Hello all, yes, I'm new here. A few of us on another forum were reading about the AR's original twist of 1/14 and the effect on terminal ballistics. We then got into a discussion of the optimum twist for M855, especially given the Swiss chose 1/10 for their 63 grn service ammo. The US went w/ 1/7 in order to stabilize our M856 tracer. What say you?
Range Report Best twist for M855?
- Thread starter backbencher
- Start date
My good sir, the question is not about Mk 262, or M856 - it's about the optimum twist for M855, a 62 grn round. 1/7 does not appear to be the optimum for M855's terminal ballistics.
You asked about the M855, my answer was about the M855.
Comparing the M855 with the M193
Also read http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA162133
And http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA542434
You'll find the M855 works quite well with the 1:7 twist.
Comparing the M855 with the M193
Also read http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA162133
And http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA542434
You'll find the M855 works quite well with the 1:7 twist.
Perhaps I should phrase the question another way - does anyone have experience in firing M855 at a twist rate between 1/9" & 1/12"? Not AT 1/9" or 1/12", but between those two twist rates. kraig, thank you for the 2nd link - although they fired all their test shots from 1/7" twist bbls, some they fired w/ a reduced powder charge which should let me work out the RPM.
Yes I've shot M855s out of 1:12s, 1:9s and 1:7s (never saw a 1:10s, I suppose they are out there, but never saw one)
When the M16a2s came out I was running the marksmanship program for the Alaska National Guard. Part of that was being the OIC of SARTS (Small Arms Readiness Training Section) meaning I was responsible for the small arms qualification for the Alaska Army National Guard.
Being the National Guard, we were the last to get the A2s. Not knowing the difference many units ordered M855 instead of M193s. Of course our M16A1's were 1:12s. M855 sucked in 1:12 M16A1'S (see the chart I posted above comparing the M193 and M855)s.
At the time the guard was using a KD Combat course for the M16s, it was shot at 100, 200, 300 & 400 yards, similar to high power. The A1's using M193 were extremely accurate to 300 yards but had wind problems at 400 plus.
I re-barreled my Colt SP1 with the same couture 1:9 barrel. That's when Sierra and others came out with heavier bullets. My SP1 with the 1:9 shot the heavier bullets (to 68 gr) farily well. It also shot the M855s pretty good. Our M16a1s don't shoot anything past 55s worth a hoot.
We started getting M16A2s before I retired, (1992), we found that the A2's 1:7 shot both the M855 and M193. The M855s did work better at distance though because of the wind. In no wind situations, (which I've never really seen) the 55 gr M193s shoot quite well.
Fast forward. I retired. And like most retired military guys, I had a supply of guard ammo when I retired. I gave my SP1 1:9 to my son, but I have another SP1 in 1:12. I also have a White Oak service Rifle in 1:7. I also have a Mann Device (1:7). and a Remington Bolt gun (1:12).
I don't have many M193 & M855 left, but again, my Mann, my WOA shoot both quite well. My SP1 (1:12) shoots M193 but wont shoot M855.
I don't really remember shooting much M855 out of my Remington.
The Remington is a BDL Varmint in 223 1:12, it was my sniper rifle with I was in LE. At the time I use M193 out of it. It shot the 55 gr bullets quite good, well with in my needs for its intended purposes. But like I said, I don't remember shooting many M855s out of it.
Speer Gold Dot 64 grn "For LE" is a different matter.
I still run LE sniper schools once in a while, but prior to a class, I ask for some of the ammo they are intending to use to work with a bit prior to the school. For that reason I have access to lot of the Speer Gold Dot stuff. Its pretty close to M855 only more accurate.
I'm limited to the four 223s I have. The Mann of course I use for accuracy control. The Gold Dots, like the M855 don't shoot worth a hoot I my 1:12 SP1. It shoots great in my White Oak, so much so, (and because I have access to it) I'm starting to use it for the 200 & 300 yard stages in High Power.
Now for the surprising part. My Remington 700 V in 1:12 shoots the Speer Gold Dots quite well. I only tried it in my back yard (400 yards) but it does quite well. (My current PD round and Rifle). I can only assume the difference between the Rem Bolt gun and the SP1 is the extra velocity. My SP1 shoots 52 - 55 gr bullets quite well. It wont shoot anything heavier.
My White Oak (and Mann of course) shoot anything from 52 -80s, I got some Berger 90s but haven't really tried them yet.
Just for information my Mann is a 5.56 chamber, 1:7 with a 17 3/4 barrel. My SP1 and WOA ARs are 20 in. My Remington is 24 inch.
In my experience and from what I've read, unless one is shooting light Hornet type bullets, there is no advantage going less then 1:7 for a 223/5.56.
Sure if you limit your shooting to 77s 1:8/9 will work, but if you're going to 600-1000 yards, you'll want 80/90s and will need the 1:7.
I just don't want to limit myself because of slow twist.
When the M16a2s came out I was running the marksmanship program for the Alaska National Guard. Part of that was being the OIC of SARTS (Small Arms Readiness Training Section) meaning I was responsible for the small arms qualification for the Alaska Army National Guard.
Being the National Guard, we were the last to get the A2s. Not knowing the difference many units ordered M855 instead of M193s. Of course our M16A1's were 1:12s. M855 sucked in 1:12 M16A1'S (see the chart I posted above comparing the M193 and M855)s.
