the rounds out of alignment and create too much friction between bullet and rib. This friction counters the upward push of the mag spring and can tilt the follower. I think we can all agree that if the follower tilts, we can get a jam.

If COAL is too small, and the mag spring tension is too low, the rounds will shift forward inside the mag. When bolt peels the round, it may not go up the ramp as designed, and may jam. Some bullets shapes are more susceptible than others. I admit I do not have a lot of data to prove that at the moment. Let's say it is a working hypothesis.

In short, anti-tilt followers and strong mags springs are 300BKL users' best friends.

Disclaimer: Everything I said above, is my opinion, based on my experience. I could be on the money, or I could be way off. Buy it at your own risk.
Last edited by civilian75 on Wed Sep 05, 2012 8:39 pm, edited 2 times in total.
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Tothemax!
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Re: Overall length question

Post by Tothemax! »

civilian75 wrote:Feeding issues are more magazine related than COAL. I'm now using strictly Magpul. No more USGI. I believe anti-tilt followers are of great help, especially true for 300BKL cartridges with COALs not close to max. Makes rounds less sensitive to differences in COAL. Here is why:

On 5.56, the rib appears to help keep the rounds in place. Maybe not a big deal considering most cartridges are loaded close to max COAL, when compared to 300BKL! In 5.56 the rib touches the case shoulder and helps keep rounds in place, when BCG strips the top round and as a result of recoil. If 5.56 shift forward, they hit the rib. If the bullet tip were to hit the mag front inner wall, IMO, they could tilt the follower and jam. Not good! Rib saves the day.

It could be said the rib is located at the wrong place for 300 BKL. It could be relocated to touch the 300BKL diminutive case shoulder, just like with 5.56. But given the almost non-existent 300BKL case shoulder, it could well be of little use. What's worst, we'd end up with a 300BKL specific mag.

Nevertheless, even in the current location, the rib can still serve he same purpose, sort of, and with a caveat. The bullets should touch the rib. It COAL is too long, rib will yaw the rounds out of alignment and create too much friction between bullet and rib. This counters the upward push of the mag spring and can till the follower. I think we can all agree that if the follower tilts, we get a jam.

If COAL is too small, and the mag spring tension is too low, the rounds will shift forward inside the mag. When bolt peels the round, it may not go up the ramp as designed, and may jam. I admit I do not have a lot of data to prove that at the moment. let's say it is a working hypothesis.

In short, anti-tilt followers and strong mags springs are 300BKL users' best friends.

Disclaimer: Everything I said above, is my opinion, based on my experience. I could be on the money, or I could be way off. Buy it at your own risk.
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mech5700
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Re: Overall length question

Post by mech5700 »

From what I've found, where the diameter of the projectile is ~0.250", that's the sweet spot where the rib should contact. The neck of a standard .223 is roughly in that area. The farther away you are from that, the less likely things are going to feed correctly without modifying/removing the rib.

The first loads I ever made for the BLK was the 110 gr Hornady VMAX to 2.040 (published on Hodgdon's website). After loading them they seemed way short and I had doubts that they would feed correctly... but I was wrong. They all fed perfectly. When I checked to see where the .250" diameter was, guess what, right on the rib. Oddly enough tho, when I checked the factory Rem 115 gr's and 220 gr's, the .250" was a little further out but they all feed fine as well. So to me, there is a little bit of tolerance in there where it doesn't have to be .250" exactly at the rib, but the closer the better. Providing the proper charge, projectile length, etc, etc.

I marked where 0.250" is on these rounds and compared them to a .223.
From Left to Right: .223, 110 gr vmax, Rem 220 gr, Rem 115 gr, and 150 gr Interlock.
Image
Image
Image
Image
Image

These all seem to feed fine out of an unmodified mag, even tho the last 3 are slightly tilted "inward" because of the rib pushing them over.
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Tothemax!
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Re: Overall length question

Post by Tothemax! »

mech5700 wrote:From what I've found, where the diameter of the projectile is ~0.250", that's the sweet spot where the rib should contact. The neck of a standard .223 is roughly in that area. The farther away you are from that, the less likely things are going to feed correctly without modifying/removing the rib.

The first loads I ever made for the BLK was the 110 gr Hornady VMAX to 2.040 (published on Hodgdon's website). After loading them they seemed way short and I had doubts that they would feed correctly... but I was wrong. They all fed perfectly. When I checked to see where the .250" diameter was, guess what, right on the rib. Oddly enough tho, when I checked the factory Rem 115 gr's and 220 gr's, the .250" was a little further out but they all feed fine as well. So to me, there is a little bit of tolerance in there where it doesn't have to be .250" exactly at the rib, but the closer the better. Providing the proper charge, projectile length, etc, etc.

I marked where 0.250" is on these rounds and compared them to a .223.
From Left to Right: .223, 110 gr vmax, Rem 220 gr, Rem 115 gr, and 150 gr Interlock.
Image
Image
Image
Image
Image

These all seem to feed fine out of an unmodified mag, even tho the last 3 are slightly tilted "inward" because of the rib pushing them over.
Very interesting. Thanks for the write up and the pics!
mech5700
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Re: Overall length question

Post by mech5700 »

No prob! I too will be taking my shot at loading the 147 pulldowns next week when they arrive. Let us know what ya come up with if you can get them to work. Seems like it's hit or miss from what I can tell. Some people suggest loads that work for them, and others can't get em to work... PNW Arms seems to have it down but I can't find much data on their specs...
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Maryland_Shooter
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Re: Overall length question

Post by Maryland_Shooter »

rjacobs wrote:
Tothemax! wrote:Thanks for the replys. Does anyone know what Noveske's preferred OAL in their barrels is? If I go and buy the hornady OAL gauge will this tell me the number I should be loading that. I am still learning what I need to set the OAL for my particular rifle at.
The OAL has NOTHING to do with the gun/barrel. It has EVERYTHING to do with the bullet you are using and its ogive in relation to the rib in the magazine. Did I not just post that? I had to double check, but I did post that basically in the post above.

Now if you take that rib out of the magazine, then, and only then, can you custom load, up to max mag length, for your bullet and your gun. UNLESS you do that, you have to load so the ogive of the bullet is at the rib of the magazine(or pretty dang close to it) for feeding reliability.
Thanks for that tip, I was looking at that danged rib last Friday and I'll modify two mags for 300 BLK use only.
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Post complete and accurate info when inquiring about loads, or be ignored.
rjacobs
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Re: Overall length question

Post by rjacobs »

mech5700 wrote:PNW Arms seems to have it down but I can't find much data on their specs...
I cant say what their OAL is(easy enough to measure), but they have posted they are running 16.5g of H110. They were running 17.7g of H110(again, as verified by them), but that was "a little to hot" according to them so they have backed it off.

The AAC spec for the 150g FMJBT(which is pretty dang close to the 147g pulls) is 2.065 which seems to be working for me. Might start there as far as COAL goes and see what works for your gun.
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