9mm velocity question.

[Unclenick]

Dunerjeff,

You are correct about headspace in principle. In practice, however sadly, it is often the case that ammunition winds up headspacing (being stopped from going deeper into the case) by the pistol's extractor hook, and never makes it to the chamber mouth. This is very common in .45 Auto. One gunsmith wrote that he thought about 70% of the 1911's he worked on were actually headspacing most commercial ammo that way. The chambers were just too deep.

I like to load lead bullets to headspace on the bullet for this reason. That is, I just seat the bullet out so it stops the case going deeper by touching the lands of the throat when the breech end of the case is flush with the back of the barrel. That way neither does the case mouth touch the the end of the chamber, nor does the case rim find the extractor hook. For bullet shapes that still feed reliably at this length, it is more accurate and reduces leading as compared to deeper seating. It also neatly prevents the primer from pushing the bullet out prematurely.


Engineermike,

You are right about COL in principle, but I don't think anyone meant to suggest that the same COL applied to all bullets; only that being consistent with whatever COL your particular bullet needs is more important to pressure and accuracy than case length.

I think it is worth mentioning here that SAAMI puts a tolerance on the lengths of all cartridge cases. Dimension specifications are a maximum with a +0/-n tolerance for cartridges, and chambers are a minimum with a +n/-0 tolerance. This way the more critical number is expressed. The manufacturers just trim for the middle of the range, as their cutoff saws are less precise than a handloader's trimmer usually is. This is another source of the variation.

For case length, the 9 mm SAAMI spec is 0.754" +0.000"/-0.010". So manufacturers will aim for 0.749" to be in the middle, but may miss by a couple or three thousandths. The chamber spec is 0.754" +0.012"/-0.000". So a total slop of 0.022" may be expected between the shortest case and longest SAAMI compliant chamber.

[RC20]

To put COAL in perspective

Keep in mind for those not in the know, GS has a normal width band at the back that engage the rifling and the front rides on the lands). Different than any other mfg.

I was going to get Golden Saber 124 for reload (they are damned accurate in factory loading in my gun). Could not get them so went with Horn XTP (COAL of 1.060)

My seater does not fit the nose well, so there is some variation, go long or go short (short would seem to be safe)

I did some playing with making a trail one long and could not get it to touch lands. Hmmm (not an active cartridge, just seeing what the variation was as the seater is bit erratic with that shape). Go long on COAL or go short? (and yes I asked and no one answered).

My brother bought some 147 Golden Saber for reload and I cold not find a COAL listed anywere. He is out of town.

So I bought a box and measured them.

Yep, they seat them with the drive band top to the case mouth (band is the same length on both the 124 and 147. So the 147 is as long as it can get before it hits the front of the magazine!

As the 124 and the 147 has the same ogive profile, COAL would seem to be a zero issue (until it won't move in the magazine at the extreme)

Be nice if someone who really knew about all that would comment. Why are we picky and list COAL if it is not an issue (references seem to indicate at times that COAL is minimum not maximum but I have yet to see anything definitive about that in semi auto pistol that head spaces on the mouth)

In the meantime, I am not worrying about COAL and if it varies I let it go long and I am loading a round that's 1.060, its no where close to being a problem no mater where the case mouth is length is wise in the minor variations we are talking about

Accuracy would seem to be in the powder and bullet, and looking at the GS powder its like no one I have seen appearance wise.

So, anyone ever see anything definitive on that COAL and accuracy?

Tons on rifles, nada on semi auto pistol

[BDS-THR]

Jeff H, for 125 gr lead bullet, I would suggest around 4.2 gr of W231/HP-38 and OAL that will feed/chamber reliably in your pistol/barrel. For me, it has been an accurate load and clean burning with less "snappy" recoil of more faster burning powders like Bullseye/Titegroup I transitioned away from yet will bring the sights quickly back for fast follow-up shots (double tap). But, Bullseye/Titegroup has produced slightly smaller shot groups than W231/HP-38 loads for me.

FYI, my reference 115 gr load has been Winchester 115 gr FMJ with 4.8 gr of W231/HP-38 loaded to 1.135" OAL. I use Winchester primers for all of my match grade loads.

BTW, here's Hodgdon's current published load data for 4" test barrel using CCI 500 primer:

125 gr Lead Cone Nose Winchester 231 Diameter .356" OAL 1.125" Start 3.9 gr (1009 fps) 25,700 CUP - Max 4.4 gr (1086 fps) 31,200 CUP

Determining Max and Ideal OAL for reliable feeding/chambering and accuracy:

As to OAL, OAL indicated on published load data is not even obtained using actual pistols, but rather test barrel fixtures. Therefore, each reloader must determine Max and Ideal OAL that will reliably feed/chamber from the magazine for THEIR PISTOL/BARREL used. Longer the OAL, the sooner the bearing surface of the bullet will engage the rifling of the barrel to produce more consistent chamber pressures, which will produce more consistent shot groups.