At the time the guard was using a KD Combat course for the M16s, it was shot at 100, 200, 300 & 400 yards, similar to high power. The A1's using M193 were extremely accurate to 300 yards but had wind problems at 400 plus.
I re-barreled my Colt SP1 with the same couture 1:9 barrel. That's when Sierra and others came out with heavier bullets. My SP1 with the 1:9 shot the heavier bullets (to 68 gr) farily well. It also shot the M855s pretty good. Our M16a1s don't shoot anything past 55s worth a hoot.
We started getting M16A2s before I retired, (1992), we found that the A2's 1:7 shot both the M855 and M193. The M855s did work better at distance though because of the wind. In no wind situations, (which I've never really seen) the 55 gr M193s shoot quite well.
Fast forward. I retired. And like most retired military guys, I had a supply of guard ammo when I retired. I gave my SP1 1:9 to my son, but I have another SP1 in 1:12. I also have a White Oak service Rifle in 1:7. I also have a Mann Device (1:7). and a Remington Bolt gun (1:12).
I don't have many M193 & M855 left, but again, my Mann, my WOA shoot both quite well. My SP1 (1:12) shoots M193 but wont shoot M855.
I don't really remember shooting much M855 out of my Remington.
The Remington is a BDL Varmint in 223 1:12, it was my sniper rifle with I was in LE. At the time I use M193 out of it. It shot the 55 gr bullets quite good, well with in my needs for its intended purposes. But like I said, I don't remember shooting many M855s out of it.
Speer Gold Dot 64 grn "For LE" is a different matter.
I still run LE sniper schools once in a while, but prior to a class, I ask for some of the ammo they are intending to use to work with a bit prior to the school. For that reason I have access to lot of the Speer Gold Dot stuff. Its pretty close to M855 only more accurate.
I'm limited to the four 223s I have. The Mann of course I use for accuracy control. The Gold Dots, like the M855 don't shoot worth a hoot I my 1:12 SP1. It shoots great in my White Oak, so much so, (and because I have access to it) I'm starting to use it for the 200 & 300 yard stages in High Power.
Now for the surprising part. My Remington 700 V in 1:12 shoots the Speer Gold Dots quite well. I only tried it in my back yard (400 yards) but it does quite well. (My current PD round and Rifle). I can only assume the difference between the Rem Bolt gun and the SP1 is the extra velocity. My SP1 shoots 52 - 55 gr bullets quite well. It wont shoot anything heavier.
My White Oak (and Mann of course) shoot anything from 52 -80s, I got some Berger 90s but haven't really tried them yet.
Just for information my Mann is a 5.56 chamber, 1:7 with a 17 3/4 barrel. My SP1 and WOA ARs are 20 in. My Remington is 24 inch.
In my experience and from what I've read, unless one is shooting light Hornet type bullets, there is no advantage going less then 1:7 for a 223/5.56.
Sure if you limit your shooting to 77s 1:8/9 will work, but if you're going to 600-1000 yards, you'll want 80/90s and will need the 1:7.
I just don't want to limit myself because of slow twist.
The best thing you could do is pull a round and check the length then put it in a stability formula, you can modify the formula to find ideal twist rate if you want.
If I'm reading the right specs on it the military had two versions of the m855 one with a steel nose and one with a tungsten, steel, tungsten, and lead all weigh differently so in order to maintain the same bullet length they probably altered length, and length is a big factor in stability.
If I'm reading the right specs on it the military had two versions of the m855 one with a steel nose and one with a tungsten, steel, tungsten, and lead all weigh differently so in order to maintain the same bullet length they probably altered length, and length is a big factor in stability.
Interesting - what velocity are you getting out of your Remington w/ those 64 grn Gold Dots? Rhyno, kraig has supplied us w/ M855 bullet lengths, do you have a formula handy? There are @ least 2 versions of M855 - M855, 62 grn, tri-metal w/ a steel penetrator core, & the new M855A1, a solid copper bullet w/ similar anti-armor characteristics. If there was a tungsten penetrator, I'm not familiar w/ it - got a link?
I've shot M855 and its equivalent from other countries in several rifles. M855 has a lead core and a steel tip, all covered with a copper alloy jacket, and has a green tip.
Needs a 5.56 chamber, high pressures and functioning problems appear with 223 Rem chambers.
SS109/M855 ammo is not particularly accurate, probably due to the three piece bullet. All shot the about the same in 1-10, 1-9, 1-8 and 1-7 barrels, or at least it seemed that the accuracy variations were not due to twist but probably other factors too. Same with reloads using M855 bullets. You may find a rifle/load combination that shoots OK or better with pulled bullets and the right load.
TiroFijo, thanks much for answering the question. The reward for answering a question is more questions : )
Do you remember what the length was on the 1/10" twist bbl? Was it SS 109 or M855, do you recall?
The 1-10" barrels were 20" and 24". The 24" 1-10" barrel shoots 69 gr SMK VERY well, and the M855 bullets are about the same length, so stabilization should be no problem. This is in warm weather near sea level.
Some of the bullets were M855, and some were similar but from other makers.
Some of the bullets were M855, and some were similar but from other makers.
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