I keep seeing people using OAL specified in the published load data or using trial and error for different pistols. This is not the best reloading practice and determining OAL should not be a guessing game.

While most pistols will feed 9mm RN bullets at varying OAL, depending on the bullet nose profile (ogive) of RN/SWC/FP/Cone bullets, you may need to use shorter/longer OAL for your pistol. With any new bullet, you should always determine the MAX OAL using your barrel and IDEAL OAL by manual feeding from the magazine to ensure reliable feeding/chambering before conducting powder charge work up.

1. MAX OAL determines the longest OAL that will drop freely in your chamber without hitting the rifling. Using your barrel out of the pistol, drop a sized case into the chamber to ensure you are full-length sizing your case (it should fall in freely). Next, make a dummy round (no powder/primer) starting at SAAMI max length and taper crimp .020" wider than the diameter of the bullet (.375" for .355" bullet and .376" for .356" bullet). Drop the dummy round in the chamber and incrementally decrease the OAL until the round fall in freely and spin without hitting the rifling.

2. IDEAL OAL determines the longest OAL that will feed and chamber reliably in your pistol/barrel/magazine. Starting at the MAX OAL, manually feed your dummy round by releasing the slide (do not ride the slide with your hand). Incrementally decrease the OAL until the dummy round feed/chamber reliably.

3. POWDER WORK UP. Once you determined the MAX and IDEAL OAL, then conduct your powder work up from start charge to identify the charge that will reliable cycle the slide and produce consistent accurate shot groups.

[BDS-THR]

Originally Posted by RC20

Accuracy would seem to be in the powder and bullet, and looking at the GS powder its like no one I have seen appearance wise.

So, anyone ever see anything definitive on that COAL and accuracy?

For me accuracy is everything and have done quite a bit of accuracy verification of different reloading variables. Yes, powder charge variation trumps OAL for JHP but for lead bullets we are discussing on this thread, OAL will be a significant factor.

JHP bullet will leak a lot of high pressure gas around the bullet base during powder ignition and rely on higher powder charges to maintain consistent chamber pressures to produce accuracy. Lead bullets produce consistent chamber pressures from proper bullet-to-barrel fit (typical .001" larger than groove diameter of the barrel), deformation of bullet base (obturation) to seal with the barrel and liquedified lube/expansion of lube from bullet base deformation/radial acceleration of bullet forming a gasket with the barrel.

If the OAL is short so the bearing surface of the bullet is far from the start of rifling, as the bullet travels through the leade (space the bullet jumps from case neck/chamber to the start of rifling), more high pressure gas will leak around the bullet and cause gas cutting/bullet base erosion and blow liquedified lube out the barrel leaving the bullet without lubrication. Longer OAL that won't hit the rifling and reliably feed/chamber in the pistol will allow the bearing surface of the bullet to engage the rifling sooner to start building up chamber pressure.

Below picture shows three different 9mm lead nose profiles (ogive) and varying lengths of bearing surface. Due to the difference in the ogive and the start of bearing surface, OAL used will be different for each bullet profile used. Although the SWC bullet in the middle will be loaded to shorter OAL (1.040"-1.050"), start of bearing surface of the bullet will be the same as the RN/CN loaded at longer 1.080"-1.100" OAL. Due to substantially longer bearing surface of the bullet base, the SWC bullet will probably generate higher pressure sooner for more consistent peak/average chamber pressures and stabilize better as the bullet rotates through air. My initial testing of the SWC bullet is producing more accurate shot groups than RN bullets with larger cut holes on target.

Originally Posted by RC20

references seem to indicate at times that COAL is minimum not maximum but I have yet to see anything definitive about that in semi auto pistol that head spaces on the mouth

Remember that published load data were tested using barrel fixtures not actual pistols. As I mentioned earlier, longer OAL will produce more consistent chamber pressures and result in tighter shot groups/accuracy (Max OAL). But the final OAL used will be determined by the Ideal OAL that will reliably feed/chamber from the magazine.

Compare these two 9mm rounds. On the left is factory CCI Blazer RN loaded to 1.145" OAL and on the right is SWC loaded to 1.045" OAL. Very different OAL but the SWC load has been more accurate. If you are looking for better match stage scores, the SWC bullet will cut a larger hole for better scoring - many USPSA/IDPA matches will push back on the paper for scoring and RN "pulls" rather than "cut" that results in much smaller hole missing from the target.

[engineermike]

BDS-THR.
Did you try this using a plated SWC and if so were the results similar? just curious as if lead is still more accurate than plated bullets.(SWC bullets)

[BDS-THR]

engineermike, I was responding to OP's original inquiry.

Originally Posted by Jeff H

Out of a 4" gun, shooting 125gr lead round nose bullets and Win231 powder, does anyone have data on what load will chrono above 1000fps?

Did you try this using a plated SWC and if so were the results similar? just curious as if lead is still more accurate than plated bullets.(SWC bullets)

I am not sure if anyone is making plated SWC in 9mm.

I did do a comparison between my reference Winchester 115 gr FMJ with 4.8 gr of W231/HP-38 and Berry's HBRN-TP (Hollow Base RN Thick Plate) and got smaller shot groups with HBRN - http://www.thehighroad.org/showthrea...69#post7266869

BTW, Blazer bullet is plated.

[bkhann]

Great timing.... I just got done developing some loads for Bayau Bullet 9mm 125 gr coated coat lead bullets. I will settle on Titegroup 4.0 gr @ 1.090" (1113 fps) or Titegroup 4.2 gr @ 1.125" (1101 fps) depending on which gives the best perceived accuracy and feel.

Following is the workup chart:

Load Development
Bayau 9mm 125 gr Green Bullet
Goal: minimum 1000 fps, optimum 1100 fps, maximize efficiency and accuracy
October 22, 2011

Primer Powder Charge C.O.L. F.P.S.
SP HP-38/W-231 3.7 gr 1.090” 1002 fps
SP HP-38/W-231 4.0 gr 1.090” 1052 fps
SP HP-38/W-231 4.3 gr 1.090” 1096 fps
SP HP-38/W-231 4.5 gr 1.105” 1095 fps
SP HP-38/W-231 4.5 gr 1.125” 1077 fps
SP Titegroup 3.6 gr 1.090” 1071 fps
SP Titegroup 3.8 gr 1.090” 1098 fps
SP Titegroup 4.0 gr 1.090” 1113 fps
SP Titegroup 4.2 gr 1.105” 1110 fps
SP Titegroup 4.2 gr 1.125” 1101 fps
SP Power Pistol 4.8 gr 1.090” 1065 fps
SP Power Pistol 5.1 gr 1.090” 1091 fps
SP Power Pistol 5.3 gr 1.090” 1121 fps
SP Power Pistol 5.4 gr 1.100” 1098 fps

[1SOW]

I'm thinking of getting into USPSA so I need to be conscious of minor power factor. My current loads are rather soft shooting so I doubt they make minor, but since I don't have a chrono, I don't know for sure.

Out of a 4" gun, shooting 125gr lead round nose bullets and Win231 powder, does anyone have data on what load will chrono above 1000fps?

1. For USPSA 125PF is the absolute minimum load allowable.
Temperature, altitude and type of powder can affect PF significantly as conditions change, so most competitors load to 130PF or even more.

2. What someone else gets in their pistol won't tell you what "your" pistol and your specific load will do.

3. Without a chrono, feel can decieve you! Borrow, rent, ask another shooter with a chrono if you (or they) can shoot your gun & loads through it.

4. Most local shoots don't chrono their shooters' loads, only the bigger matches get chrono'd.

I competed for a year with a load that was too light. I found out when I borrowed a chrono. I later bought one and it's a big plus for developing new loads.

[Unclenick]

Bkhann,

Take a look at the plot below that I made for your load data. Notice anything funny about it?



Notice the similar hook shape on the right end for each series? Typically when you increase powder charge but get no velocity increase or get an actual decrease in velocity, as you see in the hook, that is a pressure sign. It happens because metal is stretching somewhere, making more room for the powder to burn in, which lowers average pressure in the bore by allowing expansion to get ahead of the powder burn a little. In general, and not counting compressed loads, velocity should go up at roughly the same percentage as the powder charge did, as you see for the first three HP38/231 charges, or there is metal moving somewhere.

It may just be the brass, but keep an eye out. I notice your loads of HP38/231 and Tightgroup exceed Hodgdon's maximums for a 125 grain lead bullet, plus you are using a shorter COL which can raise pressure substantially by reducing the starting powder space, so excess pressure is a real possibility.

We could also be fooled by the graph. Firing just one round of anything provides no statistical confidence. If you fired 10 of each powder charge, then we plotted the result for the resulting averages of ten for each powder charge, we could better have confidence we are seeing an overpressure result. For example, if you cleaned the barrel before starting the load string with each powder, we might just be seeing the effect of fouling building up rather than pressure. Firing ten of each, cleaning between each ten, will cause the fouling differences to tend to cancel out.